I was just at Gander Mtn. looking for a an American flag but they don’t carry any so as I was leaving I picked up an issue of SWAT. There was an article about the Troy M7A1 upper in 5.56 which has a 7.5" barrel. One of the tests they did with it was set up a dummy 50 yards away with a Safariland Level III vest. They loaded 4 rounds of 75gr Tap or BH, I cant quite remember, and fired it into the vest. The article said the bullets went through the trauma plate, the body armor and the dummy. I don’t know how good the Safariland body armor is but this seemed a little strange.
The reason I thought it was stange is because I have read on this site that some people only expect their SBR to perform well at about 25 yards and that was with a 10.5" barrel.
I really don’t know much about this topic so I could be completely off base.
jman4427–I think you may have some misconceptions/misinformation.
First, are you sure the “VEST” was not IIIa soft armor, as level III armor is generally in the form of a hard plate of approx 10x12".
If the armor was IIIa, then a pointy rifle projectile fired around 2000 fps should easily completely penetrate through the vest. If the armor is indeed level III hard armor, then there is NO possibility of a 75 gr OTM round penetrating through the armor, even when fired from a 20" barrel, let alone a 7.5" one…
I am quite sure all the article said was a Safariland Level III armor. I dont recall the “a”. It continued to mention penetrating a trauma plate, body armor, and dummy. I dont know if that means level III or IIIa.
Somewhat off-topic, but there has been a rash of people lately asking about the “best” load for 7.5" barrels. I just don’t see why people hamstring themselves with ultra-short SBRs like that. They may be fun toys, but it seems like there’s no way to get decent bullet performance out of something that short - not to mention a tremendous fireball.
Agreed… But there is probably a very small niche where a 7.5" AR would work well. I imagine maneuverability in tight spaces would be the biggest asset of a 7.5" gun and not ballistic performance. That being said, if you have a 7.5" you had better know the limits of your weapon/ammo.
Level IIIa vests can have a “trauma” plate over the soft armor to help with edged weapons; level III armor IS the “trauma” plate. Again, I believe there is something erroneous regarding the parameters of the initial question.
Those who have a need to run a nominal 8" barrel AR15 for real world tasks will find 6.8mm FAR more effective than 5.56mm in these ultra SBR’s…
Doctor Roberts: Are there any published results of terminal performance for ultra SBRs or gelatin shots at reduced velocity that would mimic the CQB performance of these things?
Some may be asking, “How far out can you defeat body armor with a 7.5” barrel?" Lets find out. I took a Safariland Level III vest an wrapped my bad guy in it. Then I stepped back to the 50 yard line and fired four quick holes through the vest using Hornady 5.56mm 75-gr. BTHP/WC T2. Not a single round was stopped by the vest. It pierced the trauma plate, the body armor, the dummy, and then just kept going.
It continued
Back out at the 50 yard line, I set up a plywood silhouette, taped up a paper target, and zeroed a Trijicon Acog onto the M7A1. I then refaced the target and put three shots into a half-inch group without even breaking a sweat. I defy anyone to tell me that they can’t take down a bank robber or an errant gunman wrapped in body armor with an M7A1. Also note that the holes in the target are perfectly round. The reason I mention this is that I have had conversations with manufacturers who have said to me, “A 7.5” AR actually sends bullets downrange with an unstable wobble after only a few feet." NOT!
I tried to do some research on the T2 bullet that is utilized in the TAP 5.56mm cartridge. What I found was that it offers about 180fps more muzzle velocity than the standard .223 version which equates to an additional 50-75yards worth of fragmentation range.
This could explain the good performance out of such a short barrel. Then again I am in ignoramus when it comes to this. Can anyone confirm this?
I read that article. I don’t think the author knows that there is a difference between III and IIIA. Other than that, I’m going to bite my tongue with regard to any further commentary on the article or the author, except to say that ending a point with “NOT!” is pretty telling. :rolleyes:
For ultra SBR use, consider sticking with barrier blind projectiles vice fragmenting ones. Also, for very short barrel weapons, a faster twist rate may be necessary to ensure an appropriate rotational velocity to maximize the terminal performance of some types of projectiles…
IIRC in an article i read about Noveskes, that John routinely takes his 7.5" barrel out to 100 yds. i have a friend with an AR set up with a 7.5" (5.56) and we have not had any problem hitting the target at 100 yds., now what remains to be seen is if it would penetrate a vest at 100yds. as neither him or i wish to put up the money to get a vest, then fill it with holes, i guess we will never find out. i know at extended ranges (past 200yds.) that the projo velocity is marginally slower than the same one from a longer barrel.
