WTF happened here? Pew go boom?

[Member 34319]

Glad you got it figured out! I almost said fixed, but I still think something is funky for the amount of work you had to put in (and $$$ for various parts) to get it to run.

 

[Hueco]

Glad you got it figured out! I almost said fixed, but I still think something is funky for the amount of work you had to put in (and $$$ for various parts) to get it to run.

Right?

Total cost shouldn't be too bad after I get the triggers sold. Now I'm looking for a heavy buffer.

BCG + 7.7oz == 21.6oz total reciprocating mass. I'd like to get it up to 24 to see how perceived recoil feels up in that range.

So…wanna buy a trigger

 

[Member 34319]

Right?

Total cost shouldn't be too bad after I get the triggers sold. Now I'm looking for a heavy buffer.

BCG + 7.7oz == 21.6oz total reciprocating mass. I'd like to get it up to 24 to see how perceived recoil feels up in that range.

So…wanna buy a trigger

It would be funny to buy one from you, put it in my Aero EPC set and have zero issues.

 

[Hueco]

It would be funny to buy one from you, put it in my Aero EPC set and have zero issues.

That'd probably happen. I'm thinking I have a perfect storm of tolerance stacks…maybe an upper sitting high and lower sitting low.

 

[powermad]

BCG + 7.7oz == 21.6oz total reciprocating mass. I'd like to get it up to 24 to see how perceived recoil feels up in that range.

I seen that Vltor has PCC buffers now in a pretty decent selection of weights.
The SH2 is 7.97 oz.
Like the 5.56 buffers they go from SH0 - SH4.

 

[TheRagMan]

Looks like a classic example of case head separation. Either too hot of a load (hand load maybe?) or too weak of a recoil spring. I had a similar experience with a PC carbine that was re-barreled for 357 SIG. The 40 S&W recoil spring was not strong enough for the pressure generated by the 357 SIG cartridge, and the exact same results occurred that you are having. Had to tone down the hand loads to get it under control.

 

[Hueco]

Looks like a classic example of case head separation. Either too hot of a load (hand load maybe?) or too weak of a recoil spring. I had a similar experience with a PC carbine that was re-barreled for 357 SIG. The 40 S&W recoil spring was not strong enough for the pressure generated by the 357 SIG cartridge, and the exact same results occurred that you are having. Had to tone down the hand loads to get it under control.

Negative ghost rider. See https://www.northwestfirearms.com/threads/wtf-happened-here-pew-go-boom.396062/post-3207685

OOB likely due to bolt bounce and a trigger failing to disconnect. If you read through this whole post for specifically my posts, there's a lot of trial and error, testing, measurements, and data given that may interest you.

 

[Hueco]

As a follow up, I thought I'd share some of my recoil mitigation testing.

I got myself buffers of various weights up to 10oz and basically the entire Sprinco lineup.

I thought I'd try to get the gun to fail to cycle and lighten up from there, so I started with the 10oz buffer for ~23.9oz total mass with the BCG and the Sprinco Orange.

Holy. Wow. Gun was barely giving my shoulder a little love tap. Cycle was fine, ejection at ~3-4:00, and bolt hold open occurred shooting 115gr Blazer, 124gr Federal, and 124gr NATO. I need to find some 147gr but am optimistic it'd do well.

Suppose I need to get some heavier buffers to test further. But, since I had them, I tested lighter springs - from Orange all the way to White. The lighter springs seemed to increase perceived recoil and that's about it. There's gotta be more too it…but damned if I've found it yet.

 

[titsonritz]

I seen that Vltor has PCC buffers now in a pretty decent selection of weights.
The SH2 is 7.97 oz.
Like the 5.56 buffers they go from SH0 - SH4.

Those buffers are for an A5 RE.

 

[powermad]

They have a PCC line of buffers now as well and are heavier than the 5.56 buffers.

 

[powermad]

From my last buffer.

 

[Hueco]

From my last buffer.
View attachment 1154009

To reiterate, I'm now using a 10oz buffer with a Sprinco Orange (Extra Extra Power) Buffer Spring and a FailZero BCG. Total Reciprocal Mass is ~23.9oz.

I have shot Blazer 115gr FMJ, Federal Syntech 124gr, and Winchester NATO 124gr and all acted the same: perfect cycling with bolt hold open after the last.

My hope with tuning the recoil was to find something so wildly heavy that it failed to cycle, at which point I could back off testing different buffers and springs until I found something that cycled well, felt soft, and had minimal dwell while maintaining bolt hold open.

But, given that I'm maxed on both buffer and spring...there's nowhere to go but down.

Let me know if you see a buffer heavier than 10oz ever, as I'd like to try it.

 

[powermad]

A Law Tactical folder would give you about two more ounces with the adapter.
You would have to shave a bit off of the weight inside the carrier to fit the adapter.

CMMG has a tuning kit with a few different weights to add more mass to the carrier.
Comes with a 1,2 and 3 oz slug with roll pins.

Action Tuning Kit, Radial Delayed Blowback | CMMG - AR 15 and AR 10 Builds and Parts

Fine tune your Radial Delayed Blowback™ pistol or carbine with the Action Tuning Kit. Whether you want t

cmmg.com

The one in yours should be the 2 oz one.

 

[powermad]

Using a KVP BCG, an A5H4 6.8 oz buffer and Law adapter I was at 23 oz.
It seemed to run well with that so I didn't try any more.

Pretty much just shot 9mm NATO and Blazer 147gn.
Only 115 I tried in it was some Winchester M1152, which is pretty snappy.

 

[robstarke]

Well hell. I got the same Rise-535 trigger. I might hold onto this for the next build.

 

[FnM]

WOW this all good information but it's doing little to boost my confidence and decision to build a pcc. It's also outside my current budget. I'm stating to question my first decision to get a Ruger although it sounds like they are also having difficulties.