First, congrats OP!

Meanwhile, I know it may look like I up and "hate quit" the thread, but I've just been a little busy lately and haven't popped into the Piston forum as much.



I don't work at Sig, so there's only so much I can say (and my only Virtus-pattern gun is a Rattler upper, my MCX is a Legacy gun).

What I can say is... they're out there. Beyond that, my personal opinion is that they (the MCX) have been much better at winning special purpose contracts that would perhaps be more difficult in a "traditional" AR format (Rattler/PDW, SURG, LVAW, etc.) than as a GP weapon system, and while some units may have the option (they do) of messing with 5.56 barrel swaps and the like, I don't know that I necessarily see it gaining any sort of "widespread adoption" (I wouldn't say that the 416 did until the M27 either--there's a question of both numbers and GPF vs. SOF, at least insofar as US DoD if that gives some perspective) or replacing the M4A1/CQBR/MK 18 wholesale.

If anything, I'd look at where the SCAR program is: the clear winner has been the 7.62 variant, with the MK 16 more or less being dropped--however, the MK 17 still has a 5.56 conversion capability which pops up here and there and still gets used--not just in training, but operationally as well, but it certainly didn't ever "replace" M4A1-based weapons.

As I mentioned in my PM, it's been a few years since I looked at available vendors for this kind of work, and at that time, Jayson at IGF was still being highly recommended, and not stealing guns, so... there's that. I also have a barrel left that was pinned and welded by Randall at AR15barrels.com, so take that under advisement, hahaha...

I do understand ADCO has begun doing this kind of work, and Marvin Pitts would definitely be one of my first stops as well, though I don't really know what anyone is charging these days for this work--only that there are folks out there that can do it.

If you're a purist, Tom Bostic and other folks that cater to HK fandom will be able to replicate the exact profile of the HK416's barrel with all the weird cuts and all that that's involved, but tend to be more expensive based on again, catering to the fandom first and foremost. If you just want the barrel reprofiled to be lighter and shorter, it may be a little bit cheaper/easier--again, I don't know how much you want to "clone" and how much you just want a good, practical carbine, and I'm certainly not mocking the "clone" thing, but I had the benefit of having a machinist friend who doesn't do this full time, but has worked on a lot of HK barrels and was able to get a 14.5" 416 barrel to measure to replicate the profile correctly--and even then, I had him cut the profile under the handguards to match the "lightweight" profile, not the heavier "SOCOM" HK416 HBAR profile that most 14.5" barrels and early 10.4" barrels have.

Another option is simply to buy one of the Marvin Pitts or Brownell's 416-pattern barrels and rebarrel it completely and either sell or hold on to the original MR556 barrel for now, though at that point you're obviously not getting the proprietary HK barrel steel. The Geissele barrel nut wrench works on the HK416/MR556 barrel nut, as Geissele barrel nuts were based on the HK416's (the HK416 SMR was the first handguard they built, and the original MK1s were basically an AR15 version of that), and IIRC, the torque spec is somewhere between 81-82 foot pounds (the factory spec is metric ) and again, there are folks that can do the work if you don't want to do it yourself.

Again, my inclination would be to contact Marvin Pitts first, as he both does excellent work (I have barrels that he's done, though no HK barrels at this time) and is usually fairly affordable--and if he can't do it, he can probably recommend you someone that could, and I know he's been pretty deep into HK barrels lately making his own in-house with HK416 barrel extensions.

~Augee