I submitted a form 1 to make an SBR. I specified the barrel length as 11.5, since I assumed 10.5 would not work with the 10'' rail I got on clearance. I have also purchased a Silencerco Specwar K that will primarily be used on this SBR, and will occasionally be used on my 16'' carbine.



In the picture thread, another user with a nearly identical carbine was able to make the 10.5'' barrel, specwar and 10'' DD rail combo work. I know about the velocity differences between the two barrel lengths with xm193, but am wondering about things like suppressor wear and tear and whether or not the increased blast will make it louder. Either way, I'm going to be cutting down a 14.5'' pinned M4 barrel.

I don't think you will have an issue with the specwar k suppressor. However, I would of probably went with just the specwar 556. If it makes you feel better "SilencerCo tested the K versions on 11 inch, 14.5 inch and 16 inch 5.56mm barrels with 62 grain M855 ball ammunition with a range of results from 137 to 140 dB."

Since you're cutting down a 14.5" barrel, make it 11.0" and tell everyone to suck it.

I like 10.5" because it keeps the suppressor closer to you than an 11.5" barrel, making it feel lighter. But you should do what works with the rail you've selected.

I wanted something to take the edge off of a compact SBR, that would still be light enough and short enough to work on a 16'' barrel carbine. I have no illusions about making 556 "hearing safe."



ETA: I was lucky enough to see a picture of a carbine with identical components in the pic thread. Same suppressor, same rail, with a 10.5'' barrel. So, it is just barely possible to go with 10.5''. If I want to go super short, I may go 10.75'' just to be sure.









 

I'd go with 10.5" since it looks like it will fit with the components you're going to use. I have a 556 Specwar K in NFA jail that I'm anxiously awaiting to be released. I went with the K over the regular 556 for weight savings. It's going to go on my 10.5" upper also. I put my 762 Specwar on my 10.5" upper this weekend and shot a couple of mags of XM193. Sounded like a high velocity .22 rimfire. I used the muzzle break to reduce some of the wear on the can. I don't think you have anything to worry about going as short as 10.5".

I don't know; in the picture he posted above that is to close for comfort for me. 5.56 suppressors get REALLY hot. I would not want it that close to the rail.

Looking at that pic I'd like to have an extra 1/4" or so clearance. Since you're having something cut down I'd go 10.75" or 11" to be safe.

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I'm also considering having the flash hider removed and saving the barrel for use as a plinker in the future. If I do that, I'm leaning towards either a Bravo Company or Daniel Defense. I have most of the parts necessary to make a traditional M4 clone anyway.

Yes they do!

I IMed the guy who's build is pictured. He said he did not use a shim kit. He screwed the flash hider straight on. I intend to use a shim kit that should gain me a bit over 2mm of clearance. I may spring for the 10.5.