PCC Cycles Waaaaay Slow and It’s driving me crazy

[benlineberry]

I was hoping you guys could give me some advice. I have a 16 inch PCC rifle and I’ve tried everything I can think of to get it to cycle faster. The cycling always had a “ka-chunk” feel to it, and I’ve tried different powders, different bullet weights, and different crimps: Nothing works. Even with factory ammo, one lot of Remington 115 grain will run great, and then a different lot of the exact same brand and weight, won’t. (That’s how I know it is an ammo issue.)

 

So far, I’ve tried all combinations of CFE pistol, N320, and titegroup, With 115 grain, 124 grain, and 147 grain bullets. I’ve tried tight crimp, and no crimp, and overall lengths of everything from 1.00 to 1.16; None of it cycles fast. I’ve also tried bumping up the loads beyond max (titegroup max was 4.1 and I worked it up to 4.8) which helped a little, but still not great; It’s still easy to overrun the bolt with my trigger.

 

I am running a standard carbine spring with a buffer with the weights removed from it. Has anyone had a similar issue and did you find a solution?

 

 

Edited November 16, 2019 by benlineberry

[cecil]

stick with 115 gr bullets & fast powder ….  try a 3 stage buffer from Taccom… .& ditch the carbine spring... install a .308 spring... 

[mrd]

If you haven't already, short stroke it. Build with quarters in the end of you buffer tube behind the spring, until it doesn't cycle, then remove some. And a 308 carbine spring as cecil said. The short stroking will speed it up significantly. I'd put the weights back in the buffer too, maybe even running a heavier buffer.

[benlineberry]

7 minutes ago, mrd said:

If you haven't already, short stroke it. Build with quarters in the end of you buffer tube behind the spring, until it doesn't cycle, then remove some. And a 308 carbine spring as cecil said. The short stroking will speed it up significantly. I'd put the weights back in the buffer too, maybe even running a heavier buffer.

I have 6 quarters in it. Again, it helped a little, but it still doesn’t cycle like it does with certain lots of ammo. That is why I’m convinced it’s the ammo, not the set up. If I could just figure out the right ammo, I know it would be good.

[benlineberry]

8 minutes ago, mrd said:

If you haven't already, short stroke it. Build with quarters in the end of you buffer tube behind the spring, until it doesn't cycle, then remove some. And a 308 carbine spring as cecil said. The short stroking will speed it up significantly. I'd put the weights back in the buffer too, maybe even running a heavier buffer.

With a 308 Spring, I get FTF’s.

[mrd]

6 quarters is not much, you can do a lot more before the stroke is too short with a normal carbine buffer and buffer tube. And a 308 carbine spring should have no trouble cycling factory ammo as well as +130 PF loads.

 

I think it sounds like something is wrong with your rifle, like you are not getting constistent blowback or something is obstructing the cycling. Check for wear marks on the carrier, buffer and in the reciever and buffer tube. Also check the bolt lugs and how it fits in the barrel lugs.

 

I don't think it's your ammo. If it was, you should have found something that worked by now and factory ammo should work. OAL is easily determined by plunk test.

 

 

[benlineberry]

21 hours ago, mrd said:

6 quarters is not much, you can do a lot more before the stroke is too short with a normal carbine buffer and buffer tube. And a 308 carbine spring should have no trouble cycling factory ammo as well as +130 PF loads.

 

I think it sounds like something is wrong with your rifle, like you are not getting constistent blowback or something is obstructing the cycling. Check for wear marks on the carrier, buffer and in the reciever and buffer tube. Also check the bolt lugs and how it fits in the barrel lugs.

 

I don't think it's your ammo. If it was, you should have found something that worked by now and factory ammo should work. OAL is easily determined by plunk test.

 

 

 

Thanks- I'll add more quarters and see what that does.

 

I looked at the carrier and don't see any obvious wear, after a few thousand rounds. I agree is could be the rifle- it's a Gibbz Arms upper, lower, and bolt.

I did pull apart a few rounds each of the two lots of Remington UMC: one lot worked great and the other lot had the typical "ka-chuck" feel.

 

COL was ~the same, as was bullet weight, case length, and crimp. The big difference was the powder: the lot that worked had an average of 5.2gr of powder, while the lot that didn't work well had an average of 3.8gr of powder- the powder looked the same, but there's no easy way to verify.

[Les Snyder]

I ran into barrel battering (bolt was starting to peen the barrel shoulder) when I used a .308 spring and 6.2oz buffer... currently using an Enidine hydraulic...I'm old, so my trigger time is most likely a lot slower than yours, but with a 142 power factor load of 3.5 WSF and 135 Bayou coated did not notice any sluggishness with the blow back...the radial delay bolt has a slightly slower cycling impulse and that is the trade off for less dot movement, but I can't out run the trigger (RRA NM)

[benlineberry]

2 hours ago, Les Snyder said:

I ran into barrel battering (bolt was starting to peen the barrel shoulder) when I used a .308 spring and 6.2oz buffer... currently using an Enidine hydraulic...I'm old, so my trigger time is most likely a lot slower than yours, but with a 142 power factor load of 3.5 WSF and 135 Bayou coated did not notice any sluggishness with the blow back...the radial delay bolt has a slightly slower cycling impulse and that is the trade off for less dot movement, but I can't out run the trigger (RRA NM)

 

WSF is a pretty slow-burning powder. I have some CFE I had initially tried that didn't work, but maybe I'll go back to it and dial some more.

Edited November 18, 2019 by benlineberry

[fbzero]

8 hours ago, benlineberry said:

 

Thanks- I'll add more quarters and see what that does.

 

I looked at the carrier and don't see any obvious wear, after a few thousand rounds. I agree is could be the rifle- it's a Gibbz Arms upper, lower, and bolt.

I did pull apart a few rounds each of the two lots of Remington UMC: one lot worked great and the other lot had the typical "ka-chuck" feel.

 

COL was ~the same, as was bullet weight, case length, and crimp. The big difference was the powder: the lot that worked had an average of 5.2gr of powder, while the lot that didn't work well had an average of 3.8gr of powder- the powder looked the same, but there's no easy way to verify.

Make sure everything is unloaded, obviously, then pull the trigger and hold it back.  Now, pull the charging handle slowly.  If you pay attention, you'll feel/hear when the hammer resets.  Long and short, add quarters until it has just enough room to reset, then back off by one for good measure.  This will pre-load your buffer spring and also short stroke it as much as you can.  In mine, this increased the cycle speed and made the dot seem to recover faster. 
 

[benlineberry]

18 hours ago, fbzero said:

Make sure everything is unloaded, obviously, then pull the trigger and hold it back.  Now, pull the charging handle slowly.  If you pay attention, you'll feel/hear when the hammer resets.  Long and short, add quarters until it has just enough room to reset, then back off by one for good measure.  This will pre-load your buffer spring and also short stroke it as much as you can.  In mine, this increased the cycle speed and made the dot seem to recover faster. 
 

 

Thanks- I'll do that and see if that helps.

 

[Aircooled6racer]

Hello: Have you removed the weight in the bolt also? Keep it well oiled as well. Thanks, Eric

[mrd]

On 11/18/2019 at 11:18 PM, fbzero said:

Make sure everything is unloaded, obviously, then pull the trigger and hold it back.  Now, pull the charging handle slowly.  If you pay attention, you'll feel/hear when the hammer resets.  Long and short, add quarters until it has just enough room to reset, then back off by one for good measure.  This will pre-load your buffer spring and also short stroke it as much as you can.  In mine, this increased the cycle speed and made the dot seem to recover faster. 
 

 

On my CMMG with Hiperfire trigger, the hammer resets way before the bolt has traveled enough to be able to load the next round, so check this also. I set mine so the bolt can travel past the magazine and then some.

[fbzero]

3 hours ago, mrd said:

 

On my CMMG with Hiperfire trigger, the hammer resets way before the bolt has traveled enough to be able to load the next round, so check this also. I set mine so the bolt can travel past the magazine and then some.

Good thing to mention, thanks for adding that!  I also am using a Hiperfire in my CK Arms PCC, but that was not the case for me, so I didn't even think about it.