Reloading/ammo question - does bullet diameter affect moon clip fit?

[matteekay]

Hey all,

 

I have a bit of an oddball question. I shoot a Chiappa Rhino in 40 S&W in IDPA (like I said, oddball) and I'm trying to work up an ideal moon clip/cartridge combo for insertion and ejection. The gun is admittedly finicky when it comes to brass - when I was using TK custom moons and mixed brass, I'd have loaded clips that wouldn't drop all the way into the cylinder and fired moons that I'd have to knock out with a tool. Changing to all Starline brass alleviated 99% of the problem but I still have the occasional moon that doesn't drop all the way in (especially when the gun gets dirty). This results in a random heavy trigger due to the cylinder dragging. And yes, I've checked that the clips aren't bent.  

 

One thought I had was swapping my 200 gr SNS coated lead bullets (sized .401") for something sized .400" (probably jacketed). Obviously it would be a very minor change but my thinking is that removing a tiny amount of friction from each of the six rounds could be just enough to improve overall fit. Has anyone ever experimented with bullet diameter as it related to moon clip fit? Or seen any difference in coated vs. jacketed?

 

[alecmc]

The only thing that should effect moonclip fit is the groove around the rim of the case where the moonclip fits.

 

What your problem actually sounds like is tight / short chambers in your cylinder that are not allowing the clip to drop in fully. The "ledge" could be a bit short, or the chambers a touch tight. A finish reamer sounds like it's in order. 

[matteekay]

Could be either (though there's a good chance the chambers are tight) as either would be exacerbated by powder buildup during a match. Do they even make reamers in 40? And can an idiot like me run one?

[MikeyScuba]

Not an expert but would a lee bulge buster help?  Throwing it out there.

[matteekay]

36 minutes ago, MikeyScuba said:

Not an expert but would a lee bulge buster help?  Throwing it out there.

 

Not a crazy idea. I'm already using a FCD and gauging my ammo, but brass inconsistency would definitely cause an insertion issue.

[MikeyScuba]

Lee fcd isn’t all that imo.  I use ‘em but in my limited svi you can’t go without case gauge checking all match ammo.  Not if u want a unwanted failure to chamber on a stage!

Edited September 3, 2019 by MikeyScuba

[missed it by that much]

I'm a fellow idiot and I've ran reamers in 357/38 cylinders with success. I used clymer but not sure if they still exist or make one for 40.

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[Sanzo]

Had a lot of similar problems with my Rhino in .40.   Generally had to clean the cylinder after each stage.  It was worse with Clays, or light loads where there was unburnt powder.  The gun seemed to like copper plated better than lead coated.  I never did get it to work reliably enough and sold it about a year ago.    I would try different profile bullets and see what experience you have. 

[Toolguy]

The main problem I've seen with rimless ammo in revolvers is that the chamber is cut to headspace on the case mouth like a semi auto. That leaves a square shoulder in there where lead, powder, and carbon build up. After it gets dirty, the cases don't seat fully without pushing them. On a semi- auto, there is only one round at a time, with a springloaded slide to ram it in there. On a revo, there are multiple rounds with only gravity to get them in.

 

When I made my .40 revos out of 686 guns, I ordered a chambering reamer from Manson and specified a 10 degree taper from the case mouth to the bullet diameter (throat). That way there is no ledge for the crud to build up. It just goes out the barrel with the bullet. I had them make another .38 super reamer the same way. They both work great. For .45 ACP, I recut the chambers with a .45 Colt reamer, because the rimmed cartridge reamers all have that taper at the front.

[matteekay]

The main problem I've seen with rimless ammo in revolvers is that the chamber is cut to headspace on the case mouth like a semi auto. That leaves a square shoulder in there where lead, powder, and carbon build up. After it gets dirty, the cases don't seat fully without pushing them. On a semi- auto, there is only one round at a time, with a springloaded slide to ram it in there. On a revo, there are multiple rounds with only gravity to get them in.

I think this is the most likely culprit, exacerbated by a less than ideal moon/brass fit and potentially bullet profile and size. I just ran the Rhino at the IDPA state championship and, even though I brushed it out after every stage, I still had a moon or two that were stubborn going in (at the most inopportune times, of course).

I'm not confident in my ability to run a reamer so I'm looking into smiths at the moment (for a honing at the bare minimum). I've just about used up my 40 bullets so I might try out some .400" FMJ's just to see if I notice any change on that front.

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[GMM50]

We ALWAYS us a hone on the cylinders.  Even the Titanium ones.  This helps a lot.

[Toolguy]

If your cylinder is not Titanium or have a hard coating, I will use my reamer if you send me the cylinder. As long as it's bare stainless or blued steel. The reamer was a $200 special so I don't want to ruin it on a hard coating.

[matteekay]

If your cylinder is not Titanium or have a hard coating, I will use my reamer if you send me the cylinder. As long as it's bare stainless or blued steel. The reamer was a $200 special so I don't want to ruin it on a hard coating.

I believe it's regular blued steel. My Charging Rhinos have some kind of silver coating but I dunno what it is.

I'll drop you a PM in a bit, and thanks!

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