Quote from: shottist on June 10 2020 09:28:40 AM MDT
I reamed by hand.  Been so long ago I don't remember where I bought the reamer.  I have loaned it out to others on this site and always gotten it back.  If you would like to borrow, let me know guypalmer@bellsouth.net and I will see if I can find it.

How did you ensure they were all reamed to the same depth?


Sent from my iPhone using Tapatalk Pro

Quote from: shottist on June 10 2020 09:28:40 AM MDT
I reamed by hand.  Been so long ago I don't remember where I bought the reamer.  I have loaned it out to others on this site and always gotten it back.  If you would like to borrow, let me know guypalmer@bellsouth.net and I will see if I can find it.

I sent you an e-mail...  Many thanks in advance for the generous offer!

OK, I've just done this, and it was easy. 

Background:  I'm a historian, not a machinist or gun-smith.  I'm an avid DIYer, and I had drilled and tapped my Benellis' carrier latch releases to install bigger buttons, but that's about the extent of my experience, so initially I found this a bit intimidating...

Many thanks to Shottist for sending me his reamer:  He not only saved me the cost of renting/buying a reamer, but receiving the reamer in the mail got me to do this ASAP.

Quote from: Mike D on May 08 2020 12:24:39 PM MDT
Unfortunately I don't have the equipment and possibly the capability to do it myself.

Nonsense.  You just need the reamer, a tap wrench to turn the reamer, and a vice to hold the cylinder. 

I already had a decent vice with a set of rubber jaw pads, and I bought a used Starrett 93C tap wrench for $31 on eBay. 

Reaming the chambers was simple:  Simply turn the reamer into the cylinder, pushing straight in, and not putting any lateral force on it. 

It took me 30-45 minutes to do each cylinder.  I went slowly and stopped frequently to apply oil, brush off the shavings, and gauge the depth.  The reamer was never even warm to the touch. 

Quote from: Mike D on June 10 2020 07:58:49 PM MDT
How did you ensure they were all reamed to the same depth?

To gauge the depth, I used virgin Starline 10mm Magnum brass.  Since there are six chambers, it was easy to put a 10mm AUTO cartridge in one unmodified chamber as a reference. 

I reamed until a piece Magnum brass, with a moonclip on it, bottomed out on the moon clip:  The cylinders were then deep enough that the case was headspacing on the moonclip, not on the mouth of the case.  (Without the moonclip, the case heads were at approximately the same level, so they would probably fire without using moonclips.)

It could be that one or another chamber is several thousandths deeper than another, but I don't think that'll matter.  (NB:  many SAAMI specs are ±0.005")


In retrospect, this was a lot simpler than I expected...

Have you shot it yet?

Not yet...  I need to load some 10mm Mag ammo, and then my range is closed (due to timber harvesting, not COVID), so it's going to be a minor PITA to go shooting. 

Also, I have several other projects on my front burners, so loading ammo and actually shooting this is on the back burner. 

Very cool!

Quote from: shottist on June 07 2020 08:44:01 AM MDT
I bought a 10MM reamer about 10+ (MAYBE 15) years ago & reamed the cylinder deeper to chamber 10MM Magnum in a S&W 610.  I use Starline brass to load 10MM Magnum ammo.  The revolver will shoot 40 S&W, 10MM Auto & 10MM Magnum with moon clips.  From my Ransom Rest it is extremely accurate with all 3 cartridges.  Don't remember loosing velocity according to my chronograph.  IMHO an excellent modification, at least to me.

Update:  I finally got around to loading some 10mm Magnum cartridges, and I'll shoot/chrono them on Wednesday. 

Following Taffin's old data, I loaded 16, 17, and 18gr of 2400 under a 200gr Gold Dot.  18gr of Gold Dot just about fills the case to where the bullet seats, so that's not a compressed load, but it's close.   

Specs say length should be 1.555", but I loaded them at 1.570", because that looked right and there's plenty of space in the cylinder.  (I measured/figured max length to fit in the cylinder could be 1.660", but given that the Starline brass actually measures only 1.245", I only have 0.315" of bullet in the case.)

I'm attaching photos, compared with 10mm Auto... 

NB:  Notice how the 10mm Auto cartridges are barely visible in the cylinder (from the front), and the 10mm Mag cartridges are much closer (with 0.090") of the front of the cylinder. 

[attachment deleted by admin]

The photos of the cartridges in the cylinder...

And yeah, I know the front of cylinder is filthy.  That's some nasty burned-on black stuff! 

[attachment deleted by admin]

Looking forward to your chronograph results.


Sent from my iPhone using Tapatalk Pro

OK, so I shot my 10mm Mag reloads in my newly reamed 10 Mag S&W 610, and I'm afraid the results were disappointing... 


I had loaded 16gr, 17gr, and 18gr of 2400 under 200gr Speer Gold Dots. 

Average velocities were 1,124fps, 1,172fps, and 1,212fps...  Nowhere near what I was expecting based on Taffin's data using 2400 and 200gr XTPs (1,421;  1,503;  and 1,569fps). 

Taffin was using a 8-inch automatic, but my 6.5" revolver is also 8+ inches from muzzle to breachface, so I was expecting similar velocities.

As is, 200gr at 1,212fps is only 652ft-lbf, and that's not even as much energy than the (admittedly, crazy hot) Underwood 165 Gold Dot at 1,380fps (698ft-lbf). 


Worse:  there were already pressure signs at these velocities:  the primers look smushed to me, especially the 17 and 18gr versions.  In the first photo, the 16, 17, and 18 are left to right.

Worst of all:  one of the cases with 18gr split lengthwise...   See the second photo. 


I did some quick research on split cases in magnum revolvers, and one cause is oversized chambers...  You guessed it:  I literally got a little sideways doing my reaming and bored out the rear of the chambers, too. 

SAAMI says 10mm Auto chambers should be 0.429, tapering to 0.424, but mine are all at least 0.432 on my micrometer, and one is 0.434, and one is .437. 

I measured the spent cases as I removed them from the moon clips, and they follow the same pattern...  Most are at 0.429, but one in each cylinder is 0.433" and another is .435". 


This isn't a catastrophe, because this gun is really a range toy (and I'll be shooting mostly 155gr SWCs through it at 700fps from .40S&W cases), but I take back everything I said about how easy it was to ream chambers...


In the meantime, I'll stick with 16grains of 2400 and the 200gr Gold Dots, or maybe I'll see what I can do with 165gr bullets.  Even this "light" load is equivalent to a decent 10mm Auto load, at 550+ ft-lbf. 

 










[attachment deleted by admin]

Thank you for sharing I am still thinking about taking this journey but sending my cylinder off to a gunsmith/machine shop. I wish I could just outright purchase another cylinder to do this with but Ruger will not sell me one already called them. Though if I sent the entire revolver back to them they will fit another 10MM cylinder. UGH

Quote from: mr.revolverguy on July 06 2020 08:11:58 AM MDT
Thank you for sharing I am still thinking about taking this journey but sending my cylinder off to a gunsmith/machine shop.

Right, in retrospect, I guess I should've done that...  Or taken the time to buy a drill press and learn to use it. 

FWIW, I've been reading up more on bulging brass, and the famous "Glock bulge" is often 0.432" or so, so my chambers aren't THAT oversized, after all. 

Also, the SAAMI numbers are ± 0.005", so technically most of my chambers are in spec, and only the one oddball (oops!) that's 0.437" is really out of spec. 


I'm still mystified that velocities were so slow and pressures so high...

I have a Ruger Blackhawk 10mm that came with a 40S&W cylinder also.  I have the 40S&W over at https://pinnaclehighperformance.com/ right now getting it bored to 10mm Magnum.  I figured I would experiment with that gun in 10mm Mag before and try my M610.
Greg

Mark over at Pinnacle does awesome work.

Another update...  I shot my 10mm Mag, again. 

I tried 16, 17, and 18gr of 2400, and didn't have any cases split or other problems. 

I think I remember that when I shot the 18gr last time, I had difficulty chambering the moon clipped rounds, and then found a piece of copper shaving in one cylinder...  Maybe it's possible that one ill-fitting round caused the split case?