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Loading for short barrels

1K views 9 replies 6 participants last post by  carver 
#1 ·
I have accumulate a bunch of XTPs from free bullet promos over the last couple of years that I want to start loading. Some of these bullets will be used in 3 different guns which have short (3") barrels.

What is the basic science behind "Short Barrel" ammo? I realize sufficient velocity needs to be achieved to enabled adequate expansion while maintaining an appropriate penetration. So how is this accomplished? Do I want to use a slower or faster powder? What about bullet weight?

I have not had access to my reloading manuals for several days but I have been studying factory SD ammo for short barrels. One example in 40 S&W is Speer's GDHP for Short Barrels at 180gr. which is about 950 FPS. Initialy this puzzeled me due to the heavy bullet and low velocity. Another example in the opposite direction, same cal, is Federal's 135 gr. HS at 1200 FPS.

My EDC ammo is factory: Speer, Hornady, and Federal. I want to use these XTPs for backup SD rounds. Thanks guys.
 
#2 ·
I suspect that some factory ammo uses a slightly different bullet for their short barrel ammo that will expand more reliably at lower velocities. The only other change they can really make is to use a fast burning powder that is consumed in that 3" barrel as much as possible.

One other slight difference is that the GDHP "short barrel" ammo advertises velocities from a short barrel pistol so you're more likely to actually reach those velocities. Take the GDHP 180 grain loads for instance, "normal" loads are for a 4" barrel and give you 1025 FPS, but the "short barrel" version is from a 3.5" barrel and is 950 FPS. Both boxes of ammo may very well run around 900 FPS from your 3" barreled pistol. Federal doesn't list the barrel length used so 1000 FPS for their 180gr HS is fairly meaningless.

Were it me I'd shoot a variety of factory ammo over a chrono then reload my XTP's to be just as hot, maybe even a tad hotter. Best results will likely be from the faster powders.
 
#4 ·
I wouldn't expect the brisance to be a major factor, as it's a measure of the sharpness of the energy delivery, and doesn't impact the total energy released. It's an important figure in munitions design, as it affects whether a given package will fragment, or simply expand, but it probably doesn't change the performance of a pistol cartridge much.

In an ideal load, the powder used should be fully consumed, and the last bit of expanding gas released at or shortly before the bullet reaches the end of the barrel. If any is still burning after the bullet leaves, its energy is wasted. Of course, in an ideal world, the powder would burn at a rate that causes the bullet to accelerate as efficiently as possible right up to the moment of leaving the muzzle and then cease to burn, but that's not going to happen.

But for the OP's consideration, yes, a short barrel requires a faster powder in order to gain maximum bullet acceleration in the short distance available. When you have only 3" to work with, you have to use fast powder ( or date women who are really bad at math) to achieve acceptable results. As always, the best and safest course is to check the manuals for test conditions which most closely match those you plan to load for, and follow the recommended recipes. It's very dangerous to venture into your own, unmarked territory, and it really shouldn't be attempted by normal people.
 
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#5 ·
I did a bit of research about "short bbls requiring fast powder" a while back. I found out from a very reliable source that powder is consumed before the bullet travels very far, if any, way less than two inches in a snubby. In many handgun cartridges the powder is burned up before the bullet leaves the case. Some rifle magnums using very slow powder won't be consumed until the bullet travels 9-10 inches. The idea that a faster powder is needed for short barrel guns is indeed logical, but not necessarily true. Here's a good read; scroll down until you see the chart on peak pressure. The peak pressure in this cartridge, where most powder has been consumed, is .6 milliseconds before the bullet leaves the case. http://www.frfrogspad.com/intballi.htm

And next comes "muzzle blast is from unburned powder". Here's an explanation of muzzle blast and what it consists of; http://www.navweaps.com/index_tech/tech-090.htm

BTW, I had much the same feelings/ideas about powder burn vs. barrel length and muzzle flash as is popular today until I corresponded with a person that knows and I sincerely trust his explainations...
 
#6 ·
KISS!
 
#10 ·
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