mrd

If anyone knows the answers to my questions above, I'm still interested to hear it. Though I'm not sure I am still motivated to pay for a new barrel... It seems I have greatly managed to improved the accuracy of my rifle. I got really fed up last evening, so I tore the rifle apart and applied every accuracy trick I know. First I cleaned the bore thoroughly, though there can't have been more than 500 rounds since the last cleaning so I doubt that really did much for accuracy. Then I took the Dremel and softned the feed ramp as well as made it reach slightly lower, there was a sharp edge towards the lowest part that I removed. I think this edge might have nicked some bullets when feeding. Finished the ramp off with a nice polish. I also tried to ream the chamber with my Clymer reamer, but that did absolutely nothing - except wear on the reamer. I lapped the reciever, though I think it was good before too, nothing off that I could see at least. The barrel-to-reciever fit was outright sloppy so I used green loctite to glue/fill the barrel in place before torquing the barrel nut. I think the sloppy barrel fit and the feed ramp contributed the most to my accuracy problems. Today I went to the range to see if there was any change or improvement. My, oh my... My group sizes are now pretty much cut in half, some are even a third of what they were before with the same loads . I used to get frequent and quite bad flyers with pretty much all ammo, that seems to be a thing of the past now. I shot benched (sand bags) from a distance of 27 yards (25 meters). My best handload used to produce a 10-shot group about 1,5" (36 mm) center to center before last night plus a flyer or two, now that is down to one ragged hole of 0.8" (20 mm) CC. Even my practice load with a cheap bullet and unsorted brass provides acceptable accuracy, grouping at 1.25" (32 mm) - that load used hardly group at all at a terrible 3" (75 mm) CC. To sum up, my WORST groups of today were pretty much as big as my best groups used to be! While a major improvement, the accuracy is still nothing to write home about IMHO. But this I can live with. 0.8" at 27 yards translates to about 3 MOA, that is acceptable for a PCC in my book. So happy I managed to solve it!

I have a CMMG Resolute with Glock lower since a year now and I'm so far quite disappointed in the accuracy of this rifle/barrel. Very ammo picky and the best results I have so far are no better than 4 MOA. That is with one specific factory load, best hand load so far is about 6 MOA and that is with one specific bullet. Most loads have given results around 10-20 MOA! Also, the chamber is ridicilously short and nitrided so reaming options are limited. I have not reached roads end with testing and fixing yet, but I'm starting to consider my options. Is it possible to change to a different brand barrel and keep the Radially Delayed Blowback (RDB) bolt? Has someone done this? I have not looked into it so much yet, but the CMMG barrel seems to have a loading ramp and the lock-up part for the lugs of the RDB bolt. Is this part permanently attached to the barrel or is it easily removable and possible to transfer to a new, different brand barrel? Or would something like that require serious machining?

I did these mods this weekend, both the polishing of the trigger bar and the metal bushing that rides it as well as installed a set screw for adjusting the creep away. I was blown away by the results. My apex trigger was not bad before, but it was really held back by the amount of creep after the "wall". Now it got really really good, I left just a smidge of creep for safety. Such a clean, crisp break! And it still passes a drop test, as well as a good blow with the rubber hammer. Thank you, DBlue and MemphisMechanic!

+1

I have promising results so far with the Frontier 121 gr FP in my 16" CMMG. These have a slightly thicker copper coating and are somewhere in between plated and jacketed. I have yet to test N320 vs N340 with this bullet. The plan for me is to settle on the most accurate load and then fine tune the buffer system for it. My CMMG is very picky with bullets and very few have acceptable accuracy.... Over 3 inches groups at 25 meters is not uncommon with bullets it doesn't like.

Also consider if you really want to time the comp to be straight on the barrel or if you want to time the comp so the recoil gets straight into the shoulder, or at least so the dot moves only vertically. I prefer the latter, that usually means having the comp between 1 and 2 o'clock for me (seen from behind). My comp has only upward ports and I'm right handed. If I would have the comp on straight then dot would move slightly sideways.

I didn't. I compared the FOV on LOWEST magnification, since that is the only fair comparison. Also, at higher magnifications the FOV is just a factor of the FOV at 1x. What I was saying is that the FOV of the Vortex 1-10x at 1x is not too great, compared to Swarovski z8i 1-8x or z6i 1-6i, Kahles 1-6x, Zeiss 1-6x or Ultimax 1-6x etc. And I think a wide FOV and a big eye box are bigger factors for IPSC and 3-gun than 6x, 8x, or 10x max magnification, as fast target aquisition trumps zoom when it comes to scores. That said, I'm going for the scope with the highest magnification without comprimising on FOV, which currently is 8x in Swarovski or Zeiss variety - Swaro having the advantage of better reticle (BRT). Looking forward to the day when 1-10x scopes comes with similar FOV as the z8i.

I have a CMMG Guard. Mixed impressions. The radially delayed blowback bolt is great. The fit of the CMMG upper and lower is terrible, however, and the feel of the rifle suffers because of it. The rifle cycles flawlessly even though I have tuned the buffer system plenty. My CMMG barrel is also very picky with bullets and ammo, short throat and very few bullets are accurate through it. If I'd do it all over again I'd do a build with QC10 upper and lower with CMMG radially delayed bolt. Also curious if the CMMG bolt works in the JP.

Field of view was not too great, an important factor for fast target aquisition. About the same FOV as the March 1-10x24, but the March is more than 2 oz lighter. Vortex is a bit cheaper, though. I'll stay with my Swaro Z8i 1-8x24.

OK, I'll take a guess. Hydraulic dampening in both ends of the buffer? So it softens both the impulse of hitting the stock AND going back into battery. Smart to make it light. Easier to add a weight, than to remove.

Same as always. Proper technique does the biggest difference. Heavier buffer weight and stronger spring, for such powerful loads I would go the Blitzkrieg 5015HD with the extra weight, as short stroke as possible and a strong spring like 308 JP, Tubbs flat 308 or red Sprinco, maybe sth even stronger. A comp will provide the last touch. I prefer upward vents only to give flatness rather than softness. And 163 PF is not so bad. In my 16" CMMG the most accurate factory ammo (in my rifle) , Geco 124 gr, does 156 PF and is still very managable. Not much difference from my 140 PF hand loads. In my rifle I'm going with the most accurate load and tuning the rifle for it. Recoil is not so much a factor in rifle as with pistols.

They look awesome. Brilliant to combine the heavy frame from Stock III with the bull barrel and lighter slide of the Limited Custom. Should shoot very flat! Would like one milled for optics. Only downside is that they are only availible in the US for now.

http://blackdogmachinellc.net/ Hoping this will prove reliable and good for PCC. Higher capacity without having 20 inches of magazine sticking out of the gun would be great!

My screw is long gone. I glue the sight in place with epoxy. Need to heat the sight to remove it, but it doesn't come loose unless I want it to.

No, the z8i 1-8x is SFP. I have one, with BRT reticle.

Aimpoint ACRO is the new kid on the block. Possibly the new king of reliability, time will tell... I'm getting one for my Walther Q4.

tomv, that doesn't look like any magpul grip i can find in their catalog. Can you double check what it is exactly? It looks nice and I'd be interested to buy and try. https://www.magpul.com/firearms-accessories/grips/see-all

On my CMMG with Hiperfire trigger, the hammer resets way before the bolt has traveled enough to be able to load the next round, so check this also. I set mine so the bolt can travel past the magazine and then some.

The rifle below is my PCC, a 16" CMMG MkGs Resolute 200 that I have upgraded and made to be as similar as my AR15 (above) as possible. Upgrades include Hiperfire Eclipse trigger, Taccom ULW compensator, Aero S-one handguard, Magpul MOE SL stock, BCM carbine buffer tube, Magpul MOE K2 grip, Kynshot 5004 buffer and JP 308 carbine spring. Short-stroked, of course. Shots soft, fast and reliably. Quite unimpressed about the tolerances in the CMMG reciever and lower, though. Needed JP oversize takedown pins and a rubber thingamajig to be quiet from rattle.

AFAIK, B5 and Umbrella corp is the same grip with different names. I tried the B5 but settled on Magpul MOE-K2 grip. The ergonomics of K2 fit my hand better, personal preference. It is quite straight at 17 degrees. B5 is like 2 degrees straighter than K2 and probably at 15 degrees (not specified by them from what I can find). Between K2 and B5, the difference in angle is not noticable, but the B5 is a bigger grip, too big for me. Even though I think I'd prefer an even straighter grip angle than the K2, I haven't found anyting better for me yet. I run my stock (MOE-SL Carbine) one notch from fully collapsed.

When running the red dot sight at standard height, 1.50 inches from rail to center of optics, I have no problems with the stock hitting my ear muffs (thin MSA Sordin Pro-X). Large muffs might be a problem. I also tried running scope/red dot lower to get a tighter cheek weld, but then I got problems with my ear muffs hitting the stock.

6 quarters is not much, you can do a lot more before the stroke is too short with a normal carbine buffer and buffer tube. And a 308 carbine spring should have no trouble cycling factory ammo as well as +130 PF loads. I think it sounds like something is wrong with your rifle, like you are not getting constistent blowback or something is obstructing the cycling. Check for wear marks on the carrier, buffer and in the reciever and buffer tube. Also check the bolt lugs and how it fits in the barrel lugs. I don't think it's your ammo. If it was, you should have found something that worked by now and factory ammo should work. OAL is easily determined by plunk test.

If you haven't already, short stroke it. Build with quarters in the end of you buffer tube behind the spring, until it doesn't cycle, then remove some. And a 308 carbine spring as cecil said. The short stroking will speed it up significantly. I'd put the weights back in the buffer too, maybe even running a heavier buffer.

Cool. Not so in Sweden, unfortunately. Only 0,5 kg of N330 here. My bad, I thought it was global.

Biggest drawback of N330 IMHO is that it is not available in big 2 kg containers, making it significantly more expensive than N320 and N340. Even though I agree it is the superior burn rate for 9mm minor, I run either N320 and N340 for economic reasons.