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Mk12 Mod 0 FINALLY.

gconnoyer

gconnoyer

Terminal Lance
Supporter
Full Member
Minuteman
Dec 19, 2017
382
423
St Louis, MO
If you’re a 100% cloner, I’m going to apologize now...

Like a shitload of people I love the look and idea/premise of the Mk12.
I built an 18” SPR 5 or so years ago with that Mk12 image in my head but once it was done I never really liked it much. Its just didnt do anything for me, barely liked shooting it. So I sold it.
Got really heavy into PRS style shooting and couldnt justify building another that would likely just sit around. So I just kind of lusted for the past few years.

Finally said fuck it and put one together. Its not 100% correct because I didnt want the shitty Leupold and ARMS rings, and didnt want the A2 grip. Just waiting on the crown for my AEM5 now.

I havent had a chance to actually print any groups or do any real load development, (just threw 24gr Varget under a 77smk) but Ive ran it out to 1000 without too much trouble, and 800 seems to be the realistic “effective range”. Zero trouble getting on a 2MOA plate there.
Movers from a barricade as fast as you want to go is super fun.

Glad I wasted the money on a gun that probably won't ever serve any purpose for me other than a fun gun.

PRI Mk12 Mod 0 Upper (7tw 556)
Premier 3-15 G2 Mildot
Badger Unimount
Geissele SSAE
Surefire RC2 (for now)
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Very cool rifle. I feel the same regarding making minor adjustments to make things more shootable. I have a Mod 1 clone, added a SF brake, JP SCS and went NF 4-16 on scope. I like it much better.
 
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BEJ762 said:
Very cool rifle. I feel the same regarding making minor adjustments to make things more shootable. I have a Mod 1 clone, added a SF brake, JP SCS and went NF 4-16 on scope. I like it much better.
Click to expand...

I figured atleast the premier was an issued optic, and badgers are wideley used so I didnt stray “too far”
 
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Great looking rifle, man. I love mine. I built one as close to true as I could. Shoots 77smk’s that I load nicely about 1/2-3/4 moa. The AEM5 approval was truly the icing on the cake.

What barrel did you use?
 
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mateofeo85 said:
Great looking rifle, man. I love mine. I built one as close to true as I could. Shoots 77smk’s that I load nicely about 1/2-3/4 moa. The AEM5 approval was truly the icing on the cake.

What barrel did you use?
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Its the Douglas barrel. I’m excited to print some groups or do load development and see how well it can shoot on paper
 
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gconnoyer said:
Its the Douglas barrel. I’m excited to print some groups or do load development and see how well it can shoot on paper
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Outstanding. Same Douglass on mine and it’s solid.

I’ve been loading with a 77smk over 24.1 Ramshot TAC, Lake City brass, and FederaL match primers. Loaded to mag length (2.26”). As usual, load up with caution and enjoy shooting it!
 
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Some good looking rifles. I have always liked the MK12ish builds. Like mentioned above. Modernizing them with better accessories and glass is really nice.

I did the same thing a couple years ago and like you, ended up selling it. But have regretted it ever since. Wish I had it back.
 
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Nice rifle. I have the Douglas barrel in my mod 1. Took a while to figure out what shot best in it, but it seems to really like the 77 TMK over XBR.

+1 on the 3-15 too. the 10x in the mk4 or x24 NXS wasn't enough mag for me to get what I wanted from the rifle.

uCG87er.jpg
 
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Clocked my 24gr Varget /77smk load last weekend. Consistent enough but a but slow. Going to cram some more in and test, then swap to some different powders I suppose.

I’d love to be in the 2750ish range
 

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I use 24.1 N140 with the 77 SMK. I get 2640 FPS from a 18” barrel. Average .6 moa and not as compressed as the Varget load.
 
Probably a good idea to go through and torque the (many) screws on that. I think every threaded fastener except the barrel nut on my factory PRI came loose relatively quickly. Individual part quality was very nice, but assembly seemed to have been hurried.

Steel head said:
8208XBR is your friend.
23-24 grains in LC brass and #450’s
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This or TAC. 23.4 gr XBR or 24.3gr TAC were my loads with the 77 SMK at mag length.
 
gconnoyer said:
Clocked my 24gr Varget /77smk load last weekend. Consistent enough but a but slow. Going to cram some more in and test, then swap to some different powders I suppose.

I’d love to be in the 2750ish range
Click to expand...

I may have missed what powder you’re using, but give RL-15 and/or TAC a try. Like a few have stated along with my experience, TAC gives me velocity in the range you’re looking for without dangerous pressure signs. Shooting 77smk suppressed through the AEM5, I’m in the 2,750 ballpark with 24.1-24.3ish grains of TAC (sorry, I don’t have my load data in front of me). Keep it up man; once you get that good load, it makes the Mk12 so much fun to shoot.
 
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shlouf said:
Nice rifle. I have the Douglas barrel in my mod 1. Took a while to figure out what shot best in it, but it seems to really like the 77 TMK over XBR.

+1 on the 3-15 too. the 10x in the mk4 or x24 NXS wasn't enough mag for me to get what I wanted from the rifle.

View attachment 7341721
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Any tips or tricks that you use to keep the can tight? It seems like mine is always coming loose after very few rounds.
 
Snaz said:
Any tips or tricks that you use to keep the can tight? It seems like mine is always coming loose after very few rounds.
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Don't get stupid with it, but snug it down tighter maybe? I have never had my aem5 come loose on my mod 1 or mod h. Both have 7-8 turns to hit the shoulder.
 
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shlouf said:
Don't get stupid with it, but snug it down tighter maybe? I have never had my aem5 come loose on my mod 1 or mod h. Both have 7-8 turns to hit the shoulder.
Click to expand...

Gotcha, appreciate the response. All of my other cans are quick detach, so this is my first w/thread attachment. I'll try tightening a little tighter and see if that helps. I'm getting about a 1/4- 1/2 turn every mag.

And the big thing is mine is a form 1 w/a Ops clone mount in ASR Bravo threading. There's a very good chance that is a very big part of it.
 
gconnoyer said:
Clocked my 24gr Varget /77smk load last weekend. Consistent enough but a but slow. Going to cram some more in and test, then swap to some different powders I suppose.

I’d love to be in the 2750ish range
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I resurrected this thread because I love gconnoyers build. Here’s my not clone correct Mod 0.
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mgrs said:
Probably a good idea to go through and torque the (many) screws on that. I think every threaded fastener except the barrel nut on my factory PRI came loose relatively quickly. Individual part quality was very nice, but assembly seemed to have been hurried.



This or TAC. 23.4 gr XBR or 24.3gr TAC were my loads with the 77 SMK at mag length.
Click to expand...

I actually read somewhere about this with someones MK12 so I did do that. Everything was tight but definitely peace of mind doing it and double checking.
 
MARLINLEVER said:
So what loads have you tried and what speeds are you getting?
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Actually went through with some random powders guys usually use for lighter bullets (just to try out in the current powder situation) and 8208XBR.
8208 SHIT on everyone as far as velocity goes. I got 2850 with 77s but it was definitely leaving some "imperfections" on the brass lol.

Really just waiting for my AEM to get out of jail and for some warmer temps to finalize a load for it.
 
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gconnoyer said:
Actually went through with some random powders guys usually use for lighter bullets (just to try out in the current powder situation) and 8208XBR.
8208 SHIT on everyone as far as velocity goes. I got 2850 with 77s but it was definitely leaving some "imperfections" on the brass lol.

Really just waiting for my AEM to get out of jail and for some warmer temps to finalize a load for it.
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What charge are you running? I'm getting 2850 out of my 22" barrel AR and it is a good bit heavier than most people are running at 24.2 gr. You running 18" barrel?
 
tylerradke said:
What charge are you running? I'm getting 2850 out of my 22" barrel AR and it is a good bit heavier than most people are running at 24.2 gr. You running 18" barrel?
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Yeah, 18" but the 2850 was a pretty healthy dose of 8208XBR. Not something I would normally run lol
 
gconnoyer said:
Yeah, 18" but the 2850 was a pretty healthy dose of 8208XBR. Not something I would normally run lol
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Thats wicked. I had pierced primers when I got to 2900 with the 22" barrel. Brass was still ok just very slight marks on it. That was at 24.5 gr. 8208xbr. I absolutely love that powder though. I'm under 20 on ES with it and single digit SD. It's hard to have a bad load with the stuff.
 
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mrbedgood said:
Wow new to the site and thankfully this is the thread that first came up for me. I just finished my first Mk12 mod 0. Even have a spare ARMS SPR MOD 1 I’m looking to sell.
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No selling outside the px. No selling for non supporter members as well.

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Our Membership makes the forum, so understand that not all members have the same level of seniority. Best practice is to learn the dynamics of our community before jumping in with both feet. 2021 Sniper’s Hide Forum Rules Welcome to Sniper’s Hide 2021, a site for the serious tactical marksman...
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camocorvette said:
No selling outside the px. No selling for non supporter members as well.

www.snipershide.com

2021 Sniper's Hide Forum Rules

Our Membership makes the forum, so understand that not all members have the same level of seniority. Best practice is to learn the dynamics of our community before jumping in with both feet. 2021 Sniper’s Hide Forum Rules Welcome to Sniper’s Hide 2021, a site for the serious tactical marksman...
www.snipershide.com www.snipershide.com
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Not trying to sell outside px. Just making statement.
 
smoothy8500 said:
Like "girlfriend experience" and "200 roses" in the same sentence is just a statement? True, you didn't mention price nor inform anyone to contact you via private message...... But we can read between the lines. Maybe edit/delete the "statement".
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yup lol
 
FINALLY got the AEM5 out of jail and got it painted to match as best I could (without redoing the whole rifle)
Ditched the Harris for an Atlas PSR. The harris just sucks in comparison and is way less "streamlined" with a pic to sling swivel adapter.
Since I couldnt afford a KAC Mk11 adjustable stock, I added a flush cup to the rear so I could sling it for shooting gas gun matches (and because all rifles need a sling)

Have done a little load development with the AEM on it to atleast get it good enough for what I do with the gun. Nothing close to bolt gun performance, but I'm getting factory second 77smks for dirt cheap and I doubt its going to matter much how much tuning I do. The base to Ogive on them varies .060-.080 so its never going to be a tack driver.

Using 8208 XBR, Starline brass, CCI450s, bulk 77s getting really good velocity. Not much for pressure other than an extremely light ejector mark, primers still look excellent. 23.6 and 23.8gr shoot great, but I'll probably stick with the lighter charge just so I've got room from pressure as it heats up and if I end up shooting in the rain.
I found a bag of starline I had loaded with CCI41s and interestingly enough that same 23.6 load only shot right around 2700.

Anyway, little update for anyone that cares lol
AEM sounds fantastic and EVERY single MK12 needs one. I even bought an Otter Creek over the barrel adapter so I can run it on any other compatible setups.
 

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Looks good. Let us know how the paint on aem holds up. I haven’t painted mine yet but eventually I’ll talk myself into it.
 
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mheimer_45 said:
Looks good. Let us know how the paint on aem holds up. I haven’t painted mine yet but eventually I’ll talk myself into it.
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Oh it wont hold up well if it gets hot. Its just regular ol Krylon. But I dont care, the more worn the cooler it looks
 
gconnoyer said:
Oh it wont hold up well if it gets hot. Its just regular ol Krylon. But I dont care, the more worn the cooler it looks
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I’ve always read the paint turns grey after awhile. I’ve thought about a woodland cover but haven’t found one I liked.
 
I built mine "clone ish" using a Seekins upper and lower and a Rainier Supermatch barrel. I tried to like the PRI foreend but just couldnt....so I swapped it to a midwest 15" T-rail.
 
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