Ruger GP100 Match Champion 10mm

[Stephanie B]

So obviously, the Blackhawks headspace on the case mouths.

But the SRH and GP use moon clips. While it's possible to headspace on the moon clips, it's not necessarily best practice. I have seen enough issues with inconsistency of rim groove dimensions and variation between brands that I wouldn't be at all surprised to find some brands of ammo tended to have problems when headspacing on the clip. Some are nice and square, with a crisp corner. Others tend to be a little more rounded, maybe due to a more worn tool. I haven't done a full engineering program, but I can imagine a variety of ways that headspacing on the clip could go wrong and lead to inconsistent ignition. Certainly enough that I believe Ruger's statement.

That makes sense. Traditional revolver rounds probably have tighter tolerances for rim thickness because of how they headspace. Autoloaders may not be as tight in that dimension, for as long as the extractor snaps over the rim, everything is good.

[Spartan1980]

Someone else here may have mentioned it, but when I look at my Hornady Ballistics charts, it seems like the only real advantage this has from the get-go over a .357 magnum GP100 is that you're using moonclips for a faster reload.

Or if you've got a Glock G20 you achieve ammunition commonality.

But ballistically, unless someone knows something I don't (which in this case is a pretty low bar), I'm just not seeing any significant advantage inherent to the 10mm cartridge chambering over .357 magnum...

From the Hornady chart:

.357 Magnum 158 gr XTP: Velocity: 1250 Muzzle Energy: 548 Energy @ 50 yards: 463

10mm 155 gr XTP: Velocity: 1265 Muzzle Energy: 551 Energy @ 50 yards: 430

Am I missing something?

While I don't doubt it's a great gun, and I applaud Ruger for coming out with the chambering, for me personally it's a bit of a "Meh..." compared to my GP100 in .357.

Best, Jon

Current factory loads are anemic compared to the originals. Once upon a time factory 10mm loads were pretty much equivalent to a .41 Magnum.

[Wondering Beard]

Someone else here may have mentioned it, but when I look at my Hornady Ballistics charts, it seems like the only real advantage this has from the get-go over a .357 magnum GP100 is that you're using moonclips for a faster reload.

Or if you've got a Glock G20 you achieve ammunition commonality.

But ballistically, unless someone knows something I don't (which in this case is a pretty low bar), I'm just not seeing any significant advantage inherent to the 10mm cartridge chambering over .357 magnum...

From the Hornady chart:

.357 Magnum 158 gr XTP: Velocity: 1250 Muzzle Energy: 548 Energy @ 50 yards: 463

10mm 155 gr XTP: Velocity: 1265 Muzzle Energy: 551 Energy @ 50 yards: 430

Am I missing something?

While I don't doubt it's a great gun, and I applaud Ruger for coming out with the chambering, for me personally it's a bit of a "Meh..." compared to my GP100 in .357.

Best, Jon

I Imagine that using heavy loads (hardcast 220gr @1100fps or so) from the boutique ammo makers would make that Ruger more interesting.

[Lester Polfus]

I Imagine that using heavy loads (hardcast 220gr @1100fps or so) from the boutique ammo makers would make that Ruger more interesting.

It's funny you should mention that. Realguns did a review and got 1185FPS with a 220 Grain Buffalo Bore load.

Historically, that's been a load many autoloaders have choked on, but of course, it's a non-issue in the GP100.

Hmph. I'm vacillating...

[jeep45238]

So obviously, the Blackhawks headspace on the case mouths.

But the SRH and GP use moon clips. While it's possible to headspace on the moon clips, it's not necessarily best practice. I have seen enough issues with inconsistency of rim groove dimensions and variation between brands that I wouldn't be at all surprised to find some brands of ammo tended to have problems when headspacing on the clip. Some are nice and square, with a crisp corner. Others tend to be a little more rounded, maybe due to a more worn tool. I haven't done a full engineering program, but I can imagine a variety of ways that headspacing on the clip could go wrong and lead to inconsistent ignition. Certainly enough that I believe Ruger's statement.

Then the same should apply with 10mm.

[Stephanie B]

If they’re going to make the GP100 in 10mm, why don’t they make it in .41 magnum?


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[Sigfan26]

If they’re going to make the GP100 in 10mm, why don’t they make it in .41 magnum?


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Because they want to sell 2,000 and not 20?


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[OlongJohnson]

Then the same should apply with 10mm.

Right, but if you make the cylinder to headspace the cases on the mouth, then you can make enough clearance in the moon clip relief on the back of the cylinder to let the clip itself float. That way, it's only holding the cases in the X-Y plane and assisting ejection. It seems logical to me that the clip should have a little fore and aft (Z) clearance to accommodate slight variations in thickness of the moon clip material, minor bending, case groove geometry, etc. without getting involved in the headspace clearances.

[Lester Polfus]

Then the same should apply with 10mm.

Right. But if the 10mm case fits a little loosey goosey in the moon clip, the step in the chamber should keep it from driving too far forward for ignition to be erratic. The .40 S&W case has plenty of room to move forward with the force of the firing pin and get a click instead of a bang.

[Lester Polfus]

If they’re going to make the GP100 in 10mm, why don’t they make it in .41 magnum?


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It does make one wonder, doesn't it? The max pressure for 10mm is actually higher than .41 Rem Mag, IIRC. That's quite a bit of power in an L-frame sized gun, instead of an N-frame.