Faster powders for shorter barrels?

[Dave R]

Finally got a chronograph and had fun playing with it. Measured velocity loss in handguns with shorter barrels. Was surprised at the velocity loss from a 3.2" barrel (PPK) to a 2" barrel (P-3AT). Over 100fps.

Can you minimize velocity loss from a short barrel by moving to a faster powder? I'm using Unique. Maybe I should try Blue Dot or something like that?

Whaddaya think?

 

[WESHOOT2]

methinks

Get a few "Powder Burn Rate" charts first.

 

[Dave R]

Good catch. I meant Red Dot. Or maybe Bullseye or N320 or AA#7?

 

[ClarkEMyers]

Minimize velocity loss or maximize velocity?

My current thinking/understanding - which is not based on quite such extremes as discussed above - is that the load which is faster from the longer barrel will continue to be faster from the shorter slower barrel. That is although the performance curves for velocity against barrel length will not be parallel for different powders they also do not crossover anyplace I care about.

Your mileage will vary. There are extreme cases - some reported .22 rimfire experiments with extremely long barrels show the muzzle velocity slower from absurdly long barrels.

Other considerations of muzzle flash and high muzzle gas pressure disrupting bullet flight and so impairing accuracy may suggest a faster powder anyway of course - especially when the velocities aren't very different.

 

[Black Snowman]

To get better velocity you need to find a better pressure/velocity ratio. From the research I've done I've found that this really only varies signifigantly with case capacity so barrel lenth doesn't become a signifigant factor unless you are using a radicly differant lenght barrel than what the round was chambered for such as pistol caliber rifles or pistols chambered in rifle cartridges.

So, generally speaking you're not going to pick up any velocity for the same pressure by varying the burn rate unless one of two things happens. The barrel is so long for the round that all the powder burns before it exits the barrel and you get extra drag or there is so little barrel lenth that backing off the powder charge results in the same velocity. Things have to get pretty extreme for either of those to happen.

I don't have any pressure testing equipment to test this information but this is what I have gathered from post of people who do and information in reloading manuals and chronographed reloading data.

 

[Art Eatman]

About all I've ever seen when playing around with faster/slower powders in various barrel lengths is that the faster powders give somewhat less muzzle flash in shorter barrels.

A full-house load of 2400 in a .357 is rather "enlightening" when fired at night from a 4-5/8" Blackhawk.

Art

 

[HSMITH]

My experience has shown results along the lines of what ClarkEMyers pointed out. For example, in 357 magnum the top performer with 125 grain bullets will be Blue Dot or H110/296 for a gun with a 8" barrel, but they will also be the top performers in that 2" snubby.

Fast powders hit pressure limits too fast, lots of times before the bullet is even released from the case. Slower powders can push the bullet for a longer period of time without going over pressure, accellerating it to a higher speed. This is the case regardless of barrel length.

The best powder will be the slowest powder you can find that will still make maximum pressure in the cartridge you are working with. As you continue slower in most cases you will run out of room to put any more powder in and velocity will start to fall. As you go faster with the powder you will go over pressure before filling the case and velocity will again be lower that with the best powder.

The 'best' powder for a cartride will vary when bullet weight, OAL or any other significant factor changes. Hence the need to work up each load carefully and chronograph them.

 

[444]

I also have chronoed loads from various barrel lengths, mainly in handguns. I have chronoed .357 loads from a 16" carbine, down to a 2" SP101. In every case, the fastest velocity load was the same in all barrel lengths. Yes, you lose velocity out of the shorter barrel, but the slow burning powders will still give you the highest velocity: AA#9, H110.
In the 9mm, I chronoed loads from a 16" carbine down to a Kel-Tec P11. In this caliber, the velocity difference is not nearly as pronounced as it is in .357.

 

[Fatelvis]

Dave, playing with the chrony is fun, I know, but anything on the receiving end of that handgun, isnt going to notice the bullet is going 100fps slower. I dont think you`ll be able to close the vel difference between the two bbl. lengths much, no matter what powder you use. I think like many things in life, the tradeoff for the compactness of a shorter bbl. vs. velocity is one that has to be accepted. But, by all means, keep shooting and playing with your loads, and keep us posted!

 

[Dave R]

Thanks for the collective wisdom, folks.

444, thanks for sharing your testing results. That's particularly helpful.

 

[444]

http://www.thehighroad.org/showthread.php?s=&threadid=45283&highlight=chrono

 

[Quantrill]

ClarkEMyers is right on. Years ago, the NRA did a study on just that theory, and found that the slower powders still produced the faster projectiles, even in shorter barrels. Quantrill