I'm thinking about cheating and just buying a BCM MK12 upper to get me close enough to the real thing.  I'm not going for a clone.  I know it has a 1/8 twist instead of 1/7 but at the distances I can shoot at presently I don't see it making a difference for a few years.  By then it'll probably need a new barrel anyway

BCM makes quality uppers and mine have always been extremely reliable. However, if you are going for extreme precision, I haven't found BCM barrels to be in the top tier of accuracy. They always seem to be MOA capable, I just don't think they are on par with WOA, Larue, and the like.

For the cost of the BCM MK12 upper, you could get into a Larue Stealth upper or the new Stealth 2.0 upper kits. If you aren't going for exact clone, I would opt for the more accurate rifle.

I've had two BCM MK12s and they both sucked in the accuracy department.   I've had two of their 16" stainless barrels and they suck just as hard.

Get a barrel from Centurion, a FFRAS long from the EE, and stick 'em on a Colt upper and BCG.  Almost a 100% chance it'll shoot and it'll be right.

Shop at Precision Reflex Inc., the original manufacturer of the Mark 12 Mod0 float tube and scope rail. They sell "retro" Mark 12 Mod0 uppers and complete rifles in a variety of offerings.

All have Douglas barrels and the original configuration Ops Inc. muzzle brake and collars. Your choice of 1/7 or 1/8 twist.

CTPT:  Douglas barrel plus the Ops collar and brake FTW!

A few times a year PRI also runs 10% off sales on their uppers and 15% off accessories.

I would still build your own with a Larue Stealth barrel but I forgot about the PRI MK12 offering. Very high quality and those Douglas barrels shoot solid.

Then, BCM or DD will do just fine.  I don't like calling those guns Mk12, or Mk12 inspired.  They are just good weapons.  A Mk12 is a Mk12, and it is not a BCM.  The only question I have is, why worry about a Mk12, when you already admit you are not looking for a clone.  Design a good SPR.  Noveske is good at that, or call MTSN.

I like the looks of the MK12.  So I'll want a gun that looks and functions similarly, I just don't need to spend $300 looking for the right rings, etc that the guys in the MK12 thread go bonkers over

I get it.  Then you want an SPR of your design, and your APR design will have some Mk12 features, and it will suit your needs, and that is what matters.  Design away, and have fun...

My BCM "Mk 12 Mod 0" upper likes IMI razor core 69gr stuff.  Pretty consistently puts it in the 0.7"-0.9" range.  Gets around an inch to an inch and a quarter with Prvi 69gr stuff.  It however doesn't like 77gr stuff as much.  IMI razor core in that weight goes between 1.5-2.0", same with Black Hills and SSA.  For comparison, both 55gr and 62gr ball shoots into around 2.5".

Not laser accurate with even the stuff it likes, but more so than my carbines.  I haven't experimented with loading my own for it and will probably play with various loads and bullet types/weights over the winter.

BCM makes excellent stuff, however I'm not sure I'd choose their Mk12 if you're wanting to build a) a MK12, or b) a high precision rifle. I went with PRI on mine, and I'm very glad I did. It was a work of art, an actual MK12, and shot like a dream. I foolishly sold it, and it's one of the few I regret ever getting rid of. If you go PRI you will be very happy.

Get the PRI upper!!!!

I've thought about getting the PRI upper but I like the looks of the Mod 1 over the Mod 0.  Maybe I'll just have to go through HCS for my Mod 1 upper

Kind of old thread but was doing some research on my own. While I hear a lot about PRI over BCM. I’ve didnt have same experience. I had better luck with the Bcm. I started with a complete PRI upper purchased through them direct but didn’t have great results so sold it and picked up a Bcm mk12. As did some of the respected shooters I follow:

https://m.youtube.com/watch?v=q3vCPoCNBjU

With that said of course there are better options if just looking for accuracy.  Sale holds true with better flatter shooting calibers like 6.5. My PredatOBR in 556 came from factory with .26 group @100 yards but only 3 shot sample. With me shooting I can do little over .5   5 shoot groups at 100 with specific ammo types. As compared to my Bcm mk12 at .80’ish. Although I do have better luck at 500 yards with mo12 over Larue but assume that’s mainly to do with the barrel being almost 4 inches longer.

Kind of how I see it as well.

Here is my Mk12 inspired SPR....but with a more modern take.

CLE machined and installed Bartlein SPR profile, 1:7.7 twist, CLE chamber.

Haha oh wow this thread came back.

So I never ended up building an SPR/MK12 or whatever .  I still want to it's just that other builds came up and took over.  Once I finish buying the last parts for my SBR, I plan on coming back and building a SPR.  Although I may just rebarrel one of my 16" guns I already have and throw a PST Gen II on it.

I have a BCM Upper and Wilson Combat 18'' SPR profile barrel, WC Bolt Geissele MK8 rail.  I get .7, maybe .6 MOA on a good day.  Of course, SMK 77 OTM is all she eats.  I have also had great success with a BCM Upper and V7 Bolt and 14.5" Barrel, Geissele MK13.  Both do very well out to 500.  The SPR does quite well out to 750.  I'm not sure how she'd go beyond, I don't have the range to try.   I love getting someone who doesn't really shoot behind it and letting them shoot steel at 500yds.  Ding Ding Ding, they can't believe what they have just done.  Good way to start em out!

Another quick note* most of us are not out shooting our equipment.  Buddy of mine decided we should benchrest my 8.5" 300AAC at 500yds.  Wilson Combat barrel, BCM Upper,  Aimpoint w/ 3x, had about 16' of dope but we got her there(1/2 silhouettes).