Ruger GP100 357 MAG.

[dwo357]

Just purchased brand new GP100 357mag. for my daughter. Fired 6 rounds and one miss fired and all fired casings were stuck in the cylinder, a tough time getting out by hand. The extractor would not push them out and one round did not fire. The rounds were of 158 gr. JHP , 8.0 grs. Unique , Win. brass. I have been reloading since 1984 and I have a Ruger Security Six that all these rounds work great in so I am kind of miffed about this. Any thoughts.

 

[JJE]

Hmmm. If the pre-fired cartridges went into the cylinders easily, then it doesn't seem as if it would be a cylinder machining problem. And if it isn't that, the only other thing it could be is the ammo. It sounds as if this load recipe has proven successful in your other 357, but has this same batch of ammo worked in that other gun? If I had to guess I'd say that something about this ammo isn't what you think it is. Magnum primers instead of regular? Slight over-charge? Bad ammo is the most dangerous possibility, so I'd pull some bullets and weigh some charges. If I felt lucky i would just shoot some in the Security Six.

 

[marksg]

Was there possibly excessive oil in the cylinder? That can cause them to be hard to remove after firing.

 

[dwo357]

Not bad ammo

I have shot this same ammo in my securty six forever and had no problems.I just read something about certain primers are harder than others and I have heard that other gp100 people have had similar problems that I am having. Maybe I will try store bought ammo and see what happens. It kind of hurts your pride when this happens. I have never had a problem like this ever.

 

[dwo357]

I did use mag primers and I was under max on the powder. I just figured the load would work in the gp100 because it is supposed to be a bit beefier than my older gun.

 

[marksg]

I've got a GP also. The only time i had that problem was when i first got it and didn't get all the oil out of the cylinder. But they were all factory ammo and the brass stuck.

Cleaned it good and haven't had em stick since.

Not sure weather the magnum primers would be an issue though.

 

[ArchAngelCD]

I don't know, Alliant lists a MAX charge of unique with a 158gr Speer GD bullet @ 7.7gr Unique and that's with a standard primer. Upping the charge to 8.0gr and adding a Magnum primer could put those rounds over-pressure in that revolver. Your load is over the current Alliant max recommended charge weight plus the primer change. (note I said in "that" revolver)

 

[dwo357]

charge

That is strange because I'm pretty sure the Hornady reloading book says 8.3 is max. What's even stranger that 4 different reloading books have different max load ratings.

 

[JJE]

Another possible solution and question about internal ballistics

Another thought: Is it possible that the GP100 is tighter (less of a cylinder gap) than the Security Six, and that this is allowing higher peak pressures so that the fired cases are forced out against the cylinders with more force and therefore are harder to eject?

I'm not sure when peak pressure occurs relative to the position of the bullet, but if pressure is still building when the bullet passes the cylinder gap, then it seems like a tighter gun would allow higher pressures. Could this pressure difference be enough that a tight gun would have much stickier fired cases than a looser gun?

 

[diyj98]

Do the primers show any sign of excessive pressure? Any cratering or flattening of the primers?

 

[KeithET]

Mysteries like this are what happens when one operates at the upper end of the pressure curve. Regardless of what the max charge is in whichever book that's being consulted the load being used in that particular GP100 is to hot. Does not matter that it worked fine for years in a Security 6. Different Guns Different Results. Without ballistic lab capabilities all we can do is speculate as to why. My guess is a tight gun (Minimum chambers) pushing the pressure up into a potentially unsafe region. Tight extraction is a sure sign of potential problems. Its unfortunate that your goto load does not work in both guns. Its possible that you have been over stressing your Security 6 all along as well, just fortunate Ruger overbuilds their guns. It would be prudent to back the charge down a bit, say 7.5g and try again.

KeithET

 

[joeschmoe]

Try some factory loads to determine if it's the gun or your loads.

 

[ljnowell]

Even going back to Alliants 2000 manual they call for 7.8 with a standard primer with a jacketed 158gr bullet.

Do the primers show any sign of excessive pressure? Any cratering or flattening of the primers?

Unfortunately in a handgun that isnt a real reliable way of knowing if they are overpressure. Some load/primer combos will flatten a primer some in a 357 and not be over pressure, some will be way over pressure and the primer will look fine. Unless there are rough machining marks in the cylinder or oil in it, the stuck cases tell the story.

OP you could take some instruments and verify the geometry of the important parts of the gun.

 

[dwo357]

Well I'm looking at my 2008 Lyman reloading handbook and it says 8.3 with a CCI 550 primer (small pistol magnum). But I went ahead and made a new batch with 13.5 of 2400 and the extraction problem is gone but know every 3rd or 4th shot misfires, so Ipop it into the old S6 and fire it off. I'm going nuts trying to figure out this new GP 100.

 

[hAkron]

Could be an under powered spring, a bad transfer bar, or the hammer is dragging on something. I would drop out the trigger group and the hammer. Go over it all looking for burrs or anything that loos like wrong. It all should look very similar to your security six.

 

[tomrkba]

Let's see: defective gun or bad reloads?

I'm going to go out on a limb here and say my first thought is the reloads you made had some sort of problem. Just because you think they're good does not make it so.

The obvious answer is to try several brands of factory loads to see how they behave. If they behave in the same manner, then I would contact Ruger so they can evaluate the gun. But, you won't really know until you test it with known factory ammunition. I am 99% certain Ruger customer support will tell you the same thing.

 

[joeschmoe]

reloads, Max values, new components, new gun... what could possibly go wrong?

Try factory ammo?

 

[jad0110]

The obvious answer is to try several brands of factory loads to see how they behave. If they behave in the same manner, then I would contact Ruger so they can evaluate the gun. But, you won't really know until you test it with known factory ammunition. I am 99% certain Ruger customer support will tell you the same thing.

I agree. Factory ammo is the control. In fact, if you have problems with the factory stuff run it through your Security Six as a double check. If the ammo works fine in it you know you have a sick GP that needs to go back to Ruger.

 

[socalman]

My favorite gun is my Ruger GP 100, .357. I have shot many different factory loads and perhaps 300 various reloads with nary a problem. If you have ANY problem with factory ammo, contact Ruger customer service and I am confident they will take care of your gun.