Posted: 4/28/2009 3:30:35 PM EDT
|
I purchased a 9mm ramped bolt carrier. After installing, I noticed that the BCG feels "rough" possibly due to the machining marks on the rails of the carrier where it rides in the upper receiver. I have not fired the rifle yet but I wanted to check if this is normal. I have lubricated the BCG rails generously. I almost want to polish the rails to reduce the sound when the bolt carrier is moving if this is what is causing the roughness of operation of the bolt when I pull back the charging handle. The receiver is also a CMMG 9mm upper.
Also, I am unable to close the upper receiver unless I cock the hammer back. I believe it is due to the notch on the face of the hammer? It is a AR15 notched hammer and not a dedicated 9mm hammer. Is this an area of concern for the operation or safety? Please advise. Thanks. |
| One other person posted that his upper would not close like you describe with a notched hammer. We run all ours with a rounded AR15 hammer, but haven't tried the notched. I will look into the noise you describe. Same guy as before brought this up today also. We didn't notice any issue regarding function, and the during the testing ,we did we weren't listening for what you are describing. We will look into it over the next couple days. |
|
Thanks for the quick reply.
Yes, I assume that the machining marks on the rails would be burnished from firing over time and the rubbing noise would diminish. It just sound a bit unusual to me. I'll try to fire it this weekend and let you know how the notched hammer works. The receivers doesn't close without the hammer being cocked. But ths is not a big deal to me. |
|
Quoted:
I will look into the noise you describe. Same guy as before brought this up today also. We didn't notice any issue regarding function, and the during the testing ,we did we weren't listening for what you are describing. We will look into it over the next couple days. That would probably be me? The outside finish of both bolts I have had in my hands was very rough - the first one much more so than the second - I could feel and see the circular machining marks on the outside of the entire bolt and could literally file my nails with them. I haven't seen any current production RRA 9mm bolts, but the ones I have that are 2-7 years old are 100% smooth on the outside and have a matte park'd look to them. The first CMMG 9mm bolt I had sounded like I was filing/sawing metal when I hand cycled it and the second one still sounded similar, but more like I switched to a finer file. |
|
I wouldn't worry about rough finishing. Plenty of other brands of BCG, in all calibers, are about the same way. Roughest ones seem to be LMT, but they're known for getting everything important right, it's just their appearance and finish that suffers (the old "pick two" problem). Just keep the BCG wet. If anything, small grooves would help it hold oil.
If you can literally file things with it though (try filing the rim of an aluminum pop can), that may be where to draw the line, though. |
|
I purchased a CMMG 9mm Enhanced bolt from Spike's Tactical back in April. I have yet to fire the rifle with a live round. Took it to the range yesterday and I discovered the firing pin broke in 2 pieces.
Also, there had been several questions on this forum in regards to the finish on these bolts and causing some rough cycling. Has anyone else mentioned this? I have also emailed your customer service and would appreciate a prompt resolution to this issue. I am very concerned about the quality of the CMMG 9mm bolts and why the firing pin broke. Thank you http://i283.photobucket.com/albums/kk298/1Cyclepath/IMG_0208.jpg |
| I ended up returning it to Spike's Tactical and went with a RRA 9mm bolt. It cycles very smoothly and just like my .223 ones. According to CMMG, there are no plans to change the finish on the 9mm bolts. As far as the broken firing pin, I think it may have been caused by the firing pin hitting the shoulder of the pin hole and cracking. I think there were some pin protrusion issues as indicated by other forum threads. I am happy with the RRA but I am sure the CMMG ramped bolt will work fine in most applications. Maybe just a bad batch and tolerance issues with mine. I would recommend using a DPMS hammer if you are planning to use the CMMG bolt. I had a "notched" hammer and the receivers would refused to close on the CMMG bolt unless I cocked the hammer back. CMMG also stated that they have tested with a DPMS style hammer and not a AR-15 hammer with a notched face. |
|
I really hate to "kick a dead horse" but has anyone had any "rough" issues with the CMMG 9mm bolt. I've read in a couple other posts that the bolt has a very rough finish. People have compared it to a file. During my research I found this video on youtube:
http://www.youtube.com/watch?v=bVYsNF8bqoo (NOT MY VIDEO) Is anyone else having this problem? Is it somthing to worry about or is this somthing that will work itself out on its own? Thanks for all your help guys. |
| Haven't really heard any more complaints about it recently but I have to say that the RRA one I've used has been flawless and definately cycles a lot smoother. I've had good experiences with CMMG in the past and maybe they have improved the quality and fixed some of the issues that others have been complaining about. I am sure CMMG will make it right but I am happy with the RRA bolt. Adco will ramp the 9mm bolts for $50 if you really need it. I used a DPMS hammer with mine and everything appears to be fine so far. I am sure ramping will help more in a full auto setup where the stresses are much greater. |