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4/1/2020 4:14:10 PM
4/1/2020 6:58:51 AM
Posted: 1/12/2005 12:46:08 PM EDT
Built a new rifle using RRA lower and CMMG upper. CMMG Bolt carrier will not clear thermold mags, but it will clear USGI. When I install RRA bolt group, it will clear all mags (thermold and usgi). Where is the issue here. The bolt carriers look identical to me. Is it because I am mixing and matching an upper and lower? Yes, I know USGI are the best and I should trash the Thermolds, but I like to use them at the range.
Link Posted: 1/12/2005 1:04:13 PM EDT
Check to see if the inside edge of the mag lips are contacting the outside of the inner ridge on the bottom of the bolt carrier.

If yes, you can trim back the feed lips slightly, or try a different BC.
Link Posted: 1/12/2005 6:27:45 PM EDT
Simple answer.  The two reessses on the underside of the carrier, that are there to clear the mag lips, aren't cut as deeply on the CMMG carrier.

Had the same problem with a DPMS carrier awhile back-----and since I'm a Thermold mag user I dumped it, and put in a Colt carrier, like I already had on the other 4 ARs at my house.

Remember, the feed lips on Thermolds are physically thicker than the aluminum jobs, so the out of spec recesses on the carrier may well clear the lips of a GI mag, and grind off half the lip  thickness on a Thermold.

Good to find out that the Rock River carriers ARE in spec. Guess they have to be, now that RR has a government contract w/the ATF
Link Posted: 1/12/2005 7:28:04 PM EDT
That sucks. I just emailed them to see what can be done other than grinding all the feed lips on my plastic mag collection.....LOL.
Link Posted: 1/12/2005 8:55:06 PM EDT
I had this problem with a few of my 6.8SPC mags.

I switched to the JP Stainless Steel "Tactical" carrier and it worked better (ie, no scraping)
Link Posted: 1/13/2005 2:17:02 AM EDT
Tactical now thats a word that is used way to much in the gun industry.

I thought CMMG used DPMS carriers.
Link Posted: 1/13/2005 2:47:12 AM EDT
[Last Edit: 1/13/2005 2:49:37 AM EDT by mongo001]

Originally Posted By Gregory_K:
Tactical now thats a word that is used way to much in the gun industry.

I thought CMMG used DPMS carriers.



Not only tactical, but bling as well.  I run two of these bolt carriers and they are smooth.  I don't have the TOS part of their system.



Tactical Operating System

For police tactical duty or any application where absolute reliability is the main criteria, we have our new TOSTM or Tactical Operating System with 416 stainless steel special design carrier that includes forward assist serrations and a dust cover notch. The bore of the JP stainless carriers has a roller burnished finish for frictionless operation with no chance of peeling chrome as in standard mil-spec carriers. The exterior bearing surfaces are hand polished. When properly lubricated, both systems make your rifle feel like it was cycling on ball bearings. Both carriers feature a 100% increase in bearing surface for smoother operation and improved alignment and lower wear in the upper receiver. Both are M15 semi auto configuration in the rear with the mil-spec longer cocking pad in the front for best reliability. This is hands down the best designed and highest quality general purpose carrier on the market. Sold as carrier with installed key or complete bolt/carrier assembly
Link Posted: 1/13/2005 3:26:21 AM EDT
[Last Edit: 1/13/2005 3:27:19 AM EDT by GHPorter]

Originally Posted By mongo001:
Re the Tactical Operating System description:

... Both are M15 semi auto configuration in the rear with the mil-spec longer cocking pad in the front for best reliability.



Does this refer to the same sort of thing as RRA's "enhanced" BC, where there's a lot more metal shrouding the firing pin?
Link Posted: 1/13/2005 4:09:45 AM EDT

Originally Posted By GHPorter:

Originally Posted By mongo001:
Re the Tactical Operating System description:

... Both are M15 semi auto configuration in the rear with the mil-spec longer cocking pad in the front for best reliability.



Does this refer to the same sort of thing as RRA's "enhanced" BC, where there's a lot more metal shrouding the firing pin?



Ya, pretty much.  It has the hooded firing pin area.
Link Posted: 1/13/2005 5:33:19 AM EDT
IF that carrier was truly "tact" it would have to be "black".
Link Posted: 1/13/2005 5:41:16 AM EDT

Originally Posted By Gregory_K:
IF that carrier was truly "tact" it would have to be "black".



There's alot of high quality "tactical" rifles being built by the likes of MSTN and ADCO with high quality, chrome bolt carriers.  Tactical, to me, is a function description vs. a looks description.  YMMV.

"Tactical" builds ala MSTN

"Tactical" builds ala ADCO
Link Posted: 1/13/2005 8:23:51 AM EDT
Everyone raising and eyebrow over the word "tactical" in this thread needs to chill.

JP makes two "operating systems":

1. the LMOS (low mass operating system) which runs their aluminum bolt carrier*
2. the TOS (tactical operating system) which runs their SS carrier

JP makes rifles/uppers for competition and for duty.  They do not recommend the LMOS for duty.   Clearly the best description of the other one looking at their market is the dreaded "tactical" word.  Deal.

* they actually make a low-mass steel carrier now too
Link Posted: 1/13/2005 8:31:50 AM EDT
Mongo, I was trying to make a pun on how every firearm item is now called tacticle.

we have tact gun cases, tact scope covers, tact belts, etc etc. It is almost like there afriad an item will not sell if they dont use the word.
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