Barrel length speed testing including copper solid data

[Geno C]

I’ve been testing my copper solids from a bunch of different angles and decided to get a long barrel and chop it to find where I got the most speed as I can adjust the charge later to find a consistent spot. It was suggested that I run some lead factory ammo while I was at it to see what there was going on and to compare to. I found about the top charge that the solids would take and ran that. It hasn’t been the most consistent for speed but that wasn’t what this test was about.

 

[dutch14]

Thank you for posting this. It conferms what some others have found.

 

[Geno C]

Thank you for posting this. It conferms what some others have found.

What others? I looked for a while and didn’t find any data from the same barrel starting this long.

 

[dellet]

I learned a lot about subsonic load development and ballistics looking at rimfire when working with 300 Blackout. Some of that will likely work in reverse.

Copper solids and not really subsonic speeds, but the pressures they often operate at can be frustrating, if you want any kind of accuracy/precision past 50 yards. Your charts look really familiar.

Capture some bullets and look for carbon tracks blowing past the bearing surface. Gel or even water jugs will generally leave the carbon intact.

Most copper will need more pressure than you can get out of a 22LR case to obturate and seal the bore. Wacky chronograph numbers with vertical string and often keyholes or at least oblong holes were trade mark signs.

 

[Geno C]

I learned a lot about subsonic load development and ballistics looking at rimfire when working with 300 Blackout. Some of that will likely work in reverse.

Copper solids and not really subsonic speeds, but the pressures they often operate at can be frustrating, if you want any kind of accuracy/precision past 50 yards. Your charts look really familiar.

Capture some bullets and look for carbon tracks blowing past the bearing surface. Gel or even water jugs will generally leave the carbon intact.

Most copper will need more pressure than you can get out of a 22LR case to obturate and seal the bore. Wacky chronograph numbers with vertical string and often keyholes or at least oblong holes were trade mark signs.

I’ve recovered plenty in my testing over the last 9 months. These are 2 different diameter bullets out of 2 different barrels that the bullets were apex’s for. They seal up nice and complete.

 

[dutch14]

What others? I looked for a while and didn’t find any data from the same barrel starting this long.

Thank you for publishing the raw data. Usually when others have done it they only used 2 or 3 varities of ammo and only published their conclusions. Occasionally similar testing has appeared in magazines and on web sites with the conclusion that 22 long rifle gets the highest velocity with between 17 and 21 inches of barrel. You went one step farther and presented the raw data so we could see how much difference there actually is at various barrel lengths. I appreciate that approach.

 

[grauhanen]

First of all, thanks to Geno C for producing and publishing this data. What follows is not a criticism of the data or the effort to develop it.

What is the confidence level that the data supports the conclusion above about barrel length and MV?

It's important to keep in mind that there were only 15 rounds tested for each ammo at each barrel length (except ten rounds for the very longest -- 27"). With the exception of one 15 round sample of CX, the ES was wide for every ammo at every barrel length and the SD correspondingly high.

It's interesting that with each of the factory ammos, the 27" barrels stood out for producing notably lower MVs than with any other barrel length. All the factory ammo was notably slower with the 27" barrels, with the Wolf at 1030, CX at 1042, Tenex at 1042, and Fiochi at 1026 fps. This seems to stand out almost as an anomaly, as a result that was unique to that barrel length. Whether it represents something significant about this barrel length is not clear.

Since the 27" MVs are unusually lower than all the others, it might be instructive to disregard them for the moment in order to put the others in perspective.

The Wolf ammo averaged 1054 fps in the longer length barrels (24" - 26") and 1063 fps in the shorter barrels (18" - 21"). CX averaged 1059 and 1063 respectively, while Tenex averaged 1059 and 1071 fps. The difference in MVs between the longer and shorter barrels for these ammos was from 4 fps to 12 fps. Only the Fiochi was significantly different, with an average between longer and shorter barrels of 1044 and 1071 fps -- 27 fps.

In other words, there wasn't a big change in average MVs between the longer and shorter barrel lengths. Only the Fiochi Sub HP ammo produced MV's that were over 20 fps higher on average with the shorter barrels.

What conclusions can be drawn from the information available? Using the limited Wolf, CX, and Tenex data, the average difference in MV between longer and shorter barrels ranges from 4 fps to12 fps. Is that enough to conclude that shorter barrels significantly increase MVs?

If further testing confirmed the results here, would that support the idea that for MV reasons shorter barrels are preferable to longer ones or vice versa?

 

[Geno C]

You can draw any conclusion that you want really. That’s why I just laid the data out. What it shows me, for standard ammo anyway, is that the longer barrels might be slightly slower but their speed is also slight more stable. For my copper solids, it shows me that a longer barrel isn’t able to gain any more speed than a shorter one, even though I’m running a much higher pressure than factory match ammo.

 

[Tony K Harper]

Geno C, thank you for posting your results. You have done many of us a great service.

TKH