I am looking for an explanation as to why GP-11 cases on the shoulder ala where head space is determined are so SHORT?


I name my rifles so the K-31, the 1911 are a given. My 7.5 is a Lother Walther barrel so its the 7.5 LW though its a 7.5 Swissicon just like the K-31 and 1911. Its built on a Savage receiver and you set your head space which I had done and thought well done.

I own a LabRadar and I wanted to see how a GP-11 FPS was in the K-31 and the 7.5 LW (I had what should have been a safe reload in the 7.5 LW go seriously over-pressure)

The 7.5 LW would not fire the GP-11, dent the primer yes, fire no. Non fired round would not extract, ergo, head space way to loose (which was a ??? as no issues prior). The head space was clearly too much and should not have been.

So I took it home and began to measure things.

Chambers are real close with the K-31 and the 1911 a few thousandths longer than the 7.5 LW the way its set. Should be fine.

So I pulled a GP-11 bullet out of a case and measured the shoulder. Its .016 SHORTER than the head space gauge. Ergo, the chamber is going to be a bit more than the GO gauge.

The GP-22 cases are short by around .016 from the head-space gauges. As the head-space is not intended to be tight (a few thousandths) that means its probably .020- .025 short.

My take is the K-31 fires the GP-11 because the extractor holds it to the bolt and the firing pin get a solid jab at it.

And an oddity, the latter year GP-11 of which I had a few (79) have the grip grove on the projectile further out (the two lots of the other are 77 and 78 and as you can see from the picture, that grip grove is further Attachment 114276 from the tip.
Information
Warning: This is a relatively older thread
This discussion is older than 360 days. Some information contained in it may no longer be current.