Ruger GP 100 7 round brass ejection issue

[TheProf]

GP 100 Model 1773. (purchased around June 2018)

Quick summary: I experienced some ammo binding. Not sure if it was Ruger or the ammo brand. The issue was limited in scope. I really like this gun and decided to keep it.



I did a quick experiment with the ammo I had on hand. It consisted of loading all seven rounds, firing it, and then ejecting the spent shells. I started with the .357 loads first, then with the .38 loads...simply to rule out the issue of .357 shells sticking in the chamber due to having fired .38s.

My Informal Test Results:

White box JHP .357 = Could not fit all seven rounds. The seventh shell's rim would overlap with the other shells and would not lay flat on the cylinder, when loaded. Could I force it in? Perhaps. But I chose not to. I saw no need to try to fire with all 7 rounds. I was able to fit 6 rounds...and all fired and ejected easily. (So, in an emergency, 6 rounds would work.)


Federal .357 HP (158 grain JSP) = All seven loaded easily, fired, and were ejected with no issues.

Now, for the .38s.

White box .38 = Fits all seven. Fired all seven. But could not eject. I had to poke out each spent shell individually.
Winchester PDX .38 +P (130 grain.)= Fits all seven. Fired all seven. No problem ejecting.
Remington .38 +P SJHP (125 grain) = Fits all seven. Fired all seven. No problem ejecting.
Hornandy .38 HP (158 grain JHP/XTP)= Fits all seven. Fired all seven. No problem ejecting.


My simple test consisted of firing the different brands in exactly the order above.

The following day...I double verified the brand that I plan on using the most...Remington .38+P SemiJacketed HP. Fired about 50 consecutive rounds. (that's reloading seven consecutive times). 100% problem-free.

I really like the 7 shot format, the rugged Ruger design (the triple locking design). I also really like the look of the 6 inch version. With proper ammo selection, this is a great gun.

This is my quick way to test ammo compatibility without having to fire it:

Ammo should work if they can all be dropped freely into the cylinder. All the shells should be able to fit evenly...without one of the shell rims overlapping the other. The rims should all be able to lay evenly flat on the cylinder face...without having to force one of the shells in. The extractor should be able to extract all seven shells simultaneously....effortlessly.

If all seven rounds of my chosen ammo brand can do the above test....I can depend on all seven shots firing.

Of course, I would recommend you actually test fire the ammo brand that you plan to use in the GP 100 seven shot. Also verify that the fired shells can be extracted with ease...which would be a good thing...in an emergency reload situation. You may want to test from various boxes of said load....just in case there are minor variations from various lot numbers.

Since I am the one selecting and purchasing my ammo, I know that all the ammo on hand would work on this gun. (This is not much different from others using a semi auto... that have to select their carry ammo brand. Of course, a Glock could digest anything.....but I digress...)

 

[Elm Creek Smith]

If you shoot all seven and haven't done the job, you should probably just beat your target to death with the gun.

 

[TomJ]

If you shoot all seven and haven't done the job, you should probably just beat your target to death with the gun.

It may be more effective that way. Maybe that's why Superman stands still when being shot at, but ducks when a gun is thrown at him.

 

[JTHunter]

This may be a dumb question but what do you mean by "rimlock"? Are you talking about the exposed base (primer end) of the brass sticking together? With the heat of firing, is it possible the brass are "self-welding" themselves to each other? Is this only happening on these newer 7-shot revolvers?

 

[TheProf]

In certain ammo brands the rims of each cartridge (the base end/the primer end) are literally touching each other when they are loaded. Once the cartridge is fired, they heat up and expand to the point that they lock themselves in place. The extractor cannot move to eject the shells. It is as if they are welded together. (Obviously they are not.) You must then poke out each spent shell shell individually.

On another situation, when loading..the seventh shell's rim literally overlaps the rims of the shell next to it. Either the ammo is out of spec (rim too wide), or the overall circle of the cylinder is too small. Not sure who is at fault.

But this is limited to a small selection of ammo brands. Overall, the gun is great. There's plenty of brands where all seven rounds work with no issue.

I really like this gun...and it has become my favorite.

I have only heard of this with the seven shot version. The six shooter's cylinder holes are spaced far enough that this is not a problem.

 

[DPris]

Doesn't really have anything to do with heat or firing at all.
On loading all 7 chambers, if the cylinder encounters resistance on closing, but does close with additional effort, and AT THAT POINT, if the cylinder opens again & the rims are locked together preventing easy extraction/ejection, you've got rimlock.

It also appears more visibly in more extreme cases when you have to use some additional effort to seat the 7th round fully.
You MAY not even notice it till after you've fired & open the cylinder to eject the empties.

You don't have to fire the loads in question to determine rimlock, and the temporary heat of firing has no effect on the rim's dimensions.
And to be clear- it IS the rim, not the case wall or body.

The situation exists with a very few loads because the 7 holes are positioned in the cylinder in conjunction with maintaining sufficient wall thickness to contain pressures.
The distance between chambers has to fit within a narrow range that takes wall thickness, forcing cone centricity, firing pin centricity, and wall thickness into the equation.

If the chambers are a couple thousandths inboard of the bolt circle & the ammo rims are a thousandth or two outside normal ranges in diameter, it can all work together to jam case rims against each other, a rimlock result.

The rounds will still fire fine, but it takes extra effort to break the rimlock & push the rounds, or the brass, out.
Denis

 

[TheProf]

I think you are right Denis. In which case I will use your method of quickly checking the ammo brand compatibility.

Load all seven cartridges, close the cylinder, open it again and eject it again. If it does all that with no problem.. then that brand should be to go.

 

[DPris]

Exactly.
No need to fire them.
Denis

 

[JTHunter]

Thanks for the explanations!

 

[Elm Creek Smith]

It may be more effective that way. Maybe that's why Superman stands still when being shot at, but ducks when a gun is thrown at him.

It was easy in classic TV days to stand there while someone shot blanks at you, since "special effects" weren't as graphic as they are now. There were no "special effects" that could keep a prop gun from breaking your nose, splitting your lip, or bruising your "tender parts" back in the '50's.

 

[TomJ]

Ruger told me they'd ship the gun in 2 to 3 weeks. My FFL called this afternoon, and it's here already. With it having a new serial number, apparently the 3 day wait period applies so I'll have to pick it up next week.

 

[sequins]

I hope the new one treats you right, my six shot gp100 is one of my favourite 357 revolvers.

 

[357 Terms]

As a reloader, with many different headstamped brass all mixed together (and no desire to sort) I imagine I should hold off on a 7 shot GP.
How is Ruger going to resolve this? Larger diameter cylinder ?

 

[DPris]

Nope.
Denis

 

[Monster Zero]

Nope.
Denis

Some other solution in the works?

 

[DPris]

They had three areas they could address, but they didn't want 'em publicized.
Denis