Home Forums Reloading Handgun Reloading Troubleshooting a GP100

Back in October, I bought a stainless Ruger GP100 in 357 Mag. I had just enough time before deer season to get it out and fire some loads, and everything was as it should be. It was still quite warm out back then.

In January, I set about doing serious loading for the new pistol. I ended up cranking out close to 500 rounds of this and that on the Hornady LNL Auto-Progressive. Most of them were target loads. I used Universal for all of them. The bulk were 158 grain lead SWC. I also did 148 grain Berry's DEWC and 125 grain JHP. I also loaded some Lee 358-125-RF. Everything went through the same dies:

RCBS sizer
Hornady PWE
Hornady Powder Cop
RCBS Bullet Seater
Lee Factory Crimp set to a light crimp

My goal was to try a variety of bullets with a light load and see what would get me the best results for groups at 7 yards and ringing the plates at 20 yards. Everything was loaded to 38 +P levels.

I made it down to the farm last week and got the piece out just before starting to head home. Temps were in the high 40s when I started. I had put everything out on the bench and then went back inside for another cup of coffee and popping the cork on the water system. It takes a half-hour to drain the water, and I figured I would spend that time shooting. The first batch, the 158 grain lead SWCs loaded and shot nominally. However both plated bullets (the DEWC and JHP) had real trouble. Select rounds would not go into the chamber the last 10th of an inch. On some loads, we were talking 4 of 6 rounds. The problem got worse with the plated bullets. Eventually I could not get any fully in the chamber so that the revolver would cycle properly. I finally shot some of the lead Lee bullets and packed up and left. Those chambered fine. That surprised me. I loaded them between the two plated bullets.

I assumed there was a problem with the brass or how I loaded it. When I got everything home, I offloaded the truck into the dining room and everything sat until the next day. When I found time, I took the revolver and the loads and went to the loading bench to figure it out.

I opened up a box of some of the wadcutters that had been the worst offenders and 6 popped in like butter. I tried another six with the same result. I switched over to the plated JHP and found no problem. I could not find a problem with any of the loads. Honestly, I didn't make the connection that the biggest offenders were plated bullets until writing this post.

WT?

The only thing I can figure out is the temperature difference between the shooting bench and the loading bench. Lead rounds were unaffected. Plated bullets were.

Anyone have any ideas?

.38 brass, .357 brass or mix?

Perhaps a bit more crimp is needed? Easy to crimp a couple of the offenders a bit more and see if they chamber.

OTOH, if you crimp too much, it can cause a sort of bulge just below the crimp. This is unlikely.

Did you buy this Ruger from Paul Barnard?

It was all 357 mag brass. My buddy traded me 1:1 for my stash of 38 SPL.

That's a good idea. The plated bullets did not have a crimp ring. I was just guessing.

Another thought, was the brass fired in another.357 or new? There is just a chance the Ruger has a tighter chambers are tighter than the earlier revolver and the case near the head has expanded too much to fit. Die may or may not size down far enough to fix that.

Paint the whole case of a couple of the offenders with a sharpie and try to chamber them, that will show you where they are hanging up.

A Lee Factory Carbide crimp die could fix the problem. I've run into plated bullets that benefited from use the Carbide crimp dies.
Dave

Have had that happen quite a few times in my 88 gp. Usually it was because I got a little sloppy on pulling the handle and didnt quite size all the way. When I shot plated such as Berrys I used a taper crimp to keep from marring the bullet.

These were all 1-fired from a buddy who probably ran them through a S&W.

That sounds like the way to go. What I'll do is throw the ammo and the gun in the freezer to get them both cold and see if I can force the issue.

The cylinder on GP100's is shorter than S&W's. Check the COAL..

Is your Lee crimp die the collet type or the carbide type? If collet, one of the carbides might fix your problem.

Once again, painting with a sharpie can remove a lot of guesswork

UPDATE:
I went down this AM and dragged the GP100 and the ammo upstairs. I bagged them up and stuck them in the freezer for 4 hours. I just pulled them out and tried to get them to fit-- no problem.

WTF?

My next step is to try warm pistol and cold ammo and then do warm ammo/cold pistol.

Just a thought: Get some dims on some unused bullets to see if there’s a range, as well as the finished cartridges that don’t fit. Just speculation, but plated bullets (being a softer alloy than hard cast), perhaps the bullets are out of spec?

Maybe a Lee sizer and/or a cartridge gauge are to be considered.

UPDATE: I brought the pistol back up to room temperature, and then tried the ammo that stayed in the freezer. Everything fit just as it should.

I put the pistol into the freezer and left the ammo out to warm up.

UPDATE: Well, I finally got the GP100 out of the freezer and tried it with ammo that had been stored overnight at room temperature. Everything worked just fine.

Now my head really needs scratching. Not only can I not repeat the problem, but I'm out of possibilities as to what caused it.

I've had problems of 357 Mag ammo not feeding before, but it was all before buying my Lee Factory Crimp Die, and it was never a situation where one day it wouldn't chamber and the next day it did.

Unless you guys can come up with a reasonable avenue to pursue, I'm going to just call this a Mystery of the Universe and move on.

Crud rings in the cylinder from some loads, not allowing the next type of load to chamber fully. Then maybe the crud rings got cleaned up by firing different bullets?

Real test would be go out and fire the same amount of each in the same sequence. If it passes that test, then it was just a weird fluke.

I thought of that. That's exactly what this felt like. However, I've only shot 357 Mag out of this piece. I've had crud rings form from shooting 38 SPL in 357 Mag, That's the main reason I stopped shooting 38 SPL in my 357 Mags and only reload 357 Mag even for low-velocity target shooting.

You're right. The next time I go out, I'll try duplicating the problem at the bench.

Thanks for all of your kind attentions on this.

BTW: The one thing that I found interesting in this was how big of a chunk of steel the GP100 really is. I kept that sucker in the deep freeze (-2F) for over four hours to get it plenty cold. It took at least that amount of time to get it warmed back up in the indoor air of roughly 70F. It sweated a good deal as well.

UPDATE: I was back down at the farm with the GP-100. I could not get the problem to repeat. Same gun, same ambient temperature. I used the 4 different loads in the same order and everything slid right into place without any resistance.

As I said before: chalk this up to a mystery of the Universe.

Thanks again.

I have a GP100 that I've had for some 30+ yrs. When I first bought it I was using Lees dies and experienced the same thing that you just experienced. The problem didn't present itself every time I reloaded a batch, but when it did it was a pain in the arse!! I switched to RCBS dies and never had another problem... I can't explain it, and pass it on FWIW.... Good luck,