New AR based SBR

[KTR03]

Hey Gang,

So I have an odd situation - a problem that we should all want to have. I got a form 1 back from our ATF friends for an LMT lower. I had forgotten about it, and now get to decide what to build. Here is my issue: I have the following SBRs: ps90, 9mm AR, 300 BO AR, 5.56 AR, Sig 553, Sig 553R, Sig 551. So in terms of pistol calibers, sub calibers, and intermediate calibers, I am pretty much covered.

I was thinking I could do a 458 Socom, 50 beowolf or something like that, but I don't have a burning use for one of those. Was also thinking a Mk 18 would be cool. I could also do a 22LR, but that seems like a waste. If you all had an SBR lower and your core needs/wants are taken care off, what would you get? I know, this is a totally bourgeois angst "problem" but would still like some suggestions.

Thanks,

[fledge]

6.8 spc. Make it an SBR hog gun. 8.5, 10.5, 12.5, you pick.

[drtywk]

6.8 spc. Make it an SBR hog gun. 8.5, 10.5, 12.5, you pick.

This^^^! Keep in mind that 12.5" is the optimal barrel length for 6.8spc, per the testing that was conducted by a few .mil organizations. 12.5" maximizes the muzzle velocity in a semi-auto platform and also allows for greater expansion of the round.

[eodinert]

I'm kind of in the same boat, but I made a Mk18, because Mk18.

[drtywk]

Another idea would be a 10.4" HK416. Some of the early guns used LMT lowers.

[KTR03]

starting to lean towards a Mk 18. You guys thinking Daniel Defense or someone else?

D

[drtywk]

DD, but you may want to wait and see what Geissele's MK18 URG-I will look like and cost before you move forward. It should have the contract MK18 DD barrel, but it will come with the G Airborne Charging handle and MK18 sized MK16 rail. Some pics of the test guns are out there if you search for them.

[SteyrAUG]

starting to lean towards a Mk 18. You guys thinking Daniel Defense or someone else?

D

Look at the Colt 6945. When I began thinking about my Mk18 project that is where I ended up. Pretty much just added a SOPMOD stock and done.

[czgunner]

The 12.5” 6.8 SPC is a pretty great way to go.

[Achilles11B]

Another vote for 6.8 here. If it’s me,
I’d build a high-quality upper that would sit on the SBR’ed lower for HD purposes and use the 5.56 upper for training.

[ARx3]

Far right is my 6.8 SBR. 12.5" AR15 Performance barrel and bolt,SLR adjustable gas block, Larue Stealth Upper and handguard,Young Chrome NM bolt carrier,LMT lower.Geissele S3G trigger,Surefire FA762K suppressor,

[MistWolf]

Hey Gang,

So I have an odd situation - a problem that we should all want to have. I got a form 1 back from our ATF friends for an LMT lower. I had forgotten about it, and now get to decide what to build. Here is my issue: I have the following SBRs: ps90, 9mm AR, 300 BO AR, 5.56 AR, Sig 553, Sig 553R, Sig 551. So in terms of pistol calibers, sub calibers, and intermediate calibers, I am pretty much covered.

I was thinking I could do a 458 Socom, 50 beowolf or something like that, but I don't have a burning use for one of those. Was also thinking a Mk 18 would be cool. I could also do a 22LR, but that seems like a waste. If you all had an SBR lower and your core needs/wants are taken care off, what would you get? I know, this is a totally bourgeois angst "problem" but would still like some suggestions.

Thanks,

You're looking at this backwards. You shouldn't be asking what caliber to build. As long as the lower will accept the magazine, it can be the caliber of any upper you fit to it. Your real question is, what kind of lower should you build? Do you have a lower using a collapsing or folding stock to keep your SBR as short as possible? Do you want to fit it with special or ambidextrous controls? Is there a grip, trigger or stock you need or want?

Focus just on how you want the lower configured. Once it's put together, you can run almost any upper on it you want.

[eodinert]

starting to lean towards a Mk 18. You guys thinking Daniel Defense or someone else?

D

If you are making a Mk18, there is no one else but DD. Brownells has complete uppers, with proper sized gas ports and the all-important rail. For a 'true' MK18, you'd swap the DD upper for a colt (keeping the barrel and rail), but I forgot to do that on mine.

[ccosby]

I'd reconsider a 22 upper. Get a cmmg 4.5 inch 22lr barrel, put a rail over it, and put a 22 suppressor on the end. Get a better mag adapter and run smith and wesson m&p15-22 mags. Its a stupidly fun tiny combo.

https://imagizer.imageshack.com/v2/800x600q90/923/KvWUWW.jpg

[KTR03]

You're looking at this backwards. You shouldn't be asking what caliber to build. As long as the lower will accept the magazine, it can be the caliber of any upper you fit to it. Your real question is, what kind of lower should you build? Do you have a lower using a collapsing or folding stock to keep your SBR as short as possible? Do you want to fit it with special or ambidextrous controls? Is there a grip, trigger or stock you need or want?

Focus just on how you want the lower configured. Once it's put together, you can run almost any upper on it you want.I am asking about the upper because I already have lower configured the way I want it(ambi controls, soomod stock...). I was asking about calibers because thats what I want info about, whether you think kthat is backwards or not. Thanks for contributing to the thread.
In terms of the others thanks for the info.


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