My 610 No Dash 10mm Magnum project *Range Report in post #16*

[BLUEDOT37]

Judging from my velocities, I would call these mild to slightly warm loads.
There’s not much load data on the 10mm Magnum, so I was working off what Taffin published...

Yeah, pretty good velocities. Having the extra 2.6" of barrel length is nice too (-vs- my 3.875" bbl.).

I test fired, but didn't (have a) chrono, 180gr w/2400@ 18.6grs. FWIW, QuickLoad estimated 38.2Kpsi. Didn't see any issues with it, other than some jump-crimp, which wasn't unique.

LOL, that vertical split is the way just about every 40S&W I've had split looked (in my auto pistols).

I've split 10MAG brass horizontally. The Manson reamer I used was machined to tighter specs than what S&W originally cut the chambers to which leaves the slightest of a "transition" between the two cuts.

I need to try some more to reduce those transitions in my chambers, without ruining the chamber shoulder's sharpness. (I like having the option to shoot without moonclips so a good shoulder to headspace the case mouth on is necessary for that.)

Anybody else run into this? Thoughts on fixing it? I was going to invest in a custom reamer of slightly larger diameter, to clean them up, but haven't committed to that yet.

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The "transition" is the faint line near the mouth of the case. They split/separate where the brass starts to thicken, as it get closer to the web. I suspect because the case doesn't freely move rearward to the frame's breechface, when fired, because of the transitions resistance on the case mouth?

I don't think it's the brass' fault but I'm not 100% on that either.

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[Kyler Hamann]

Thanks to the advice on this site, I found the info I needed to ream a new 610. On the advice of a friend, who has put a long career into making and chambering barrels, he recommended reaming one chamber and doing some testing, before I did the rest. I used a standard Clymer 10mm Auto Finish Reamer and had great results getting to the correct Magnum depth. By hand, I did one chamber one evening, and after some testing, did the other 5 on a weekend afternoon. It took good cutting oil (Viper) and lots of elbow grease, but it was pretty simple and quick. So far I've had good luck shooting Mag rounds against the shoulder in the chamber (without a moonclip - in case that feature is ever needed).
I don't seem to have any issues with an "Auto shoulder", but I've shot a very limited amount of 10mm Mag. My Magnum brass has been backordered with Starline for 7 months... so I only have one box of 20 from factory loaded Double Tap that I've been playing with.
Any advice on finding brass and loading data (I have the Taffin and Accurate Arms data) would be GREATLY appreciated.

 

[BLUEDOT37]

I used a standard Clymer 10mm Auto Finish Reamer and had great results getting to the correct Magnum depth.
It took good cutting oil (Viper) and lots of elbow grease, but it was pretty simple and quick.

Slow & easy, that's the way to ream them by hand, to get the most consistent results.

So far I've had good luck shooting Mag rounds against the shoulder in the chamber (without a moonclip - in case that feature is ever needed).
I don't seem to have any issues with an "Auto shoulder", but I've shot a very limited amount of 10mm Mag.

The only problem I see, & have experienced, with cutting a revolver chamber (with a shoulder) for auto ammo -vs- a revolver chamber cut (without a shoulder), is that you can more easily get bullet interference with the throats in the former than the latter.

I've ran into this in my 45WSM (with "auto cut" chambers) using cast LSWC bullets that leave more of the bullet's shoulder outside the case.

(I really like my 45WSM, as a wildcat "auto cartridge" in a revolver, over the 10MAG, if for no other reason than the availability of bullets with cannelures. Anything .45 is just cool anyway. )

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My Magnum brass has been backordered with Starline for 7 months... so I only have one box of 20 from factory loaded Double Tap that I've been playing with. Any advice on finding brass...

I've had a back-order with S-L since Apr-2021 for 10mm MAG brass. Don't know if they lost my order or they still haven't made a run of them yet?

I got some from a forum member here. You might try putting an ad in the WTB section.

...and loading data (I have the Taffin and Accurate Arms data) would be GREATLY appreciated.

I've tested a lot of different powders with 165gr JHPs in the 10MAG.

Here's some LabRadar chrono results:

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- USE AT YOU OWN RISK! -
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[Kyler Hamann]

Thanks BlueDot for all the great data! I'll definitely give some of those loads a try.
I've checked with Starline a couple times in the past 6 months and they claim 10mm Mag is on their list to fill Backorders at some point. In the meantime, the WTB section is a good idea.