5.56 Usability by Barrel Length

[PappyM3]

Hey all, I put together this chart to determine the best usable range of a certain barrel length, shooting 77gr TMK.

Most of the muzzle velocities were averaged, extrapolated, and interpolated based on available data around the internet. The 11.5 was then just averaged halfway between 10.5 and 12.5 because of an unusual low spot in the data that likely wasn’t representative of most 11.5 users. The 14” BRT is my own Black River Tactical barrel with Black Hills 77 TMK. However, this is just a rough guide. Chrono your gun and line it up with a similar muzzle velocity.

Also, the descriptions of lethality from certain velocity ranges came from a professional deer culler, who has used 77 TMK and Barnes TSX considerably.

Okay, nerding out time:

 

[mac1911]

I thought Sierra expresses the TMK’s are not good for hunting? I dont know anyrhing about the TSX bullet.
I think for practical accuracy there wont be a huge diffetence in barrel length other than some velocity loss.
I load a 77 gn Nosler ar slower than average velocities for 200 yard matches and they shoot very well
My shortest barrel is my custom 17.2145” AR barrel.

 

[xtry51]

TSX and TTSX are the bees knees. Accurate and devastating.

 

[PappyM3]

I thought Sierra expresses the TMK’s are not good for hunting? I dont know anyrhing about the TSX bullet.
I think for practical accuracy there wont be a huge diffetence in barrel length other than some velocity loss.

They say that because they’re designed to be match bullets, but they’re very effective against hogs and deer. The TSX is from Barnes, and is a solid copper bullet that mushrooms nicely. It has more consistent performance across a velocity range, but doesn’t have the peak terminal performance of the TMK.

And yeah, the only factor in accuracy would be an individual barrel shooting it well. Obviously the shorter barrels will be affected by wind more at the farther ranges, but the 77 TMK is slippery for a .224 and most people won’t be shooting out to a point where holds will be too different.

I load a 77 gn Nosler ar slower than average velocities for 200 yard matches and they shoot very well...

77 on the short line? I guess if it shoots well for you, why not. My match barrels always seem to like 69gr SMKs.

My shortest barrel is my custom 17.2145” AR barrel.

Is it rifle length gas?

 

[mac1911]

They say that because they’re designed to be match bullets, but they’re very effective against hogs and deer. The TSX is from Barnes, and is a solid copper bullet that mushrooms nicely. It has more consistent performance across a velocity range, but doesn’t have the peak terminal performance of the TMK.

And yeah, the only factor in accuracy would be an individual barrel shooting it well. Obviously the shorter barrels will be affected by wind more at the farther ranges, but the 77 TMK is slippery for a .224 and most people won’t be shooting out to a point where holds will be too different.


77 on the short line? I guess if it shoots well for you, why not. My match barrels always seem to like 69gr SMKs.


Is it rifle length gas?

I bought enough 77 Nosler CC to not matter , i do have 69s and 80s also.
Im not shooting enough XTC or well enough to matter with bullet choices. The price difference is moot also. 2017 nosler had a sale plus a 15% code and free shipping. In the end i bought alot of 22cal, 30cal and 8mm custom comps averaged .14 cents each shipped.

Yes rifle length gas system. I custom cut my barrel to shed weight for cmp Mondern Military match. Was hoping to get to VT this year

I figure there has to be better bullets for hunting even at lower velocities than the 77s?

 

[PappyM3]

Ha, I was thinking of doing the same thing with an old service rifle barrel. Didn’t end up going through with it though.

For hunting, there are obviously a lot of bullet choices. Most in .223/5.56 focus on penetration, but the wound track leaves something to be desired. Even the good TSX doesn’t destroy as much tissue as TMK, according to the deer culler who who was providing the information. The 77TMK fragments violently down to 1900 FPS, and at least in ballistics gel, penetrates up to 18” too. It’s proven to be an effective boar and deer bullet. That said, my chart is mostly intended for 2 legged predators, but has applicability for medium game too.

 

[mac1911]

Ha, I was thinking of doing the same thing with an old service rifle barrel. Didn’t end up going through with it though.

For hunting, there are obviously a lot of bullet choices. Most in .223/5.56 focus on penetration, but the wound track leaves something to be desired. Even the good TSX doesn’t destroy as much tissue as TMK, according to the deer culler who who was providing the information. The 77TMK fragments violently down to 1900 FPS, and at least in ballistics gel, penetrates up to 18” too. It’s proven to be an effective boar and deer bullet. That said, my chart is mostly intended for 2 legged predators, but has applicability for medium game too.

For them pesky 2 leg garden varmints , im less concerned about penetration and expansion as there shall be bigger problems surrounding those circumstances?
Any how If really looking for best expansion at lower velocities im sure there are some expwnsive choices from lapua or norma or any of the controlled expansion designs that will expand even at low velocities say down to 2000fps.
If you reload you could find a powder that will give you a bit more veloci ty out of a 10" barrel.
although im sure that might be pushing chamber and gas system pressures to the edge?

 

[PappyM3]

I’ve updated my chart to include M193 and 62gr and 70gr TSX loads. Considering the TSX is pretty nicely barrier blind, it seems ideal or people who only ever intend to engage within the POA/POI range of 5.56 with a 50 yard zero (225/250 yards and in).

For the TSX muzzle velocities, the 10.5”, 14.5”, 16”, and 20” were all averages from load data provided by Barnes with 6 different powders and using 90% of the velocity between min/max loads. The expansion/fragmentation assessments for a given velocity were derived from various reports/research I could find.