I have a Ruger GP-100 367mag with around 300 rounds of 357mag (about 100rds 110gr, the rest 158gr) and 300 rounds of 38 special through it.

I detail cleaned the heck out of the gun with Hoppe's and Breakfree CLP.
When inspecting the chambers, I noticed that I couldnt get some residue out of them just ahead of a 357 case. After a lot of rubbing with patches and a nylon brush I gave up. I did notice that if you look closely you can see what looks like tiny little cracks about 1/16" long directly in front of a 357mag case. I dont know for sure if they are cracks, scratches, or simply spots were the powder residue came off.

Any ideas as to what this is?

I'll try to take pics and post them tomorrow.

Without seeing your weapon I can’t say for sure...but I would bet you have nothing more than built up corrosion in the throat area from shooting the shorter .38 specials in the magnum chamber. I used to get the same thing in a .44 mag whenever I shot allot of lead .44 specials in it.

Nylon brushes and cleaning solvent won’t be much help in removing this gunk. You need to use something a bit more aggressive like JB bore cleaner and patches wrapped around a brass brush and work it in a circular motion rather than in and out.

somebody correct me if I am wrong on this, but in a 357, if it is ahead of the 357 case then dont' some of the manufacturers have a slight difference in the cylinders cut at this point? maybe to keep from using too long brass or something? I have noticed this in revolvers that have not been fired, a line around the chamber just ahead of the end of the brass.

are you having difficulty chambering rounds? or extracting them? if not then I probably wouldn't worry about it. I also almost never shoot 38's in my 357. not worth the possible errosion.

Red

i have heard erosion described as looking like a sun-baked mud plain or like the skin on an alligator's back.

True erosion, like that found in a rife's throat just looks rough to the naked eye. Under magnification, like with a bore scope, it will look like a dry, cracked mud flat, or lake bed.
What you are seeing is probably just built-up fouling. For powder fouling remove the cylinder & soak it in carb cleaner, then scrub with a brass brush. Maybe even use your drill to spin the brush. Use at least a .40 caliber brush. Then follow up with an agressive copper solvent, like Sweets or Barnes CR-10, Do the same, except only let it soak about 10 minutes before brushing and cleaning it off. If you leave some of the stronger copper solvents on too long, they will etch. It'll ruin a good brush, but you CAN get it clean.

This built-up 'fouling' is why they make Stainless Steel cylinder brushes.

Nylon brushes and patches may work well on your pretty rifle, but when you get into handguns, they are a little less refined and need a more aggressive cleaning regimen.

-Spencer

Thanks for the info guys.

I haven't uploaded pics yet because my girlfriend took the digital camera with her when she left town. I had pics of it but didn't get to transfer to my computer yet.

After reading your comments I beleive what I'm seeing is just stubborn fouling with lines that maybe got scratched into the fouling by a 410 bore bronze brush that I ran through the chambers. I'll upload pics, then try cleaning it again within the next few days (been busy with final exams).

Steel wool wrapped dipped in Kroil wrapped around a brush will work very well in cleaning this up too.

Don

Okay, after being so busy with senior projects and exams I'm glad to say
1-I'm graduating with a BS in forest management
2-I finally got around to posting pics of the chambers

This is it:
http://www.thewolfweb.com/photo_photo.aspx?user=8984&photo=403928&filter=all

It's not the best pic, but its the best I can do with what I have.
I found an old bottle of Remington bore cleaner in my cleaning box. It is slightly abrasive, a lot like Flitz. I put a little on a 45ACP jag and gave the chambers a few spins with an electric drill. The result was very clean chambers with the exception of that little area that you can see in the pic. I also tried a brass brush with oil and the bore cleaner and it made no difference.
So, whats yalls guess on what this is?
Pushing the 45cal plug down the chambers with a patch on it you can feel that when the plug hits that area it fits just noticeably looser.

Fumbler,

Ouch... that is certainly what erosion looks like alright!

That gun has had ALLOT more .38 specials than it has had cleaning patches run through those chambers.

Great pictures though! And congrats on your schooling.

Is it errosion from 38 specials if that ring is ahead of a 357 case?

Do any dangers exist from excessive errosion in the chambers?

BTW, I have not had problems chambering or extracting cartridges.

Fumbler,

Those chambers were pitted and eroded due to poor cleaning (or no cleaning) no matter what rounds were being fired from it. The .38’s just tend to produce a bit more fouling because of their shorter seating depth in the chamber. The “ridges†you see are a part of the boring and chambering process. On your gun that area has just been accentuated due to fouling and poor cleaning.

The gun isn’t necessarily ruined but you are going to have to pay close attention from now on to cleaning those areas really well after shooting as those pits are going to grab and hold allot of fouling that will just keep building up and eating away at the metal if it is left there.

A target shooter would replace the cylinder because those areas will have an effect on bullet expansion and exit alignment of the rounds to a certain degree...but for plinking and normal use you probably won’t notice any negative effects.

You could always take it to a good pistolsmith and have him give it a good inspection and cleaning and see what he says. New cylinders aren’t that expensive, but having them installed and timed will add considerably to the cost. That’s a decision only you can make for yourself depending on what you plan on doing with the gun and how much money you want to put in to it.

Cylinders in revolvers are often overlooked or neglected when cleaning since they are not an integral part of the barrel.

I'd like to see that same picture with a 38 brass stuck in a chamber and the next with a .357 brass stuck in one. I believe that would prove the erroision of the cylinder bore "forcing cone" idea. I have a retired police revolver that never saw a magnum legth load until I got it and it sticks brass something fierce.

Thanks for the info. I'll try to get a pic sometime soon.

On another forum, one man said he thinks it was poor machining that worsened due to lack of cleaning much like you mentioned Rick.

I'm just going to keep on shooting it and monitoring any changes and keeping it clean.
Maybe down the road I'll have Ruger replace it.

Fumbler,

You might want to get a Lewis Lead Removing kit from Brownells. They work really well at cleaning out chambers and forcing cones on revolvers.