Suggestions from anyone running a 7.5" 556...

[ShooterwithNoName]

I got a really nice barrel in a trade here in the PX. It's a 7.5" 5.56 1:7 Pac Nor barrel. I know all the downsides to having a 7.5" 5.56, velocity drop, muzzle blast, etc...

I'm going to build it anyway. The reason being I want to have as small of a footprint as possible with a can attached. I'm having trouble deciding on the gas system. Since a lot of you guys on here are AR guys I'm hoping some of you have reliable 7.5" barreled 5.56's.

Right now my first choice on the gas system is the SA pistol length piston system. With all the pressure and heat at the gas port I thought this may be the way to go vs. a standard DI arrangement. It's adjustable also which is a big plus. I have their bleed off gas blocks and couldn't be happier with them. Anyone running one of these yet?

If I go with DI gas system, is the pigtail gas tube suitable for a 7.5" 5.56? Or is it just going to be getting super hot and cause problems? If I go this route I'll run a SA adjustable gas block most likely. I'm open to suggestions if you guys have any...

I don't do mag dumps or bump firing. I do wish to use this "pistol" in a defensive capacity if needed. It will be a compact pdw basically. I only care about ballistics within 50yds with this thing. I'll hand load to find the best combo ammo wise. I'm hoping to find at least one decent factory load for it too.

This will wear a Liberty Constitution can pretty much full time. I've talked to them regarding the 7.5" length and they say it's good to go. It's affordable, tough and will do all I need it to do which is harness that muzzle blast to a manageable level. But... I would like to run either a flash hider or blast device on it that works also. I've looked at the Surefire Warden over the Surefire muzzle brake, Noveske flaming pig, etc... My favorite is the PWS Diablo, though I really prefer the gen 1 version, only the gen 2 is in stock anywhere. Unless I stumble across one used, I never see them for sale so they must work.

Do you guys have any luck with these flash cans/devices? I know they really only direct the blast forward and don't do much if anything for flash. Would I be better off just running an A2 birdcage? They are pretty hard to beat from what I've heard, cheap too.

Let me know if any if you guys have any recommendations on this stuff. I know I would be better off with a 300blk, 6.8, pretty much any other round but 5.56, I know. But I have the barrel, it's gassed right, I've done a 300blk in this length before and didn't care for it. For the price, might as well shoot 5.56 out of a short barrel and I have thousands of rounds of it and reloading components for it.

Thanks...

 

[RyanScott]

I don’t see a point to putting a long can on a short barrel. If you do that an M4S on an 11.5 starts to make more sense.

 

[slothlacrosse]

Back in the day before adjustable gas blocks, I had an 7.5” upper that I dicked around with for a while.

A2 flash hider did nothing but direct the muzzle flash up and the curly gas tube just made the forearm hot. The KX3 did a good job of directing muzzle flash forward. It burped a 3 ft flame, but it wasn’t as bad as the A2 when firing.

The only way I could get it to cycle consistently was to put different springs and buffer weights in it. An AGB would would probably do the trick.

FYI- it was a cheap gunshow barrel (not the one I traded to you) and it was used exclusively for mag dumps!

 

[ShooterwithNoName]

I don’t see a point to putting a long can on a short barrel. If you do that an M4S on an 11.5 starts to make more sense.

Yea I get all that, I have an 11.5" upper and it's a great upper. The 7.5" barrel plus the length of the Liberty can: 6.35" puts me at roughly 13.5" which is close to the same length as an 11.5" with flash hider, a little over...

There's a purpose to this thing being compact as possible. I need to fit a certain compartment and with this setup I can leave the can mounted and with a LWRC UCIW stock it will perfectly fit the compartment I need to fit it in without breaking it down.

Thanks for the reply slothlacrosse, I really like the barrel btw... I appreciate the experience with the A2 that's the kind of info I'm looking for. Appreciate it.

 

[ShooterwithNoName]

I think I'm gonna be a guinea pig on this SA piston system... It seems to be just the ticket for what I'm wanting. It won't blow all that hot gas blasting off that pistol length gas system into my upper. It looks solid to me, I'm gonna order one after Christmas and try it out.

I'm gonna run a blade until I get it sbr'd... I need that little bit of space that the UCIW stock affords me. Only problem with the UCIW is that buffer. Pretty limited on options, though heavybuffers.com has one for it. I'm gonna get one and most likely run it to give me as much weight as possible, I'm sure I'll need it.

Probably get a couple heavier buffer springs and try them out. I don't care to tinker with it to get it running. I've got to come up with a good hand load for it too. I have a 1000ct Speer 53gr HP. I'm hoping these feed as they have a pretty big HP opening. I am thinking going lighter will be the ticket with the projectiles. I will load up a bit of everything and see what works. I think I can get it to do what I want within 50yds... May take some tuning but I want to make it work.

 

[Reverie Ranges]

Seekins SP223 5.56 with Sig 7.5" piston and SWR 7.62 Suppressor (7.5" is very loud without). Seems to work good for me. Had it out to 330m bowling pin consistently. Fun to shoot!

 

[gunner442]

I've used an A2 birdcage and a flash can on my 7.5 and the flash can makes a world of difference with usability. The birdcage was teeth rattling.

 

[USMC_JA]

I have two 7.5 inch AR barrels. Both are Ballistic Advantage. One is a Hansen and the other the cheaper modern series I bought on clearance for a song.

On the Hansen build, I have an SLR AGB, Echo trigger, and Dead Air Sandman FS. I run both a Sandman K and Pyro on it (when i want a light show). I've broken the adjustment screw twice on the AGB but SLR has been quick to replace/repair. I admit to running the gun hard with the Echo. But when I have it dialed in correctly, it is dead nuts reliable.

On the modern series BA 7.5 build, I have a fixed gas block from BA and a KX5 on the end of it. This gun also has been flawless but with only 200 rounds down the pipe. The KX5 makes it noticeably front heavy. I prefer the handling of the other gun...even with the suppressor.

I would not want to run either gun without some type of muzzle device.

Here's the 7.5 Hanson with the Pyro. I strangely find myself alone on the range when I run this gun in doors......

 

[Romeo458]

I have the 4 piece on my SLR106 12inc booster that's like the flaming pig but more of a booster blast deflector and it works great. I had a 7inc at but I used a Smith vortex on it. Weall took turn running that thing hard.the DI works on a short AR is fine but I would highly reccomend doing a homemade gas buster on the charge handle. RTV silicone where it meets the receiver. I have only went as low as 10.5 suppressed but if its DI the gasket helps immensely.

 

[Reverie Ranges]

Ha HA HA!!!! That's awesome! Shoot your meal and cook it too...

 

[digitalshooter]

Looks like a 7.5" is great when you need an all in one solution for a rifle and a flame thrower.