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dylan_b 02-21-2012 08:04 AM

reload vs factory accuracy question
my go to load for my .308 win is a 168 grain a-max with a hornady match case trimmed to 2.000', cci br2's, 44.3 grains of vihtavuori n150 loaded to 2.800 coal. yesterday at -2 celcius the chrony read 2715 with a rather high deviation of 35 fps over 5 shots.

i noticed that hornady has a almost exact dulicate of my load with the only difference being the powder, primer and velocity, averaging 2735 fps with a really tight deviation of 12 fps over 5 shots. coal load length is also 2.800 inches +/- 0.002 across 2 boxes, about the same tolerances my own loads reach.

given almost everything being equal and the hornday factory load being tighter over the chrony, why are my loads more accurate on paper then the factory ones? coal is the same, bullet is the same, case is the same, velocity is within 20 fps of each other, point of impact is almost exactly the same at 200, and now that i think of it the factory bullets use the new amp jackets and my loads do not yet have the amp jacket. i thought that maybe the primer was doing it but the primer just needs to fully and consistently ignite the powder and if the factory is doing with less velocity deviation im thinking it might be a better primer. then i thought the powder, but again if the velocity is tighter then there is no way its burning less consistent.

fyi my loads on that day and most days produce 0.6-0.5 moa unless i slip up and the hornady factory produces 0.75 moa consistently across the 2 boxes i had on hand.

Topgun 3006 02-21-2012 09:19 AM

It really doesn't take much to make that kind of a difference. I woudn't sweat it as I doubt you will ever find out the reason.

Prairie Wolf 02-21-2012 12:07 PM

It is possible to have the same velocity but not the same barrel time because the pressure curves are different.

skb2706 02-21-2012 06:18 PM

New brass or once fired?
Full length sized or neck sized?

the Razorhead 02-22-2012 06:09 PM

progressive burn rate of the VV vs who knows what of the who knows what powder from Hornady?

Gromky 02-22-2012 08:59 PM

Maybe they don't seat the bullet as accurately linearly, so they tend to first contact the barrel differently. Or they use the "same" bullet, but are produced with somewhat lower standards. Or it's a sample size issue, and you had a few more bad shots testing the factory ammo. A difference in crimping?

sm 02-24-2012 09:26 AM

I would guess that you are re-using your brass, and it is a better fit to your chamber than the factory brass, which must be sized a little small to fit anybody's chamber.

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