PCC inconsistent cycling???? Why?

[chendersby]

GMR-13 complete from JP

124 Berrys FP bullets

5.1gr auto comp powder

 

While shooting fast splits i notice the gun cycles noticeably slower occasionally. Like 3 or 4 times during a typical stage. I think it may be firing slightly out of battery which may be resulting in slightly less pressure thus the slow cycle.

 

Anyone else experience this?

 

Chris

[Xanatos903]

I had the same problem when I was shooting FP bullets. It felt like a really light load, and I was always afraid that I had a squib.When I switched to RN bullets, the problem went away and now I've got totally consistent cycling. 

 

My only theory was that my headspacing was inconsistent enough with mixed brass that some of my rounds were jamming into the lands on my short-throated barrel, but I'd think that would cause harder-recoiling rounds instead. Maybe I had a majority which were jammed, and the shorter rounds were actually the ones that felt softer. I never tried seating deeper before I changed to the RN, but that would have been my first attempt at fixing the issue. 

 

 

Edited December 10, 2017 by Xanatos903

[Aircooled6racer]

Hello: Check the crimp on your reloads. I have seen some reloads on some PCC's that get either bullet setback or the bullet moves forward since they don't have enough crimp to hold the bullet in place. Others will be able to hear it as you shoot. Thanks, Eric

[longbeard]

Chamber a few and eject and inspect. I cannot run FP profiles. It completely gouges the edge of the FP and sets the bullet back a great deal. 

[bladewurk]

I got chugchug slow cycle with some bad mags and Flatpoints also, then a casehead separation..

ETA: I use RN only now and tested mags, and I cant outrun it yet!

Edited December 11, 2017 by bladewurk

[L9X25]

Have you tried this ammo in another gun?   

 

Make 100% sure it is the gun before you start "fixing it", it could be the powder measure.

[Tampa-XD45]

Do you have any factory ammo on hand that you can test with?

[L9X25]

Also, try more than one magazine, preferably factory Glock magazines, and see if that makes any difference.  

[chendersby]

 Going to shoot some factory ammo this weekend to see if it's that. Also loading some RN bullets I have. 

[sandrooney]

Did you figure your cycling problem out ?

[chendersby]

OK here is what I figured out so far:

I have 3 Glock mags I use 36round with the arredondo extensions. I shot the first 3 stages with my old ammo in all 3 mags. First 2 everything felt fine the 3rd stage and mag had a couple slow cycles during the stage. Switched to a 115 RN  load with the offending mag and had no issues. Other 2 mags no problems as well. Thinking it's the bullet and mag combo. 

One thing i did find out is i like the 115 RN load. Will probably shoot up all the loaded 124TC that I have and not use the one mag until I switch to 115s. 

[L9X25]

May be developing a weak spring in that bad mag.

[sandrooney]

Thanks chendersby.

[Darqusoull13]

Ditch the arredondo's if they are giving you issues or switch to 115 RN. If it's only the extended mags that are giving you a problem you can switch extensions to Taylor Freelance, Taran Tactical or MBX. Or you can order an extra power mag spring and see if that resolves the issue with your extension. 

For your ammo I would also definitely case gauge if you are not already doing so. I'd also check OAL before and after manually cycling your ammo. From an open bolt, drop the bolt on a round and re-measure the ammo and check for setback.

 

I'd also strongly suggest switching to a fast burning powder like Bullseye, Titegroup or N320. I suspect you may be getting unburned powder in the blowback action. I know when we tried HS-6 it was filthy because of this issue. 

Keep us updated! 

[chendersby]

Only one of the 3 mags gave me an issue. They all have the Arredondo extensions. 

Did the case gauge and also checked oal after chambering. No change. Now that i have a suspect mag I will do the chamber test with that specific mag.

Will try different powder. Don't think i have an unburned powder issue but it is filthy.

Edited December 20, 2017 by chendersby

[L9X25]

Whether I am shooting Open, or PCC, I have 3 mags loaded up and ready for each stage.  The reality is that I only use my favorite mag, and occasionally use the 2nd mag for a few rounds, never the 3rd mag.  My primary mag's spring will need to be replaced long before the other 2 mags.  With the PCC I use my favorite mag 95% of the time and only mandatory reloads cause me to use my 2nd mag.  

 

If you have been using the questionable mag for a while, and it is your favorite, having a worn spring is pretty common.  Cycles wear out a spring, not time.

[sandrooney]

I must be missing something, how can a weak mag spring cause a slow cycling issue ?

[L9X25]

Bullets noses barely getting out of the mags, bouncing their way into the chamber, likely having the projectiles seated deeper into the cases.  

 

You notice more of an inconsistency in the cycling.

[sandrooney]

Could a dirty bolt with insufficient lube cause this issue ? I use Titegroup and man does this thing get dirty and dry quick.  I was reading in my JP owners manual and it says to oil the bolt every 2 to 3 hundred rounds.

Edited December 22, 2017 by sandrooney

[L9X25]

He said he tried two different types of ammo, in 3 different mags, and it worked fine in 2 of the 3 mags. 

The common denominator seems to be one of the 3 mags. 

 

 

[L9X25]

He said he tried two different types of ammo, in 3 different mags, and it worked fine in 2 of the 3 mags. 

The common denominator seems to be one of the 3 mags. 

 

 

[chendersby]

It has happened with a clean gun so not a cleanliness issue although it does get filthy pretty quick. 

[L9X25]

C,

 

I totally agree with the TG being FILTHY, but I went to WSF and it is only slightly better (if at all).  I think the answer to dirt is N320 powder, but I have not experienced any 

failures as a result of being too dirty.  The dirt is more sooty and does not seem to affect the function of mine.

[longbeard]

If you have a smart phone the slow motion camera modes could be helpful diagnosing stuff like this.  Get someone to video the action while you shoot.  You might be able to see what's happening.

[sandrooney]

I had what I believe was the same issue happen the other day toward the end of a practice session, never happened before. The last couple mags (33 rounders) I shot, had several rounds feel like puffers and cycled slow, mostly in the last 40 rounds. I had not cleaned or oiled the gun in several hundred rounds. The gun is a GMR 15 with approx. 2,000 rounds down the tube. I cleaned and oiled the gun and went back out today and shot 220 rounds through the same mags , used the same ammo and even mixed in some factory. Did not have the issue on a single round.

I just thought I would throw in my experience.

Thanks,

SR