Help debugging Colt PCC

[mahamoti]

I've had this Colt mag PCC together for almost 2yrs now, and it's run great until recently.  I've tried everything, so I'm looking for other ideas.  20rd mags still run fine.  I have 2 TF+10s on 32rd mags that *used* to run, along with a 32+20 coupled mag that *used* to run.  All Metalform mag bodies and metal followers, chamfered to work smoothly with the +10s.  Now I get both double feeds and nosedives from the mags.  Swapped in new Wolff +5% springs, no help.  Tried clipping 1/2 coil off of some of those springs, no help.  Tried TF delrin followers, no help, seemed to worsen nosediving.  The only thing different is, around the same time, I switched from a JP SCS to the Taccom 3-stage buffer system.

 

I had traded off the SCS, but put another one on order today, just to see if the Taccom 3-stage was contributing.  Anything else anyone familiar with Colt setups can suggest, that might have to do with a "less than new" setup that needs refreshing?  No discernable wear on bolt, firing pin, extractor, ejector.  Problems are limited to first ~10 rounds in 42rd or larger magazines.

 

Details:

* JP 16" barrel

* JP 9mm bolt

* Taccom 3-stage buffer with the spring it comes with, no short stroke

* Hyperfire 3G trigger

* 124gr Precision Delta FMJ / 3.6gr Titegroup / 1.15" OAL / CCI primers / ~135PF

[OPENB]

You've done what I'd suggest already. Is Wolf+5% the same as the extra power spring that TF sells? Clean and degrease the inside of your tubes, make sure the follower isn't binding on the trip up the tube, no burrs. Check the lip spacing against mags that work 100%.  If the mag is crapping, dump it. Don't fall in love with mags, they are consumables. Do they run with a regular base pad on them? The buffer system should not effect mag feeding, just a coincidence I think. Since it's just the first 10 rds. in a 42 rd. mag, I bet it's the TF combo.

[mahamoti]

The TF spring is very different than the Wolff +5%.  I tried both, and the Wolff springs were better by far.  I really wanted the TF spring/follower combo to work, but got nothing but nosedives.

 

You're right about the mag bodies.  Went ahead and ordered a new set.  They're pretty cheap nowadays anyway.  FWIW, every one of my mags, 32 and 20, the feed lips back and front only vary by 5 thou.  The Metalforms are such thick metal, I don't even know if I could tweak the feed lips easily.

 

The only thing that kills me is, the same TF extension/mag combo has worked for more than a year, trouble free.

 

I'm going to keep at it, but I'm also going to be loading up some pistol ammo instead of PCC ammo...

[bwikel]

When I clean my mags I spray the inside of the tube and follower with PTFE, it seems to help. The only time I had all my big stick colt mags quit feeding reliably I had changed bullet profiles, that doesn't seem to be your problem. 

[HoMiE]

Oal is 1.15”, are you sure the nose of bullets aren’t dragging in mag as they stack towards bottom. 

[bwikel]

12 minutes ago, HoMiE said:

Oal is 1.15”, are you sure the nose of bullets aren’t dragging in mag as they stack towards bottom. 

You can load beyond SAMMI max length with 9mm in metalform colt mags, like 1.20" +.  I have run RN profile out to 1.17" without issue. 

[mahamoti]

50 minutes ago, HoMiE said:

Oal is 1.15”, are you sure the nose of bullets aren’t dragging in mag as they stack towards bottom. 

I know at least one Colt PCC gunsmith recommends no longer than 1.13" OAL for his rifles.  It's on the list of things to try, along with upping the PF, if new SCS buffer and new mags still don't help.

 

But again, what irks me is, the same load has run for more than a year w/o problems.

[rishii]

If I read this right, the gun stopped running after you switched to the taccom buffer

i just did the same, and had a similar problem, I did 2 thing to fix it, first I removed the plastic disk, second I locked my bolt back for a week and now my gun runs

[tha1000]

I was getting a lot of double feeds, but new springs fixed my issues (thus far).  I did have one mag body get out of spec to a point where it would not drop free.  No idea how it happened, but I banged it back into square with a hammer and it works fine now.  Colt pattern guns are incredibly finicky.

[ericskennard]

Try installing a new extractor. I had one do the same thing. I replaced many different parts to no avail. I finally tried a new extractor and BINGO problem solved. So I polished the old one and increased the tension a little bit. I put it back in the PCC and the problem was back. It is like the extractor lost it's temper or something.

[mahamoti]

On 3/25/2019 at 12:47 PM, rishii said:

If I read this right, the gun stopped running after you switched to the taccom buffer

i just did the same, and had a similar problem, I did 2 thing to fix it, first I removed the plastic disk, second I locked my bolt back for a week and now my gun runs

New SCS should be here today.  That will confirm or rule out the Taccom 3-stage being an issue, at least.

 

22 hours ago, tha1000 said:

I was getting a lot of double feeds, but new springs fixed my issues (thus far).  I did have one mag body get out of spec to a point where it would not drop free.  No idea how it happened, but I banged it back into square with a hammer and it works fine now.  Colt pattern guns are incredibly finicky.

New mags coming in as well, so I can mic out the feedlips to look for changes.  Also took my existing mags and polished the followers and inside the feedlips, along with dry lube inside the body when reassembling.  Yet another thing to try.

 

10 hours ago, ericskennard said:

Try installing a new extractor. I had one do the same thing. I replaced many different parts to no avail. I finally tried a new extractor and BINGO problem solved. So I polished the old one and increased the tension a little bit. I put it back in the PCC and the problem was back. It is like the extractor lost it's temper or something.

I'll keep that on the list, but I'm not sure if that's my problem.  The nosediving issues, the extractor hasn't even gotten to touch the round yet.  And when it's running, ejection pattern is fine.

[Tampa-XD45]

1 hour ago, mahamoti said:

New SCS should be here today.  That will confirm or rule out the Taccom 3-stage being an issue, at least.

 

New mags coming in as well, so I can mic out the feedlips to look for changes.  Also took my existing mags and polished the followers and inside the feedlips, along with dry lube inside the body when reassembling.  Yet another thing to try.

 

I'll keep that on the list, but I'm not sure if that's my problem.  The nosediving issues, the extractor hasn't even gotten to touch the round yet.  And when it's running, ejection pattern is fine.

Are you running a dedicated 9mm lower or a magblock?

[tha1000]

1 hour ago, Tampa-XD45 said:

Are you running a dedicated 9mm lower or a magblock?

 

 

The question wasn't intended for me, but I have definitely had more feed issues with my dedicated Spikes lower compared to my hahn block SBR lower.  The Hahn block is decidedly tougher to reload as well.  

[mahamoti]

2 hours ago, Tampa-XD45 said:

Are you running a dedicated 9mm lower or a magblock?

Black Creek Precision dedicated lower.

[StealthyBlagga]

You can try squirting some graphite powder inside the mag as you load it.

[mahamoti]

Got 3 new 32rd mags today.  All mags, new and old, are +/- 5 thou, both front and back.  So doesn't seem like the feedlips are out of sorts.

 

Will see if I have any issues this weekend.

Edited March 28, 2019 by mahamoti

[bwikel]

22 minutes ago, mahamoti said:

Got 3 new 32rd mags today.  All mags, new and old, are +/- 5 thou, both front and back.  So doesn't seem like the feedlips are out of sorts.

Check the specs on the mag slots on the mags and mag catch on the lower also to determine wear. 

Edited March 28, 2019 by bwikel

[mahamoti]

12 hours ago, bwikel said:

Check the specs on the mag slots on the mags and mag catch on the lower also to determine wear. 

This was a good idea to check, but no discernible wear on any mag slots or the catch.

[tha1000]

 I’ve had issue with my spikes lower that the detent slot in the feed ramp is a different size than the hex screw that serves as the detent. Long story short, this allows the feed ramp to push up higher than it should be and causes bullets to feed north of the chamber.  Probably not your issue, but something easy to check anyway. 

Edited March 29, 2019 by tha1000

[mahamoti]

53 minutes ago, tha1000 said:

 I’ve had issue with my spikes lower that the detent slot in the feed ramp is a different size than the hex screw that serves as the detent. Long story short, this allows the feed ramp to push up higher than it should be and causes bullets to feed north of the chamber.  Probably not your issue, but something easy to check anyway. 

Feed ramp was the first thing I checked.  The setscrew had come slightly loose, so I was hopeful that was the issue.  After cleaning, polishing, and loctite-ing in place, no dice.

[Tampa-XD45]

On 3/29/2019 at 8:57 AM, mahamoti said:

Feed ramp was the first thing I checked.  The setscrew had come slightly loose, so I was hopeful that was the issue.  After cleaning, polishing, and loctite-ing in place, no dice.

Have you reverted back to the JP SCS?

[tha1000]

The Louisiana guys at the Leograndis class this weekend said you're on the verge of rage quitting pcc and dusting off the production gun.  Say it ain't so!!

[mahamoti]

2 hours ago, tha1000 said:

The Louisiana guys at the Leograndis class this weekend said you're on the verge of rage quitting pcc and dusting off the production gun.  Say it ain't so!!

They're not wrong.

 

I need to get some pistol practice in anyway between now and BwB 3gun.

[mahamoti]

5 hours ago, Tampa-XD45 said:

Have you reverted back to the JP SCS?

Got it installed, haven't had a chance to test.

[Silver_Surfer]

After all your changes does your 20rd mag still work?