A question on short barrel ammunition selection

[CQC.45]

Hi, Im new to the forum, but have been lurking on both here and TF for a while. I just read the thread on Double Tap ammo and it got me thinking...

Recently I have been looking very hard at a Kahr PM45 for times when the M&P is too large to carry. However it has the setback of having a very short (3.14") barrel. I know that .45ACP, because it is such a large round, barrel length plays an important role in attaining a certain velocity to expand and penetrate properly. I have heard that the rule of thumb is a barrel length of 4" or longer. I have actually had the chance to shoot the PM45 and the recoil is very soft for such a little .45.

However since Double Tap's ammo is loaded hotter than regular Speer Gold Dots, I had the thought that the combination of DT ammo and the short barrel length would duplicate standard Speer velocities out of a 4" or 5" barrel.

To do a very informal test, I checked out some of the reviews by various Gun Mags on the PM45 where they had shot various loads and choreographed each. I then compared those loads to the factory velocity specs that the manufacturer gave. It seemed that in 230gr. loadings it lost around a 100fps. (sometimes a little more) going from a 5" to 3.14" barrel. With 185s the loss was a little less. Then I looked a the difference between Speer and DTs velocity ratings and it would seem to work out pretty close where it would bring the DTs fairly close to normal Speer velocities.

As I said, this is a very informal, but it gave me some basis to create this theory :D.

My last question would be, if I am on about this theory, would you recommend 230gr or 185gr. DT loads?

So having said all of that, I was hoping some of the forum experts could evaluate and correct me if needed.

Thanks!

(P.S. I would really like to see some hard data for the DT .45 loadings in the future ;))

[Jim from Houston]

Well, one issue to keep in mind is increasing the velocity in a round by adding powder to make it +P is not necessarily going to work with a short barrel weapon...in shorter barrels, often times the entire powder charge might not have time to burn, and I've seen tests where the +P rounds lose relatively more velocity in a short barrel than standard pressure rounds...

The word on the 230gr .45 bullets is that you want them to be achieving velocity in at least the upper 800's fps in order to achieve proper function...if you chrono rounds and they're dropping into the low 800's fps, that's likely going to cause a problem with proper ammo performance...

In short, chrono your rounds and see what sort of velocity you're getting out of your particular weapon...

But realize that it would be much easier to just use a 9mm or .40 S&W if you want a shorter barrel weapon, since barrel length is WAY less relevant to 9mm and .40S&W performance. A 9mm round like the 147gr RA9T does pretty much the same thing regarless of whether you shoot it out of a Glock 19 or a Glock 26.

[DocGKR]

"Jim from Houston" gave a good answer. Do you really want to put up with increased blast, flash, recoil, possible pressure issues, potential unburned powder, and accelerated weapon wear? The short answer is simple--get a small 9 mm or .40 S&W (G26/G19, M&Pc, P239, S&W3913, etc...).

[Marcus L.]

As others have posted, the .45acp runs best in 5" barrels. When your barrel gets shorter than 4", then you have a considerable amount of powder burning outside the muzzle of the barrel.....not inside. So, all that charge is wasted.

The 9mm and .40S&W are designed around the 4" barrel, so they can handle going down to 3.5" with no problems. I'm partial to Sigs and here's my P239 in 9mm:

http://i480.photobucket.com/albums/rr169/sgalbra76/Guns001.jpg

Lastly, you'll get a much better overall product if you stick with the big four ammunition companies. Winchester, Federal, CCI Speer, and Remington. Double Tap has a long history of sending out ammunition that had the potential to cause serious injury. Examples are early .45acp loads that were only tested in a 1911 and when used in a Glock it swelled to borderline KB. Then of course you have DT using 115gr 9mm bullets which have an elongated bullet taper in the .357sig which resulted in setbacks with only the slightest pressure.