PD 124JHPs and a Shadow 2: Feed Issues

[rougeqc21]

So, I ran into a string of issues with my two Shadows 2s.

The issue presented as follows:

• Shot fired > Case failure to extract > Double feed created

Problem load:

• PD 124gn JHP
• 4.1gn VV N320
• OAL 1.110''
• Primer at .005''
• Crimp at ~.001''

 

I have run about 7k of these PDs without issue so I did not suspect the gun - also given that this is my match gun and I replace parts on it proactively like a maniac. What had changed was the OAL, but even then only +.005''. I wanted a little less FPS and didn't want to change the charge .

 

Well, I came home and my autistic tendencies took over. Some good friends let me run their loaded Zero 147gn JHPs (at 1.130'') and the gun in same state ran perfectly - this focused me into the load. I did though, swap the extractor since Nats are close as a 'why not'. The old one was 100% clean and the extractor spring also less than a month old.

 

Today I loaded up 150 rounds using the same recipe but to 1.095'' OAL and they ran perfectly. Curiosity bested me and I loaded a mag of the longer rounds and sure enough the demons reared their heads again. So, I feel conclusively that I know the what here, but I do not fully understand the why.

 

Ramp on the barrel is flawless, followers are in good shape. Both lengths plunk properly (I put the barrel in a vice, drop the round in and test that I can freely rotate it).

 

The ask here is what is the why. Why does the longer round induce that failure mode with this bullet?

 

Other relevant info:

1.140'' is on the lands

1.139'' will rotate freely when dropped into the chamber

 

Video of failure happening:

https://youtu.be/1V1Zxx5LD0c

Edited October 7, 2019 by rougeqc21

[Dwbsig]

I been shooting the same bullet at 1.085 because the bullets was touching the rifling around 1.105 in my s2 , never had any issues so for.

Good luck.

[rougeqc21]

What I don't understand is why the change in length creates this extraction issue that is wholly not related to the extractor or spring. Why does the OAL with this bullet impart this issue when, in the plunk test I conducted, the bullet is not interacting with the lands.

[himurax13]

Have you measured the OAL of a sample of your load? If you measure like 10 or 20 cartridges you may find enough of a variation to cause this issue on occasion, especially with used brass.

 

TBH, I would just go back to the previous oal that worked for you since changing the OAL that small amount won't yield that much difference in velocity. Or you could ream your barrel so that you will have more free bore.

 

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[muncie21]

The extractor holds the loaded round in place prior to firing.  Could be that the new extractor hook or location of pin dimension have changed the way the bullet is presented. 

[rougeqc21]

12 hours ago, himurax13 said:

Have you measured the OAL of a sample of your load? If you measure like 10 or 20 cartridges you may find enough of a variation to cause this issue on occasion, especially with used brass.

 

TBH, I would just go back to the previous oal that worked for you since changing the OAL that small amount won't yield that much difference in velocity. Or you could dream your barrel so that you will have more free bore.

 

Yes is get a hundredth or so of variation in the mixed brass sampling I am using to load.

I am more curious around WHY that induces the failure when I still am well off the lands with both loads.

Am I simply getting faster peak pressure on the longer load and seeing a piston effect from the case strong enough that the ejector cannot maintain control?

[rougeqc21]

Can close the case here. It was a pressure issue.

[himurax13]

 

Yes is get a hundredth or so of variation in the mixed brass sampling I am using to load.

I am more curious around WHY that induces the failure when I still am well off the lands with both loads.

Am I simply getting faster peak pressure on the longer load and seeing a piston effect from the case strong enough that the ejector cannot maintain control?

 

Actually, I am expecting .005 or more variation in OAL between each case so I expect some rounds may reach .010 longer than you would like.

 

Unless the white plastic cube is not seated right on the powder thrower, I don't see how this could be a pressure issue.

 

 

 

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