GP-100 and cast bullets?

[FergusonTO35]

Hey guys. I fired my new Geep last night using my favorite .38 Special load. It consists of a 158 grain LFP at 870 fps. Accuracy was good but I noticed what seemed to be an awful lot of discharge out of the barrel/cylinder gap. I could feel it hit my hands as I was shooting. Also I saw the same discharge fouling on the frame just below the rear sight. Is this the norm with these revolvers? I plan to use almost exclusively lead slugs in it. Would it be wise to have a smith open up the throat some?

 

[Iron Mike Golf]

Discharge? Is it lube? I find I seem to get more lube blown out the B/C gap with lower pressure loads. I don't know why.

You need to make some measurements before you can know if you need work on the throats. Slug the bore to find the groove diameter. Slug the throats or use pin gauges to get each throat diameter. You want to fit bullet diameter to the barrel and then throat diameter to that bullet diameter.

 

[FergusonTO35]

Thanks, it may be bullet lube. I'll try some copper plated slugs and see if that changes anything. I'm really liking this wheelgun, wouldn't mind finding a .38 Special fixed sight model to go with it!!

 

[the fatman]

Here is a link to the ruger forum net http://rugerforum.net/ruger-double-action/8025-gp100-lead-v-jacketed-bullet-choice.html where a retired gunsmith named Iowegan talks about the GP100.

 

[FergusonTO35]

Thanks!!

 

[surveyor47]

The symptoms you describe are typical forcing cone/barrel alignment to barrel issues. Send the gun back to Ruger with a letter describing the issue. The gun will come back with half its parts replaced and I promise that it will shoot so much better. 1 sometimes 2 trips back to Ruger shortly after purchase is pretty normal. Same for S&W, except that it frequently takes 4 to 6 trips back to straighten them out.

 

[FergusonTO35]

Thanks. I'll shoot it a few more times and see what happens.

 

[GP100man]

Measure the cyl gap , I like .006" , .008 is in "spec" but a little much for my likes!

 

[Hugh]

Here is a link to the ruger forum net http://rugerforum.net/ruger-double-action/8025-gp100-lead-v-jacketed-bullet-choice.html where a retired gunsmith named Iowegan talks about the GP100.

Not my thread, but that is some very useful information. Thank you Fatman.

 

[protoolman]

Im betting its just bullet lube. I shoot a lot of cast and thats just the way it is. nothing to worry about. I have not seen a GP100 with alignment issues but I guess anything is possible.

 

[GP100man]

I use a soft lube & it gets on my shooting glasses , talk bout a mess to clean off !!! windex won`t touch it !!!

But if I don`t go & change everything my barrel is shiney clean !!!!

 

[surveyor47]

Im betting its just bullet lube. I shoot a lot of cast and thats just the way it is. nothing to worry about. I have not seen a GP100 with alignment issues but I guess anything is possible.

According to a gunsmith who specializes in accurizing black powder revolvers, ALL manufacturers have cylinder hole to barrel alignment issues and the only way not to have such issues is to place a jig into the frame, cock the hammer and drill into a blank cylinder. Cylinders are usually made independent of the frame and alignment issues are certain, particularly when the bit chatters. At least according to my gunsmith.

If you take an EMPTY revolver, cock the hammer and look down the barrel into bright sunlight, you can actually see misalignment on Italian black powder revolvers, usually on 1 or 2 chambers on a good gun. Also note that the Italian guns use a RIFLE twist barrel, rather than a 1:16 twist, appropriate for a revolver. This is the reason that barrels are replaced on accurized revolvers.

Bill Ruger knew all that and designed the Old Army accordingly.

 

[firescout]

Curious as to what powder is in your favorite .38 Spl loads? I've been using W231 for two decades for all my .38 Spl and 9mm practice loads. There are always some soot deposits on the frame and cylinder after a session, but they wipe clean easily. I can't recall what I measured my GP-100's cylinder gap at, but I know it was within Ruger's spec.

 

[DanAKAL]

FWIW I simply do not shoot 38 loads in my 357 GP100 any more because of all the fouling issues you describe. I've shot reloads and factory ammo 38 Special and it just makes a total mess of the gun. I switched completely to 357 loads and don't have the fouling prioblems anymore. Before you ship your gun off perhaps try some 357 loads to see if it makes a difference. I really can't say why but it made a huge difference in my GP100.

Dan

 

[WESHOOT2]

38 Special loads = W231 (or sometimes Universal, or for special needs HS6. Or 'other').