Hello All,
Myself and a coworker are changing out our Colt 6920's into pistols or possibly the SBR route. I doubt very seriously I will ever run a suppressor, but he is saying he might eventually. He is leaning on me to help him as he has never built an AR or has much armorer experience. Not that I am an expert (hence me being here) but I have built a few and help maintain a few guns for folks. Any helpful suggestions would be appreciated. We are trying to make the lightest weight rifles possible. Budget friendly would be great, but I am aware sometimes you have to "pay to play".
I have picked out the BCM Lightweight Fluted 11.5" barrel for us. Should I lean him towards 12.5" if he is wanting to go suppressed at some point?
Also, does this BCM Barrel ever even come in stock? Because I am beginning to wonder... So what are some alternatives we should consider? Ballistic Advantage? Roscoe?
Ideally all we are trying to change is the barrel, the rail, and the stock. Keeping everything else for now as we move down the road. Speaking of rails. I was under the impression a barrel nut had to be used with the specific rail or the D ring. I am guessing this isn't always the case?
They won't be used for anything realistically outside of 100 yards. We are wanting these for "SHTF/Truck Gun's" to replace our longer rifle that's a burden to us getting in our of trucks an UTVS with.
We will be running red dots with maybe magnifiers.
I believe that's all the information I could give to everyone to try and get some insight. If I missed something please let me know.
Any information would be greatly appreciated. Thanks
Out of boredom, I re-read this thread. Lots of information flying around. As I mentioned above, 11.5" is a good way to go. It's a solid compromise between compactness and velocity. Don't over think the whole profile thing. It isn't that important with a short barrel. As much as I like BCM stuff, I don't buy their barrels. They are good barrels, but the accuracy just isn't on par with something like a Criterion Hybrid or Geissele barrel, and they cost about the same.
12.5 is an oddball length. It really doesn't get you much in terms of performance. What it does get you is an extra inch or more of rail space, and on some rigs an inch makes a big difference. For suppression, I'd go with 11.5. It's just plain easier to tune with some cans. 12.5, with some cans, will mean way too much dwell time and less tuning window.
As for investing in a bunch of springs and buffers, I dont know about that. Have you seen what springs and buffers cost? I know ... a bunch of guys can pop up swearing to the magic that some Gucci spring worked on their rig. Come on ... it's a spring.
Truth is that the spring rate has very little to do with closed bolt lock time. All it does is alter bolt velocity and, in some cases, lead you to believe that your rifle is tuned correctly, due to ejection pattern, when you are actually still over gassed. There are only two ways to control closed bolt lock time. Either control the gas or increase/decrease buffer weight.
I've found that a gas port size of around .070 is optimal for an 11.5" barrel. Assuming that you get a barrel with an oversized gas port, what I do is get a Yankee Hill Machine suppressor gas block. They are around $20. They come with a very undersized gas hole. I drill it out to the gas port size that I want.
As for springs, a plain Jane carbine spring should do you. I tend to go a few thousand rounds between cleanings, so I run a springco white hot spring to help with chambering when things are dirty. This is not to tune the rifle. This is just to help with chambering reliability.
An 11.5 with a .070 gas port, white hot spring and an H or H2 buffer will be the ticket.
If you want some tuning ability with buffer weights, find yourself an H3 buffer on sale or something. This is usually the cheapest way to find tungsten weights. Then order yourself a few steel weights, from someplace like KAK. To go from an H3 to anything down to a standard buffer weight is as simple as driving out a roll pin and replacing the tungsten weights with steel ones.
