COL Longer is better?

[tiberiumgold]

For instance a 124 grain bullet loaded with 7.8 grains of imr 7625 produces around 1440 average at an oal of 1.255 if loaded longer should the velocity slow down or speed up?

[kneelingatlas]

Slow down

[1SOW]

For instance a 124 grain bullet loaded with 7.8 grains of imr 7625 produces around 1440 average at an oal of 1.255 if loaded longer should the velocity slow down or speed up?

Posted Today, 07:00 PM

Slow down

Same amount of gas generated in a larger container = less pressure = slows down

Edited September 29, 2014 by 1SOW

[jstagn]

If you bullet is getting knocked around as it hits the feed ramp something is mighty wrong. If there is that little bullet left in the case then you are using the wrong bullet or loading way too long. Infinity recommends that in their 40, (aet barrel) you load 1.210, that is longer than most 40 which load 1.135 - 1.180. I will ask them why so long next time I have an opportunity to speak with them. I used 1.210 OAL (200gr blue bullet,vitn320) in a friends STI and they shot very accurate and fed without jamming. As someone suggested, EVERY GUN/BARREL is different, you have to test for yourself.

Edited September 29, 2014 by jstagn

[djeffers]

With my Glock 34, I did one test at max length to get to power factor. So I loaded at 1.155 and bumped the powder until I got to a little over 125 power factor. Then I loaded 10 each OALs from 1.085" to 1.155" in .01" increments. Then I shot these all for groups. I found in my gun, with my load, 1.125" shot the most accurately, had no feeding problems, and made about 130 PF. I shot from 1.155" down, checking velocity and for pressure signs at each step. Even at 1.085", I think I was only at 134 PF. So, after establishing that 1.125" shot the most accurately and made PF, I loaded up 200 of them and shot them in a local match (I don't have anywhere I can currently shoot that allows me to simulate match conditions. Probably a better idea to try this in practica). They functioned flawlessly, and now I have my load. That's my process, hope it will help you.

My ADHD/ADD would never allow that!

[mizer67]

Longer is not better, necessarily.

If you're loading for accuracy in 9mm look at the length the Bullseye or NRA AP competitors are shooting. I can duplicate several of those loads and make them shoot well in any gun I've tried, regardless of the maximum length I can load to is in that particular gun/barrel.

[Powder Monkey]

10 Shot Group Sizes

1.085 OAL = 6.694"

1.095 OAL = 5.462"

1.105 OAL = 6.353"

1.115 OAL = 6.058"

1.125 OAL = 3.163"

1.135 OAL = 8.303"

1.145 OAL = 9.407"

1.155 OAL = 9.088"

This looks more like 1.125 being a flier. What were the conditions for the shots? Sand bags?

[johnsons1480]

This looks more like 1.125 being a flier. What were the conditions for the shots? Sand bags?

I shot with my forearms on sandbags, and I was seated. It was a pretty steady position. 25 yards shooting at dots. It wasn't super windy, not that that really matters at 25 yards.