MK12 Build Questions

[viper42]

Hey guys,

I’m wanting to start an MK12 clone build. Looking for direction on how to make the most accurate rifle I can.

Looking for recommendations on barrel mfg.

Looking for direction on what action, bcg, hold tighter tolerances and accuracy.

Any specifics on gas operating system.

Any other recommendations on tips for accuracy during the build. Kinda a newbie here.

Appreciate it!

 

[GhostFace]

Mod 0 get with Precision Reflex, nuff said.

Mod 1 is going to be difficult and costly because of the rail system. I'm fond of Mod 1 myself. Get with MSTN or Charlie's custom for a mod 1 if you don't want to piece the parts yourself.

Or you could do your own take on a "Mod 2" so to speak and go with a modern rail. I did that back in '05 and went a continuous picatinny top quad rail. I don't regret it and I still have the rifle.

 

[viper42]

Mod 0 get with Precision Reflex, nuff said.

Mod 1 is going to be difficult and costly because of the rail system. I'm fond of Mod 1 myself. Get with MSTN or Charlie's custom for a mod 1 if you don't want to piece the parts yourself.

Or you could do your own take on a "Mod 2" so to speak and go with a modern rail. I did that back in '05 and went a continuous picatinny top quad rail. I don't regret it and I still have the rifle.

I didn’t see any kind of guaranteed accuracy or mentioning on their website. What kind of groups do these guns shoot? I’m trying to build a gun that can hold 1/2 moa at 100 yds with hand loads.

 

[FredHammer]

I didn’t see any kind of guaranteed accuracy or mentioning on their website. What kind of groups do these guns shoot? I’m trying to build a gun that can hold 1/2 moa at 100 yds with hand loads.

LOL. How many rounds for that 1/2 MOA? This is pivotal information. Trust me.

 

[viper42]

LOL. How many rounds for that 1/2 MOA? This is pivotal information. Trust me.

Lol I’d prefer 5 shots, but 3 could work…

 

[nn8734]

Lol I’d prefer 5 shots, but 3 could work…

Grab a Douglas MK12 bbl (1:7 rht) from either PRI or CLE or whomever has one avail. That is the only barrel that would be considered correct to my knowledge and the most precise barrel for the mk12. If you assemble it correctly, you wont need any stupid accuracy guarantee. Besides, its up to you to be accurate (hitting what you're aiming at).

 

[FredHammer]

Lol I’d prefer 5 shots, but 3 could work…

Damn. Don’t make it too easy on them! I build uppers that ring .5MOA with 10 shots and .8ish MOA with 20 shots. I’m told any Nancy can do 5 shots .25MOA. I’ll agree.

 

[viper42]

Damn. Don’t make it too easy on them! I build uppers that ring .5MOA with 10 shots and .8ish MOA with 20 shots. I’m told any Nancy can do 5 shots .25MOA. I’ll agree.

Curious on details of builds that can hold 1/2 moa with 10 shots? Still trying to understand what makes these gun accurate other than the barrel? I’m assuming closer tolerances with more precise machine work.

 

[jzerfoss]

Curious on details of builds that can hold 1/2 moa with 10 shots? Still trying to understand what makes these gun accurate other than the barrel? I’m assuming closer tolerances with more precise machine work.

He's being a troll...

 

[viper42]

Grab a Douglas MK12 bbl (1:7 rht) from either PRI or CLE or whomever has one avail. That is the only barrel that would be considered correct to my knowledge and the most precise barrel for the mk12. If you assemble it correctly, you wont need any stupid accuracy guarantee. Besides, its up to you to be accurate (hitting what you're aiming at).

So that is the correct for the build. I’ve thought about shilen, Krieger, etc. thinking they would be more accurate than the Douglas. Is there anything else specific about Douglas other than it’s the original for the mk12 that makes it more desirable?

 

[sinister]

Douglas was and still is a go-to barrel blank manufacturer who produces very good, consistent barrels in quantity -- why many military project rifles (service team M1s, M14s, M16s, DMRs, SPRs, etc) and some benchresters use their air-gaged match blanks.

Tell them you want 500 air-gaged match barrel blanks and send them a check or purchase order.

Lots of other barrel makers out there -- not sure how many offer air-gaging and large lots capable of holding consistent precision.

As an individual it makes sense to pay a little more for a cut-rifled blank -- but if you're outfitting a larger number of guns you'll probably have to wait.

 

[viper42]

Douglas was and still is a go-to barrel blank manufacturer who produces very good, consistent barrels in quantity -- why many military project rifles (service team M1s, M14s, M16s, DMRs, SPRs, etc) and some benchresters use their air-gaged match blanks.

Tell them you want 500 air-gaged match barrel blanks and send them a check or purchase order.

Lots of other barrel makers out there -- not sure how many offer air-gaging and large lots capable of holding consistent precision.

As an individual it makes sense to pay a little more for a cut-rifled blank -- but if you're outfitting a larger number of guns you'll probably have to wait.

Appreciate that. I’ll look into Douglas.

 

[nn8734]

So that is the correct for the build. I’ve thought about shilen, Krieger, etc. thinking they would be more accurate than the Douglas. Is there anything else specific about Douglas other than it’s the original for the mk12 that makes it more desirable?

Any barrels from those others will work just as well....you really start splitting hairs when it comes to trying to determine what's "best" amongst them. So id go with whatever your preference is if having the correct bbl isnt super important for you. But id personally go Douglass for your mk12

 

[FredHammer]

He's being a troll...

I guess we haven't met yet.

 

[FredHammer]

Curious on details of builds that can hold 1/2 moa with 10 shots? Still trying to understand what makes these gun accurate other than the barrel? I’m assuming closer tolerances with more precise machine work.

Aero Precision and Ballistic Advantage. Let the arrow be straight, but the indian even straighter...

 

[LRRPF52]

Which Mk.12 are you looking to clone and is clone more important to you that practicality?

There were the prototype SPR uppers. Then there were at least 6 basic frames with specific core parts for the different Mk.12s:

1. Mk.12 Mod 0 with PRI tube, PRI rail, ARMS flip-up rear, PRI flip-up front sight/gas block, M16A1 lower receiver and Type E buttstock, KAC 2-stage trigger. Parts list here.

I saw no less than 2 different types of ARMS Swan sleeve-style rails used on these, one of which had a PEQ-2A interface up front at 12 o’clock to mount the PEQ-2 LAM. The other had a straight Mil-Std 1913 rail that was continuous from rear to the front end that is better for Clip-On TWS. Straight 1913 in background, PEQ-2 model in foreground:

2. Mk.12 Mod 0 with all of the above (PEQ-2 ARMS rail option) but telescoping stock or M4A1 lower:

3. Mk.12 Mod 1/M16A1 Lower:

Mk.12 Mod 1/M16A2 lower:

4. Mk.12 Mod 1/telestock lower:

Mk.12 Mod H (16” barrel):

6. Mk.12 Mod H rifle stock:

 

[sinister]

The USAMU buys barrel blanks from A LOT of good barrel makers. The problem they run into is not many want to block off what could be a big chunk of their annual production to a single buyer.

Many buyers get cranky when they can't source the same items Uncle Sam and his allies buy because of contract demands.

 

[LRRPF52]

I like these, and the predecessors for all the Mk.12s even better (modified 723s with float tubes and sleeved-over Ops Inc Suppressors).

 

[sinister]

SLR Rifleworks now makes a free-float "SD" rail with a larger diameter front end that wraps around the suppressor

 

[VJJPunisher]

White oak or lick a fat lady’s ballsack

 

[FredHammer]

I like these, and the predecessors for all the Mk.12s even better (modified 723s with float tubes and sleeved-over Ops Inc Suppressors).

Muther Phuck that is a sexy bitch!

 

[redneckbmxer24]

I've have numerous 1/2moa gas guns, some factory some not. A top shelf barrel attached to a thick walled upper ideally with a handguard that doesn't clamps to the barrel nut is going to be your best bet but that's obviously not possible if you're sticking to a MK12 clone.

Personally I'd just buy a PRI. I've had a few and they all shot ragged holes. They have just as much of a possibility of being a sub 1/2moa gun or not than one put together by anyone else with another barrel.

 

[Oakland Tactical]

We have had sold multiple rifles from PRI. My employees own 6 between them, we have shot them side by side with every precision AR out there. If you get the Douglas barrels they will shoot better or at least as good as anything else. You dont see a difference between them and my personal High Caliber Sales upper in accuracy.

 

[LRRPF52]

Big questions people need to answer for themselves when going this route are:

1. Is a clone the most important focus? If so, am I willing or able to:
a) address both the cost of some unique parts (KAC FF RAS, unique ARMS rails, small parts)
b) go with older ARMS QD rings vs modern rings?
c) still have money left for the suppressor and optics

2. Do I want the ability to clip-on thermal in front of the day optic for hunting/night shooting?

This can be done with the Mod 0 with ARMS 38 SPR Top Rail, non PEQ-2 option, the Mk.12 Mod 1 with KAC FF RAS, and the Mod H depending on scope height/Clip-On base height for optical alignment between the day and clip-on tubes.

3. Do I want compactness for maneuverability or do I prefer more of a range and tripod precision carbine?

For a compact direction, the telestock variants are the way to go obviously, with the LMT SOPMOD being the most common stock for that. The most compact overall length option among the Mk.12s/SPRs is the Mod H with a telestock, since they have 16” pipes vs 18”.

I’m more of a fan of the pre-SPR JSOC and USASOC Sniper carbines since they don’t really sacrifice compactness, and still deliver all the precision you will need with correct barrel sourcing. They had shorter gas systems though, which don’t run as smooth as a RLGS SPR, but it’s 5.56 so not really an issue when dialed-in with the suppressor.

From prone and other supported positions, I’ve found the RLGS 16” and 18” suppressed SPR variants to be one of the smoothest and pleasant shooting experiences you will ever have, so there is a lot more merit to the performance of these weapons even when you go full clone correct.

Best thing to do is buy your Allen Engineering suppressor now, get it transferred to your dealer, and start the infringements with GayTF paperwork. That’s your biggest bottleneck after the KAC RAS if you’re going Mod 1 route.

Another thing to consider is the Mil-Std conformance of your critical core parts, namely the BCG, barrel extension, and LPK. You don’t want one of these modern nitrided BCGs with loose tri-bore dimensions, a run-of-the mill bolt, and weird parts imported from some place in the Pacific. Get Colt or FN parts for durability and a set of TDP compliance on them, although I’m not a fan of the High Pressure Test requirement on the bolt.

 

[viper42]

Aero Precision and Ballistic Advantage. Let the arrow be straight, but the indian even straighter...

I was looking at mega lower and mega GTR-3H AMBI receiver.

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[roostercogburn98]

I was looking at mega lower and mega GTR-3H AMBI receiver.

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I’m happy with my mega set