FINAL: EPC PCC Build -- Intermittent Light Primer Strikes

[ksosay]

Love it when a pile of parts come together. Especially since I’d been collecting them since February.

Here's the build sheet:

• Receiver Set - Aero Precision EPC - 9mm
• BCG - Aero Precision EPC - 9mm
• Buffer Tube Set - Aero Precision EPC - 9mm
• Replaced AP's .308 carbine buffer spring w/ AR15 carbine buffer spring (softer shooting)
  
• LPK w/ FCG - Aero Precision EPC - 9mm
• Grip - Magpul K2+
• Charging Handle - FoxTrot Mike Warhammer - Ambi
• Muzzle Device - VG6 Epsilon
• Safety - Battle Arms Development Inc. - BAD-Ass Pro Safety Selector Ambidextrous
• Barrel - Macon Armory 'Guaranteed to Feed'
• Handguard - Odin Works O2 Lite M-LOK Free Float Forend
• Optic / Red Dot - Lucid HD7 swapped out for a Swampfox Liberator Gen1 greendot (10oz weight savings)
• Mags - Magpul (Glock) 21 round

1st time out I was able to zero the red dot and feed it a varied diet. Ran it a little too dry I think. After about round 25 I had a FTF with 124gr Federal FMJ, cleared, ran a few more another FTF, rinse repeat. Deformed the cases.

Ran a full magazine of 147gr Federal HST JHP through, no issues.

Ran 50 rounds of Federal 147gr flat nose FMJ 1 FTF and then action mortared and deformed the case.

I hit the works w/ some Ballistol and the matter seemed to resolve itself. In all I put about 150 mixed rounds through it I'd like another 500 w/o hiccups before I call it finished.

A subsequent range session after a thorough cleaning and lubrication resulted in 99/100 rounds fired without malfunction. (Federal 124gr FMJ)

Ran another 150rds through it this weekend had 3 light primer strikes and case deformities. (Federal 124gr FMJ)

Accuracy is good out to 50yds.

Any thoughts or suggestions?

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[mRad]

I didn’t see you say what trigger, but that’s the place I’d start.


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[ksosay]

LPK w/ FCG - Aero Precision EPC - 9mm

Aero's trigger package for the EPC., figured I'd keep it simple the 1st time through. Anything in particular I should look for?

https://www.aeroprecisionusa.com/epc-moe-k2-lpk

[Clint]

Which buffer?

[ksosay]

Which buffer?

Aero's EPC Buffer Kit (7.7oz buffer, 308 spring, enhanced buffer tube).

https://www.aeroprecisionusa.com/epc-buffer-kit

[Clint]

Aero's EPC Buffer Kit (7.7oz buffer, 308 spring, enhanced buffer tube).

https://www.aeroprecisionusa.com/epc-buffer-kit

Is it solid or does it contain weights like a normal buffer?

What is the length?

[ksosay]

Solid, 4.2"

https://www.aeroprecisionusa.com/epc-buffer

If you check my build list in the original post you'll see I kept the internals all EPC specific.

[1168]

LPK w/ FCG - Aero Precision EPC - 9mm

Aero's trigger package for the EPC., figured I'd keep it simple the 1st time through. Anything in particular I should look for?

https://www.aeroprecisionusa.com/epc-moe-k2-lpk

Not to insult you, but are you certain you’ve installed the springs correctly? Facing in the correct direction, and both hammer legs above the trigger pin?

As for needing to mortar to clear, I’ve found that it is not be unusual to have trouble clearing some PCCs with certain 147 gr loads.

[Clint]

The solid buffer is almost certainly causing bolt bounce and is likely contributing to the light strikes.

Also, there's no need for a super strong spring on these.

A regular rifle spring (if it fits) should be plenty.

[ksosay]

Not to insult you, but are you certain you’ve installed the springs correctly? Facing in the correct direction, and both hammer legs above the trigger pin?

As for needing to mortar to clear, I’ve found that it is not be unusual to have trouble clearing some PCCs with certain 147 gr loads.

No insult taken as I'm the one asking for advice. I was going to confirm the spring orientation but haven't gotten to it yet though at a glance I recall both hammer legs to be above the trigger pin but will reconfirm and post backup here.

Good to know on the 147gr loads, thanks.

The solid buffer is almost certainly causing bolt bounce and is likely contributing to the light strikes.

Also, there's no need for a super strong spring on these.

A regular rifle spring (if it fits) should be plenty.

I went with what Aero recommended for this build it's a carbine length 308 spring that is included w/ the buffer tube and buffer. Seems all I've read along the way is that tuning a PCC can be tricky at times.

To add, when I first encountered this issue I did open a support case w/ Aero Prec. and they spent a decent amount of time with me on the matter. The tech kept going back to insufficient lubrication.