Acceptable Velocity Variation

[RT]

After years away from reloading Im just getting back into it. Lately I have been on abit of a 218bee kit.

For accuracy Ive settled on 9.8gr Lil Gun and a 46gr hp bullet. Groups almost touch at 100yds wich is way better than I need or expected. Im just going to carry this mainly on the trapline.

Today I decided to run some through my crony. And heres what they cronyed at (in order) 2723;2536;2527;2612;2502;2507. This was through a warm barrel.

I first shot a 4rnd group of factory 46gr ammo and it was 2673:2689:2759:2778

So the factory ammo varied by approx 100 fpm and my handloads varied by approx 220fpm, however the handloads are slightly moree accurate than the factory.

So, Im quite happy with the accuracy. But the difference in velocity has me wondering if I can get it more consisteant.

Any suggestions ?

 

[todbartell]

I'm guessing your case capacity varies a lot due to mixed lot numbers, if not mixed headstamps

I like to see an extreme spread of 25 fps or less, standard deviations of 10 fps

 

[RT]

I'm guessing your case capacity varies a lot due to mixed lot numbers, if not mixed headstamps

I like to see an extreme spread of 25 fps or less, standard deviations of 10 fps

Its all winchester 1f brass.

 

[tiriaq]

Could be neck tension, crimp, etc.
Given how its shooting, I don't think I would worry about it.
Velocity variation might show up more at long range, but from what you have observed at 100, it is irrelevant.

 

[Ganderite]

Most likely poor technique on the chrony. Too close and muzzle gases give funny readings.

back up to about 20 feet from the unit and repeat.

 

[Carbon12]

After years away from reloading Im just getting back into it. Lately I have been on abit of a 218bee kit.

For accuracy Ive settled on 9.8gr Lil Gun and a 46gr hp bullet. Groups almost touch at 100yds wich is way better than I need or expected. Im just going to carry this mainly on the trapline.

Today I decided to run some through my crony. And heres what they cronyed at (in order) 2723;2536;2527;2612;2502;2507. This was through a warm barrel.

I first shot a 4rnd group of factory 46gr ammo and it was 2673:2689:2759:2778

So the factory ammo varied by approx 100 fpm and my handloads varied by approx 220fpm, however the handloads are slightly moree accurate than the factory.

So, Im quite happy with the accuracy. But the difference in velocity has me wondering if I can get it more consisteant.

Any suggestions ?

I would recommend testing it with another chronograph or make sure the chronograph is 5 yards away from the muzzle.

Because of the randomness of your velocity data it could be the nature of such a small powder volume.

 

[RT]

I hadnt thought about the distance from the crony. Ididnt measure it today but I was probly 8-10ft from it. Ill try again tomorrow and double the distance.

 

[qtip]

I'm guessing your case capacity varies a lot due to mixed lot numbers, if not mixed headstamps

I like to see an extreme spread of 25 fps or less, standard deviations of 10 fps

Is it harder to achieve low SDs with a small case, as small powder variations have an affect that is more pronounced?

 

[Ganderite]

Is it harder to achieve low SDs with a small case, as small powder variations have an affect that is more pronounced?

I find that the smaller the case the more I have to lie about my great SD.

 

[220]

Ganderite, now you wouldn't do that would you

 

[yodave]

as close to to each other as you can get by counting the last few kernels of powder.......bullet seating depth has more to do with velocity variance then the powder charge itself