Tuesday, April 27, 2010

A couple of years ago I tried loading some hollowpoints in 7.62x25

and had a notable lack of success. Trouble was, after firing one or two rounds some of the others in the magazine would not allow the slide to close completely. And occasionally, before firing, one or two would not allow it when cycled through by hand. Drove me nuts.

Well, a while back I bought one of the Lee Factory Crimp Dies for the cartridge and tried it again. Maybe the crimp from the seating die just wasn't cutting it; if I seat only with that die, then use the FCD to do the crimp, the stuff works fine. Today was the second time I've put a couple of magazines of Hornady 90-grain hollowpoints through, all with no problem.

I'd still like to know exactly what the problem was, but I can live without it.


Roger said...

Sounds like you need to polish your chamber. There's probably some machining marks filling with fouling that cause the problem.
Lee factory crimp squeezes the neck of the cartridge to a smaller diameter than the std crimp.
Full length resize a case, drill out the primer hole & install a rod & epoxy it in place. Then coat the case with fine abrasive & gently run it into the chamber with an electric drill on SLOW until the chamber is smooth.

Firehand said...

Wondered about that, but tried them in another pistol and had the same result. Looked at both chambers and they were nice and shiny and smooth.

Tried the loads in a CZ52, same problem.

Firehand said...

And yeah, that method of polishing a chamber works nicely.

MauserMedic said...

Here's a couple possibilities, based on experiences I had some years ago. On those that would chamber after a few had fired, it could easily be one or more of three problems.

First, without sufficient tension by the case neck, a bullet could be gradually move out due to recoil; this is how kinetic bullet pullers work. A taper crimp die solves this problem, all other things being in spec.

Second, insufficient head space. If the brass is overly long, and headspaces on the case mouth or shoulder, the slide will fail to return to the locked position.

Third, insufficient crimp/excessive belling of the case mouth will create an oversized diameter of the cartridge case. It doesn't take much to create this. In fact, over-crimping the case can lead to a bulge in the case as the bullet is driven down by the press while the crimp is applied, again leading to increased diameter.

These are the three biggest causes of the problem you describe that I've experienced; hope this helps.

One other thing; after spending money and time to attend a match I couldn't shoot at all due to a reloading crimp error on my part, I bought some devices from Midway that are essentially a "test" chamber for reloaded rounds. It's simply a piece of steel chambered for a particular cartridge; if the cartridge won't seat by finger pressure in it, something is out of spec. Don't recall the proper name, but they've been worth every penny, and saved me from several jams.



Anonymous said...

From the Lee Precision website the Carbide Factory Crimp die for 7.62mm Tokarev, sizes the loaded cartridge to factory specification as it crimps. That would remove any bulges or improper profiles from your handloads.

One more reason to like and admire Dick Lee.

Gerry N.

Firehand said...

I first ran into that 'bulge from over-crimping' with .30-30 a long time ago; sneaky thing.

I thought of the bullet slipping forward, but measurement didn't indicate it.

First couple of times I loaded these, I cycled all the rounds through by hand; no problem. Soon as started firing, multiple rounds would not work; saved those to examine but couldn't figure it out(yeah, I probably overlooked something, but no idea what).

Obviously something wasn't setting up right with the standard die doing the crimping; and the FCD does it right. Down the road may load a few the old way and then measure EVERYTHING on any that show the problem, I'd really like to figure it out.

Yeah, I've got a chamber-checker(I call it) for .45acp; very handy thing it is. I wonder if they have one for 7.62x25...

MauserMedic said...

Your comment makes me wonder it there was just a bit of flair left on the case mouth; pulling back the slide manually and releasing it might give enough kinetic energy to overcome this resistance, compared to cycling due to normal powder combustion.

Firehand said...

May well have been a factor.