.38 Special rim thickness? (Ruger binding)

[Coyote3855]

I posted a similar thread in Gunsmithing and got a helpful response from 243winxb.

Two students are shooting the same brand new Ruger SP101. After 90-95 rounds, it gets hot and to binds up. Loaded cylinder won't turn single or double action. Works fine unloaded.

Tolerances are very tight at both ends of the cylinder. No significant fouling at the forcing cone, recoil shield or the back of the cylinder. No crud under the ejector star.

243winxb recommended trying different ammo. They were shooting American Eagle .38 Special. I put the caliper to some AE and Winchester WB. Seems the WB averages just a hair thinner. Does anyone know what brand of .38 would have the thinnest rim?

We recommended sending it back to Ruger, but I'd like to help them finish the class first.
Thanks

 

[Sunray]

Rim thickness is a SAAMI spec thing. Mind you after 90 or 95 rounds heat isn't your issue. It's crud or parts have come loose. Possibly the ejector rod has come loose. Happens more often with Smiths though.

 

[murf]

do the fired cases eject easily? if not you probably have one tight chamber that gets tighter when heated up. had that problem with a blackhawk. sent the gun back to ruger and they installed a new cylinder.

luck,

murf

 

[gamestalker]

Shouldn't really be an ammo thing, either crud build up is causing it, an out of spec cylinder is responsible, or cylinder gap is out of spec, or too tight. Heat would certainly cause any of the above possible causes to amplify the situation also.

Trying to find ammo with thinner, or thin enough rims to solve the issue isn't going to be an easy task, nor likely effective, as all ammunition is manufactured to SAAMI specifications.

GS

 

[Malamute]

SAAMI spec is a range, not an exact number. Anyone that thinks ammo is made all exactly alike or to perfect optimal specs hasnt measured much of it.

I believe Winchester* brass usually has the thinnest rims. The guys that use moon clips like them, from what I recall. Check with moon clip makers and see what they recommend, or a google search may turn it up.

That gun may just be tight. In average practice shooting it likely would never matter, or in a defensive shooting. Who carries that much ammo on them? Or is able to shoot that many rounds that fast in a real defenisve situation?

Ruger is likely to say its in spec, and it likely is. Again, "spec" is a range, not an exact number.

*Edit: I was mistaken, winchester was the one to avoid. That may partially be the groove depth as much as the rim thickness.

http://www.brianenos.com/forums/index.php?showtopic=149644

TK Custom is showing NOT to use win brass in their regular moon clips, saying the difference is the extractor groove, but all the clips shown to fit Win brass are .005" thinner. One note said

These clips are NOT made to fit Winchester, Hornady Critical Defense & Speer Gold Dot ammo! These cartridges must use .020 thick Stainless Steel, which are available in the shopping cart.

 

[rcmodel]

See this about rim thickness.

http://www.thehighroad.org/showthread.php?t=563715&highlight=colt+commando

rc

 

[Coyote3855]

Thanks for the responses. The spent casings eject easily. As noted, no visible crud buildup on the rear of the cylinder or recoil shield. Did recommend a good scrub with a brass toothbrush between shooters. I will check the ejector rod, although the gun has worked fine until the 90-95 round count during two consecutive range sessions.

I agree that a defensive shooting incident or slow fire at a range would probably not be a problem. However, this is an older couple (well, not older than me) with their first firearm. I think it's critical they have confidence in their self defense gun.

You're correct, the cylinder may be at the near the limit of tolerance and Ruger may say it's in spec. They bought from a good dealer who will help them with a return or maybe replacement.

Edit: Thanks rc. Spot on as usual. From your info (I can't remember what I had for breakfast and you recalled this thread from 2010??), looks like I should try some R-P ammo and see if that makes a difference.

 

[Malamute]

That was a bit confusing, seeing the post from two different places. I tend to look at the "new posts" rather by sections, and look at the title, not where everything is posted.

 

[rule303]

If there isn't build up under the ejector star, I would be willing to bet that your cylinder (front) gap is too tight. You can check it fairly easily with a feeler gauge. Usually if that is the case, you will be able to see rotation marks in the carbon on the front of the cylinder after firing, from it dragging on the barrel. I'm sure Ruger will take care of you, or a gunsmith should be able to touch it up pretty easily.

 

[Coyote3855]

If there isn't build up under the ejector star, I would be willing to bet that your cylinder (front) gap is too tight. You can check it fairly easily with a feeler gauge. Usually if that is the case, you will be able to see rotation marks in the carbon on the front of the cylinder after firing, from it dragging on the barrel. I'm sure Ruger will take care of you, or a gunsmith should be able to touch it up pretty easily.

Rule303: I'm thinking out loud here (well,what passes for that on the internet). If it were binding on the forcing cone, would it still bind with an empty cylinder? It works fine unloaded. Would the cartridge heads would put forward pressure on the cylinder, just enough to cause the problem?

Just eye balling, the front gap is very tight. I'll haul some feeler gages to the next class. My old Speed Six is a go at .006, no go .007. I've not had a problem with it, but I've never put 100 rounds through it 20 minutes either.

 

[J-Bar]

Perhaps the gun is saying "lube me!" Have you tried a spritz of oil in there at, say, 75 rounds?

 

[Jim K]

Don't get all tied up about the rear of the cylinder and forget the front. If the barrel-cylinder gap is too tight, even a relatively small amount of rapid firing can cause the cylinder to expand lengthwise and bind on the barrel. If the b-c gap is under .003", I would definitely have it increased to .006-007", which I consider optimum.

Jim

 

[AirForceShooter]

Call Ruger

They'll fix it for free

AFS

 

[tightgroup tiger]

My SP101 gets tight on the cylinder pin after a while. Crud gets in there and a good cleaning takes care of it.
I eject the cylinder and spray brake cleaner in the groove on the under side of the pin the cylinder spins on and spin the cylinder at the same time. I can't believe what all comes out of there.
I then spray it with Rem oil and it spins like a new one. If I'm shooting lead bullets it could tighten up in as few as 50 rounds.

Jacketed bullets will go to about a hundred and it will need to be cleaned again.
My SP101 is .327FM with reduced loads but it's the same problem your having.

 

[Caswell Ranch]

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