I’m frustrated and wondering if I’m missing anything while trying to work up a revolver load. While I’ve been reloading some 30+ metallic cartridges for around 45 years, I’m running out of ideas how to work up a safe and reasonably fast load for the 10mm Mag.
This isn’t the 10mm Auto, which I’ve been reloading for since 1988, but this is the longer case of the 10mm Magnum (brass offered by Starline). I know this cartridge isn’t needed, and it won’t do anything as well as my beloved .44’s, but I’ve always wanted to rechamber a S&W 610 revolver from 10mm Auto to also accept 10mm Mag - just to tinker with it. Again, I know it has no purpose, but I thought it would be fun to play with a revolver that I could rechamber by hand (simple project for just the cost of a finish reamer) to accept the 40 S&W, 10mm Auto and 10mm Mag interchangeably.
To the loading: There is very little published load data available (and worse yet, I’m hoping to work up a hunting load for a copper bullet that has basically NO data).
John Taffin wrote an article years ago, that has a lot of jacketed bullet loads (he mentions that they are pretty hot), Accurate Arms published quite a few loads for several jacketed bullet weights, and a member on another forum offered me his significant personal spread sheet of JHP loads. But I’m getting really frustrating conflicting results as I’m trying to approach a usable load for any of the jacketed bullets similar to the load data.
While I’m not expecting to work up anything crazy fast, the velocities I’m getting are hardly any better than my 10mm Auto loads (and sometimes slower). Given, my revolver just has a 4” barrel, so I can’t expect much more, but I should be able to get most bullets somewhat faster than the smaller 10mm Auto with so much more case capacity in the 10mm Mag brass.
Double Tap offers a 10mm Mag factory load that I’ve tried. The velocity is pretty good (better than I feel I can safely work up to), but I pulled down one of their loads and the charge weighs about 30% more (!!!) than I would expect for the type of powder it appears to be. (Under magnification, I compared it to many different powders and it “looks” extremely similar to AA #7 or #9 – and not very similar to any other powder). It’s a much heavier charge than I’m comfortable using and even though I’m not completely sure what powder Double Tap is using; the charge is significantly more than any powders listed in the data and a much heavier charge than I can reasonably extrapolate from data of the somewhat similar 10mm Auto, .41 Mag or .401 Powermag.
While I only shot a few of the Double Tap loads, I don't recall them having sticky extraction or flattened primers (I don't think I measured the case expansion on them).
As I get toward the middle of the suggested charge weights from the sparce data, my case extraction gets sticky, and the case expansion above the web is several thousands more than shown in the hottest loads Taffin measured in his article.
Obviously, one factor to watch for pressure on rifle rounds is by reading the primer. Correct me if I’m wrong, but revolver pressures shouldn’t be nearly high enough to be flattening primers (about 10K to 20K psi too low as I recall), BUT I’m getting really flat and even cratered primers (Federal LP and maybe some Federal LPM in this case) on these 10mm Mag loads, long before they are near max powder charges. I know that very light charges in revolvers can have the primers back out, and then the case moves back and “flattens” the primer, but it shouldn’t crater the primer from a light charge.
Even though the chronograph says the velocities are mild, the flattened primers, coupled with the excessive case expansion just ahead of the web (even on virgin Starline brass), and sticky extraction, makes me nervous that I really am getting excessive pressure (even though I’m at the lower end of the published charges and never approaching max).
Bottom line is that I’ve gotten frustrated with the 10mm Mag project and shelved it - going back to shooting 10mm Auto in this revolver. But I figured I’d run it past the experts here and see if I’m missing something on how to watch for pressure as I try to work up a safe load for this revolver.
Sorry for the crazy long post, but I wanted to explain that I’ve tried a TON of things and done a lot of research before posting that I need load help.
Thanks,
Kyler

Working up a load is not that difficult.

But with pistols, you are limited to the powders available.

Might as well try all of them, and see what that gets you.

I have had problems with rimless cases in revolvers.

I just stick to rimmed cases in my revolvers.

Good luck but you just might be chasseing your tail.

OP,
Did you ream the 610 cylinder bores to a shoulder to headspace the 10mm Mag brass or are you using moon clips?

Have you attempted to see if your S&W 610 will ignite rifle primers?

My 610 will NOT take the pressures that my SIG P220R5 10mm's will devour.

fed primers are fairly soft and are the easiest to ignite.

if it were me I'd switch primers, and go to a slower powder.

7 and 9 are fairly quick for a large case,, would you use them to get your highest speed in a 44 mag?

Good points.
The chambers are reamed to the 10mm Mag headspacing, but I've always used moon clips. The measurements should be right for it to fire (the mag case) without clips, but I haven't tried it just for easy extraction.
Valid point about the soft Fed primers. This 610 has had some ignition problems... so I haven't tried harder, but I should explore that.
I've tried a ton of powders, but I can experiment more with 296/110. I've done some work with them, but they seem like the obvious choice on the slower side. I think it was Taffin's article that felt those two powders were too slow.
Seems like Lil'Gun and Enforcer should have some potential too, but no luck so far without early pressure.
Thanks,
Kyler

I could not make it through your OP. However, you can't "work up" revolver (or auto pistol) loads based on pressure signs.
They aren't bolt action rifles. A friend blew up a Ruger Blackhawk trying to do just that.
Be careful.

First off throw reading primers in the trash. That a very bad way to judge high pressure. Also in revolvers the combustion blasts the case back against the recoil shield and that helps flattening the primer even more. One thing after you reload your round wipe all the sizing lube off the cases and make sure your chambers are clean and oil free.

Might read this, John Taffin is a very knowledgeable shooter and reloader.

https://sixguns.com/t/taffin-t...-the-10mm-magnum/330

Enforcer is slightly faster than 2400.
MP-300 is slightly slower than H-110.

you have a few other powders in between that range, but not a lot.

Case capacity means slower powder but; with a 4” revolver with cylinder gap, that extra capacity is clearly not buying you much. Experiments are not always a positive outcome.

Folks need to remember that large rifle primers are longer than large pistol, and you would need to ream out the primer pockets of the cases to use them.

My 610 also doesn’t tolerate the pressures my other 10mm guns do. I think the moon clip design has something to do with that.

That would also explain why Taffin’s tests with an automag are having different results than yours with the 610.

If you are getting sticky extraction, then the gun is telling you too much pressure or that there is something wrong with the cylinder.

I’d shoot some more of the factory loads first and make sure.

Be careful; you can't' "work up" loads for a revolver like you do for a bolt action rifle. You will blow a cylinder eventually because you will exceed allowable pressure before you get good pressure signs, for most calibers.

asking a question, NOT making a suggestion -

it's the 10mm Magnum really REALLY close to a rimless 41 mag?

quote:

Originally posted by jeffeosso:
asking a question, NOT making a suggestion -

it's the 10mm Magnum really REALLY close to a rimless 41 mag?

Yes it is. The 10mm mag case is quite a bit longer then the 10mm case. Thing is do we need it? Probably not.

quote:

Originally posted by shootermetal:

quote:

Originally posted by jeffeosso:
asking a question, NOT making a suggestion -

it's the 10mm Magnum really REALLY close to a rimless 41 mag?

Yes it is. The 10mm mag case is quite a bit longer then the 10mm case. Thing is do we need it? Probably not.

if they are VERY close, i might start with loads, if they match up in the books