Overgassed MK12 Mod1 Issues

**John Moses** · 31 January 2016, 21:08

Hey guys, I am wondering if anyone has any suggestion for an overgassed MK12, namely suggestions for a heavier buffer, or spring set up.
I have an issue with the Bolt over running the catch on the last round.(failure to stay open) This only happens on the last round, and usually with a 20 round PMAG while suppressed. I have a clone, 18" White Oak Rifle gas , FA BCG (LMT) , and the AEM5 can. I am running a standard Rifle buffer, spring, and A2. Everything is accurate for a clone, except the WO barrel. My gut tells me their gas port is a little hot compared to the Centurion, or the Douglas, but I have not measured it.

Here is what I have tried: NON-suppressed , no issues. Suppressed I have thrown it on a SBR lower with a Springco Green, and the 5 oz VLTOR A5. That will lock back most of the time with a 30 round P-mag bu not the 20 round.

I have spoken to Ron Allen at Ops/Allen Engineering who suggested an adjustable gas key. Before I do that I was hoping to find a heavier buffer/spring combo, as I really want to keep the Clone alive so to speak. I have seen 10 oz Buffers from Heavy Buffers inc, the Hydro (KYNshot), and JP silent capture. Has anyone used these? While there are tons of CAR buffers , there just aren't that many options in a rifle length. I know an adjustable gas block would solve everything, but I want to (again) keep the clone alive. Thanks for any suggestions/input.

**UWone77** · 31 January 2016, 22:05

Adjustable Gas Block out of the question?

**John Moses** · 31 January 2016, 23:09

Originally Posted by UWone77

Adjustable Gas Block out of the question?

No, but it's a stupid clone thing, and having it look original. Pretty lame, but the MK12 Mod1 uses a slightly different shaped gas block that protrudes outside the rail, so it will stick out like a sore thumb. I run the SLR Sentry on a couple Suppressed SBR's and they are great. I just took apart a couple buffers and added weight to the rifle buffer by swapping the spacer for a tugnsten rod. I have it up to 6.3 OZ, so I will try that tomorrow at the range. I'm being a real nerd on this, and I really know the adjustable gas block is the answer, but its just one of those things that drives you nuts. The MK12 was made with a .100- .105" gas port to make sure it ran Full auto with the rifle length gas system. Needless to say, the buffer is really zinging, and I'd like to smooth it out. I run it suppressed 100% of the time, so I may just have a barrel made with a smaller gas port. I wish someone made an adjustable gas block that was dimensionally the same as the KAC, but with an adjuster on the backside....then it would look correct, and still allow a hidden adjuster. . .

**Slippers** · 1 February 2016, 01:34

How about one of the gas port inserts from black river tactical?

**Former11B** · 1 February 2016, 05:48

How about a Gemtech suppressor BCG? Stay in line with the clone externally, but gas adjustment internally, and leave the reciprocating mass the same.

**Slippers** · 1 February 2016, 05:49

Originally Posted by Former11B

How about a Gemtech suppressor BCG? Stay in line with the clone externally, but gas adjustment internally, and leave the reciprocating mass the same.

I think voodoo has one of those, and likes it. See if he'll chime in.

**schambers** · 1 February 2016, 06:17

I use a 10oz heavy buffer from Slash (heavybuffers.com) on my rifle length MWS and it does what its advertised to do. He specs his buffer for standard power springs (at least on the 308 rifle length platform) so you're not locked into some weird proprietary spring format.

Slash's stuff is well made too, so that's a plus.

**voodoo_man** · 1 February 2016, 06:24

Originally Posted by Slippers

I think voodoo has one of those, and likes it. See if he'll chime in.

yes.

buy one.

its magic.

solves all suppressed DI problems.

wow.

edit; photos because awesome

**Slippers** · 1 February 2016, 06:46

I just received the LMT enhanced carrier, and now I want one of those. Never ends....

**UWone77** · 1 February 2016, 08:52

Originally Posted by Slippers

I just received the LMT enhanced carrier, and now I want one of those. Never ends....

Ha! I was going to buy one of those Gemtech carriers until Rainier Ran out. It does never end!

**voodoo_man** · 1 February 2016, 10:21

Originally Posted by UWone77

Ha! I was going to buy one of those Gemtech carriers until Rainier Ran out. It does never end!

Oh you want one? Guess i should make sure that doesnt happen.....

**John Moses** · 1 February 2016, 10:31

I just ordered a Rubber City adjustable Gas key. From what my contact at Crane says, they work well. I also added a weight to the standard buffer to get it to 6.3 oz, and have the Wolff XP spring coming. The HX buffer from Heavy Buffers is my next option. I appreciate the suggestions, and i will let you know how this works. The E Carrier works well, but the bolt is not so good (LMT) from what I have heard(but never tried myself). Also I run the Gas port vent that replaces the Forward Assist, and those also work very well. The Black River Tactical is exactly what I had going on in my head, and I may try one just to try it..........great advice, and not one condescending remark! That's why I like WE

**mtdawg169** · 2 February 2016, 11:54

I've got a High Caliber Mk12 barreled rifle (Not a clone). They have a Crane spec, 0.100 port and still seem to run a little hot. Mine is set up with an LMT enhanced carrier & Vltor A5. I'd have to check to see if it's got the H2 or H3. I had some similar issues, but it was always with older 20 round Pmags. I've just about chalked it up to the mags. They were a known problem a few years ago.

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