I've been trying some experiments with a fussy 300 wby ultralight regarding runnout. Somehow I actually discovered something that seems more positive...at least to this gun. I've been prepping and sorting some Rem brass and some hornady match grade brass in that gun. I've tried fl sizing and sorting to rounds over and under .003" runnout and I've tried the lee collet die with redding body die bump.
What I'm finding is that the capacity of the two cases seems the same and the velocity is consistant between the two. BUt, everytime I feed the gun the hornady brass I get much better groups than the Remington. Even with runnout over .004" with the hornady it will outgroup the rem with zero runnout.
It seems strange as I'm loading the two brand of brass on the same days, with the exact same powder, bullet, seat depth, exact everything.

I'm doing my testing at 300 yds. The rem seems to give me vertical grouping and the hornady nice round groups. Today with my last 7 rounds I got a nice round 4" group at 300 yds with 15-18 mph winds that were swirling all around the range. And this batch of ammo had .003" runnout to 006".

Am I crazy or just seeing some wierd luck going on here?

The Hornady match brass is probably much more uniform in weight and internal dimensions. Have you sorted cases by weight in each brand?

No, you are not crazy, some guns prefer different brands of brass.

I own a Remington 700 Classic chambered in 300 Wby Mag that defintely shoots better groups using Weatherby brass than Remington. Why, I do not know, but it has been well established.

My buddy has a 243 that shoots entirely better groups when using Norma or Lapua, I cannot remember which, than when using Remington or Winchester.

Heck, I have a another friend who swears his 280 AI will only shoot well when using Winchester nickle plated 280 brass.

On the other hand other guns like my 25-06 or 338 Win Mag shoot just the same with any number of different brands of brass.

I think the answer is brass consistency. It seems once brass has been formed to your chamber things would equal out. One comment is brass "springback" with the Remington brass and its effect on chamber fit.

Kraky, When dealing with two apparently "equal" cases by different manufacturers from a reloaders perspective I would think that there are metallurgical issues which we cannot assess that will have an efect on ballistics. While I am sure there are many more factors at play here then I am aware of, my 2 cents would lean to the varying neck tension and the differences that would occur during the initial motion of the projectile and the concurrent variation of the pressure curve. To my way of looking at this, the barrel harmonics would be playing a different "note." One sour and one sweet!

Good post 308

Hey kraky

Have you measured the neck thickness and see if there is a difference between the two. A thicker neck will have a different bullet grip which would definitely cause a difference in accuracy.

Maybe one reason for neck turning even without a custom chamber. Uniform the neck thickness.

Just guessing.

Brass matters. I shot a benchrest match a few years back with a friends HV class rifle. He had 10 individual Cases that were the ones to use for shooting for score. The other 15 or so were for foulers etc.. He said that you could actually get (very) slight differences in impact from the different cases!
Such variations wouldn't be seen in an average rifle but switching headstamps is a lot bigger change of variables and can have a signifigant impact on group size. If it didn't Lapua wouldn't sell nearly as much 308 Winchester brass as they do!.......... ............DJ