7.62х25 cases stretching - problem?

KotKotofeich

KotKotofeich

CGN Ultra frequent flyer
Rating - 100%
77   0   0
Location
Ottawa Valley
x0sgcky.jpg


I asked this in the pistol section, but the most knowledgeable crowd on this subject is probably in this section.

The 4 leftmost brass were shot from a p762, two on the right from tokarevs.

Seems that the p762 stretches the brass a lot and it's not just my pistol (from the second import by North Sylva) my friend's pistol (first Canada Ammo import) does it too - the leftmost case is his. Most noticeably the steel cases. I tried all of this ammunition in the barrel removed from the pistol (plunk test) and I don't notice it dropping into the chamber abnormally...

Could this indicate a headspace problem? Is there another test I could do?
 
Neck portion of chamber on this pistol is a bit shorter than on Tokarev barrel, most likely rifling starts sooner than on tok. Due to this when cartridge is fired and bullet has less distance to travel to rifling, therefore pressure is higher this causes case to fireform to the chamber and expand. If it shoots ok and ejects ok, no reason to worry about it.
 
Hitzy said:
My eye micrometer isn't working very well...
What was the length of the case before and after firing?
Click to expand...

sdGH8bO.jpg


The shoulder bump (?) is what's concerning me the most, I guess I did not describe things correctly. The actual length of the case doesn't appear to change that much.
 
Last edited:
gewehr76 said:
Neck portion of chamber on this pistol is a bit shorter than on Tokarev barrel, most likely rifling starts sooner than on tok. Due to this when cartridge is fired and bullet has less distance to travel to rifling, therefore pressure is higher this causes case to fireform to the chamber and expand. If it shoots ok and ejects ok, no reason to worry about it.
Click to expand...

Thanks! That makes sense - my reloads won't chamber because the hornady hp bullet with it's higher (?) ogive jams into the rifling... I'll have to seat them deeper for this pistol...

We did have one of the czech cases get stuck and refuse to extract from the chamber but that was the only one...
 
Last edited:
I load 13gr of Win 296,Starline brass,either 86gr SP or 90gr HP............never had a jam with any ammo factory or mine yet.Polish TT33 new
 
mbogo3 said:
I load 13gr of Win 296,Starline brass,either 86gr SP or 90gr HP............never had a jam with any ammo factory or mine yet.Polish TT33 new
Click to expand...

My reloads are fine in tt as well as in a c96 (I load low for the c96 and they also work in the tt). It is in the p762 that my reloads jam and I can see rifling marks on the bullet when I pry the cartridge back out. I think this confirms that the rifling starts sooner in the p762?
 
You must log in or register to reply here.
Back
Top Bottom