10mm reloading Glock 40 KKM barrel and Smith 610

[Alaskapopo]

Range Report 10mm testing
3-19-22 Range Report
Guns:
1. Glock model 40 (10mm long slide) with a 6.5 inch threaded KKM barrel.
2. Smith and Wesson 610 4 inch 10mm Revolver.
Ammo tested.
1. 200 grain RMR FMJ, 8.3 grains Longshot, Federal large pistol primers, New Starline brass.
2. 200 grain Speer Gold dot, 7.3 grains Longshot, Federal large pistol primers, new Starline brass
3. 200 grain Rimrock hard cast, 8.3 grains Longshot, Federal large pistol primers, new Starline brass.
Well last year I ordered 2 KKM barrels for my Glock 40 one in 10mm and one in 40sw and I have not had time to test them out fully until now. I also had some Speer 200 grain Gold dots and 200 grain hard cast bullets I wanted to test as a new bear protection load. I originally set my press up for 7.8 grains of Longshot not 8.3 but I confirmed the powder charge at the end of reloading the lead and FMJ bullets and found it was 8.3 grains. I checked again 3 more times and still got 8.3 grains.

The book max I was using is 8.2 so I was a bit concerned. But then I read Rimrocks load data and found I was inside their parameters. But to play it safe I decided to bring my Smith 610 revolver out to try the loads with first since this gun was built around 44 magnum pressure levels.
My anxiety was relieved after I fired the first round from the revolver no issues. Then I moved to the Glock. While I was getting my chronograph data I was shooting at a 6 inch steel target at 15 yards. Later I shot groups on 3 inch dots on paper 1 group for each load with each gun. All shooting was done standing with no rest.
At the end of the day, I wanted to test the reliability with the Glock with a fully loaded magazine. Up to this point I had been shooting 5 round groups with no issues. But in the past I have found with my former Glock 20 that hold loads would be more likely to malfunction with a fully loaded magazine in the first few rounds due to weaker spring tension on a full magazine.

To do this test I did not want to just do a magazine dump as this is expensive. So I decided to do a modified Bill drill instead. I did not have holsters with me so I started at low ready with a cardboard target at 7 yards. I fired 6 rounds as fast as I could keep them on target. The Glock has 15 round magazines with 1 in the chamber that is 16 rounds. So I did two 6 round bill drills and a third drill with just 4 rounds. I repeated the above with the Smith and Wesson 610.
I was faster with the Glock but had better hits with the Smith 610. I had no reliability issues with either gun.
At the end of a shooting day I usually like to return to some accuracy work to relax. I changed the paper targets to 2 inch dots and fired 2 groups with the Glock the first coming in at 1.25 inches and the second coming in at 1.58 inches. I also moved the 6 inch steel plate to 50 yards and fired 5 rounds at it hitting it 3 times missing twice. I am very happy with both guns and the loads I tested. Below is the data collected.


Glock 40 KKM barrel 6.5 inches

1. 200 grain Gold dot 7.3 grains Long Shot Average 1126 SD 8 Spread 23 Accuracy 15 yards 2.38
2. 200 grain RMR FMJ 8.3 grains Long Shot Average 1209 SD 9 Spread 27 Accuracy 15 yards 2.56
3. 200 grain Rimrock lead 8.3 grains Long Shot Avg 1270 SD 7 Spread 17 Accuracy 15 yards 2.82

Smith and Wesson 610 revolver 4 inch barrel

1. 200 grain Gold dot 7.3 grains Long Shot Average 1082 SD 13 Spread 38 Accuracy 15 yards 1.78
2. 200 grain RMR FMJ 8.3 grains Long Shot Average 1153 SD 14 Spread 42 Accuracy 15 yards 1.85
3. 200 grain Rimrock lead 8.3 grains Long Shot Avg 1211 SD 4 Spread 10 Accuracy 15 yards 3.75

Modified Bill Drill Starting in Low ready with target at 7 yards. Fire 6 rounds center mass.
Glock 40 KKM 6.5 inch barrel
1. 2.50
2. 2.18
3. 1.51 (4 shots only wanted to test full mag for reliability 16 shots total)
Accuracy results 10 A zone hits 6 C/B zone hits

Smith and Wesson 610 Revolver 4 inch
1. 2.79
2. 2.65
3. 1.89 (4 shots only to keep consistent with Glock for comparison.
Accuracy testing revisited.
I switched to a 2 inch target at 15 yards and fired two three shot groups with the Glock and got one group at 1.25 inches and the 2nd at 1.58 inches. This was using the 200 grain RMR FMJ load.

[GJM]

I thought the Smith 10mm revolver was less not more tolerant of pressure than a semi?

[Alaskapopo]

I thought the Smith 10mm revolver was less not more tolerant of pressure than a semi?

I figured it would be more due to the cartridges the NFrame houses I maybe wrong

[03RN]

That's a good question. .44 mag is rated at 36,000psi, 10mm at 37,500.

Having more steel around the holes it is probably safer.

[Clusterfrack]

I thought the Smith 10mm revolver was less not more tolerant of pressure than a semi?

I don’t know much about this, but Buffalo Bore has a warning about their heavy .44 Mag loads and S&W revolvers (but Rugers are ok).

[Oldherkpilot]

I figured it would be more due to the cartridges the NFrame houses I maybe wrong

I love the N frames but they weren't actually designed for the magnums we associate them with. They are just BIG so the magnum calibers all fit in the frame. If I recall, the .38-44 was the first chambering. The big Rugers are (gnashing of teeth) stronger by far.
Regarding the 610, I doubt you have any worries in the 10mm even with hot loads. The .41 Magnum was originally rated at 43,500 (same as .44 Mag) but is now rated at 36,000. The 10mm is rated at 33,000, so there is not quite 10% margin there.
I've owned a couple of 610s, a couple of 1066s and a 1006 and have decided that, for my purposes, the 10mm is a pistol round and my N frames are for magnums. Is this a great country or what!