...or in our case fixed mag "pistols".
I wanted to compile some data I've found comparing SBR length ARs using .300 Blackout or 5.56. In the future I plan on doing a fixed mag AR pistol and wanted to see the terminal performances of each for short barrels for use at short ranges. This stuff may already be evident to some people, but I'd like to compile it for people who want to see it.
I'll compare an 8.5-9" barrel .300BLK barrel to multiple barrel lengths of 5.56. We'll be looking at premium ammo out of both. I'm going to use some pictures instead of typing this all out. Here's a good starting point. These numbers were found by a member on m4carbine forums:
This is good performance. I've heard a number of police forces are using these or similar rounds. Now for some numbers for a shorter barrel. Based on user data from m4carbine forums, out of a 10.5" barrel muzzle velocity drops to about 2500 fps (for 64gr). This leads to an energy level of about 900 ft-lbs.
For .300BLK, here is a chart of velocities and energy levels, it also shows M193 velocities. I took this off of AR15 forums, but I'm sure I originally saw this in a gun blog article, I just can't find the original.
As you can see a 9" .300BLK using Barnes 110gr is surpassing a 12.5" (a commonly used length) barrel 5.56 (M193) in terms of muzzle energy.
Now a quick look at terminal expansion. It's common to use expanding 5.56 in SBRs as opposed to rounds designed primarily to fragment due to the lower velocities. Shown in the above m4carbine forums test, 64gr Gold Dots get above .4" for a 16" barrel. This round expands to pretty low velocities, so SBRs should get the same expansion numbers. I've typically been seeing average best case expansion numbers around .45" for these types of premium expanding defense rounds. Looking at Barnes 110gr TAC-TX .300BLK rounds from an Outdoor Hub article (1st pic is test parameters, 2nd is results):
Now here is the expansion info from a Guns & Ammo article:
So we're getting 20" of penetration and .667" of expansion from an SBR, impressive.
So the point is if you're thinking about going short, a 9" bbl .300BLK is giving you all around better terminal performance compared to an even longer 12.5" bbl 5.56. A side note, this is not even including that .300BLK should give better peak energy transfer in gelatin due to the larger frontal area and weight.
Some extra notes. In this analysis I'm not trying to compare every factor of choosing .300BLK vs 5.56, e.g. cost, ammo compatibility with other owned rifles, reloaded ammo etc., this is simply to look at short range terminal performance of some comparable defensive rounds. Also this is not comparing .300BLK vs. ever other SBR caliber, just .300 vs 5.56.
Let me know what you guys think! Later I'll add some gel test videos.
I wanted to compile some data I've found comparing SBR length ARs using .300 Blackout or 5.56. In the future I plan on doing a fixed mag AR pistol and wanted to see the terminal performances of each for short barrels for use at short ranges. This stuff may already be evident to some people, but I'd like to compile it for people who want to see it.
I'll compare an 8.5-9" barrel .300BLK barrel to multiple barrel lengths of 5.56. We'll be looking at premium ammo out of both. I'm going to use some pictures instead of typing this all out. Here's a good starting point. These numbers were found by a member on m4carbine forums:
This is good performance. I've heard a number of police forces are using these or similar rounds. Now for some numbers for a shorter barrel. Based on user data from m4carbine forums, out of a 10.5" barrel muzzle velocity drops to about 2500 fps (for 64gr). This leads to an energy level of about 900 ft-lbs.
For .300BLK, here is a chart of velocities and energy levels, it also shows M193 velocities. I took this off of AR15 forums, but I'm sure I originally saw this in a gun blog article, I just can't find the original.
As you can see a 9" .300BLK using Barnes 110gr is surpassing a 12.5" (a commonly used length) barrel 5.56 (M193) in terms of muzzle energy.
Now a quick look at terminal expansion. It's common to use expanding 5.56 in SBRs as opposed to rounds designed primarily to fragment due to the lower velocities. Shown in the above m4carbine forums test, 64gr Gold Dots get above .4" for a 16" barrel. This round expands to pretty low velocities, so SBRs should get the same expansion numbers. I've typically been seeing average best case expansion numbers around .45" for these types of premium expanding defense rounds. Looking at Barnes 110gr TAC-TX .300BLK rounds from an Outdoor Hub article (1st pic is test parameters, 2nd is results):
Now here is the expansion info from a Guns & Ammo article:
So we're getting 20" of penetration and .667" of expansion from an SBR, impressive.
So the point is if you're thinking about going short, a 9" bbl .300BLK is giving you all around better terminal performance compared to an even longer 12.5" bbl 5.56. A side note, this is not even including that .300BLK should give better peak energy transfer in gelatin due to the larger frontal area and weight.
Some extra notes. In this analysis I'm not trying to compare every factor of choosing .300BLK vs 5.56, e.g. cost, ammo compatibility with other owned rifles, reloaded ammo etc., this is simply to look at short range terminal performance of some comparable defensive rounds. Also this is not comparing .300BLK vs. ever other SBR caliber, just .300 vs 5.56.
Let me know what you guys think! Later I'll add some gel test videos.
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