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Old December 30, 2017, 00:45   #201
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Originally Posted by lysanderxiii View Post

there are no bending stresses.) (on connecting rods in an engine)

You sure about that? Then I won't ask you to explain why an I beam connecting rod is better than an H beam rod.
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Old December 30, 2017, 12:06   #202
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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.
What are the compressive and bending loads?

(And, it is a much smaller cross section, so the stresses are much higher.)

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Old December 30, 2017, 12:09   #203
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You sure about that? Then I won't ask you to explain why an I beam connecting rod is better than an H beam rod.
The complete quote:
Quote:
(and just for the record: A FAL receiver does not see anywhere near the loads a connecting rod sees, there are no bending stresses.)
What bending loads does a FAL receiver see?
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Old December 30, 2017, 12:26   #204
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Gas turbine blades aren't made from cast iron or steel, either.
Your big commercial airliner engine's usually get titanium or some nickel alloy, yes; but, many smaller auxiliary turbines still use stainless steel alloy blisks. And, the ultimate and yield strength of inconel is about the same as a good alloy steel. In any case, it is extremely rare to see a forged turbine blade.

Same goes for compressors, turbo-pumps and other high-speed rotating designs.

As stated earlier, the question is not, "Does forging have advantages over casting?"

The question is, "Are the advantages of forging worth the extra expense and effort in a FAL receiver?"

The answer is "No, they do not."

Last edited by lysanderxiii; December 30, 2017 at 13:28.
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Old December 30, 2017, 15:37   #205
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The complete quote:

What bending loads does a FAL receiver see?
Is that a legit question? Let's see, 10K in thrust applied through the bolt to a locking shoulder that sits below the bore centerline and has a 12 degree surface. You can figure it out.
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Old December 30, 2017, 15:57   #206
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This thread has gone from ridiculous to entertaining .








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Old December 30, 2017, 19:36   #207
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This is how it's done.

https://www.youtube.com/watch?v=j0NbnJnpNa4
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Old December 30, 2017, 20:18   #208
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This thread has gone from ridiculous to entertaining .








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Old December 30, 2017, 21:00   #209
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Is that a legit question? Let's see, 10K in thrust applied through the bolt to a locking shoulder that sits below the bore centerline and has a 12 degree surface. You can figure it out.
Seriously, you don't know, do you?

Ever wonder why Saive chose a 12 degree angle on the locking surface? The bending moment from the off-axis thrust is positive, it wants to bend the receiver into a "U" shape with the highest stress on the bottom. The bending moment from the 12 degree angle is negative, it tries to bend the receiver the opposite direction with the highest stress on the top. Both moments are around the same magnitude, give or take. They cancel out for the most part.

The bending loads are negligible. (Saive was a smart guy.)


Last edited by lysanderxiii; December 30, 2017 at 22:09. Reason: added image
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Old December 30, 2017, 22:18   #210
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The pressures and stress on the bolt and receiver are the same because the thrust on the receiver mag well and sides is transferred through the bolt. Can't have more thrust on one than the other.
The LOADS are the same.

Stress is the load divided by the area. Since the areas are different, the stresses are different.

As far as the bolt is concerned, there is a shear load on the locking abutment, since the shear area on the bolt is smaller than the cross-sectional area of the receiver through the magazine well, the stresses are higher. Also, the shear strength of steel is roughly 57% that of its tensile strength, the bolt is a more highly stressed part.

Last edited by lysanderxiii; December 30, 2017 at 22:24.
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Old December 30, 2017, 22:47   #211
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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.
Doesn't it depend on the race? I mean, there are quite a few cars with cast internals engines that won regional rallies, rallycross, and even national level autocross. (Sometimes) the classes limit what you can change. Also, the earlier ABAs did have forged cranks and oil squirters but the later went to cast but still could handle 2x the HP using turbos, which of course would not be allowed in many races to begin with.

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This thread has gone from ridiculous to entertaining .








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Old December 30, 2017, 22:51   #212
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Originally Posted by hkshooter View Post
Back to cast vs forged. There are no cast bolts, correct? That alone should settle the debate about which is stronger.

This debate is always fun. Amazingly there are always some really smart guys touting cast being as *as good* or even *better* than forged, but the guys that push parts to breakage in the field all say the same thing. Cast is brittle and it fails sooner.

I know several engineers. Some are much better than others. They are not all created equal. Some convince themselves of almost anything and cherry pick an data to support their *opinion*. I had one customer, who was an engineer, bought a camshaft and lifters from a cam company, and that guy is a retired GM engineer. It featured a rollerless roller lifter. No wheel, just a radius on the end of the lifter. I tried to explain to the guy it wouldn't work. The friction would kill it. He told me basically to leave that stuff to the guys that know. It wiped out the cam and all the lifters on the first pull on the dyno.

Is a cast FAL receiver better? No. Is it *good enough* for most people? Yeah. But it's not better, which was the question posed in the first post.
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Old December 30, 2017, 22:54   #213
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Originally Posted by lysanderxiii View Post
Seriously, you don't know, do you?

Ever wonder why Saive chose a 12 degree angle on the locking surface? The bending moment from the off-axis thrust is positive, it wants to bend the receiver into a "U" shape with the highest stress on the bottom. The bending moment from the 12 degree angle is negative, it tries to bend the receiver the opposite direction with the highest stress on the top. Both moments are around the same magnitude, give or take. They cancel out for the most part.

The bending loads are negligible. (Saive was a smart guy.)


At least you admit now that something does take polace between the receiver ring and the locking shoulder when an FAL is fired.

Are you still sticking with your assertion that there is no bending load on a connecting rod in an engine?
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Old December 30, 2017, 22:58   #214
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My terminology sucks, I admit that.
I believe I see what you are saying. The area of material that's transferring the load is smaller on the bolt than that of the receiver. Trying to wrap my head around the physics of it.
Back to cast vs forged. There are no cast bolts, correct? That alone should settle the debate about which is stronger.
Bolts are higher stressed parts, and you don't see any cast bolts out of FN or any of the licensed manufacturers (to my knowledge). I have no idea how the new production ones are made, but I'll wager they are castings from their appearance. (Does any one have one that can check for as-cast surfaces to confirm or negate?)

There is no debate over which is tougher and more fatigue resistant. The debate is it worth the extra machine time and expense. FN, in the later years, felt that there wasn't and began to cast them. It was cheaper and there was no loss in durability.

If it makes you to say you have a forged receiver, that all well and good, but it does not mean someones else's choice in a casting is bad, wrong or inferior. With this particular shape of steel, forging does not gain you anything. When heat treated properly, and made from the correct steel alloy, the loads are well enough inside the yield limits for either it doesn't matter.

Last edited by lysanderxiii; December 30, 2017 at 23:09. Reason: spellinf
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Old December 30, 2017, 23:01   #215
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FN did state a reduction in service life for their cast receivers.
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Old December 30, 2017, 23:44   #216
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FN did state a reduction in service life for their cast receivers.
From what to what?

And any citation?
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Old December 30, 2017, 23:45   #217
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FN did state a reduction in service life for their cast receivers.
Details? FA use? or semi auto? Round counts?
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Old December 30, 2017, 23:51   #218
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From what to what?

And any citation?
It's on this board somewhere. This horse has been beat to death so many times it isn't funny. But I saw documentation on here that demonstrated FN claimed a much shorter service life when they switched to cast receivers on the FAL. It was strictly a cost saving measure, not an improvement.

I think the FN cast receivers were probably far better than anything offered now. Considering the current manufacturers can't even machine a round hole correctly I'm not going to trust them on the quality of their casting abilities.

http://www.falfiles.com/forums/showthread.php?t=156559

https://www.remtek.com/arms/fn/fal/index.htm

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Old December 31, 2017, 00:50   #219
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It sure is a good thing that Ruger does not use cast bolts or receivers in their model 77....

......especially the 300 Winchester Magnum.

I have been told that that cartridge is one of the most deadly ever made.


Maybe a real gun guy can explain what that means.



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Old December 31, 2017, 00:56   #220
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Well that settles it then......cast is awesome. Front locking lugs are a different app, but what the hell.


You know enough to be dangerous.
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Old December 31, 2017, 01:07   #221
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It sure is a good thing that Ruger does not use cast bolts or receivers in their model 77....

......especially the 300 Winchester Magnum.

I have been told that that cartridge is one of the most deadly ever made.


Maybe a real gun guy can explain what that means.



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Old December 31, 2017, 05:40   #222
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FN, in the later years, felt that there wasn't and began to cast them. It was cheaper and there was no loss in durability.
IIRC the difference in service life was 50%.
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Old December 31, 2017, 06:47   #223
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I found it.

The original design life was supposed to be 80,000 rounds, however the Canadian forged receivers started showing cracking at around 60,000 rounds. FN estimated that the cast receiver should last to 40,000 rounds, but as of the writing of that article no cast receiver was reported as cracked, probably because none had reached that high a round count.

So, the average military rifle, in peace time, sees about 300 rounds a year (semi-annual qualification, 150 round each), so the average service lives would be 200 and 130 years for forged and cast respectively. (Obliviously, the Canadian ones that saw 60,000 rounds in their thirty-year service life were not average).

If you shoot 100 rounds each month, every month, expect to have to replace your cast receiver in 33 years, or around 2050, or 2067, if forged.
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Old December 31, 2017, 08:35   #224
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I found it.

The original design life was supposed to be 80,000 rounds, however the Canadian forged receivers started showing cracking at around 60,000 rounds. FN estimated that the cast receiver should last to 40,000 rounds, but as of the writing of that article no cast receiver was reported as cracked, probably because none had reached that high a round count.

So, the average military rifle, in peace time, sees about 300 rounds a year (semi-annual qualification, 150 round each), so the average service lives would be 200 and 130 years for forged and cast respectively. (Obliviously, the Canadian ones that saw 60,000 rounds in their thirty-year service life were not average).

If you shoot 100 rounds each month, every month, expect to have to replace your cast receiver in 33 years, or around 2050, or 2067, if forged.

.....and you'll have a rifle that has superior resale. Cast uppered kit guns don't sell nearly as well as a forged.

IIRC those tests were done in FA.

That 60,000 count has a type I cut at the rear. The metrics added the II & III cut which added to longevity.

IIRC Lithgow ran tests up to 200,000 without failure. May have been the owner of Onyx that posted that years ago when he was sourcing from Lithgow.

A modern cast type I may be a great receiver but I have doubts as to how well it would perform in FA against a forged I, II or III. FN rated their cast type III's at a substantially lower service life and they were much heavier. The cast type I is an unknown.
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Old December 31, 2017, 11:48   #225
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Cast bolts are not the only place DSA has failed.

Maybe the source is as important as the process.

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Old December 31, 2017, 12:10   #226
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Did anyone mention cast bolts?

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Old January 17, 2018, 21:11   #227
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The best is one forged in a logarithmic casing of prefamulated amulite, this will require a sinusoidal dingle arm but will eliminate side fumbling through digital gameters.
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Old January 17, 2018, 21:18   #228
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LOL, the kid in the video in post 230 can hardly put a sentence together (poor guy), but he's still smart enough to know cast parts don't stand up to the loads a well made forged part will.
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Old January 18, 2018, 07:38   #229
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The best is one forged in a logarithmic casing of prefamulated amulite, this will require a sinusoidal dingle arm but will eliminate side fumbling through digital gameters.
There is always Terkonit Steel. Bonus points for those who know where that came from without asking Dr. Google.
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Old February 14, 2018, 16:48   #230
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Maybe the source is as important as the process.

.......
Guys, I look at this stuff every day. I inspect, accept, and reject components for a wide range of applications that are life and limb dependent, from oil & gas to aerospace & manufacturing components, and even some very well-known munitions and firearms manufacturers. I see both pre-sevice and in-sevice components, as well as conduct material failure analysis on failed parts. Using specific inspection technologies like magnetic particle and dye penetrant for surface inspections to digital radiography, shear wave and phased array ultrasonics for volumetric visibility, I can tell you the most significant and salient point in this whole ridiculus thread is the quote above.

Cast or forged, both are subject to premature failure given substandard raw materials, design parameters, processing conditions, or application. Finer grain structures and better-defined (manipulated) lattice structures are benifits of forgings. However, advances in investment casting processes and alloy formulations allow castings to surpass forgings in many applications where processing a comparable forged component would introduce thermal & mechanical stresses that may increase the probability of field failure in the forged part, while the cast part experiences no such liabilities. Aerospace, especially propulsion, is FULL of cast components. Power generation is the same. Again, see quote above.

I refrain from these discussions because like politics and religion minds are already made up, and no amount of subject matter expertise I may hold on the issue will change that. So continue on, like most things those that truly know the least tend to be the loudest in their claims.
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Old February 14, 2018, 16:53   #231
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I refrain from these discussions because like politics and religion minds are already made up, and no amount of subject matter expertise I may hold on the issue will change that.
Fair enough, but please answer me one question, Whose receivers do you own on your FALs, and if the manufacturer produced both forged and cast, which of the two do you own?
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Old February 14, 2018, 17:10   #232
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I currently own 3 cast Coonan receivers, two DSA (1 forged Grayslake, 1 more recent cast Type 1), and 1 forged GL Imbel.

I care infinitely more about the diminsion correctness of a receiver and the reputation of the manufacturer than I do about the receiver’s genesis. If a receiver isn’t dimensionally correct, it is much more likely to be the result of machining processes rather than forming processes. Also, forging won’t make subpar materials stronger, and just like casting with a poor alloy will result in failure.

So to answer the second part of your question, given a reputable manufacturer with proven success in each form, there will most likely be a difference in price. That difference in price may be a deciding factor for me, but if the price difference is nominal then I may opt for the forged simply because the market believes it to be superior and resale (if I were concerned about that) reflects that belief. If budget were a bigger concern than resale I’d get the less expensive one. Because again, dimensional correctness and manufacturer reliability are far more important than cast vs. forged to me.

ETA: Availability is also a concern these days, so if cast was my only option and my conditions above have been met, then I’d buy cast without hesitation.
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Old February 14, 2018, 19:23   #233
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Thanks for your reply; your choice of receivers reinforces my own. I have a couple of forged GL IMBELs, a forged DS prefix DSA and a cast Coonan.
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Old February 14, 2018, 20:02   #234
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IMO, part of what happens with the whole cast vs forged debate is memberís inability to see that correlation does not imply causation with respect to a receiverís suitability for service. For example, forged DSA and Imbel receivers have a near-impeccable record for going together free of or with minimal fitting required. On the other hand, cast receivers from Coonan, Fed Ord, Hesse, etc. and recent DSA have had spotty reputations for fit and assembly issues plus some possible heat treat problems (an issue completely independent of forming process) that many lump into being ďcast receiverĒ problems. No. Those are finish machining and dimensional tolerance (QC) issues. To say those manufacturing defects are due in any way to the genesis of the receiver blank is plain ignorance. Sloppy manufacturing process will junk a forged receiver just the same as a cast one. But as with many topics, the critics opine without a proper foundation of knowledge and dig their heels in to validate their beliefs.

The parallels to racing are especially entertaining, since those guys should know better than anyone how sinking TONS of additional $$$$ is required for tiny gains the closer to the top you go. Same holds true for metallurgy to a fair degree. Ask around, when was the last time you read on here of a properly heat treated cast receiver actually failing on someone in use?
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Old February 14, 2018, 21:23   #235
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The question is which one is better. Forged. Is cast good enough for an FAL, for casual use yeah. I've owned one, and only one, cast receivered FAL. It stretched .004" after a couple hundred rounds and I had to re-headspace. So as far as Im concerned they suck.
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Old February 14, 2018, 21:43   #236
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The question is which one is better. Forged. Is cast good enough for an FAL, for casual use yeah. I've owned one, and only one, cast receivered FAL. It stretched .004" after a couple hundred rounds and I had to re-headspace. So as far as Im concerned they suck.
Did it really stretch? Or was it just the LS settling in? I'm betting the latter, unless you placed some very precise tram marks on it when you built it.

Can you actually prove it stretched?
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Old February 14, 2018, 21:44   #237
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“Better” is relative. That’s the point. If you like forged recievers that’s fine. You experienced a material failure, which I would argue most likely was due to poor heat treatment rather than form, but without further analysis that is nothing more than my educated SWAG. Anecdotal evidence that is only corollary in relation to your recever being cast is just that and nothing more. A forged reciever with a poor heat treat may have exhibited the same results.

I don’t care one way or the other if you love or hate cast receivers, just love or hate them for the correct reasons.

ETA: I’m assuming RSU has actually proved his receiver stretched. I’d like to know how and where he measured his stretch.
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Old February 14, 2018, 22:17   #238
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This is like talking to women. Ok you guys caught me. My receiver didnt really stretch. I made it all up.
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Old February 14, 2018, 22:26   #239
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This is like talking to women. Ok you guys caught me. My receiver didnt really stretch. I made it all up.
Thatís a childish response. Nobody accused you of anything. Itís pertainent to the discussion. How did you come to establish it was the receiver that stretched?
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Old February 14, 2018, 22:41   #240
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This is like talking to women. Ok you guys caught me. My receiver didnt really stretch. I made it all up.
OK, lady... Do you have definitive proof that your receiver did stretch? show some proof and you win.
I've had forged DSA receivers gain .003"headspace from settling in, it's nothing new. Now I just set them tight initially and don't obsess over it.
I have never said cast steel receivers were better, just an acceptable alternative to the forged ones that are now unobtainium.
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Old February 17, 2018, 12:08   #241
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Is RSU going to tell us how he measured his receiver stretch, or is he still pouting?
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Old February 17, 2018, 17:04   #242
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I don't know anything about metallurgy. I just look at history and follow the logic of what has happened.

FN I'm sure does know about metallurgy and did a bunch of testing. They figured a forged T-1 receiver was good enough. Most of the free world agreed.

Eventually FN decided that a forged T-1 wasn't quite good enough(or maybe could be made better with just a tiny bit of extra metal left in strategic locations)and developed the forged T-2. Call it a Gen2. Cool.

Later, when it was obvious that the FAL "platform" was dying and about to be replaced by "everything else", FN decided that a cast T-3 receiver could be manufactured cheaply enough to offer to third world *shitholes* as Trump would say,......and what the hey,.......it would be 'good enough' for them. No first world country would accept it, but they were going with the "other stuff" regardless. And oh yeah, the US commercial market would be fine with them.

Imbel and FMAP, being too lazy to develop cast receivers themselves, simply dropped the lightening cuts and offered the forged T-3 receivers. Nothing wrong with that.

Then all the garage manufacturers in the US who know nothing about metallurgy but know a damn fine bit about producing crap for the ignorant US market jumped in with cast T-3 receivers. Such stellar operations as Hesse, Century, Entreprise, Coonan and a few more I've successfully forgotten about produced some receivers that didn't blow up by relying on (luck) and the belief that FN wouldn't have done it if it wasn't OK. And they were right,......it was OK.

Then these same guys in their infinite wisdom and ignorance decided that if American buyers preferred a T-1 receiver, then by golly that's what they were gonna make and sell. Remove structural metal from a semi-proven cast T-3 and produce a cast T-1,........based on exactly what knowledge is that even "good enough"? That's where I start scratching my head and looking at other options.

Forged T-1,.....proven.

Forged T-2,.....proven.

Forged T-3,.....proven.

Cast T-3(FN),...proven.

Cast T-3(from sub-standard manufacturers),.....proven(reasonably).

Cast T-1(from sub-standard manufacturers),.....uhmmm,......not proven to my satisfaction(but then, I admittedly don't know anything about metallurgy). They're all yours.

Doesn't really matter. Other than the early Coonans it doesn't look like most of the cast T-1 receivers can be made into functional rifles anyway.
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Old February 18, 2018, 02:00   #243
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Yeah, those T-1 Coonans are just blowing up all over the place.
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Old June 08, 2018, 16:08   #244
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You sure about that? Then I won't ask you to explain why an I beam connecting rod is better than an H beam rod.
Connecting rods bend, but not because there are bending loads on them.

They bend due to compression loads.
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Old June 08, 2018, 22:16   #245
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That depends on how well centered the beam of the rod is in the bore. Any offset causes a bending motion, but you knew that right. All engines have the rods off center some amount due to manufacturing tolerances. The only connecting rods that are truly centered in the bores are the engines set up for piston guided rods.
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Old June 10, 2018, 01:45   #246
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Probably said this before..... but the Imbel receiver, which is forged, but uses the type 3 casting dimensions so it is much beefier, has to be the best receiver out there.... I know it is spot heat treated only- the question is- were FN type 3 receivers spot heat treated, or fully heat treated?

When in doubt- go with an Imbel!

Lots of pitfalls in building a good FAL receiver it seems. If it was easy everyone would be doing it. Seems the two higher cost US maufacturers have a lot of QC trouble on dimensions lately.....who is is to say their heat treat is as good as it should be? It isn't something that is noticeable easily, and thankfully most of us will never wear one out...

Now my older DSA's seem just fine- thanks for the good work LMT!
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Old June 10, 2018, 07:33   #247
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Probably said this before..... but the Imbel receiver, which is forged, but uses the type 3 casting dimensions so it is much beefier, has to be the best receiver out there.... I know it is spot heat treated only- the question is- were FN type 3 receivers spot heat treated, or fully heat treated?
I'd love to know why you think this and where your information comes from. Do tell, please.
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Old June 11, 2018, 18:40   #248
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That depends on how well centered the beam of the rod is in the bore. Any offset causes a bending motion, but you knew that right. All engines have the rods off center some amount due to manufacturing tolerances. The only connecting rods that are truly centered in the bores are the engines set up for piston guided rods.
Sorry, no.

The load goes from the center of the bearing on the piston end to the center of the bearing on the crankshaft end, wherever those centers are in relation to the body of the rod. Since the two bearings are unrestrained in rotation, other than the minute moments cause by friction between the pin and bearing, and perhaps some inertial loads, there is no bending moment on the rod from the piston force. Most of your "bent" rods are buckled in compression.

There are bending moments on the piston, due to the piston offset.

Here is a free body diagram of a connecting rod, (b), from that you should be able to calculate the bending moment rather quickly.


A Von Misses stresses contour for actual connecting rod:
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Old June 11, 2018, 19:06   #249
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You have no idea what you're talking about.
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Old June 11, 2018, 19:17   #250
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Here are pics of real racing connecting rods, not drawings. And here is also a real explanation.


Rod that is offset in the bore. Typical of 99% of the engines going down the road. Rod sees a side load (bending motion to you). After enough cycles it breaks.



A rod that is centered on the bore. See's no side load on the combustion stroke, runs practically forever.



Your'e welcome.
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