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Mk12 Mod Dawg: Part Deux

mtdawg169

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The Hen that laid the Golden Legos
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Some time ago, I built up an SPR based on a genuine Mk12 Mod1 barrel. I wanted to use that specific barrel, but I never cared about making a correct clone of the Mk12. So, I decided to build out what I envisioned as an updated version with a more modern rail, and other modern improvements like the Vltor MUR, Vltor A5 buffer system, etc.

That gun can be seen here:
https://www.theoutdoorstrader.com/index.php?threads/1319982/

Shortly after finishing it, I added a Vortex Viper PST 4-16 with mrad reticle and adjustments. And more recently, I swapped out the rail for a slightly longer 16" Geissele. This is the gun in its current form:

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Initially, I was running it with my M4-2000. But I found that groups actually opened up with the can mounted. Screw that, right?! So last Summer, I bought a Silencerco Harvester to run a direct thread suppressor on this rifle.

I usually shoot Black Hills 5.56 77gr SMK (MK262) in this gun. The more I shot the rifle, the better it shot. Sub MOA was pretty typical.

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Recently, I decided to try out a Mk262 clone from CBC/Magtech. Mainly because it was 40% cheaper to shoot. So I ordered a case of it a few weeks ago. Range reports that I'd seen were pretty decent, so I thought that I'd give it a shot. This load uses the same 77gr SMK bullet at similar velocity.
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RANGE REPORT
Before shooting, I ran a patch down the bore with my Otis kit and MPro7 cleaner. Dry patch x2. Wet patch with Slip 2000 x2. I had not cleaned this rifle in a while and thought it might be a good idea before testing a new load. So let's get to it.

1st group of the day - Black Hills Mk262
Pulled one? I don't know, maybe I was a bit rusty.
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Previous examples using the same ammunition.
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2nd group - CBC/Magtech 5.56 77gr OTM
Ugh. Looks like it might be a long day. This one gave me some real worries about this new ammo. Did I mention that I bought a CASE?
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Three more groups of the Magtech. These are posted in the order they were fired.
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Now we seem to be getting somewhere. One thing I've always seen with this gun is that it shoots better as the bore becomes fouled and it has a few rounds through it after cleaning.

cmshoot cmshoot Thoughts on that?

One more group of Black Hills (2 total fired) This is pretty representative of a good group with that ammo. Sometimes I can squeeze out a 0.75 or better. But, 0.75-1.20 is a pretty good representation of that ammo in this gun and my sorry shooting skills.
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My last group of the day - Magtech
Pretty happy with that one.
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Summary: all in all, I think this is going to be a great substitute for the more expensive Black Hills version. Accuracy is on par and POI was very similar. A couple of clicks was all that was required to be back on zero.
 
Barrels are like women.......just cuz your old girlfriend performed best when handled a certain way doesn't mean the new girlfriend will handle the same under the same conditions.

Some barrels shoot better clean, some like some fouling in them, some don't seem to care one way or the other.

The last SWAT Sniper rifle I was issued was an HS Precision HTR-2000 with a 20" barrel. With a CCB, my POI was .5MOA low and .25MOA left from my CFB/HFB. If I cleaned her, shot 3 fouling shots, and put her up, she'd be dead nuts on next time I pulled her out. My current primary rifle shoots dead on whether she's hot, cold, clean or dirty. That's a little different from what you're talking about, but it shows a difference.
 
seems like your rifle likes to be dirty. Nice build, I'll finish my Mod 0 when I get back from shot. I love my Mod 1.
On a serious note, I'm going to experiment with this a bit. I'm going to keep shooting it to see when groups start to open back up. The only issue is that the chamber fouling from the suppressor can start to cause extraction issues. So at some point, I'll have to clean the chamber.
 
Have you tried shooting 69gr rounds? Mine seems to like them better.
Yes. But getting them in bulk for under a buck each is difficult. Mine definitely likes the 69gr SMK and the Hornady 55gr vmax. Both are capable of better accuracy than the Mk262. But for bulk purchases and the majority of my shooting, I usually shoot the 77gr due to cost.

I've got some Copper Creek 69 that is really good, but their lead times can be flaky. And I used to shoot ammo from another loader that was really popular on the Hide, but they basically imploded as a company because they couldn't deliver product. I had an order outstanding for 6 months, couldn't get a refund and eventually had to dispute the charge. Can't remember their name? (southwest)
 
Can't remember the last time I loaded my ammo, and I've got an upgraded Dillon 650 setup. I've got bullets, primers, powder, brass.........everything I need........except for TIME! LOL
 
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