Armory Sponsor
Posted: 10/19/2016 11:56:06 PM EDT
|
So, I have been reloading for my 308 for about a year and a half now. I have done many different ladder tests and tweaks to my load and recently I have been paying a bit more attention to detail. I have noticed that my OAL varies by about .003 of an inch. How much of a difference in accuracy will a few thou OAL make?
Btw my load is as follows: Black hills match 308 brass Case length 2.010 178gr Amax seated to OAL of 2.800 Federal bench rest large primers 42.3gr of Hodgon 4895. This load keeps me around 2730 for muzzle velocity with minor pressure signs on my primers. I have shot several superb groups with this load. |
|
The tips of the bullets are not exactly all the same. Some are a bit more pointy that others, some are a tad 'rounder', meaning those come up a bit short of overall length. There is only one cure for this...
Hornady and others sells a bullet comparator. This is simply a metal 'donut' that fits on your calipers. You end up measuring the cartridge from the casehead to the ogive on the bullet. While the cartridges may show a variation of 0.003-0.005", the case head to ogive dimension will be spot on. A variation of 0.003 from base to tip is pretty good. Use something with an irregular tip, like a open tipped Sierra matching, and even though the cartridges are very uniform, bullet tip differences will show 0.005" or more variation |
|
Ah ok, thanks. So that variation won't cause any visible changes in accuracy?
I dont get to shoot as often as I would like but I maintain a average of 1moa with my groups likely limited by my own skill, but twice I have produced groups that are close to miracles. One group was .140 CTC, although it was only a 3 shot group. My second awesome group wasn't as good but was still a 5 shot group measuring .310 CTC. |
|
Quoted: Ah ok, thanks. So that variation won't cause any visible changes in accuracy? The length of the ogive to the end of case will all be the same as the seating die references off the ogive. This is what you want. Cartridge length only matters in that the round must be slightly shorter than mag length to feed from a mag. I dont get to shoot as often as I would like but I maintain a average of 1moa with my groups likely limited by my own skill, but twice I have produced groups that are close to miracles. One group was .140 CTC, although it was only a 3 shot group. My second awesome group wasn't as good but was still a 5 shot group measuring .310 CTC. |
|
I think your on the hot side and consider 41.5 grains of H4895 as a working maximum with 168 grain bullets in commercial brass.
41.0 grains would be more appropriate IMO, it won't beat the gun and the brass up. I look at +/- 2600 fps as a useable velocity range for 175/178 grain bullets fired from 24" barrels. A little over is one thing, 2730 fps is close to 2.0 whole grains over what I would use. As already mentioned every bullet tip is different and will measure longer or shorter when loaded. It has zero effect on bullet jump to rifling because the seater die touches the bullet much closer to the ogive. Specialty tools are available from Sinclair International and other sources that will allow you to separate bullets by actual ogive variations. This tedious process is best left to 1000 yard F-Class and other Long Range disciplines IMO. Very good ammo can be loaded with much less trouble. |
|
Quoted:
I think your on the hot side and consider 41.5 grains of H4895 as a working maximum with 168 grain bullets in commercial brass. 41.0 grains would be more appropriate IMO, it won't beat the gun and the brass up. I look at +/- 2600 fps as a useable velocity range for 175/178 grain bullets fired from 24" barrels. A little over is one thing, 2730 fps is close to 2.0 whole grains over what I would use. As already mentioned every bullet tip is different and will measure longer or shorter when loaded. It has zero effect on bullet jump to rifling because the seater die touches the bullet much closer to the ogive. Specialty tools are available from Sinclair International and other sources that will allow you to separate bullets by actual ogive variations. This tedious process is best left to 1000 yard F-Class and other Long Range disciplines IMO. Very good ammo can be loaded with much less trouble. Ah ok, welllllll, now I have to pull 200 bullets lol. I'll work up another ladder and see where I get. Thanks for the advice. |
|
That's more like it although still on the "warm" side. Honestly, I read your OP not long after you posted it and 2730 with that weight bullet was screaming WOW!! to me.
Remember the 08' started life as the 7.62x51 shooting 150gr bullets at around 2750. Basically the same velocity as the original 150gr Garand round. Motor |
Armory Sponsor