Reeder Custom Guns - 10mm Magnum handloading

I see that you offer the ultimate 10 here, and I've recently rechambered my S&W 610 for the 10mm Magnum, so I'm wondering if anyone has an available resource for starting loads to work up. My 610 is the 4 inch model and is primarily intended for woods carry. I have a .41 mag, and load for it, but there's enough of a difference in case size and volume that I'd be rather hesitant to use .41 mag load data directly. I've already ran across the Taffin test load date, but I didn't see anywhere in that article that shows specifics on the starting load, so I'm left to assume a start of minus 10 percent. The Loaddata.com is all AA7 and AA9. Tha Taffin and Loaddata.com info gives me at least a little something for powders that I have, notably AA7, AA8, W296, and H110, but I'd like to work up loads for some other powders I have on hand....specifically Ramshot Enforcer, Alliant 300-MP, Vihtavuori N-105, and 800-X. I shoot cast bullets (18 BHN) in the 200 to 220 grain range currently.

Anyone who has some info or resources to pass, or would care to collaborate on this endeavor, can contact me directly at meat.whiz@gmail.com.

Thanks in advance....Sean

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it literally is the same capacity and bullets. You can manufacture unique bullets by allocating a LEE .401 push through sizer and after lightly lubing, forcing .410" .41 magnum projectiles through it, on a SINGLE STAGE press. I've done hundreds for 10mm and .38-40 applications.

.41 Special data is also useful. Generally you can begin with 10mm auto data and work from there. The greater capacity will ensure slightly reduced pressures. Keep in mind listed precautions reducing slow burning powders in relation to case capacities.

The .400 is great caliber and fun with a little imagination. I can shoot 135 - 230 gr. for special applications.

I was trying to replicate ancient shot loads, still working at it.
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Those bulllets are BUTT UGLYii

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it makes great "looking" 170 and 210 gr. JHC 0.401" bullets for me. I have squished a lead core before and it made a bit mash out but it did not seem loose. The bullets do become longer.

It's about as far as you can go sizing down, 0.010". I's much easier taking .311-.314 to .308, .360 to .358-.355 etc. My .38-55 mould throws .380" bullets. So I mash them to .376". I think a lot of old .38-55's had oversize bores. Some old .38/40 ran 0.403" too.

I've done a bunch of cast .41 to .401, it can rub the grease grooves pretty good. You should see the bag of home made Paco Kelly bullets I ended up with, it is a wonderous study in itself.

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I think he dreams about it. Never seen anyone so obsessed with an outdated obsolete caliber before.

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Magazines. It was marketing injustice. The .41 Remington was the most senseless round ever. No reason for it. Herter had his .40 Magnum out in ‘61 I think. Made by Norma of all people. The six gun was sound and got Bill Ruger’s attention, enough he filed suit against sharing the name single-six. The .44 Mag was in general population by that time. S&W, Ruger, Herters, Jager, Hawes, all had a .44. Why in the world would we need a .41 when the .44 was actually a .43? S&W and Remington hated any little guy muscling in on the action. Especially a blow hard like George Herter. Besides Keith was going off the hinge hawking his own ideas of a police wheel gun. He too could not stomach Herter’s niche success. Such were the days of “He-men”.

The .41 made as much sense as if someone came out with a REAL .442” 44 Mag. today.

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for the 10mm Magnum and work up half a grain at a time until you see pressure signs.

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It occurs to me that I left some stuff out of the original post. I've been resizing 41 mag cases to use as rimmed 10mm for most of the 12 years I've had my original 610. I actually have 2, a 6.5 inch and a 4 inch, but I was trying to keep the initial inquiry based on the 4 inch I'll be carrying most often. Both were converted just recently.

One thing I do know from resizing the 41's for use as 10mm is that the case volume is somewhat reduced from the original rimless 10mm cases. Additionally, 41 mag cases, according to Starline are 1.285", while 10mm mag cases are 1.250. Having swaged down and trimmed the 41's to 10mm really squeezed the capacity, and my go-to load for that ended up being a compressed load of 10gr of 800-X under a 200gr cast bullet. It's a hot load, but shoots the best out of anything else I've tried. Magnum powders (296, 110, etc) just wouldn't work well at all in the short case.

I did try to pull up what was available or the .401 Herters, and the case length is pretty much the same as the 41. So, with the swaging and the trimming, I would be hard pressed to believe that the case volume would be the same between 10mm and 401's....I don't know how much that 0.035" would matter, if it all, but I did chase a rabbit hole to see what I could turn up.

I agree with Gary that starting with 10mm data and working up will work for some of this, and there's the already published data for h110, 296, AA7 and AA9....but I'm now into the magnum level cartridge and would like to see if I can get some performance from the 3 other magnum powders I have.....namely, the 300-MP, Enforcer, and N105.

As far as bullet stock, I have a buttload of 200 grain cast from Missouri Bullet, and they have some 220's I'd like to make use of that were just too long for the shorter case, but should work dandy in the magnum. I have the Lee .401 sizer, and have resized some bullets in the past, but I'll save that task for now and maybe make use of it when the time comes that I want to venture into REALLY heavy bullets. Best I concentrate on the basic part of it that I'm on right now.

I hope this helps everyone understand where I'm at and where I'm trying to go. I'll probably invest in a chronograph sometime soon to help with development. Just off the top of my head, I think a conservative goal at this time is to aim for pushing a 200-220 grain pill between 1350 to 1550 feet per second.

So that's my thoughts so far.

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The reformed .41 mag brass I use ends up being 1.29-1.33 etc. it won’t fully chamber till I trim cases to 1.27. That’s two hundredths ahead of a 10mm Magnum at 1.25, so close enough to use starter loads and like Gary said work up. The 10mm Auto loads are even more conservative.

My .41 mag. to .401 Herters brass need a few thousandths turned off the external web area of the case. A fun trick I figured a way. It’s the part that the shell holder hides and you can’t size a solid web anyway, it won’t go. That Smith 610 dimension must be more generous than the old Herters. The OD of a 10mm, .40, 10mm Mag., .4O1 Herters case are all nominally 0.429”. I tried some rimmed 10mm autos in my custom GP100 but the rims got into the pawl gears and thickness was an issue against the recoil shield. I made (6) cases that worked! Lol

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I got into reloading when back in 2009 with that shortage....started converting the 41's shortly after the first 610 purchase in 2010. As for that shoulder, I rigged up a thing that sits on top of the shell holder, centers on the primer pocket, and pushes the entire case into the die up to the rim. Then I zip off that shoulder next to the rim with a file as it spins on a dowel I chuck into my drill. It works pretty good, but I just ran across a case head swage die on CH4D that would likely do a much cleaner job of it.

I'm not sure why the trim length was sticking in my head so much....I just did the math on 0.035", and it's less than a millimeter, so probably negligible with regard to starting loads. I think the combination of factors with case length and transitioning to the magnum powders started to overwhelm me. Not to mention that I've been mostly dormant with the reloading the past 5 years, and I'm not too proud to ask what others might advise.

Comparing the case dimensions of 10mm mag and 401 powermag, the cases are pretty much the same diameter from head to mouth....so I'm not so far off with re-sizing and trimming the 41's. Just seemed like I trimmed more off the length than I actually did....lol.

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10mm Magnum handloading

Sean, the 10mm mag is the .401 Herter's rimless

Sorry WB but

LOL, I've had good luck with Serria

I think WB has 401 Herters tattooed on his chest

Lol, I loved the research. Buying and trading old books and

you can use the top end 10mm loads as a starting point

10mm Magnum continued

The .401 Herters needs 1.27” or shorter cases

WB