Surprising .45 ACP revolver velocity

[johncantiusgarand]

I range tested some handloads yesterday that left me pleasantly surprised but scratching my head as well. The 452423 ideal mold I borrowed cast a somewhat heavy (for its design) 250 grain bullet with the range scrap alloy I was using. 6 grains of SR7625 was predicted in my lyman reloading manual to give 850 f.p.s. with a 225 grain lead bullet. Imagine my surprise when that same 6 grains averaged about 900 f.p.s. with the 250 grain lead bullet in my 4-inch TRR model 22. Accuracy was so-so (about 4 inches at 25 yards), and it was about 4 inches low at 25 yards. But 250 grains at 900 f.p.s. out of a 4 inch revolver is much better performance than I expected out of that load. That is .45 Colt performance, which is what I was hoping to eventually reach after some careful load development.

On an unrelated note, I found that I have to size my bullets to .451. ANYTHING bigger will leave the forward driving band a tight fit in the cylinder throat and lead to great difficulty in seating the moon clip. That seems like a pretty tight cylinder throat to me and a major departure from S&W's model 25 reputation from long ago.

 

[Jellybean]

Which Lyman manual are you using? I can't find the data you're talking about in the few I looked at.

 

[Jellybean]

Oops, never mind, I was looking at .45 AR data. And maybe you should too. While the data for the auto rim cartridge is pretty low compared to the ACP, they do list data for both the 452374 and the 452423. If you have that data in your manual, look at the 4.9 gr max load for the 452423 against the 5.0 gr. start charge using SR-7625, your increase would be predictable.

 

[fredj338]

I range tested some handloads yesterday that left me pleasantly surprised but scratching my head as well. The 452423 ideal mold I borrowed cast a somewhat heavy (for its design) 250 grain bullet with the range scrap alloy I was using. 6 grains of SR7625 was predicted in my lyman reloading manual to give 850 f.p.s. with a 225 grain lead bullet. Imagine my surprise when that same 6 grains averaged about 900 f.p.s. with the 250 grain lead bullet in my 4-inch TRR model 22. Accuracy was so-so (about 4 inches at 25 yards), and it was about 4 inches low at 25 yards. But 250 grains at 900 f.p.s. out of a 4 inch revolver is much better performance than I expected out of that load. That is .45 Colt performance, which is what I was hoping to eventually reach after some careful load development.

On an unrelated note, I found that I have to size my bullets to .451. ANYTHING bigger will leave the forward driving band a tight fit in the cylinder throat and lead to great difficulty in seating the moon clip. That seems like a pretty tight cylinder throat to me and a major departure from S&W's model 25 reputation from long ago.

I would open the throat a wee bit to allow for a 0.452" bullet. It's probably a better fit for the bbl. You getting any leading?

 

[Paul5388]

More than likely, the deeper seating of the 452423 will account of some of the increase in velocity. I've run into the same situation when using some Oregon Trails Laser Cast that seated deep.

Here's a comparison of crimping groove position with the 270 gr bullet on the left seating more shallow than the others. The velocity varied by seating depth, not weight.

 

[Dale53]

I home cast an NOE 454424 that weighs 250 grs in my alloy. I use this, on occasion, in my two 625's (both are .45 ACP). In the 5" 625-6 Model of 1989 using 7.0 grs of Unique, I get a chronographed velocity of 900+ fps when crimped in the normal crimp groove. This is suitable for deer hunting within reasonable ranges.

Now, to the original question: Seating depth, as Paul 5388 points out, is paramount regarding both velocity and pressure. Weight also plays a part but seating depth (particularly in a small case like the .45 ACP) plays an even bigger part. Of course, all parameters are important when reloading.

Dale53

 

[amazingflapjack]

I have both a 625-8 (not the JM) and a 25-5 .45LC that have .451 throats. John Taffin just had an article, I think last month, where he talked about these issues regarding sizing to the throats, and The guy Jones, can't remamber his first name, in shooting times, had a recent article where he stressed leaving that earlt full diameter portion of the bullet where it can get a hold of the cylinder throats. I really was helped with some problems I was having by this information. Flapjack. OH, and man what an APC round, 7 gr of Unique, I'll say it would be suitable for hunting!!