Heaviest bullet for ar15 in 5.56 (single feed)?

Jayhawkhuntclub · January 10, 2019, 01:33 PM

I know magazines will take Hornady OTM and some 77 gr bullets. But what about single feed? What's the heaviest bullet most ar15s can chamber?

Jim Watson · January 10, 2019, 01:45 PM

Mine is a 6.5 twist made for 90 grain SMK and VLD.
I had the throat lengthened to allow longer OAL for more powder space but it did not make much difference.
A regular A2 7 twist should handle 80-82 grain bullets.

kraigwy · January 10, 2019, 02:00 PM

I've shot 80s and 90s out of my 1:7s, worked good.

lordmorgul · January 10, 2019, 06:42 PM

Chambering by single feed is not the main issue but stability when fired, and good engagement in case mouth (cylindrical area of the bullet). Start with stability, bullet length, barrel twist, and then load longest bullet your specific barrel can handle stabilizing because why bother launching it otherwise.

I have 1:8 twist 75gr Hornady ELD bullets working in 20” barrel. It’s listed as not stable in 1:8 by Hornady but I think it is just marginal and seems ok in my shooting environment and barrel. They make up to 90 gr ELD with long ogives so it’s relatively easy to chamber a bullet without being lodged into the rifling lands but be something too long to stabilize.

I’ve measured these bullet lengths, it is not super easy to find them for all bullets.

Hornady 75 gr ELD-M 1.116”, G1 .43, G7 .220
Hornady 70 gr GMX 1.047”, G1 .350
Hornady 73 gr ELD-M 1.056”, G1 .398, G7 .200
Hornady 75 gr BTHP OTM 0.988” G1 .395

Andrew - Lancaster, CA
NRA Life Member, Calguns.net contributor, CGF / SAF / CRPA / FPC / NAGR / NRA-ILA contributor, USCCA member

Jayhawkhuntclub · January 11, 2019, 05:30 PM

Thanks for all the information. My twist is 1:7 so I think I'm good there.

bfoosh006 · January 13, 2019, 11:41 AM

Remember... there is a lot of difference throat / freebore between the various manufacturers.

What heavy weight .224 bullet works for one barrel may not work well in a shorter throated barrel.

And your OAL will be effected as well from the variety of chamber dimensions.

January 10, 2019, 01:33 PM	#1
Jayhawkhuntclub Senior Member Join Date: December 13, 2007 Posts: 581	Heaviest bullet for ar15 in 5.56 (single feed)? I know magazines will take Hornady OTM and some 77 gr bullets. But what about single feed? What's the heaviest bullet most ar15s can chamber?

January 10, 2019, 02:00 PM	#3
kraigwy Senior Member Join Date: June 16, 2008 Location: Wyoming Posts: 11,061	I've shot 80s and 90s out of my 1:7s, worked good. __________________ Kraig Stuart CPT USAR Ret USAMU Sniper School Distinguished Rifle Badge 1071

January 10, 2019, 06:42 PM	#4
lordmorgul Senior Member Join Date: August 18, 2016 Posts: 206	Heaviest bullet for ar15 in 5.56 (single feed)? Chambering by single feed is not the main issue but stability when fired, and good engagement in case mouth (cylindrical area of the bullet). Start with stability, bullet length, barrel twist, and then load longest bullet your specific barrel can handle stabilizing because why bother launching it otherwise. I have 1:8 twist 75gr Hornady ELD bullets working in 20” barrel. It’s listed as not stable in 1:8 by Hornady but I think it is just marginal and seems ok in my shooting environment and barrel. They make up to 90 gr ELD with long ogives so it’s relatively easy to chamber a bullet without being lodged into the rifling lands but be something too long to stabilize. I’ve measured these bullet lengths, it is not super easy to find them for all bullets. Hornady 75 gr ELD-M 1.116”, G1 .43, G7 .220 Hornady 70 gr GMX 1.047”, G1 .350 Hornady 73 gr ELD-M 1.056”, G1 .398, G7 .200 Hornady 75 gr BTHP OTM 0.988” G1 .395 Andrew - Lancaster, CA NRA Life Member, Calguns.net contributor, CGF / SAF / CRPA / FPC / NAGR / NRA-ILA contributor, USCCA member Last edited by lordmorgul; January 10, 2019 at 06:50 PM.

January 10, 2019, 01:45 PM	#2
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,540	Mine is a 6.5 twist made for 90 grain SMK and VLD. I had the throat lengthened to allow longer OAL for more powder space but it did not make much difference. A regular A2 7 twist should handle 80-82 grain bullets.

January 11, 2019, 05:30 PM	#5
Jayhawkhuntclub Senior Member Join Date: December 13, 2007 Posts: 581	Thanks for all the information. My twist is 1:7 so I think I'm good there.

January 13, 2019, 11:41 AM	#6
bfoosh006 Senior Member Join Date: February 17, 2009 Posts: 1,089	Remember... there is a lot of difference throat / freebore between the various manufacturers. What heavy weight .224 bullet works for one barrel may not work well in a shorter throated barrel. And your OAL will be effected as well from the variety of chamber dimensions.