Page 14 of 19 FirstFirst ... 41213141516 ... LastLast
Results 131 to 140 of 187

Thread: CMMG .22lr conversion - a brief review

  1. #131
    Join Date
    Jan 2009
    Posts
    26
    Feedback Score
    0
    Probably a stupid question, but is anyone running the CMMG .22 unit with BDM mags in an LMT MRP upper?

    Spikes offers a dedicated .22 MRP barrel in 16" and 11.5", and separately a .22 bolt for use with the .22 MRP barrels. The cost-out difference between the Spikes set-up and the CMMG unit is obviously substantial.

    I'd like to go with the CMMG, but was curious about its reliability in an MRP, if anyone knows.

    Thanks ...
    Last edited by steppenwolf; 03-26-09 at 07:25.


    "That rifle hanging on the wall of the working-class flat or laborer's cottage is the symbol of democracy. It is our job to see that it stays there."
    George Orwell, 1941.

  2. #132
    Join Date
    May 2008
    Location
    Humboldt County, CA
    Posts
    2,057
    Feedback Score
    0
    I finally got my kit, and I finally took it to the range last weekend and shot 100+ trouble-free rounds through it.

    My kit came totally dry, so I liberally oiled it with Mobil 1, 15w50.

    Per the recommendations here and elsewhere, I shot 70 rounds of CCI Mini-Mags, interspersed with 30-40 rounds of Federal "value pack" copper-plated high-velocity.

    I've got a 1/7 14.5" CMMG upper.

    I used the three 15-round mags that I bought with my kit, though I only loaded 10 rounds in them at a time (I wanted to keep very careful track of how much I was shooting, and I run out of fingers at 10).

    There was no trace of any seam or crack on the chamber insert before or after shooting it.

    My impressions:

    It IS "drop in" (knock on wood). I had to give mine a good shove to get the chamber insert to go forward the last 1/2", but I had NO problems with mine at all (mine slipped right back out).

    It's fun. Recoil is minimal, but there's a real "crack" when it fires a .22lr. Shooting without ear protection wasn't painful, but wasn't pleasant (I did this for a couple rounds out of curiosity).

    Accuracy sucks. At 20yds I shot 1-1/2" and 2" 10-round groups, with one flier. At 50yds my 10-round groups were 6" or so. I was kneeling, shooting off a rest (the hood of my car). By comparison, my Marlin bolt-action .22 shoots 1-1/2" groups at 50yds.

    It's dirty. After only 100 or so rounds, there's carbon and powder fouling throughout. The regular BCG doesn't look anywhere near this dirty after 100 rounds of 5.56.


    Now, where can I get another box of the Federal "value pack!?"

    Bimmer

  3. #133
    Join Date
    Jan 2008
    Location
    Republic of Texas
    Posts
    4,088
    Feedback Score
    5 (100%)
    Quote Originally Posted by austin12gauge View Post
    Another brick of Federal # 750 bulk down range today - 50 out of my Buck Mark and 500 out of my CMMG 22LR AR conversion. Not one hiccup with either gun and no failures to fire due to bad ammo. I am still a happy camper with the CMMG. That makes about 2,300 trouble free Federal rounds thru the CMMG to date.
    It has been awhile since I have been shooting, but I put another 200 trouble free rounds of Federal #750 thru my CMMG conversion this morning.

    What is all the more remarkable is I didn't clean it after my last session of 500 rounds in March. It has just been sitting. I didn't even oil it before shooting today!

    That brings my trouble free round count to 2,500.

  4. #134
    Join Date
    Jun 2006
    Location
    Virginia
    Posts
    1,224
    Feedback Score
    0
    Somehow I had missed this thread.

    Very informative! Thanks to all who have contributed.
    GLOCK PREFECTION

  5. #135
    Join Date
    Jun 2008
    Location
    Roseville/Lincoln CA
    Posts
    91
    Feedback Score
    0
    Great info here! I just bought one from Rainier arms and cant wait for it to show up!

  6. #136
    Join Date
    Sep 2009
    Posts
    7
    Feedback Score
    0
    Ok, I have an UPDATE on several tips suggested within this thread I have tried.

    First, as with all new guns, I start with the feed ramp and polish that sucker up. I noticed my feed ramp was cut kinda cock-eyed, more deeper cut on the right side (defect?) I used a dremel grinding tool to even this out and then polish. With the ramp left that alone, I think I would have had a FTF.

    Second, when inserting the conversion unit, the last 3/4 to 1/2 inch would not go in with out serious pressure. Since some of the folks here has had problems getting the unit back out, I decided not to push it in too deep. When I pulled it back out, I noticed some scraping marks along the phosphate coating where it was catching. Using 1000 wet/dry sandpaper, I sanded the entire insert area and removed the phosphate coating. The unit is made of SS so rusting is a not concern. I applied a small amount of anti-seize lube (choke tube lube) to the insert and it fit like a glove. Removal was much easier. Anti-seize lube must be cleaned from .233 chamber prior to shooting .223 ammo again.

    Third, with the 1000 grit again, I sanded the rails as I always do to a new gun. This is equivalent to shooting 500-1000 round break-in. All sliding rail parts, inside and out, get a drop of oil and then sanded. The phosphate coating CMMG uses is great on the parts that don't touch but when in contact they actually grip each other much like taking two pieces of sandpaper and rubbing together. Removing this 'tooth' from both parts, then lubed, will make it slicked than snot.

    Fourth, after reading how others where having firing pin problems, I decided to remove mine and check it. Lo and behold, my FP would not fall straight through either and hung up. Following the advice of others here, I sanded the pin with 1000 grit, removing most of the phosphate coating, dropped it in again and BAM, slid right through, no hang up.

    Now I am convinced the phosphate coating is causing most of people's problems with these units. A little sandpaper on the right areas and these puppies will be smoking.


    The BDM Big Dog magazines also were causing some folks problems. One person suggested taking the magazine apart and sanding out the bumps, so I did. Along the way a figured out a few more tips to these mags. My mags were new and I could barely load 20 rounds, a thumb buster for sure.

    After taking the mag apart (careful not to lose any of the 3 red plastic parts and 2 springs) and sanding the inside channels where the followers ride until almost smooth, I liberally spread powdered graphite in the channels with a Qtip. Looking at the red plastic follower I noticed mold marks and bit of plastic left on from where it squeezed out during manufacture. These were grabbing the inside of the mag when I was loading and making it bind up, sooo I sanded them off, too and applied graphite. I reassembled, and I'll be a monkey's uncle if I couldn't load all 26 rounds and without hardly any pressure. Worked like a charm! I even sanded the outside corners and side ends of the mag where it contacts the mag well insides for a smoother insertion.

    Anyway, I hope this helps. The CMMG is an inexpensive way of shooting but like all higher volume companies, final finish is very subjective and may require addition fine tuning. Otherwise, if they did the fine tuning themselves, they would become a lower volume, higher quality but with a much higher price tag!

    Rob
    Freedom Firearms of Kentucky
    Last edited by RVGP; 09-25-09 at 13:40.

  7. #137
    Join Date
    May 2008
    Location
    Colorado
    Posts
    13,168
    Feedback Score
    0
    No offense, but what drunk hillbilly monkey does CMMG have making their kits? The only thing good about their tooling marks is that someone had to have worked on it to make them. My feed ramp looked almost like it was dimpled on purpose. The bore was Rough, and even with some bore paste it seems like there are weld marks in the bore? I used up to 6000 wet sand paper and while the rails are smooth, the bolt still doesn't 'slide'. I even tried bore paste, which I've used on crappy AR BCs to slick up, and that didn't really help much.

    I've used the unit once and after about 100 rounds it started to not extract. Had lubed pretty generously and I think it was HV American Eagle ammo. Looking forward to trying it after the polish job I've done, it does seem a bit slicker.

    I really enjoyed the kit while it ran. Nothing like pulling out a UBR Stocked AR with 18in JP upper with a TA11 Acog at the indoor range and watch people give you odd looks. I only shot it offhand and it was about an inch or so at 15 yards.

    I don't mind tweaking things when I get them, but to me, the CMMG kit is just built to a poor standard. Hopefully I can get it to run.
    I just did two lines of powdered wig powder, cranked up some Lee Greenwood, and recited the BoR. - Outlander Systems

    I'm a professional WAGer - WillBrink /// "Comey is a smarmy, self righteous mix of J. Edgar Hoover and a gay Lurch from the "Adams Family"." -Averageman

  8. #138
    Join Date
    Sep 2009
    Posts
    7
    Feedback Score
    0
    Ok, so I went to the range and tried out my 'modified' CMMG and I've got to agree, monkeys must have made these.

    Even after the 'mods',I had made described in this thread, I still had major extraction problems AND FTF because of light primer strikes. I never did get to finish a full mag. After the mag was removed and gun recocked, the round fired and ejected. It seems the bolt does not close with enough force to allow the ejector rod to 'catch' the rim of the .22. Either this is caused by not enough blowback force OR the ejector rod spring is too tight and/or the ejector rod needs to be removed and cleaned up to operate more smoothly. The mags could also be rubbing on the underside of the CMMG unit and causing it to slow down when closing the bolt. I did try CCI Stingers, which are 1640 FPS and had the same problems as with MiniMags at 1280 FPS. Honestly, I didn't remove the ejector rod or lube it when I did my mods; I'm now thinking this needs to be done.

    As far as the light primer strikes, I think this could be caused by the bolt not being in battery as far as it should because the ejector being too tight and can't make it over the .22 rim when it closes. The only other thing I can think of right now if all this fails is to stretch the main spring a bit to give it more 'umph' when closing. I know this is a hillbilly way of doing it, but short of sending it back... Somebody in this thread mentioned cutting a link out but wouldn't that actually make the spring weaker and the opposite of what is needed?

    When I did get my AR to fire the whole unit was accurate and I had fun shooting it. I'm not ready to give up yet, but Brownells should be prepared for a return.

    Rob

  9. #139
    Join Date
    Jan 2008
    Location
    Republic of Texas
    Posts
    4,088
    Feedback Score
    5 (100%)
    Quote Originally Posted by RVGP View Post
    Ok, so I went to the range and tried out my 'modified' CMMG and I've got to agree, monkeys must have made these.
    I am sorry you are having problems with your CMMG kit, but if monkeys made mine they were good monkeys. My CMMG keeps right on ticking with narry a problem. And no sanding either. Same goes for my BDM mags - no sanding here either and they run fine.

    I am not making fun of your problems, but I didn't want someone searching for info to think they all had problems.

    Did your's have problems before you modified it, or did you do the mods before you shot it?

  10. #140
    Join Date
    Sep 2009
    Posts
    7
    Feedback Score
    0
    Thanks Austin, I know you're not making fun, although some would have. The quality control must have gone down from the time you got yours last year OR I got unlucky and had one made by an inexperienced person.

    Truthfully, the firing pin did not 'fall thru' the hole until I sanded it smooth; the feed ramp was definitely not cut right and the unit would not slide in all the way until I sanded the insert. As far as sanding the rails, I admit I did that on my own, but only from past experience with other gun stuff coated with that type of finish.

    What I noticed last night when I took it apart after the test firing was the bolt itself moved side to side while in the complete rail assembly and was kinda binding up when closed. When I took off the insert portion, the bolt became tight side to side in the rails, like I would expect. The cutouts in the rail where the insert sits are somewhat rough cut. So, either the grooves in the 223 insert are cut too shallow or the rail cutouts are too shallow. Either way the rails are being forced out, side to side, maybe making contact with the inside of the upper receiver and making insertion and extraction harder AND making the bolt sloppy and not locking up properly to extract the empty. I could file the rail down until the bolt becomes tight.

    Would you mind checking to see if your bolt move side to side?

    What do you think, should I just say 'hell with it' and send it back for replacement to try to keep fixing it?
    Last edited by RVGP; 09-28-09 at 12:06.

Page 14 of 19 FirstFirst ... 41213141516 ... LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •