Masterpiece Arms 6mmCM has arrived

vanfunk

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The widening gyre
My payment (sent by USPS priority mail) took 8 days to travel 1100 miles to its destination, but arrive it did. The selling FFL had my prize boxed up and on its way to me by 11AM that day (amazing!) and I picked it up at my LGS this morning. Well the description of “LNIB” certainly wasn’t deceptive; this thing is clean as a whistle and not an errant mark anywhere. Ok, one corner of the adhesive barrel temperature strip is lifted up ever so slightly, so there’s that disappointment. Otherwise, the rifle is brand-new. I took off the monopod and installed the bag rider instead, and mounted the Sightron S6 5-30x in Burris Zee rings. I spun the Hellfire muzzle brake on and heard a collective groan from the range buddies who will be shooting next to me at the range. I had a Harris bipod around so that found its way on there. Done for now but I think I’ll probably replace the pistol grip with something more vertical than the A2 grip that’s on there.

The Triggertech trigger is breaking at a pound and a half and is oh so crisp with a teeny-weeny bit of overtravel. I’m very glad this takes AICS magazines as I have a pile from my AR-10. I have a small assortment of factory loads to try out and am not yet set up to reload for 6mmCM so I have to take that on. Snow storm’s on its way tomorrow afternoon so this new rig will have to wait a little bit to get sighted in, bummer. Man, this is nice. Obviously there are nicer precision rifles out there but I feel like I got a LOT of value for $1700. Happy, happy, joy, joy!

Oh, does anyone know how to tell what receiver this is? I didn’t take the barreled action out of the chassis to see if there are any identifying maker’s marks but there’s nothing up top other than the MPA stuff and the serial #.

Thanks!

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My payment (sent by USPS priority mail) took 8 days to travel 1100 miles to its destination, but arrive it did. The selling FFL had my prize boxed up and on its way to me by 11AM that day (amazing!) and I picked it up at my LGS this morning. Well the description of “LNIB” certainly wasn’t deceptive; this thing is clean as a whistle and not an errant mark anywhere. Ok, one corner of the adhesive barrel temperature strip is lifted up ever so slightly, so there’s that disappointment. Otherwise, the rifle is brand-new. I took off the monopod and installed the bag rider instead, and mounted the Sightron S6 5-30x in Burris Zee rings. I spun the Hellfire muzzle brake on and heard a collective groan from the range buddies who will be shooting next to me at the range. I had a Harris bipod around so that found its way on there. Done for now but I think I’ll probably replace the pistol grip with something more vertical than the A2 grip that’s on there.

The Triggertech trigger is breaking at a pound and a half and is oh so crisp with a teeny-weeny bit of overtravel. I’m very glad this takes AICS magazines as I have a pile from my AR-10. I have a small assortment of factory loads to try out and am not yet set up to reload for 6mmCM so I have to take that on. Snow storm’s on its way tomorrow afternoon so this new rig will have to wait a little bit to get sighted in, bummer. Man, this is nice. Obviously there are nicer precision rifles out there but I feel like I got a LOT of value for $1700. Happy, happy, joy, joy!

Oh, does anyone know how to tell what receiver this is? I didn’t take the barreled action out of the chassis to see if there are any identifying maker’s marks but there’s nothing up top other than the MPA stuff and the serial #.

Thanks!

View attachment 1246675

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View attachment 1246677
From their website, they use an MPA action (arc coup de grace)
 
From their website, they use an MPA action (arc coup de grace)

The new MPA PMR's use American Rifle Company Coup de Grace actions. The older versions used Curtis Axioms. Not all of the Axioms used in MPA rifles accept prefit barrels - yours has an "MPA" serial number, which means it's one of the "Curtis MPA" actions, which (to my knowledge) take the same prefit barrels as the late-model Axioms (MPA and AO serial numbers = prefit compatible, AXS = no go).

I’m very glad this takes AICS magazines as I have a pile from my AR-10.

AICS mags are not AR-10 mags. AR-10's don't take AICS mags.
 
Whoops, I thought I had the mags straight, lol. What are these magazines, then?

That’s what I was hoping to hear about the prefits as I’ll probably need a new one by the end of the summer if I get to shoot this as much as I want.

Thank you!
 
Whoops, I thought I had the mags straight, lol. What are these magazines, then?

AICS footprint magazines are a (relatively) standardized bolt action rifle magazine format. They were originally produced by Accuracy International for their Acc. Int. Chassis System - hence AICS, but have now become the industry standard for short action bolt action rifle magazines (there ARE long action and CIP length AICS footprints as well, but less broadly standardized).

MDT makes phenomenal AICS pattern magazines, I prefer their 12 round mags. Magpul polymer AICS footprint mags absolutely suck. If your Axiom is cut for AW mags, which also fit the same AICS magwell, that’s another fantastic option, although you may want or need the adjustable mag catch from MPA to use them (AW 10 round mags are much shorter than AICS 10 round mags, almost the same length as AICS 5 round mags).
 
I’ve (carefully!) hand cycled rounds through the action with my Magpul magazines, whatever they are (use ‘em in my Daniel Defense DD5 AR-10) and they feed perfectly, thankfully. I’m not a huge fan of plastic magazines but in the absence of a problem, there is no problem.

Now I am getting all worried about barrel twist; this rifle has a 1/8” twist and I’m now concerned that it may not properly stabilize the 108’s and 115’s that are now out there fir the caliber. Will I need to stick to 105’s and below until I can rebarrel with a 1/7.5” or 1/7” twist?

Thanks!!!
 
I’ve (carefully!) hand cycled rounds through the action with my Magpul magazines, whatever they are (use ‘em in my Daniel Defense DD5 AR-10) and they feed perfectly, thankfully. I’m not a huge fan of plastic magazines but in the absence of a problem, there is no problem.

Now I am getting all worried about barrel twist; this rifle has a 1/8” twist and I’m now concerned that it may not properly stabilize the 108’s and 115’s that are now out there fir the caliber. Will I need to stick to 105’s and below until I can rebarrel with a 1/7.5” or 1/7” twist?

Thanks!!!
I'd get on jbm bullet length list and jbm stability calculator and punch in some numbers for sure if i were in your shoes, but instinctively, I'm thinking 1:8 should be good to go.
 
Thanks! That stability calculator has bullets greater than 105 grains (well, it’s length that’s the issue but in these instances the heavier bullets are the longest) to be “marginally” stabilized at typical 6mmCM velocities. Hmmm. I guess the only way to know for sure is to try them. I don’t think I need 115’s but I sure would like to shoot 108’s and 109’s accurately and at distance.
 
I’ve (carefully!) hand cycled rounds through the action with my Magpul magazines, whatever they are (use ‘em in my Daniel Defense DD5 AR-10) and they feed perfectly

Post a pic of these magazines, because this doesn't make sense.

Something is very, very wrong if AR-10 mags are fitting into an AICS magwell in an MPA BA chassis and very, very, VERY wrong if they are locking in. Frankly, there is just no way this is possible.

This is a Magpul AR-10/LFAR magazine which is what Daniel Defense sells with their DD5 rifles. You can see on the side of the magazine, top right in our view here, the magazine catch recess, corresponding to the side mounted magazine catch in AR pattern firearms.
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This is an AICS pattern Magpul polymer mag. You can see that there is NO mag catch notch in the side of this magazine, because the mag catch is on the rear spine of AICS magazines, corresponding to the mag catch lever on the front of the trigger guard in bolt action rifles with AICS magwells, such as the MPA chassis.
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I can't get any AR-10 magazine to even begin inserting into my Masterpiece Arms chassis - or any of my other AICS bottom metal on other rifles. The thickness of the AR mag is too wide at the rear to allow insertion. And of course, even if the magwell WERE machined oversized, there no side latch which would lock an AR-10 mag into the MPA BA chassis.

*The only exception I am aware of to this incompatibility in market currently is the Ruger Precision Rifle which includes a dual mag catch design which includes an oversized magazine well, and employs the standard bolt action mag catch in the rear of the trigger guard, for AICS pattern magazines, plus a pivoting side mag catch for SR-25/AR-10 magazines, which is activated by the standard mag catch lever.
 
@vanfunk - the mag you have pictured above inserted into your rifle is a Magpul AICS footprint mag. It isn't the same as your Magpul SR25/AR-10 mags which came with your DD5, and the two won't mix and match between these rifles.
 
Thanks! That stability calculator has bullets greater than 105 grains (well, it’s length that’s the issue but in these instances the heavier bullets are the longest) to be “marginally” stabilized at typical 6mmCM velocities. Hmmm. I guess the only way to know for sure is to try them. I don’t think I need 115’s but I sure would like to shoot 108’s and 109’s accurately and at distance.
Did you tweak the environment to match your conditions? And subtract the plastic tip from bullet length?
 
That stability calculator has bullets greater than 105 grains (well, it’s length that’s the issue but in these instances the heavier bullets are the longest) to be “marginally” stabilized at typical 6mmCM velocities. Hmmm. I guess the only way to know for sure is to try them. I don’t think I need 115’s but I sure would like to shoot 108’s and 109’s accurately and at distance.

The 105 Hybrids are the belle of the ball for variable distance, long range shooting, so you won't be disappointed with the 105's. But...

The 109 Hybrids, 110 A-tips, 108 and 109 ELD's all stabilize just fine in 1:8" twists from a standard length 6 creedmoors, as do the 112 MatchBurners, 107 and 110 Sierra Matchkings. BTDT with all of these bullets in the 6 creed case in 1:8" barrels.
 
I also do not ever subtract the plastic tip length from my bullet lengths when doing stability calcs. Poly tipped bullets aren't so different in principle than conventional BTHP's - a few grains of empty jacket extend in front of the core, in the same way does the few grains of the plastic tip. But the Center of Pressure remains relative to the point of the bullet, and the center of gravity remains relative to the mass of the core, so the displacement between them is still the same. Subtracting the tip length artificially improves the relationship between center of pressure and center of gravity, and will overestimate the stability of the bullet.
 
Dear Lord, I’ve lost it. A true senior moment. Going back over my little mag experiment I must’ve failed to recognize I was using the mags that came with the MPA and not the AR-10 mags I had on the workbench. Total dunce, mea culpa!

10-4 on the above bullet weights; I’ll proceed with confidence my barrel can handle the 8’s and 9’s!

@horsey300, I did input the environmental conditions but I didn’t subtract for the tip - lesson learned!
 
Delighted is the word. I finally got the Masterpiece Arms 6mm out to the range as the temp was finally above freezing (though the wind still made it feel like 20*F, can’t win in January). I had limited time and only two loads to try, both factory; Hornady Black 105 grain match and Hornady Varmint Express 87 grain. Thankfully I remembered my Garmin Xero and popped it in my pocket on the way out. I sighted in at 25 yards before moving to 200, the longest range currently open at my club.

The 105’s averaged 2952 fps and four groups of five ranged in size from .912 to 1.32 inches; I was quite happy with that for affordable factory ammo. Similarly, the 87 grain screamers were a little faster than the factory rating and did 3262 fps; these were also identical in accuracy give or take a few hundredths. Handloads will follow once I accumulate enough brass.

The verdict? Excellent! The rifle is superb and the Sightron S6 is a worthy piece of glass to top it. I love the 6mm Creedmoor - impressive performance and virtually no recoil. I can’t wait to try some 108’s at extended range when it’s warmer, and I can stand to trudge a quarter mile or more out to the targets! Thanks to all for your help thus far in my journey!
 
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