04-10-2012, 11:36 AM

When I chrony my reloads im getting velocity differences of 40 FPS. I know the powder is the same because i double check each powder load on two scales before i put it in the case. The guy at hornady said that it could be because i have defference in my neck tension (bullet release). How can i fix this? Im using an RCBS FL sizer die.

I've also heard it could be because weight and volume of my brass, i check for weight but not volume, should I and how?

Let me know what you guys think please

(this is in the "ammo and reloading" forum too, but i usually get more response's here.)

04-10-2012, 2:17 PM
Different how? Do you mean a 40 fps fluctuation between shots, or a 40 fps difference from some quoted figure in a reloading manual?

Do you separate cases by manufacturer?

I'm not real sure I would stress too much over 40 fps.

04-10-2012, 2:23 PM
I just happen to have some data I collected for 55gr FMJ with 24.0 grains of IMR-4895 out of a 16" CMMG.
19 shots
Hi 2688
Lo 2583
Average 2630
Standard Deviation 24

As you can see, there is a 100 fps difference between hi and low for the series. Each load was measured separately on an RCBS 505.

I wouldn't sweat 40 fps.

04-10-2012, 2:27 PM
What kind of accuracy do you get with your 40fps variation loads?

Honestly if you want to dig into the minutiae of reloading hang out at snipers hide.

04-10-2012, 9:32 PM
I use only Remington cases, I get a 40 FPS difference and I'm shooting .9" @ 100 Y. What is sniper hide?

04-11-2012, 2:21 AM
how consistent is the ogive length? with my experience with the RCBS seater die is that it varied as much as 10 thou when i used to use it (which is completely unacceptable to me and dont even get me started on the run out). if you are compressing the loads and/or jamming it more than others, it could give you the inconsistent velocities that you are seeing due to the pressure build up.

is the brass all from the same lot? the may have different case capacities between lots. to measure it, just fill a spent case with water than weigh the water that you pour out of it

another thing that comes to mind is if the number of reloads on the case is all the same? brass prep is another factor (clean case inside... flash hole not obstructed... blah blah blah)

also what are your components that are you using for your reloads and what is it being shot out of? primers and powder quality are a big factor in getting that ES down. is this is a semi auto, well an ES of 40ish isnt too bad, but can be improved.

how was weather when you were using your chronny? they can be picky with the amount of light that is over them.

good luck with it. SD in the single digits and a ES in the 10-20s are very achievable with a little work.

04-11-2012, 2:31 AM
I use only Remington cases, I get a 40 FPS difference and I'm shooting .9" @ 100 Y. What is sniper hide?

Another Hi Speed forum for killers like you!!! AAAHHHHH! :gun_bandana:

04-11-2012, 8:02 AM
My brass is all Remington brass fired the same amount of times. I use Forster competition seating die and check each bullets base to ogive. I double check all my powder charges, using RL 19. I fix run out using Hornady concentricity gauge. I think it has to do something with the bullet release so ima try Puting a light crimp on it using lee FCD.

04-11-2012, 9:50 AM
(this is in the "ammo and reloading" forum too, but i usually get more response's here.)

So, cross-posting is okay because you get more responses here?

If that's the case, just post it here.