OAL Limits for AR15? Heaviest Grain Bullet?

[gryffinwings]

I'm doing a bit of research on loading 5.56/.223 for my AR15, it's a PSA with a 16" 1 in 7 twist barrel M4 profile barrel.

I've been seeing that for OAL of the cartridge shouldn't be any longer than 2.260", the heaviest grain bullet I'm seeing in my 50th Lyman manual is a 77 gr. Jacketed HPBT bullet at the max OAL.

Are there any heavy grain bullets that will seat properly to the recommended maximum OAL and feed reliably from a magazine in an AR15?

I didn't see any information on their websites.

Recommendations are appreciated. Or even website to look over bullet load data for various bullets from manufacturers would be great.

Personal experience on this particular twist rate on the AR15 platform would be great as well.

[highpower790]

For all practical purposes the heaviest bullet that can be shot mag length will be one in the range 73-77gr.
As a option to shoot 80s, the front of the mag can be channeled to allow for extra length of bullet.

[gryffinwings]

For all practical purposes the heaviest bullet that can be shot mag length will be one in the range 73-77gr.
As a option to shoot 80s the front of the mag can be channeled to allow for extra length of bullet.

Thanks for this information, I found Nosler has quite a bit of information on their load data and it mirrors what you say, the 80 grain they posted has an OAL of 2.360", so it sounds like 77 grains it is.

So theoretical situation, if I channeled the magazine, I'm assuming I'd need a metal mag, the 80 grain bullets should feed?

[highpower790]

Thanks for this information, I found Nosler has quite a bit of information on their load data and it mirrors what you say, the 80 grain they posted has an OAL of 2.360", so it sounds like 77 grains it is.

So theoretical situation, if I channeled the magazine, I'm assuming I'd need a metal mag, the 80 grain bullets should feed?

Friends of mine that shoot highpower using the Berger 80.5 have channeled old gi aluminum mags,I myself have not and don't know anyone that has used a polymer mag for this application.
If the decision is made to channel mag,start with the narrowest dimension possible and widen as necessary.

[Kwikvette]

Based on a target you posted in another thread, I take it you're looking to gain a bit of accuracy since you're looking at 77gr projectiles.

I ventured as far as single loading rounds for one of my AR15's after measuring my chamber; rounds came out to 2.2750" OAL (.020" off the lands).

77gr SMK, 24gr of RL15, and Winchester 7 1/2 benchrest primers loaded to 2.26" OAL netted me +/- 0.6" 5-shot groups at 100 yards. It could've been me but I think I saw almost a tenth of an inch difference when I loaded them to my AR's chamber.

Long story short, load to mag length.

[zouaveherb]

http://www.bergerbullets.com/twist-rate-calculator/

Going to a heavier bullet may or may not be more accurate. Especially out of a shorter barrel.

[ocabj]

Don't waste your time trying to modify magazines to fit 80gr. You're better off sticking with 77gr Lapua Scenars. If you need maximum BC, then just single load 80gr VLDs.

[McGuiver]

OAL Limits for AR15? Heaviest Grain Bullet?

Don't waste your time trying to modify magazines to fit 80gr. You're better off sticking with 77gr Lapua Scenars. If you need maximum BC, then just single load 80gr VLDs.

I single load my 80gr Nosler bullets. They are longer than mag length.

I use a Bob Sled to help load them one at a time.

http://www.originalbobsled.com/SemiAutoSleds.aspx

Just throw a round into the ejection port and it lands in the sled, then hit the bolt release.






Sent from my iPad using Tapatalk

[Metal God]

The issue you run into with heavier bullets that fit in the mag is that they must be seated deeper & deeper into the case . This results in less case volume for powder so you actually loose the benefit of the higher BC by reducing velocity do to less powder . I don't know if you've ever seated a 77gr bullet into a 223 case but it goes deep into the case . My best loads using 77gr SMK and stick powders are compressed and that's when using a 8" drop tube/funnel . There is just not enough room in a 223 case to load heavy bullets while using the traditionally more accurate stick powders .

There is no benefit to going heavier then 77gr if you are going to seat to max mag length . IMHO if your barrel wont shoot 77's it ain't going to shoot 80's any better .

[McGuiver]

OAL Limits for AR15? Heaviest Grain Bullet?

The issue you run into with heavier bullets that fit in the mag is that they must be seated deeper & deeper into the case . This results in less case volume for powder so you actually loose the benefit of the higher BC by reducing velocity do to less powder . I don't know if you've ever seated a 77gr bullet into a 223 case but it goes deep into the case . My best loads using 77gr SMK and stick powders are compressed and that's when using a 8" drop tube/funnel . There is just not enough room in a 223 case to load heavy bullets while using the traditionally more accurate stick powders .

There is no benefit to going heavier then 77gr if you are going to seat to max mag length . IMHO if your barrel wont shoot 77's it ain't going to shoot 80's any better .

If I shoot heavy bullets at mag length I will usually shot 77gr ones, but the 80gr, and the 80gr ELDs cut thru the wind so much better at 600 yards and beyond. I do load every thing heavier than 77gr longer than mag length.

If I'm shooting long distance, I like the 90gr ones too but my 1-in-7 twist barrel (16" long) was not enough for them. The 90gr ones wanted to tumble after 100 yards. The 90gr ones I tried were Sierra BTOTM. On the box is says minimum is 1-in-6.5 twist. I would like to get a barrel some day for the 90gr bullets. I get spoiled when I shoot 77gr or 80gr bullets and go back to 34gr of 55gr bullets.


Sent from my iPad using Tapatalk

[waveslayer]

It's not a matter of the bullet fitting and shooting well from a mag, it's the lack of powder you get from a bullet in the 80 grain range. It takes up so much case capacity that it's not worth it. I load 77gr. No problem. 80's work better with a bolt gun because you can get more powder in the cases by seating the bullet longer

My wife thinks I only have 3 guns

[smoothy8500]

For NRA "across the course" I'm using 77 gr Nosler CC's at 200 & 300yds. At the 600yd line I have Nosler 80's loaded long. However, I have used 77's loaded mag length at the 600yd when I forgot my 80's. Other than slightly less forgiving wind calls, the 77's perform fine. Barrel is a RRA NMA2, 1-8 twist.

[Archon_g24]

I've loaded a bunch of Hornady 75gr BTHP rounds to magazine length and am only magazine loading rounds measured 2.260" or less but can't seem to get them to feed from my PMags. The rounds will pick-up from the magazine but the bolt will not fully seat and lock.

I've tried 4 different 10 and 10/20 Pmags and all seem to have the same issue. Single loading worked fine though.

Should I seat them deeper until they feed?

[highpower790]

I've loaded a bunch of Hornady 75gr BTHP rounds to magazine length and am only magazine loading rounds measured 2.260" or less but can't seem to get them to feed from my PMags. The rounds will pick-up from the magazine but the bolt will not fully seat and lock.

I've tried 4 different 10 and 10/20 Pmags and all seem to have the same issue. Single loading worked fine though.

Should I seat them deeper until they feed?

I use the same 75bthp with pmags without issue,and don't think seating deeper will be the cure for your problem.Try a new buffer spring.

[Archon_g24]

What OAL are you setting your cartridges to?

I'm having the same issue with these mags on three different lowers:
Rifle length, A1 butt stock with a JP Spring
Carbine length, PSA lower
Vltor A5