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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, 08:00   #202
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Gas turbine blades aren't made from cast iron or steel, either.
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Old December 30, 2017, 12:06   #203
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Originally Posted by Right Side Up View Post
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.)

Last edited by lysanderxiii; December 30, 2017 at 12:29.
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Old December 30, 2017, 12:09   #204
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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   #205
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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   #206
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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   #207
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This thread has gone from ridiculous to entertaining .








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Old December 30, 2017, 19:36   #208
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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   #209
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This thread has gone from ridiculous to entertaining .








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Old December 30, 2017, 21:00   #210
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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, 22:07   #211
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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.
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Old December 30, 2017, 22:18   #212
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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, 22:34   #213
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Originally Posted by lysanderxiii View Post
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.
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.
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Old December 30, 2017, 22:47   #214
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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   #215
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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   #216
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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   #217
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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   #218
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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   #219
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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   #220
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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   #221
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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

Last edited by Right Side Up; December 31, 2017 at 00:06.
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Old December 31, 2017, 00:50   #222
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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   #223
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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   #224
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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   #225
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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   #226
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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   #227
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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, 09:39   #228
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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.
The original topic is which is "better" according to the op. I took that to mean forged vs cast, not value of one over the other. But I may have been wrong in my assumption.

FWIW, DSA tried cast bolts. They failed. And there's a thread or two about that around here too.
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Old December 31, 2017, 11:48   #229
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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   #230
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Did anyone mention cast bolts?

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