Ballistics by the inch

Now, about those thunderbolts…

Some weeks back I put up a post about my preliminary experiences with a .460 Rowland conversion for my Glock 21 Gen 4. In it I mentioned how much I like the resultant gun, but also how I was having some problems with magazine wear when shooting full-force .460 loads.

Well, after thinking a lot more about it, as well as discussing it with people online and with the other BBTI members when they were here for the recent tests (one of whom has been a Glock armorer for 15+ years) a couple different strategies emerged for me to test. Briefly, those were:

  • See whether putting in a heavier mag spring would help
  • See whether the problem was due to the case length of the .460 Rowland cartridges (they’re 1/16″ longer than .45 ACP).
  • See whether the problem was due to the *power* of the cartridges rather than the length of the cases.

To test the first, it was a simple matter to get a more powerful mag spring and test it in one of the magazines. I picked up a Wolff magazine spring from Midway and did so.

To test whether it was the simple case length of the .460 Rowland cases, I made up some .460 Rowland rounds using .45 ACP reloading standards.

To test whether it was the *power* of the .460 loads but not the case length was another matter. Here’s where we get to the Don’t Try This At Home part of today’s blog post: I made up a number of .45 ACP rounds which were loaded to .460 Rowland specs.

Let me repeat that again: Don’t Try This At Home. These are wildcat rounds, and potentially dangerous. Shooting them in a gun not rated for .460 Rowland stresses could very well result in catastrophic failure of your gun, of the “KABOOM!” variety. Even shooting them in a gun designed to handle .460 Rowland power was risky, since the .45 ACP cases do not have the same strength as the .460 Rowland cases. I made up just 10 rounds of each of these loadings, and was careful to make sure I shot them all, so that they didn’t accidentally wind up in a .45 not strong enough to take the punishment.

Here are each of the loadings I made up, just for reference, along with their approximate chrono results:

  1. 185gr XTP bullet, .45 ACP case, .460 Rowland power  1480fps
  2. 200gr RNFP bullet, .45 ACP case, .460 Rowland power  1440fps
  3. 230gr RNFP bullet, .45 ACP case, .460 Rowland power  1350fps
  4. 250gr LFN bullet, .45 ACP case, .460 Rowland power  1250fps
  5. 230gr RNFP bullet, .45 ACP case, .45 ACP power  920fps
  6. 230gr RNFP bullet, .460 Rowland case,  .45 ACP power  925fps
  7. 185gr XTP bullet, .460 Rowland case, .460 Rowland power  1490fps
  8. 200gr RNFP bullet, .460 Rowland case, .460 Rowland power  1420fps
  9. 230gr RNFP bullet, .460 Rowland case, .460 Rowland power  1355fps
  10. 250gr LFN bullet, .460 Rowland case, .460 Rowland power  1265fps

No, I’m not going to give the specific powder amounts for any of those. I used Hodgdon Longshot powder, and you can look up the specs if you want to know more.

In addition, I had these factory loads on hand for comparison, along with their approximate chrono results:

11.  185gr DPX .45 ACP +P  1110fps

12.  230gr GDHP .45 ACP 850fps

13.  230gr JHP .45 ACP +P1040fps

14.  230gr JHP .460 Rowland  1380fps

15. 255gr LFN .460 Rowland1260fps

.460 Rowland loads

.460 Rowland loads

OK, a couple of comments before I go further: those are “approximate” chrono readings because I wasn’t being anywhere near as careful as we are when we do formal BBTI testing. To wit: I was just using one chrono; I wasn’t worried about getting the exact same number of readings (so long as I got three or four, I wasn’t too worried about it); and I didn’t do anything to control for consistent lighting or suchlike. But they should all be in the right ballpark.

So, looking over all those, you will see what I see: that there was a remarkable consistency in power levels, whether you’re looking at my reloads or factory loads, and between those rounds which used either .45 ACP cases or .460 Rowland cases. That tells me that following the published data for .460 Rowland reloads, and making some intelligent decisions on how to adapt those to the .45 ACP cases for purposes of this experiment, was by and large successful. Meaning that I can use those loads to fairly evaluate what makes a difference on the basic problem I was investigating: what is causing the magazine damage and how to resolve it.

So, what conclusions did I draw from all this?

First, the more powerful magazine spring seemed to help with consistent loading. I will be swapping out all the Glock 21 mag springs I have. This makes intuitive sense, since the slide is moving faster when shooting the more powerful rounds.

That doing a little customizing on the magazines also seems to help a great deal. Here’s a pic showing an unaltered magazine and one I have taken a Dremel tool to:

Glock 21 magazines

Glock 21 magazines

Note that these are just the magazine ‘boxes’ — the guts (spring, follower, etc) have all been removed for clarity.

With the altered magazine and stronger spring, any problems I had with Failure To Feed was minimized.

And most important, it is the *power* of the round, not the case length, which seems to cause damage to the unaltered magazines. Shooting the .460 Rowland power loads in the .45 ACP cases demonstrated this.  Conversely, shooting the .45 ACP power loads in the .460 Rowland cases didn’t cause any magazine damage at all.

Two additional notes I want to add: the first is that I had pretty consistent problems with the heavy Lead Flat Nose rounds in all configurations. They kept getting jammed up in transitioning from the magazine into the chamber. I’ll probably continue to experiment with this in the future, but I’m not too worried about it, since many guns run into some ammo specific problems.

The second is that once again I was really impressed at just how well this reconfigured Glock 21 did with .45 ACP loads. Seriously, with the .460 Rowland conversion in place, there was very minimal recoil (more than a .22, but not much) and it was VERY easy to control and shoot the gun well. I suspect that going forward the vast majority of the shooting I will do with this will be using standard .45 ACP reloads, saving the much more powerful .460 Rowland rounds for occasional practice. In this sense, I am thinking of the .45/.460 relationship the way I think about .38/.357 — it seems to be a perfectly appropriate analogy.

Now that I have all this sorted, I can go ahead and write up a formal review. But I thought I would share a little of the process of how I got to this point.

 

Jim Downey

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October 15, 2013 Posted by | .357 Magnum, .38 Special, .45 ACP, .460 Rowland, Anecdotes, Data, Discussion., General Procedures | 20 Comments