Whats the most powerful round I can put in an AR-10 build?

You’re kind of all over the place here…

What AR10 was fielded with as full auto?

The FAL is a great rifle but it’s not an AR platform. Yes there are other similar platforms but are we speaking about any platform or the AR10?

Considering we are on a precision rifle forum we tend to bias towards that type of use and consideration, not so much towards machine gun utilization.

Gotcha.

Armalite and Colt made the fully auto AR10.
The Dutch made it under AI.
Sudanese Government made the AR10.
I think Portugal used the AR10 for a bit.

Not too many around.
 
The 300 Accubond has a G7 BC of .394, with a sectional density of .375. That gives you a form factor of 0.95 G7. A 130 grain .338 bullet of that form factor will give you a G7 BC of .171. You need a muzzle velocity of around 10,000 fps to reach that range with that bullet.


Okay. So what would happen if you take a traditional bullet and fill it with Aluminum or Titanium for example. Or polymer?

Take a 147 gr M80 ball profile and make it a partition style with a thick copper jacket. Instead of lead, put in Aluminum.

Would it shoot good out to 600m?

Would a .338 be good? A .375? A 6-7mm profile?

7.92x40 is my best example of what my brain is thinking. But in modern loadings.
 
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I was going to suggest you look that one up.
As for Heavy other rounds, Powell River Laboratories, experimented with all sorts of heavy 5.56 loads.

https://www.google.com/search?q=Pow...nBJIBATiYAQCgAQHIAQLAAQE&sclient=gws-wiz-serp

Yes. I have followed this research over the years.

I have always thought that blended metal techniques and heavy for caliber bullets and cartridges were fantastic, albeit at the expense of attained velocity. I need to study up on form factor. I know about sectional density requirements.

I bet a 90 grain SMK profile 70-77 grain .224 bullet stuffed into a .224 Valkrie would be good.
Not too radical as long as it gets 12-18" of penetration.

The bearing surface may be a little high for sustained fire however. But with modern high nickel content barrels like with the Sig M5, this may be okay.
 
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The 300 Accubond has a G7 BC of .394, with a sectional density of .375. That gives you a form factor of 0.95 G7. A 130 grain .338 bullet of that form factor will give you a G7 BC of .171. You need a muzzle velocity of around 10,000 fps to reach that range with that bullet.


So if 7.92x40 @ 105 grains gives me 2650 fps and around .399 b.c. and a i7 FF of 0.76....

What would a .338 or .375 Dia based cartridge with i7 FF of 0.70-0.76 look like?

What Calculator are you using?
 
So if 7.92x40 @ 105 grains gives me 2650 fps and around .399 b.c. and a i7 FF of 0.76....

What would a .338 or .375 Dia based cartridge with i7 FF of 0.70-0.76 look like?

What Calculator are you using?

You aren’t getting a BC of .399 from a 105 grain 7.92. BC is sectional density divided by form factor. A .399 BC with a FF of .76 needs an SD of .303. That equates to a 221 grain bullet. You’d need a lathe turned solid for that kind of form factor and sectional density.

The Berger 407 grain .375 has a FF of .79. The Flatline 550 grain .416 has FF of around .71, if my math is right.
 
You aren’t getting a BC of .399 from a 105 grain 7.92. BC is sectional density divided by form factor. A .399 BC with a FF of .76 needs an SD of .303. That equates to a 221 grain bullet. You’d need a lathe turned solid for that kind of form factor and sectional density.

The Berger 407 grain .375 has a FF of .79. The Flatline 550 grain .416 has FF of around .71, if my math is right.

Pardon me. 0.192 G7 b.c. not .399 G1 b.c.

At what point do FF's get too low?

.60?

.50?
 
Despite all this math, I fail to see how a .338 RCM or .338 Federal or .358 Win or .375 Raptor SR25 in 16" barrel firing high b.c. pills at 3200 FPS would not rip my thigh off at 600 meters.
 

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Despite all this math, I fail to see how a .338 RCM or .338 Federal or .358 Win or .375 Raptor SR25 in 16" barrel firing high b.c. pills at 3200 FPS would not rip my thigh off at 600 meters.

Your math leaves out too many variables.

There is an inherent energy and pressure limit to what your large frame standard MSR platform can take along with fairly well known limits on the overall round length. To get to 3200fps in your standard large frame MSR, you are probably going to be in the 100gr range, give or take a bit, unless you want to risk blowing up your rifle. Suggesting you also want a 16" barrel is going to limit your option to get more speed out of the barrel length.

Very light for caliber diameter bullets tend to have problems with stability in the wind and drift, they also bleed off energy and speed very quickly, and have a lot of wind resistance losses and excessive bullet drop.

At 600 meters, someone with a very accurate 6.5CM standard large frame MSR platform rifle would have a significant advantage over you on a two way range.

Sure you can try it and sure you might make something that works and maybe figure out how to get dope for the distance you want.
But somebody with a proven capable system will have you bleeding out while you are still trying to get your wonder gun to hit them.
 
That’s like saying a 350 small block making 1200 horsepower on pump gas, getting 30 mpg would be sweet.

This exists in a Camaro Iraq Z format. 350ci LT4 with a 10:1 compression ratio on 91 octane pump gas with a 21 PSI Vortech YSI supercharger with 2.42 gears and a 6 speed T56 with cylinder deactivation.


Also would work in a 1990 Suburban with a 10 speed transmission and a 250 Shot of nitrous with aforementioned engine setup.

Custom Job. Must be going a 60mph with no wind.
 

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Your math leaves out too many variables.

There is an inherent energy and pressure limit to what your large frame standard MSR platform can take along with fairly well known limits on the overall round length. To get to 3200fps in your standard large frame MSR, you are probably going to be in the 100gr range, give or take a bit, unless you want to risk blowing up your rifle. Suggesting you also want a 16" barrel is going to limit your option to get more speed out of the barrel length.

Very light for caliber diameter bullets tend to have problems with stability in the wind and drift, they also bleed off energy and speed very quickly, and have a lot of wind resistance losses and excessive bullet drop.

At 600 meters, someone with a very accurate 6.5CM standard large frame MSR platform rifle would have a significant advantage over you on a two way range.

Sure you can try it and sure you might make something that works and maybe figure out how to get dope for the distance you want.
But somebody with a proven capable system will have you bleeding out while you are still trying to get your wonder gun to hit them.


I highly doubt that. I would never go up against professionals that had 6.5's unless I was dialed in.

If you took a bunch of 225 grain .338 Accubonds or 250 grain .358 Accubonds and filled them with sintered metal formulations, you would have big bore and big b.c. frang rounds that have less drop then a 130 grain 6.5 Creedmore or 175 grain FGMM.

They could weigh 175 grain for the .338 and 200 grain for the .358.

Those are more advanced rounds then the 6.5 Creedmore.

Just like .573 B.C. 8mm Mauser was more advanced then .400 b.c. .303 British or 150 grain 30-06 Springfield.
 
I highly doubt that. I would never go up against professionals that had 6.5's unless I was dialed in.

If you took a bunch of 225 grain .338 Accubonds or 250 grain .358 Accubonds and filled them with sintered metal formulations, you would have big bore and big b.c. frang rounds that have less drop then a 130 grain 6.5 Creedmore or 175 grain FGMM.

They could weigh 175 grain for the .338 and 200 grain for the .358.

Those are more advanced rounds then the 6.5 Creedmore.

Just like .573 B.C. 8mm Mauser was more advanced then .400 b.c. .303 British or 150 grain 30-06 Springfield.
At this point you should probably start your own thread about theoretical bullets that don't exist yet and their virtues
 
Gotcha.

Armalite and Colt made the fully auto AR10.
The Dutch made it under AI.
Sudanese Government made the AR10.
I think Portugal used the AR10 for a bit.

Not too many around.
Fairchild ArmaLite in Hollywood made the prototype AR-10s and AR-15s.
The Dutch were the only ones to produce the AR-10 and filled contracts for Sudan, Portugal, and Cuba. The Cuban contract went when Batista was still in, and a subsequent shipment was intercepted by Castro’s forces in 1959. A CIA front company named InterArms ran those shipments and even got Castro to pay for the intercepted shipment after meeting with him in Havana.

Colt started tooling up to make the smaller frame ArmaLite AR-10A in 1959, but then McDonald sent them a wire telling them he was ready to start filling military and police orders for the AR-15 in SEA instead, so they switched tooling over to the AR-15, USAF wanted it, and got the initial production contract in March 1962.

I’ve not seen evidence of any of those ArmaLite/Colt AR-10As other than one photo set in The Black RIfle Volume I. It was the first small frame AR-10, taking a lot of lessons-learned from the Dutch developments and the AR-15. Note the single carrier key fastener to allow use of a smaller receiver set (no impact into the RET thread boss), the roller cam pin, and Dutch Paratrooper charge handle design with right side purchase.

iu
 
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When asking what is the most powerful round you can load in the AR-10, the real question needs to be where are you measuring that power?

At the muzzle or downrange and at what ranges?

Your maximum bore diameter cartridges with the most propellant, chamber pressure, and projectile weight will have the most muzzle energy, but due to low BCs, will bleed momentum faster than other bullets with better SD/BC. This would cover your .40-.475 bores. Think 450 Marlin (Accuracy Systems does this build in AR-10s), 45 Raptor, and 475 Bishop Short Magnum.

450 Marlin
marlin_450_2.gif


475 Bishop Short Magnum
iu


Your mid-bore size (.338-.375) high SD bullets fired from the same propellant mass will provide better momentum at medium to long range. 325 WSM, 338 Federal, 358 Winchester, 375 Raptor, 375 Bishop.

iu


SHOT-2022-New-.375-Bishop-Short-Magnum-Cartridge-1.jpg


Your smaller bore, high BC and lighter cartridges fired with similar propellant mass will maintain momentum at longer ranges, but will have less energy on-target at closer, typical hunting ranges, though they will be more than enough. This will cover your 270, 7mm, and 30 bores like 6.8 Western, 7 SAUM, 7 WSM, 300 SAUM, 300 WSM.

Normally when we’re talking about big bores or high muzzle energy and closer range performance, it’s about some type of hunting setting based on “bigger = better” logic.

For a hunting rifle, that also means portability. Most of the big bore AR-10 conversions I’ve seen are pretty heavy, not ideal for carrying in the field. They kind of need the weight to counter the torque experienced from larger bores, heavy projectile mass, and large propellant mass because it swings the magazine like a pendulum around the bore axis away from the position of feed presentation. With a heavier cartridge stack due to the combined weight of multiple 200-390gr projectiles, the magazine spring really needs to be stronger as you get into those weights. The magazine needs to be designed around the cartridge to get it to reliably lift, strip, and feed up the ramp or ramps, which also need to be looked at for correct feeding at BCG velocity into the breech.

The .338 Federal actually has noteworthy performance to it that had its limelight taken by interest in more of the 6.5mms at the time it was introduced. You basically get .30-06 velocities from a short action, with projectile weights ranging from 180-225gr, no need to modify mags other than maybe increased power springs for the 200-225gr, though I don’t think it would be necessary for 5rd AR-10/SR-25 mags.

The absolute brute of the bunch appears to be the 475 Bishop Short Mag more for bragging rights than anything. The 375 Raptor and 338 Federal seem more practical.
 
Personally I adore my 16" .375 Raptor Takedown. Easy to use commercially available magazines, no special bolt required, just barrel and bob's your uncle.

Quiet as a 300blk with a Dead Air Primal and Maker 400gr solid coppers, even quieter since I have a gas block that can be easily cut off if desired.

Build:
Aero M5 Upper and Lower
X-caliber custom barrel with RCA matched bolt
Cry Havoc Barrel Take-down system
Law Folder
Strike Collar Adjustable gas block
Aero BCG
JP SCS
Keymount muzzle (forget exactly whose, jmac I think)
rounded out with a 1-10 LPVO on a bobro mount for perfect return to zero on removal/remount.

breaks down into 4 pieces + mag, no loss of zero or accuracy.

Basically built that way for giggles. Currently tinkering with using Sig .277 fury bimetal brass to do silly things with the supersonic rounds.

Obligatory and relevant image:
375-VS-300.jpg
 
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You’re kind of all over the place here…

What AR10 was fielded with as full auto?

The FAL is a great rifle but it’s not an AR platform. Yes there are other similar platforms but are we speaking about any platform or the AR10?

Considering we are on a precision rifle forum we tend to bias towards that type of use and consideration, not so much towards machine gun utilization.

You know you're being trolled

Right?
 
I highly doubt that. I would never go up against professionals that had 6.5's unless I was dialed in.

If you took a bunch of 225 grain .338 Accubonds or 250 grain .358 Accubonds and filled them with sintered metal formulations, you would have big bore and big b.c. frang rounds that have less drop then a 130 grain 6.5 Creedmore or 175 grain FGMM.

They could weigh 175 grain for the .338 and 200 grain for the .358.

Those are more advanced rounds then the 6.5 Creedmore.

Just like .573 B.C. 8mm Mauser was more advanced then .400 b.c. .303 British or 150 grain 30-06 Springfield.

Troll level 11/10

Impressive
 
How about LR in 45 Raptor handloaded with a 300 grain Parker "match" bullet? Loaded cartridge overall length fills a LR308 mag without modification. MVs over 2000 fps. Picture from left to right: .243 Win, .308 Win, and 45 Raptor.
 

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Troll OP or not, it could be a fun discussion.

A 700 grain bullet at 1000 fps would put a thwackin’ on a pig…
…, 45 Raptor, and 475 Bishop Short Magnum.



475 Bishop Short Magnum
iu




The absolute brute of the bunch appears to be the 475 Bishop Short Mag more for bragging rights than anything. The 375 Raptor and 338 Federal seem more practical.

375 Raptor is interesting to me, but I fear it will fall away with 8.6blk getting so much industry support.

That 475 Bishop Short Mag looks like quite a doozy.

But if you want 700 grain subsonics, there is soon to be the 510 Grizzly:
1D796E91-E1D8-4A1F-AD77-673A39929C16.jpeg


And it’s straight wall for those that need it.

Not gonna lie, a silenced break action single shot chambered in this would be a hoot.
 
You'll be challenged to shoot anything subsonic to 400 yards. Since you're limited to (about) 1125 FPS, those bullets drop like a rock.
For example, assuming a 100 yard zero, a 220gr 30 cal bullet would need about 45 MOA of elevation to drop in there. That's roughly what it takes my 6.5 Creed to get to 1350 yards.
22LR will get there but being accurate is expensive. 21.5mils is what it takes me from zero at 50.
 
Most powerful cartridge is 500 Grendel AMC (Advanced Murder Cartridge).
I owned and drove a car from the same factory. It was called the AMC Gremlin (Advanced Murder Car Gremlin).

Its looks could kill.

AD97D434-46AA-408A-9D4B-EDBED45E3655.jpeg
0E8C13D7-1957-4648-870A-5E153C527EC8.jpeg
188676B3-C2EE-442B-9F12-395DEEE94C33.jpeg

That’s effing Levi’s jean seats, yo.

The AMC Gremlin was much better than the Advanced Murder Car Ford Pinto, which tended to, ahem, murder its owners.
 
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When's the release date? A standardized WSM based 510 is pretty interesting. I hope it works out.
Not sure. Grizzly Cartridge doesn’t have info on their website from what I can tell, so you’d need to contact them.

Isn’t it illegal in some states to have a hunting cartridge bigger than .500”? In Iowa it is.
I guess so? Seems a little silly, given many black powder guns are bigger than .500”. I’m guessing they are trying to prevent hunting with the 50 BMG or with cannons. But just using 0.500” as the discriminator is pretty odd.
 
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Not sure. Grizzly Cartridge doesn’t have info on their website from what I can tell, so you’d need to contact them.


I guess so? Seems a little silly, given many black powder guns are bigger than .500”. I’m guessing they are trying to prevent hunting with the 50 BMG or with cannons. But just using 0.500” as the discriminator is pretty odd.
Maybe be silly, but with precedent…


The definition of a "destructive device" is found in 26 U.S.C. § 5845(f). The definition reads as follows:

(1) any explosive, incendiary, or poison gas, (A) bomb, (B) grenade, (C) rocket having a propellant charge of more than 4 ounces, (D) missile having an explosive charge of more than 1/4 ounce (109.4 grains or 7.09 grams), (E) mine or (F) similar device.

(2) Any weapon by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, the barrel or barrels of which have a bore of more than one-half inch in diameter (.50 inches or 12.7 mm), except a shotgun or shotgun shell which the Secretary finds is generally recognized as particularly suitable for sporting purposes;”

Note that destructive devices are regulated by the NFA.
 
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Maybe be silly, but with precedent…


The definition of a "destructive device" is found in 26 U.S.C. § 5845(f). The definition reads as follows:

(1) any explosive, incendiary, or poison gas, (A) bomb, (B) grenade, (C) rocket having a propellant charge of more than 4 ounces, (D) missile having an explosive charge of more than 1/4 ounce (109.4 grains or 7.09 grams), (E) mine or (F) similar device.

(2) Any weapon by whatever name known which will, or which may be readily converted to, expel a projectile by the action of an explosive or other propellant, the barrel or barrels of which have a bore of more than one-half inch in diameter (.50 inches or 12.7 mm), except a shotgun or shotgun shell which the Secretary finds is generally recognized as particularly suitable for sporting purposes;”

Note that destructive devices are regulated by the NFA.
It’s the same diameter as 50 bmg and uses 50 bmg bullets. .510 is the bullet, 0.50 is the bore.

Edit: Correction, the lands diameter in the bore is 0.498
 
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As a side note to all of this... X-caliber is making 7mm PRC barrels for ar-10s now. Heavily assuming its single feed, but they said if you want a gas port for it they can add it. But you have to be quick on your fingers to semi-auto it.:rolleyes:
 
Ar 15, 450 Bushmaster 16 twist, with 500 gr bullet on the right, .510 whisper on the left with a 750 gr Amax. A 1002 gr bullets available for the .510 all with super high BCs...
 

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Have you seen an AR10 510 Whisper? Mag bolt face long action bolt guns are all I've seen.
No, not in its current form, unless you use shorter bullets in the 500 gr range, or less, cut the case heads down to fit 308 bolt face, & cut a new extractor groove, or maybe Use a different case. But it can be done. Too expensive and time consuming for the average guy...but not for a retired machinist, cause all the work is free...I have a .510 10 twist barrel ordered and a reamer from PT&G but it's for a long action bolt gun...so the 1002 gr copper bullets can be used.
This is a barrel chambered for a .500 dia case in an AR 15, not much chamber wall left limits it to about 42000 psi. Its threaded for the barrel extension. In next photo after the extension has been torqued down (I use 125 ft/lbs) the head space checked, and gas block journal turned and gas port drilled, & threaded for muzzle brake, all done in a day, if ya have all the tools ready to go. So yes it would be a different animal but it can be done.
 

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A picture is worth a thousand words. I was planning in a LA bolt gun...but it "can" be AR 10 friendly... these are actual. 510 whisper cases ...but what do ya want to shoot out of it? Notice the shortened case with a 650 gr bullet it has a machined rebated rim and a COAL 2.8" it will fit the AR 10 platform. Then there is the homemade 550 gr bullet that will fit in the standard 510 whisper case and meet the 2.8" AR 10 requirements....but would need the cartridge head turned down for the rebated rim to fit the AR 10...so it's a rebated rim 510 whisper, but limited to bullet selection...unless single load on the longer bullets.
My AR 10 is modified to feed 2.940" to 2.960" cartridges depending on the mag. So there ya go it all depends on how ya want to attack it...the standard case with rebated rim and shorter bullets or short case with long high BC bullets. The 550 gr on a full super, regular 510 whisper case length load... the recoil would be rather substantial...but even subsonic it would smack pretty hard but leaving the above 650 grain bullets mostly off the table, unless ya shorten the case. So you can but it but it must be modified or compromised a bit, to suit your needs. Waiting on a barrel, for the bolt but might order another in the future for an auto. This is all pretty easy stuff on a good well equipped lathe, and too bad more shooters haven't spent time on machine tools. There is just almost no limit to what you can do...
 

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