What is the consensus on what the best 5.56 defensive load is in a PDW sized AR (7-8" barrel)? I’ve tried searching the info and can’t seem to find very much, no chronos or ballistics gel tests, etc.
Cant rely on fragmentation at that velocity, so use something that expands like Barnes 50gr. https://www.m4carbine.net/showthread.php?128698-BH-5-56-50gr-TSX-vs-BH-223-55gr-TSX-from-SBR
Black Hills 50g TSX
Thanks for the link, I’ve actually read that very thread and found it useful. However, my only worry with 50gr BH TSX is how big is the window of expansion going to be out of a 7" barrel? 8" barrel MV is reported to be around 2,600FPS with the basement of expansion being 2,300FPS, giving you 75 yards range of expansion. So my new question would be, how much MV is lost going from 8" to 7" with BH 50gr. TSX?
I was actually thinking on the 7" perhaps 55 or 62gr TSX would be preferable, but that’s just an idea I as I don’t know first hand.
The 55gr and 62gr TSX will be adequate, just like the a black Hills 50gr TSX, 62gr TBBC and Gold Dot.
You have to look at it like this. FMJ and OTM from a 7" barrel will likely not fragment at all and just punch holes. The lighter bonded or solid copper bullets will still expand as designed within the typical engagement ranges of a PDW. That may only be 50 yards for 100% reliable mad expansion, but that doesn’t mean it just stops at that point. At 100 yards it’ll still expand, just not to it’s fullest.
I’ll post back with some numbers, but I’d use 50 yards as a baseline for now. This is why I’m moving more and more towards 300 blackout for my short rifle needs. I’m not suggesting anyone else do the same, just explaining why I did. A 9" rifle works well for me since I spend a lot of time in a vehicle. A little better than my 11.5" 5.56, but a 9" loaded wih 110gr Vor-TX black tip gives me performance on par with a 16" 5.56 in terms or terminal ballistics. I actually never intended for ithe blackout to fill this role. I kind of fell into one and ran with it. Meant to be a hog rifle but the benefits for me were noticeable and I figured “what the hell”.
My suggestion to you would be to get the black hills 50gr TSX, some 55 and 62gr as well, then try to find some TBBC and Gold Dot. I’d personally stick to 223 pressure ammo in that type of rifle. Then, I’d run a box or two of each through my rifle and see what was the most consistent and accurate. That’s what I’d run as my primary ammo.
I’ll see what I can dig up on expansion, but the differences will be small and not enough for me to make a choice based on that over accuracy.
Just noticed it posted in that other thread. Apparently I haven’t changed my mind in 8 months. That must be a record for me.
Bayonet
I saw that, and the BH TSX was at the top of my desired list, I just didn’t see data on sub 8" barrels. Perhaps a moot point but the reason I was interested is because I’d like to have an AR pistol I can put in a bag to have in my car and even conceal on my person. I was thinking 7-8" AR pistol with the sig SB15, law tactical folding stock and maybe the 5.11 sling carry bag would do the trick. Certainly not my first choice of weapon but better than the M&P I carry and I just wanted to make sure I had effective ammo for it… I will probably switch over completely to 50gr. TSX for all my rifles.
You’re better off with a handgun in that area. The terminal ballistics will be about the same and you won’t have to deal with the extra bulk and extra blast and flash. Not to mention the reliability issues with ARs that short.
Well first off I’d have a traditional handgun on me anyway, but to say handgun and AR in 7-8" would be about the same, well I don’t buy that at all, the handgun will not have as much punch or range… Not sure what reliability issues you are talking about? I love DI AR’s but this is the one exception I’ll make going piston… And finally, you are right blast and flash will be increased but it’s my understanding the BH loads in particular are not bad in regards to flash out of short barrels.
Two year old thread but it’s what came up in a search…
There are at least a couple youtube vids I saw this year demonstrating that the 45-60 gr JHP/BT bullets do expand and penetrate well from these 7.5-8 in barrels at their typical velocities (1950-2200 fps) Precise too, since most of these AR 5.56 pistol barrels have 1:9 twist and may not do well with heavier, slower bullets.
So to answer the OP my opinion is the lightweight varmint rounds (BT, JHP, or JSP) that expand at “low” velocities (And may not be the best choice for longer barrels) are the way to go for the 5.56 PDW. If less flash is wanted loads with flash retardant are available. (TAP, Ranger, others)
It’s inherently big vel loss from 7in . Your choice , but consider priorities of the 2in or so difference in length.
I only go down to 10.5in , but just picked up BH 50gr TSX with intent for deer. TSX best of option for expand & penetrate. Plan B is go to light wt varmit bullet , & accept the trade off of shallow penetra(ion.
I’d long forgotten this thread and long ago ditched the idea of running anything 5.56 under 10" with 11.5" being my preferred length.