bullet weight limitations?

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9 years 11 months ago #43684 by grizgrin
bullet weight limitations? was created by grizgrin
Hi. Just coming over from the world of M1A's, and had always been told that you didnt want to shoot bullets heavier than 168 grains out of that platform. No idea how valid that advice was. Is there any such recommendation for an AR10T? Thank you.

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9 years 11 months ago #43685 by dickn52
Replied by dickn52 on topic bullet weight limitations?
Model: AR-10(T) with Free Float Handguard in Black
Caliber: .308/7.62 X 51mm NATO
Barrel: 20" AISI 416R Triple Lapped, Stainless Steel, Match
Rifling Twist: RH 1:10" 150-175 Grain Ammo
Muzzle Device: None
Front Sight Base: Picatinny Rail Gas Block. Top of gas block is .398 (+/- .010) lower than top of receiver
Upper Receiver: Forged Flat Top Receiver with Picatinny Rail and Forward Assist 7075-T6 Aluminum
Lower Receiver: 7075-T6 Aluminum (forged)
Trigger: National Match two stage - 1st stage 2.5 lbs - 2nd stage 4.5-5 lbs
Overall Length: 39.6"
Weight: 10.3 lbs
Finish: Hard Anodized Aluminum, Manganese Phosphated Steel
Accuracy: 1 MOA

Limitations are guides dependent on twist rates. The above is the 'recommended' bullet wt per Armalite in a 1:10 barrel
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9 years 11 months ago #43687 by grizgrin
Replied by grizgrin on topic bullet weight limitations?
Not quite what I was discussing. Let me clarify. What I was being told was not for purposes of stabilization, but for purposes of preventing catastrophic mechanical failure. Supposedly sustained shooting of hi-weight bullets would damage the lugs in an M1A reciever. Now whether thats true or apocryphal is neither here not there for me at this point, but I was curious as to the possiblity of such recommendations existing for AR-10T's. Thanks for bringing up the stability point though, not sure there is a reason to go above that weight wise unless you are willing to forgoe accuracy.

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9 years 11 months ago #43688 by dickn52
Replied by dickn52 on topic bullet weight limitations?
I have to say that I have never heard of bullet weight affecting pressure related issues which is what I think you may have meant. Sorry, can't help you with that one.
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9 years 11 months ago #43689 by grizgrin
Replied by grizgrin on topic bullet weight limitations?
Not necessarily pressure but what I was getting was more along the lines of the reciever losing its lugs. I guess a snap in the lower where the buffer tube screws in would be the equivalent in an AR pattern rifle. But thanks for the input!

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9 years 11 months ago - 9 years 11 months ago #43690 by Siscowet
Replied by Siscowet on topic bullet weight limitations?
Grizgrrn, I think it has more to do with the design of the two platforms. Armalite recommends 168 grn bullets, as a matter of fact. The M1A, bless its heart, uses a long operating rod system to drive the action, rather then a direct impingement system such as the AR10. With a heavier bullet, the pressure and delay in release of the gas is longer, raising the force exerted on the operating rod. In the absence of an adjustable gas regulator, there is no way to adjust the gas and pressure on that rod and the bolt and the lugs when using heavier bullets. With a direct impingement system such as the AR10, excess gas is dissipated as the Bolt carrier group is pushed back. Unless you impede the exhaust with something like a silencer, you really don't need to worry too much, about an adjustable gas regulator. Simply put, there are more places for the excess gas to go on the AR10 than the M1A.
Last edit: 9 years 11 months ago by Siscowet.
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9 years 11 months ago #43691 by Libertarian623
Replied by Libertarian623 on topic bullet weight limitations?
I have been feeding mine 180 gr pills for a long time, I would say that the only thing that will limit your bullet weight will be COAL.
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9 years 11 months ago #43758 by OleCowboy
Replied by OleCowboy on topic bullet weight limitations?
If the question is: Will bullet weight affect the lugs on the bolt to the point they will break.

Simple answer is sure, heck yea, bet on it...but as Paul Harvey said. Page 2 for the rest of the story.

Page 2. We know it can and will end up in a catastrophic event. But how much weight would it take? Mucho, A LOT and how much chamber pressure are we talking about.

Well a look see will show bullets up to .210 gr are available for it. I would say with confidence they would not sell it if it blew guns up or broke lugs.

While I do not have the exact answer, I would feel confident shooting it beyond 168 gr in a factory load (I will let the reloader chime in with their thoughts.

Bear in mind in testing the M1 it may well have been fired underwater which increases chamber pressure due to it having to push a lot of weight and water down range.

I don't think you have anything to worry about at all...

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