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Old February 19, 2013, 17:07   #151
Tim Dreas
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Originally Posted by Cava3r4 View Post
another automotive analogy for you:
YOu build an engine with 10 to 1 compression with ALUMINUM heads. (the Alum heads supposedly will allow you to RUN ONE more compression point VS. cast iron heads due to the additional "cooling". So 9 to 1 with cast iron, 10 to 1 with Alum).
Okay, so you build a 10 to 1 engine. (pick your favorite brand.. 454 Chevy, 428 Ford, 440 Mopar).
With the CRAP gas you have today, SUPPOSEDLY 91 octane with SUPPOSEDLY only 10 percent "ethanol" you are going to PING.
PING or Detonation is when the flame front violently explodes. This is described as a force equal to hitting your piston with a sledge hammer.
Cast pistons are going to SHATTER.
FORGED pistons might survive but not for a LONG time!!
It's not only due to the reduced heat using an aluminum head that allows a higher static compression ratio, but the valve seats are ground on a cold head using the valve guides as centers. When an aluminum head heats up and expands the valve guides and valves usually go off center from the valve seats a bit, reducing their sealing and reducing the cylinder pressure. The valves just don't seal as well in an aluminum head resulting in lower cylinder pressures.
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Old May 16, 2013, 06:38   #152
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One more thing, Titanium is not a "miracle metal." It's very notch sensitive. This means, you put a divot in it and it has a great propensity to crack at this flaw. I work with CP and Ti6AL-4V daily and we've researched and tested every aspect of this metal.
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Old July 10, 2013, 15:02   #153
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When Browning adopted the .40 cal round, they changed their frames from forged to cast. Perhaps each is better in its own little niche........
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Old July 13, 2013, 12:49   #154
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When Browning adopted the .40 cal round, they changed their frames from forged to cast. Perhaps each is better in its own little niche........
At the same time, they changed from carbon steel to chrome moly steel. The change in steel resulted in stronger frames. The change from forged to investment cast may have allowed a reduction in cost while upgrading the steel, which likely would increase cost.
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Old July 15, 2013, 15:46   #155
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I think these discussions are always derailed by the generalized experience of pretty much all men who grow up playing with zinc-pot metal toys, watching them break, and then inculcating in themselves a deep-seated aversion to the whole concept of casting as a method of producing anything...even toys.

Ghost said it way back yonder in the thread that technology has advanced us to the point where production methods and metallurgy combine to allow the use of casting to produce exceptionally strong gun actions.

This whole discussion reminds me of the 70's when it was said by some that Ruger M77's were all lining up to self destruct at any moment. As most of you know, this has not yet happened. Maybe next year... I hope not, as they are my favorite bolt guns..........

A comparison between the AK and the FN is not a good one when it comes to stampings and forgings, as the FN is a rear locking rifle and demands a longer receiver to contain the force where the AK is a front locking action and thus needs a relatively short locking extenstion, with the rest of the receiver merely guiding the reciprocating parts and also forming the ejector. Apples and oranges as far as designs are concerned. The AK is of course an amazingly strong action.

So, as others have said, you can get a strong action that was cast, or a weak action that was forged, and vice versa.

Nobody answered, but I believe the answer to the point that Coonan receivers are machined after heat treating is primarily to maintain tolerances. Heat treatment can induce warping especially if the part is of complex shape as is a receiver. Since the Coonan receivers are relatively soft {as far as heat treated machinable steel is concerned} this process may have only one downside which is somewhat accelerated wear of tooling, assuming of course that a proper relationship is maintained between the hardness of the receiver and the locking step on the bolt.

25-30 is of sort of softish spring temper. I make knives and I can tell you that if it was a knife it would require constant resharpening and would be a lousy knife. Some Indian Army Enfield bayonets I had tested 25RC.

But the FAL receiver is NOT a knife and thus the properties of a knife should not be interpolated to describe proper hardness of an FAL receiver. I personally do not know if a 25-30RC receiver is a good one but I see no reason to state that it would not be the proper hardness for one, or whatever they actually are. My point is that sometimes I hear folks say "Oh, that is soft" as if every stress bearing steel part must be as hard as their favorite hunting knife edge.

Having said that, I do find it interesting that military FAL receivers are said to be hard only at the locking step. Just about ALL bolt actions {with boltreciprocation being VERY slow compared to the speed of a semi and full auto rifle} have hardened bolt raceways, accomplished by spot hardening using several methods or using receivers of harder finish than 25-30. Evidently the design of the FN does not require much in the line of a hardened path for the carrier to travel. Interesting.
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Old July 15, 2013, 16:10   #156
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Investment castings are not sand castings. I don't think all military receivers are only spot heat treated. I think that is true for chrome moly type 3 receivers. The Australian receivers were made, "softer" than originally spec'd to prevent cracking of the receivers. The Australians did experience some stretching of the receivers that required replacement of the locking shoulders after so many rounds to maintain headspace. This receiver stretching was considered acceptable to prevent the receivers from cracking due to being too hard. So Australian receivers were softer than most. I've seen a lot of Canadian receivers that had the locking shoulders replaced and staked in place because the locking notch for the locking shoulder tab became loose.

FN's answer to type 1 receivers that sometimes cracked was to beef up the receiver design with the type 2 design. The early type 3 receivers saved machining and the last ones were made of tougher chrome moly steel instead of carbon steel used in the earlier receivers.

FN was competing with the H&K G3 that has a sheet metal receiver, fewer parts and a non-chrome lined barrel.

I think if FN had allowed Germany a license to make the FAL, the CETME would have never been improved and made in Germany. FN would have had an even larger share of the international market.
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Old January 30, 2015, 13:23   #157
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Angry DSA GONE CAST like RUGER

BECAUSE they want to make a TON more money on us and sell guns like RUGER! all CAST! receivers. john
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Old February 22, 2015, 07:26   #158
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In the case of DSA, forged or cast, are the recievers finished by hand? Maybe to remove burrs or get the part up to spec if it is not fitting properly?
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Old March 06, 2015, 00:25   #159
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There is some broaching and hand finishing on forged and cast.
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Old March 12, 2015, 16:47   #160
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There is some broaching and hand finishing on forged and cast.
So the R1 recievers were milled as you can see tooling marks on them unlike the DSA recievers which are completely smooth?
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Old March 12, 2015, 17:16   #161
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There are milling marks in Dsa as well, just how all of them are made , the r1 maybe did not care about looks and cost and availability of sharp cutters would have played into it, remember we were under an embargo
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Old April 17, 2015, 18:23   #162
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Old thread, but from start to finish, a thumbnail sketch:

1) The manufacture of steel billets - All the alloying materials are tossed in a furnace and melted together then poured into a large bloom. It is then forced between many, many sets of rollers to squish it into bar stock, round stock, plate, or whatever the final form is going to be.

During the rolling process, the grain is elongated and stretched out.

1) If, at this point you take a chuck of steel and cut off a hunk and machine it into the shape of a receiver (M14, FAL, AK, it doesn't matter) you have a "billet" receiver. The entire surface may be machined, or some surfaces may be the original billet surfaces, depends on how the design is and how well it fits the original billet. The billet keep the same elongated grain originally in the stock and there can be a huge amount of waste material, some aircraft parts are machined from billet and the pile of chips weigh more than the finished part. You can only make chips so fast, so machining time is factor as well.

2) If at this point, you whack off a hunk, toss it in a furnace until is is about 60% of the melting temperature, put it in a die and place the other half of the die on top and press the two together with several million pounds of force, you get a "forging".
It can be almost finished in appearance, or it can only vaguely resemble the finished part:




Again the part is machined to its finished dimensions, and again some surfaces may be left "as forged" or all of the surfaces may have a machined finish. A forging will have a grain structure that is somewhat aligned to the shape of the original forging. There will be less waste material and it doesn't take as long to machine.

3) If you remelt the steel, and pour it into a mold, you have cast a blank. For receivers, all are investment cast. The advantage of investment casting is it yields a very close approximation of the finished product.



As before, the part is machined to final dimensions. And again, as before, some surfaces may be left as cast, or all of the surfaces may be machined. I don't know about current production, but in the 1980's all Springfield M1A were investment cast and all exterior surfaced were machined, and only the most difficult internal surfaces were left as cast. Casting grain is different from billet or forgings, and there can be very minimal waste and little machine time.

No matter which of the above methods are used, all of them then go to be heat treated[1]. The heat treating varies depending on what you want the final property of the steel to be, tough and flexible, glass hard and super strong, or anywhere in between. Sometimes there is post-heat treat grinding or machining to true up things if the design is particularly susceptible to warping during heat treating.

Then on to final finishing and application of the protective coating.

Tool marks, their presence, or absence, doesn't tell you much about how it was made. A good final cut on a mill will leave very small tool marks that can be grit blasted off, similarly, with enough effort you can hide 'as cast surfaces' with aggressive blasting, although there is little point, with a good cast surface. And as we have seen, all of the methods used in the manufacture of receivers require some machining.

After good steel is delivered, really only forging and casting can be screwed up with internal flaws.

If, when forging, the part in heated to too high a temperature, the steel will be burnt. The problem with burnt steel is that it looks exactly like good steel to the naked eye. Only looking at the grain structure will tell if the steel is burnt, or if it breaks, the break will show evidence of being burnt.

Casting has its own set of difficulties, temperature of the melt, temperature of the mold, how fast it is allowed to cool, does the mold design allow enough for shrinkage, etc, etc.

Needless to say, all of the difficulties in forging and casting are well understood by their respective industries, and they know just how to turn out quality forgings/castings.

Quote:
There is some broaching and hand finishing on forged and cast.
In this day and age of CIM, the only "hand finishing" better be some deburring. Maybe during final assembly, but even then...

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1. You also have what is know as "prehard" or bar stock that has been heat treated prior to sale. and you machine your part out of steel that is already heat treated. This makes it easier for small shops that do not have heat treat capability and do not wish to send it out for heat treat. It does have its limitations, it can't be too hard, otherwise you could not machine it.

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Old May 25, 2015, 14:11   #163
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no more forged fal receivers are made

DS arms informed me they no longer make forged receivers and they are vacuum cast. I also talked to Enterprise and they no longer make the billet receiver and now are cast. The only way to get a forged one is by finding an old used one.
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Old September 27, 2015, 11:56   #164
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https://www.sfsa.org/sfsa/pubs/cvf/ecs.php


I will just leave this here
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Old January 05, 2016, 01:13   #165
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https://www.sfsa.org/sfsa/pubs/cvf/ecs.php


I will just leave this here
Perfect.
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Old January 10, 2016, 20:31   #166
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https://www.sfsa.org/sfsa/pubs/cvf/ecs.php


I will just leave this here
WOW....

Very impressive. This link will be a good one for any of these kinds of discussions.

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Old January 11, 2016, 02:19   #167
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How many of you work on your own cars and have wrenches, sockets, etc. Those are forged. There is a reason for that.
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Old January 12, 2016, 23:41   #168
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How many of you work on your own cars and have wrenches, sockets, etc. Those are forged. There is a reason for that.
I just picked up a set of Craftsman sockets/wrenches. No forging there...

I have 2 14" pipe wrenches that are aluminum with steel inserts. Not marked forged...

Maybe they were all forged in "the old days" (I have a bunch so marked) but no more...

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Old January 13, 2016, 00:14   #169
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Every wrench I own is forged.




I'm glad you brought up some sockets being cast. The cast ones break frequently. The forged ones do not. When I'm torquing down heads at 140 foot pounds guess what ind of sockets has never split on me? Forged (impact sockets) Thanks for helping me demonstrate my point.
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Old January 13, 2016, 00:34   #170
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I also note they are stamped "U.S.A.".

Maybe that's the real difference...

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Old April 08, 2016, 10:43   #171
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DS arms informed me they no longer make forged receivers and they are vacuum cast. I also talked to Enterprise and they no longer make the billet receiver and now are cast. The only way to get a forged one is by finding an old used one.
DSA just made a run of 400 forged receivers in 4 different configs.once they are gone that's it.......and the L1A1s have the proper British nose cuts.
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Old February 15, 2017, 15:44   #172
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DSA just made a run of 400 forged receivers in 4 different configs.once they are gone that's it.......and the L1A1s have the proper British nose cuts.
Damn, I wonder if the 23,000 to 24,000 range of DS Arms SA 58s are Forged??!!
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Old February 23, 2017, 19:23   #173
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For about anything except HARD military use, I don't think either forged or cast will make any difference.
In a quality product anyway.

In the last ten years on this Forum, I can't think of hearing of a single instance where a receiver failed that could be traced to it being cast or forged.

FAL receivers have been blown up with bad ammo and ruined by overzealous and under-talented builders on occasion.
But even the worst of the "out-of-spec receivers seem to have held up.
With the notable exception of the Williams "Aluma-Bombs" anyway.
Well said. This pretty much nails it. I've had both cast from Hesse and forged and cast from DS Arms. Never had one problem from either type. Just purchased a cast Voyager 16 inch from DS Arms and have no worries about how long it will last.
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Old April 17, 2017, 21:18   #174
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Damn, I wonder if the 23,000 to 24,000 range of DS Arms SA 58s are Forged??!!
DSA 29,000 range type 1 are supposed to be cast. A lot of confusion revolves

around when receivers went to being cast. Easy way to tell cast from forged

is remove magazine and tap mag well with a wrench. Cast receiver has a clunk

sound, similar to a cow bell. Forged has a high pitched ring to it, sounds like a

bell. Hope this helps
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Old April 28, 2017, 11:11   #175
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For me, the argument over forged vs cast with FALs isn't pertinent. I used to have a Belgian FN FAL LAR competition with cast receiver which I sold along with my entire gun collection at the time. I now have a FAL with a forged Imbel receiver. When I had the LAR, I shot the snot out of it, as you could purchase extremely accurate and reliable Israeli IMI 308 ammunition for $3.99 a box of 20.
I shot cases of that stuff through my LAR - which had a great trigger and iron sights that would rival the accuracy of my bolt Remington 700 with a fine scope. Never a problem of any kind....not one.

The gun rivaled a Swiss watch in its precision and smoothness. My Imbel FAL has a horrible trigger, rough surfaces, poor accuracy by comparison with the LAR and just doesn't feel like a precision instrument. Who cares if the Imbel receiver may last a few thousand rounds longer than my old LAR. Guess I don't need to say which I prefer or kick myself regularly for parting with.
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Old May 12, 2017, 22:20   #176
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Cast is better. It performs as well, looks as good, and costs less.
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Old December 16, 2017, 08:19   #177
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Keep in mind, the metal parts in your automobile motor are cast and they hold up to extreme heat, especially the heads.

Ruger has perfected castings, but it is important to note the discontinued 44 magnum carbine were forged, because Ruger was concerned a cast receiver wasn't strong for the pressures of a 44 magnum. They were expensive to make, therefore discontinued.

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Old December 16, 2017, 09:32   #178
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Keep in mind, the metal parts in your automobile motor are cast and they hold up to extreme heat. Especially, your heads, where the pistols work.

Ruger has perfected castings, but it is important to note the discontinued 44 magnum carbine were forged, because Ruger was concerned a cast receiver wasn't strong for the pressures of a 44 magnum. They were expensive to make, therefore discontinued.
Your logic has a fault in that cast automotive parts can be measured in inches while gun parts, tiny by comparison, are measured in thousandths of inches. A cylinder head that's an inch and a half thick where it counts the most can have a flaw in the casting and it'll never show. A similar flaw in .120 of material and exposed to 50,000psi is nothing anyone desires close to their face.

BUT....

The argument works both ways, the same anomalies can happen, to different degrees, of course, with forged materials. So your POV is really not a point at all. Therefore it doesn't validate cast or villainize forged.

I still prefer forged, you know what the old cliche' is, they don't make things like they used to. It's said for a reason. Having said that, I'll take a properly cut and well made cast if offered, without hesitation. Currently we don't have anybody making such a thing.
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Old December 16, 2017, 19:32   #179
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Cast brake rotors are not measured in inches and offer a great example of the quality of today's castings.
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Old December 16, 2017, 20:25   #180
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Cast brake rotors are not measured in inches and offer a great example of the quality of today's castings.
You missed HK's point...

Cast parts for automobile's are significantly thicker for obvious reasons, i.e; structural support for the weight they carry being foremost, and heat dissipation in the case of brake rotors/drums, and engine parts.

Yet they don't have to experience the explosive forces a rifle receiver, near paper thin in comparison, time after time....for thousands of cycles.

So again as HKS said, when your dealing with cast parts for firearms measuring far less than .250 in comparison to automobile parts STARTING in thickness above .250, the comparisons invalid.
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Old December 16, 2017, 20:33   #181
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Performance engines have forged rods, pistons , and crankshafts.

But brake calipers are cast. Really it means nothing , but my sockets and

wrenches are ALL forged. Spend your money how you like. I'm in for the long

run.
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Old December 16, 2017, 21:02   #182
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Cast brake rotors are not measured in inches and offer a great example of the quality of today's castings.
A cast iron rotor exploded on a customers race car about 150 mph and he hit wall causing about 10k in damages. That car has steel rotors on it now like it should have in the first place.
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Old December 16, 2017, 21:45   #183
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You missed HK's point...

Cast parts for automobile's are significantly thicker for obvious reasons, i.e; structural support for the weight they carry being foremost, and heat dissipation in the case of brake rotors/drums, and engine parts.

Yet they don't have to experience the explosive forces a rifle receiver, near paper thin in comparison, time after time....for thousands of cycles.

So again as HKS said, when your dealing with cast parts for firearms measuring far less than .250 in comparison to automobile parts STARTING in thickness above .250, the comparisons invalid.
Also appears that some confuse cast Iron with Cast Steel.
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Old December 16, 2017, 21:48   #184
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Also appears that some confuse cast Iron with Cast Steel.
And there's that, yea..
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Old December 16, 2017, 22:32   #185
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Also appears that some confuse cast Iron with Cast Steel.
Is DSA still using sand molds
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Old December 17, 2017, 08:08   #186
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A cast iron rotor exploded on a customers race car about 150 mph and he hit wall causing about 10k in damages. That car has steel rotors on it now like it should have in the first place.
Would that indicate all cast iron rotors are crap or that specific one had issues?
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Old December 17, 2017, 11:35   #187
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Good question. My guess would be if one has the funds to build an expensive
vehicle capable of speeds up to and above 150 mph, parts utilized should be of
the highest quality.You only have one life, extra money spent to insure longevity is well spent.

Turning wrenches for over 30 years and I have never
seen a rotor explode. But I work on stock cars to get people from point A to
point B. Most people will never drive at speeds in excess of 90 mph.

Defective part? I don't think so. It's a hunk of metal.
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Old December 17, 2017, 17:47   #188
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Would that indicate all cast iron rotors are crap or that specific one had issues?

I didn't say all cast rotors aren't up to their task.

On the car in question the rotor used was incorrect, the manufacturer even stated it was a light duty/street use rotor. The kids that built the car used it anyway. When the rotor self disassembled.... pieces of it punctured the inside of the wheel, which caused the tire to go down and the car to lose control.

Cast iron parts are fine as long as they're built massively like the OEM's do. If you use a brittle material you have to add mass to it. If you want to skeletonize something to save weight you had better use a better material.
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Old December 17, 2017, 19:29   #189
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I didn't say all cast rotors aren't up to their task.

On the car in question the rotor used was incorrect, the manufacturer even stated it was a light duty/street use rotor. The kids that built the car used it anyway. When the rotor self disassembled.... pieces of it punctured the inside of the wheel, which caused the tire to go down and the car to lose control.

Cast iron parts are fine as long as they're built massively like the OEM's do. If you use a brittle material you have to add mass to it. If you want to skeletonize something to save weight you had better use a better material.
WTF do cast iron brake rotors have to do with Rifle receivers made of cast STEEL or forged STEEL?
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Old December 17, 2017, 21:21   #190
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The rotor I was discussing was cast steel. It was a wide ventilated rotor and that design can only be cast. The discussion ventured outside of FAL receivers. Sorry that upset you.
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Old December 17, 2017, 22:37   #191
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The rotor I was discussing was cast steel. It was a wide ventilated rotor and that design can only be cast. The discussion ventured outside of FAL receivers. Sorry that upset you.
Didn't upset me at all. But your original post said it was cast iron. So which is it?
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Old December 28, 2017, 12:35   #192
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The rotor I was discussing was cast steel. It was a wide ventilated rotor and that design can only be cast. The discussion ventured outside of FAL receivers. Sorry that upset you.
Car brake rotors are usually made from grey cast iron, as iron has a higher coefficient of friction, casts better, machines more easily, and is cheaper than steel. Aircraft are just now moving away from normally having cast iron rotors with composite ones.

As to cast-vs-forged receivers.....

If you look at the physical properties of aluminum alloys, they are divided into two classes, wrought alloys and cast alloys, and alloys with the same chemical composition have different physical properties. However, if you look up steel alloys, you will note that only the chemical composition differentiates alloys, for instance, there is no listing for wrought 4140 steel and cast 4140, like there is for aluminum.

That is because the difference between cast steel alloys and wrought alloys (forged or rolled) are much less than that of aluminum and far more dependent on other factors.

The added benefit of forging is the realignment of the grain structure, and just because someone dropped a hundred ton hammer on a block of steel does not automatically means the grain structure is magically better. It is better only if the grain structure is moved from where it was and is arranged correctly according to the expected loads.

Let's take an extreme example, suppose you drop a hammer on a block of steel 6.25 inches long, 3.25 inches wide and 3.25 inches deep and forged it into a rectangular block that was 6 x 3 x 3 inches with a lot of flash. Would that be appreciably tougher than a cast block of the same dimensions?

No, it wouldn't. Because you have not altered the grain structure at all.

Look at the receiver forging Springfield, Winchester and H&R used in the original M14s:



Note how the area of the locking buttresses has been formed on the M14, meaning the grain structure now follows (roughly) the external contours. This is how toughness was added.

Compared that to a FAL receiver forging:

:

This forging is only a very slight improvement over a billet or casting, because the grain structure has not been altered significantly and is essentially straight through the entire billet. That straight grain structure will subsequently be cut through when the magazine well is broached.

People will state that casting are subject to bubbles and voids, forging are not. However, if you have an inclusion in the billet before to forge it, you'll get something worst than a bubble, you'll get a pipe or a stringer. Imperfections in the pre-forge billet don't just go away after forging. The rolling and forging process make inclusions stretch out in the longitudinal direction, and if there is significant transverse elongation it will widen as well, resulting in an internal scale. So, forging has its share of internal quality issues that must be checked for, just like castings. All casting from any caster worth their salt is x-rayed to check for bubbles or voids.

Grain size is often cited as something that is better in forgings, but grain size is altered by the subsequent heat treatment. Castings are always normalized after casting for the exact purpose of refining and equalizing the grain size. Further some people will state, with authority that you get a 10-15% increase in strength. But this is not the case. The ultimate tensile strength between forged and cast is exactly the same for a given alloy, and the yield strength changes in relation to the primary grain direction, and is a function of the reduction ration (that is how much squishing was done). For some directions, it is actually below that of a casting.





What you get is an increase in impact energy, i.e., toughness. It is the increase in toughness that gives better fatigue properties. For a FAL receiver, with the size and shape of the locking buttresses, and the actual loads, neither of these are major concerns. With the bolt, however, these factors are much more important due to the higher stresses on the lug. So, a cast receiver is more than adequate, but a forged bolt is very important.

There are many people that like to espouse the benefits of forging, but lack the metallurgical background to quantitatively define those benefits. Just how big, and in what places, are those advantages seen? The tensile yield strength of heat treated cast 4140 receiver is 135,000 psi, and the ultimate strength of either cast or forged 4140 is around 165 KSI. What are the tensile loads through the magazine well (which is where the highest loads will be), and just how much increase in toughness is gained by the improved grain structure? How susceptible is the receiver to fatigue? (Hint: if it is, it is in the high cycle regime, i.e., millions of cycles.)

Forging has advantages over casting, that is not under debate, but casting has advantages as well, however, most of those advantages are in the economics of manufacture.

And, everyone knows that things that cost more are better, right?

There are many people that keep saying “forged is better” and it has “better grain structure”, or “better grain size”. These are qualitative statements and usually made just to poo-poo the manufacturing choice of someone else, especially amongst manufacturers, but equally bandied about by the consumer. Qualitative statements are quite meaningless if one wishes to compare a forged receiver to a cast receiver. In order to compare two things in a meaningful manner, we need quantitive statements. How much tougher? And further, these need to be compared to the actual service loads?

In the end, the important factors are the choice of material, and the method of heat treating, because if these are not done correctly, it doesn’t matter whether it was forged or cast, it will fail.

Last edited by lysanderxiii; December 28, 2017 at 12:48.
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Old December 28, 2017, 19:19   #193
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lysanderxiii, stop confusing people with facts.
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Old December 28, 2017, 20:18   #194
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lysanderxiii, if you built yourself a racing engine would you use cast rods, crank, and pistons and wrist pins? Or forged? Why?

Thanks.

Last edited by Right Side Up; December 29, 2017 at 00:39.
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Old December 28, 2017, 23:32   #195
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lysanderx!!!, if you built yourself a racing engine would you use cast rods, crank, and pistons and wrist pins? Or forged? Why?

Thanks.
Is a Semi auto FAL a top fuel dragster? I recall some Chevy SB engines were better off for mild street use with a nodular iron crank VS steel crank. I cant remember where that came from for sure and... well I may be sucking swampwater on that, but I do remember reading that in some 4X4 rag. Just cant remember which engine, 400 SB ?
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Old December 29, 2017, 00:39   #196
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The bolt thust on a .308 Winchester is approximately 10,000 pounds, which all is applied through the bolt to the locking shoulder area of the receiver. That's how I *think* it applies.
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Old December 29, 2017, 22:44   #197
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lysanderxiii, if you built yourself a racing engine would you use cast rods, crank, and pistons and wrist pins? Or forged? Why?

Thanks.
I would decide based on sound engineering principles and cost restrictions. I would ask myself, "how much improvement am I getting for the buck?" (and just for the record: A FAL receiver does not see anywhere near the loads a connecting rod sees, there are no bending stresses.)

I'll ask you - "Why are most gas turbine engine blades cast?" They see loads far in excess of any rifle receiver.

As I stated above, no one is arguing that forging has benefits in toughness and fatigue, the question is - "How big are those gains and are they worth the added expense?"

EDIT:
Oh, and one more thing, illustrating the poor analogy of a racing engine to a FAL receiver... Most racing engines use aluminum pistons, would you say that would be a good choice for a FAL receiver?

Last edited by lysanderxiii; December 30, 2017 at 13:24.
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Old December 29, 2017, 22:50   #198
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The bolt thust on a .308 Winchester is approximately 10,000 pounds, which all is applied through the bolt to the locking shoulder area of the receiver. That's how I *think* it applies.
Well, you're incorrect, the highest stress in a FAL receiver is tension through the magazine well webs.

The area behind the locking shoulder see only compressive stress, and because of the large area and huge amount of material there, the stresses are actually relatively small.

Last edited by lysanderxiii; December 29, 2017 at 22:56.
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Old December 30, 2017, 00:36   #199
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Most racing engines use aluminum pistons, would you say that would be a good choice for a FAL receiver?
No it wouldn't. It's not strong enough, which is my point exactly.
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Old December 30, 2017, 00:43   #200
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Well, you're incorrect, the highest stress in a FAL receiver is tension through the magazine well webs.
What stretches the receiver between the receiver ring and the locking shoulder on firing? The bolt thrust applied through the bolt to the locking shoulder. What force causes the moment of inertia that springs the receiver causing vertical dispersion? Bolt thrust.

BTW, a 350 Chevy turning 10,000 RPM only puts 8700 pounds of tension on a connecting rod. Just to give you an idea.

Last edited by Right Side Up; December 30, 2017 at 00:55.
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