Colt mag tuning?

[scffacenter1]

My searches have not turned up what I am looking for. I am having an occasional issue of a failure to feed. I have a spikes lower with Hahn mag block, faxon bolt in spikes slick side upper. My problem is that occasionally i will have a round leave the magazine in an extremely upward direction. The round ends up aimed much higher than the chamber, and rams against the back of the barrel above the chamber. Has anyone had this issue before, and are there any known fixes. I'm building a new pcc that will have a dedicated lower and glock mags, but this one will still be the back up, so I need it dependable.

[ericskennard]

Try switching the mag spring to the Wolff XP mag spring.

Are using a long buffer or a spacer?

[mahamoti]

Which magazines?

[scffacenter1]

Brownells mags. I'm using a blitzkrieg buffer and 308 spring, but I've tried other combos with the same problems.

[mahamoti]

Maybe try adjusting the height of the mag block to see if that helps.  Never had an issue when I was running a Hahn block with Metalform mags.

[MemphisMechanic]

Mag height is everything.

 

Strip the guts out and get them as high as possible, without the bottom of the bolt dragging on the feed lips as you monopod the gun on the magazine.

[BartCarter]

I have run across this problem with more than one Colt PCC.  The solution for me has always been to contour the feed ramp.  Now I do this as part of a PCC build.  Some of the rounds will hit the bottom of the feed ramp that is not ramped and kick up.  Look at the bottom of the ramp and see if you can tell it is being struck by the bullet.  It should be easy to see where it is being hit.  I have found rounds in Colt mags mayh nose up or down depending how many rounds are loaded.

 

You can file or Dremel the ramp down at the flat part.  Then polish it.  I also use Eezox as a dry lube in my PCCs and it works great.  Easier to keep clean and is a great lube.  If you use it, be sure to use it on the feed ramp also, which would ordinarily be tough to oil.

 

Hope this helps.

[BartCarter]

1 hour ago, MemphisMechanic said:

Mag height is everything...

I agree, but have found it is easier to contour the feed ramp than to work over a bunch of mags.  Now I can use any Colt mag and not worry. 

[MemphisMechanic]

That does indeed make sense.

 

However in my gun I had no choice; the CMMG Guard was never intended for Colt mags and when inserted itwas impossible to run the bolt forward.

 

I had to weld & recut the notches in all of my mags to lower them nearly 1/8” just so they’d fit into the gun and permit the bolt to cycle.

 

...The joys of building a frankengun.

 

Edited July 13, 2018 by MemphisMechanic

[BartCarter]

32 minutes ago, MemphisMechanic said:

...However in my gun I had no choice; the CMMG Guard was never intended for Colt mags and when inserted itwas impossible to run the bolt forward.

 

I had to weld & recut the notches in all of my mags to lower them nearly 1/8” just so they’d fit into the gun and permit the bolt to cycle.

 

...The joys of building a frankengun.

 

Yes, followed and loved your thread.  One of the best things I got out of it was the differences you found and how you overcame them.  It added to my knowledge of PCCs and what you can do with them. 

[MemphisMechanic]

Thanks!

 

I’m just happy it’s finally at 600 round without a single hint of a hiccup. 

 

Look for an embarassing video of my first USPSA match after we shoot Saturday

[scffacenter1]

Thanks for the suggestions, I'll give them a shot. Bart: Are you talking about the feed ramps on the front of the hahn block or are you talking about a ramped barrel. I bought this PCC knowing absolutely nothing about the AR platform, and it does not have a ramped barrel. (and of course this leaves a "jump" from ramp to chamber.) This is one of the reasons I am looking to purchase/build another with a 9mm lower and pre-built upper. I'll make some changes and put a thousand through it to see if I have any more hiccups, and report back. 

Edited July 13, 2018 by scffacenter1

[BartCarter]

3 hours ago, scffacenter1 said:

...Bart: Are you talking about the feed ramps on the front of the hahn block or are you talking about a ramped barrel. I bought this PCC knowing absolutely nothing about the AR platform, and it does not have a ramped barrel. (and of course this leaves a "jump" from ramp to chamber.) This is one of the reasons I am looking to purchase/build another with a 9mm lower and pre-built upper. I'll make some changes and put a thousand through it to see if I have any more hiccups, and report back. 

No, the feeding block.  The barrel should have a chamfer to help, but it is not like the feeding ramp (block).

[Dannybot]

Try disassembling the mags and giving them a good, thorough cleaning.  Gheye is a lot of carbon and debris that comes out of a 9mm upper.  The magazines are not taperes, so this build up inside the straight wall magazines can cause resistance.

[scffacenter1]

After cleaning and examining the gun, it appears the mag block ramp is much too low for good feeding. The bullets change angles a few times as the bolt pushes it forward from magazine to ramp to chamber taper to chamber. I'm going to see if I can pull the mag block apart and raise the ramp up, even though it's not made to move.