Lee Loader

Couldn't sleep so got on and start surfing. Searched "Reloading Myths" and had some interesting reads. I had no "what" moment until I read a post that said that there is no benefit in using a slower powder in a longer barreled rifle. Hmm says I to me and I flashed up Quickload and tried to do some comparisons. Perhaps it is my poor old brain but I can't figure out how to figure out if slow powder- long barrel is a myth or true. Long barrels will give more velocity as there is still lots of pressure pushing the bullet up to when it exits the muzzle but this applies equally to the same powder so doesn't prove anything. This little puzzle should keep me busy for a bit. Anyone have any thoughts?

I'm in to see if I learn something myself. I always thought longer barrel could spike the pressure, but in recent years I am doubting it now after certain lengths. without equipment to test and be sure.

I can tell you H322 under a 350 in a 45 Colts 16" carbine will clean up and run 1240 fps but makes a huge 900 fps fire ball in a 7.5" revolver .

One of the greats Hatcher maybe did a one lot test at Springfield armory starting with a 36" barrel on an 03A3 and cut 1" at a time firing 100 rounds per step .
Each step got faster down to 24" where the average went basically flat with a jump at 22" then slowing .

For practical application yes a slower powder will go faster in a longer barrel and a longer barrel will be faster than a shorter barrel until you reach the limits of case , cartridge , and bullet acceleration . Per powder .

I'm not sure that QL could help you solve this mystery Macd, as it functions around a set of "norms" for lack of a better word. You can put in a 20", 100", and 200" barrel and it will record higher and higher velocities. The percent difference between the intervals decrease, but it is still an increase.

In QL, the calculated value to consider might be "Amount of Propellent Burnt" which is in the "Results" panel, usually the lower right quadrant of your windows. The point that any powder and or barrel length combination reaches 100%, would be the point that barrel length will no longer increase velocity.

Ranch Dog wrote:I'm not sure that QL could help you solve this mystery Macd, as it functions around a set of "norms" for lack of a better word. You can put in a 20", 100", and 200" barrel and it will record higher and higher velocities. The percent difference between the intervals decrease, but it is still an increase.

In QL, the calculated value to consider might be "Amount of Propellent Burnt" which is in the "Results" panel, usually the lower right quadrant of your windows. The point that any powder and or barrel length combination reaches 100%, would be the point that barrel length will no longer increase velocity.

I hear and agree QL is not going to solve this question easily but it is all I have ATM. I have tried a number of regressions using QL data but all come out with low correlations including % FPS change based upon barrel length for each of five powders. There are a lot of variables to consider and finding dependencies among and between them is not simple. My constants are calibre (6.5x55) and bullet (Hornady 140 HPBT) I haven't tried "Propellant Burn" yet. The powders are also kept the same and burn rates (BR) range from Ram Magnum (BR 62) to Varget (BR 42). All are listed powders for this calibre. I am using two barrel lengths: 24 and 29 inches. I have checked the QL results for velocity and pressure against published data and for velocity against my own shooting records. They are comparable.

Why go to all this trouble. I am paying a premium for shipping in powder like IMR7828 that I can't source locally. My admittedly limited experience seems to support that slower powder in long barrels gives better performance in terms of efficiency, consistency over the chronograph and accuracy. I also am something of a bass fisherman, love to get down in the weeds, muddy the water a bit and see what I can catch and land. Being retired, bad weather and a bout of insomnia also helps