Current Production Lightweight 11.5 or 12.5 Barrels?

**opngrnd** · 04-28-20, 14:50

Originally Posted by js8588

I was originally going to go with an 11.5 because I couldn't find a 12.5 chrome lined below ~$400 (Noveske or Hodge). The Criterion is interesting. No need to do an ammo test on my account, though I'm sure the rest of the internet wouldn't mind having the results.

You may have specified further up thread, but what buffer/carrier setup are you running with it?

Vltor A5H2/Green Sprinco, standard BCG. I'll test it out when I have a chance.

**CoGT3** · 04-28-20, 16:31

Originally Posted by themonk

I am interested how it shoots with heavier loads.

If work behaves, will hit the range Thursday. Don’t expect any super small groups, will be mounting a T2 on a Unity FAST mount to start. Will shoot some 10 rounds groups at 50 with BHA 50 TSX, Gold Dot 64 and 75gr, Federal LE223T3 62gr, BHA TMK, 77 SMK. Hopefully will have some pics to share soon.

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**hotrodder636** · 04-28-20, 18:36

Great, interested to see what your results are.

Originally Posted by CoGT3

If work behaves, will hit the range Thursday. Don’t expect any super small groups, will be mounting a T2 on a Unity FAST mount to start. Will shoot some 10 rounds groups at 50 with BHA 50 TSX, Gold Dot 64 and 75gr, Federal LE223T3 62gr, BHA TMK, 77 SMK. Hopefully will have some pics to share soon.

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**rainman** · 04-28-20, 19:42

Originally Posted by Biggy

My Hodge 12.5" inch barrels weigh exactly 21.5 ounces and my Criterion Core 12.5" barrel weighs exactly 22.8 ounces. Criterion had the 12.5 Core barrel's weight listed as 1.45 lbs or 23.2 oz's on their website. A .4 ounce difference from my accurate calibrated scale. I'm waiting on the redesigned BCM MK2 stripped uppers to come out to give these barrels a home. Bravo Co told me it would be later this year on the MK2 uppers, and that been a couple of months ago. I haven't pin gauged the gas port on my 12.5 Core barrel yet, but using what I had laying around, I am guessing it is between .066"-.067" ID

Any insight as to what drove the MK2 redesign (issues, etc.) and what changes BCM might be making?

-Rainman

**Biggy** · 04-28-20, 21:08

Originally Posted by rainman

Any insight as to what drove the MK2 redesign (issues, etc.) and what changes BCM might be making?

-Rainman

The Gen 1 BCM MK2 upper receiver was not compatable with most handguards with ant-rotational tabs, due to it being thicker in the front compared to the standard mil-spec dimensioned AR upper receiver. The handguard’s anti-rotation tabs wouldn't fit over the upper receiver. IMHO, it was in BCM best interests to either make a new upper receiver mold, or if possibly modify the original one. so that the MK2 Gen 2 upper fits every hand guard out there that would fit on a standard dimensioned AR upper. I imagine the Gen 2 MK2 upper will be a very small percentage less rigid than the Gen 1 MK2 upper, because it will have less material in those areas, but certainly not enough to matter.
Below are some Pic of two handguards that I modified to work with the BCM MK2 upper. The handguard's anti-rotational tabs to upper fit on both are perfect and look factory.

**rainman** · 04-29-20, 03:06

Originally Posted by Biggy

The Gen 1 BCM MK2 upper receiver was not compatable with most handguards with ant-rotational tabs, due to it being thicker in the front compared to the standard dimension AR upper receiver. The handguards anti-rotation tabs wouldn't fit over the upper. IMHO, it was in BCM best interests to either make a new upper receiver mold, or if possibly modify the original one. so that the MK2 Gen 2 upper fits every hand guard out there that would fit on a standard dimensioned AR upper. I imagine the Gen 2 MK2 upper will be a very small percentage less rigid than the Gen 1 MK2 upper, because it will have less material in those areas, but certainly not enough to matter.
Below are some Pics of two handguards that I modified to work with the BCM MK2 upper. The handguard's anti-rotational tabs to upper fit on both is perfect and the mods looks factory.

Thanks for the reply. I attempted a build with an early MK2 and found that the LaRue handguard would not fit. I completed the build with another upper and haven't tried the MK2 with any other handguards (Hmmm...haven't done a build in a while...need to do something about that!).

I read several reports in another M4C thread about 'handguard incompatibility' so would agree that if it applies to a significant number of handguards, then it would behoove BCM to redesign.

-Rainman

**CoGT3** · 05-11-20, 21:59

Finally got a break in the weather and work on the same day. Ran flawlessly as expected. Zeroed in nicely and shoot some decent groups at 50 yards just using unmagnified T2 red dot on a tall boi mount. Groups were shot at the end after at least 50 others, all suppressed. CORE barrel seems to do as advertised, tolerates heat and shifts weights toward the breech. The 6 groups where shot one after another, suppressed, without a break and groups did not open. Shoots well with heavy rounds also. Didn’t notice any problems with flyers. They where shot on a 1 shot/sec cadence. The 12.5 pistol weighs the same as my 10.5 SBR despite 2 more inches of barrel and rail. Balance point is 1/2” closer to magwell than my 10.5 SBR with same can, front sight, light, switch, and grip stop despite being pushed out 2” longer.

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