looking for a little help. built a 10.5 pistol love it when it runs. However the rounds do not always chamber from the mag, and I have to re cycle the charging handle to chamber the round.
I have an AIM bolt and C Mag 20 mags.
I believe I need a stronger recoil spring, but just checking. Overall I love the thing!
thanks

Is it locking back on an empty mag?  Where is it throwing the fired cases?

Greg

when done yes. And it is flying back correctly to my right

If it's tossing them with some good effort you can play. Some like the heavy springs or varied buffer weight. I'm guessing factory ammo.  Springs are cheap. I might consider, it it were mine, a lighter buffer for increased chambering velocity. I know heavy vs. light bullet theory here.

I've been lucky in over three dozen uppers all I've ever run was standard buffers and springs. I also run adjustable gas blocks on most of them and the only probewlmetic one I had was a 7.62X39 that I drilled the port on and then put an adjustable on it.

I'm looking forward to your fix.

Greg

This failure generally results from the bolt carrier moving too fast - try a heavier buffer first.

Bolt bounce coming into play? That would make sense.

Greg

alright I have one in the basement. lets do this.
will report back

Do you have C Products mags or C Products Defense mags?  My understanding is the C Products Defense mags are the latest version of the mags.  I also have read that some of the name changes had to do with lawsuits and business restructuring.  I have a 16" 7.62x39 and I bought the C P Defense mags and so far I have had zero issues.  I only have 200 rounds through it so take it for what it is worth.  I am interested in your solution because a 10.5" 7.62 is on my to do list.

I think it is just the earlier model got them a few months ago from AIM.
I don't see any problems with the mag at all. The barrel is a Faxon 10.5 and loud as hell but awesome as HELL!!!!!
I will post a pick of the build soon

Magazines are usually the #1 cause of problems in 7.62x39mm AR-15's.

Ammunition quality, or lack there of #2.

I had one 7.62x39mm (rifle gassed 20" DPMS barrel) I had to open the gas port up to get it running 100%.

I use reloads 95% of the time. IMI or PMC brass. Sierra 125 grains .311" Pro-Hunter's or Hornady's .310" 123 grain SP's seated at 2.190". 24.5 grains of H4198 or 28.0 grains of H322.

My loads have been very accurate and reliable. Because of the Communist bloc steel cases and copper washed steel bullets causing premature barrel wear I won't use it. Expect 50% of the normal barrel life when using that ammo. In other words 4000 to 5000 accurate rounds vs. 10,000+ using copper jacketed lead core bullets. My hand loads routinely print 1.5" groups at 100, much better than any ball ammo I have ever tried.

I could try some brass 7.62x39 and see if that is the prob instead!

I have watched a video where a guy did some sanding on the inside of his feed lips because they were sharp and cutting into the cases.  Try taking a loaded mag not in the gun and push or pull a round out of it.  Do you see much damage to the finish on the case?  Just some suggestions.  Like stated above mine has ran flawlessly so I have not tried any of my suggestions myself.

I have a Sprinco heavy spring in mine.  It is a 14.5 Colt upper.  M4 stock.

I wouldn't need it if I had more DPMS Frankenmags. All of the games are to make the CP Mags run.  I also have AK-47 Wolf heavy mag springs in my CP mags.  I have the last gen of the mags before all the company shake up occurred.  Even with that batch it took 20 mags to find 10 that would run.  I have one of those ten now that won't run.  I modified the rails to remove any obstructions and also cut the front of the mag like some people recommend.  That mag resides in my junk bin.  It just won't run.  Recently I saw where someone recommended cutting a couple legs off the follower.  Since I have two DPMS franken mags, I just run them and that bad mag will stay in my junk bin.  

Since the 7.62x39 Colt is currently on the front row of my safe, I think I will run the CP mags through it this weekend.  I might just use the bolt carrier and lower with my Echo installed just to run them quickly.  I need to test some .30-.30 Fudd-tactical rounds so I has to get to the range!!!!!

So are you saying CPD mags are now bad? I have been buying and using them for a few years and they have worked 100%. I haven't shot all of them, but I buy maybe 10 and use 2 and they have all worked. I haven't bought any in a year or so.

I run ASC 20 round mags and my rifle runs great. I did do some cleaning up of the mag sides where the case comes into contact but that is it. I have ASC 28 round mags as well and they run fine as well. I believe they were from Aim Surplus or Fatboy Tactical.

Check the size of your gas port. The gas port on the Faxon 10.5" barrel I got a couple of years ago was undersized and I had to open it up to get it to run correctly. 

I have 4 in 7.62x29 and very seldom do I have feeding problems, just light primer strikes,
I have 4 different bolts and firing pins from several places , I just installed a Wolfe xtra power hammer spring in one and one already has one , also polished up the bolts and firing pins  some, will try them soon
my newest 10.5" Faxon is very accurate also in a pistol  model

What kind of magazine is that in your picture?

They look like the D&H mags.

http://www.brownells.com/magazines/rifle-magazines/magazines/ar-15-7-62x39-steel-magazine-30-rd-sku100022693-95439-190714.aspx

How many rounds do you have through it?  CPD mags are the best, but in my experience they needed cycled about 5 times to free up.