What's going on here?

[amlevin]

Yesterday I went to the range and shot some loads I've been working on. .308 Hornady 168 gr A-max.

Shot at 100 yards and 300 yards. Group size at 100 yards was about 3/4" and the same load, almost exact conditions (calm to 2 mph wind) was 3/4" at 300 yards.

A not very good group for 100 yards and a great group for this rifle at 300 yards.

Had some other ammo along that was extremely accurate at 100 yards. Shot a 5 shot group of 1/2" and at 300 yards it only yielded a 1-1/2" group at best. The Bullet was a HPBT Nosler 168 gr Custom Competition.

Both bullets are boat tails, only difference is the "ballistic tip".

Looked strange to me that the 300 yard group would be same size as 100 yard, all things being equal (or at least close).

Any thoughts?

 

[Steve Wilson]

This is going to date me somewhat. Back in the late '70's I bought my first centerfire rifle. A Golden Eagle 7000, in .270 Win. I had a Redding 6-18 scope on it. That darned thing would shoot smaller groups at 200 than it did at 100, quite often. I always felt it was because I had to take a finer point of aim at the longer distance. Concentrate harder, you know. At 100 it would put three shots into the size of your little fingernail all day long, until you just got tired of doing it or ran out of ammo.

As to the .308, I don't have any experience with it, though I do have an old Sako L61R .300 Win Mag that I load with 180 Ballistic Tips. It shoots nice one hole groups at 100 also.

Anyway, there seems to be a school of thought that some, large for caliber, bullets don't "go to sleep" for a couple of hundred yards and will often shoot smaller at say 300 than they do at 100. I wouldn't consider your bullet "large for caliber" though.

So, the bottom line is that I don't have a clue.

 

[fdshuster]

Try measuring and sorting your bullets using one of the bullet comparators. Maybe even weighing them. My son first tried the 80 gr. A-Max for his F-Class match's at 600 yds. Results were not good. The 80 gr. Sierra's easily outshot them.

Then wanting the higher BC downrange, for forecast windy conditions, he measured & weighed the A-Max's, found a large difference between them ( all from the same box/ lot), sorted them & loaded & used them accordingly, and had a very noticable tightening of groups & higher scores. When seperated, they outshot the 80 gr. SMK's.

His final 5 shot group, at 600 yards, using the sorted 80 gr. A-Max was well under the 3" diameter of the X ring. I have a copy of the tgt.

Cannot comment on any Nosler bullet's, never used any. I limit my bullet choices to Sierra, Berger & a few customs.

 

[articmp]

I have saw the same thing happen before too. Had an old SMLE Mk1 no 3 that would shoot around 2 inches at 100 yards (scoped), then turn around and shoot 2.25'' 10 shot at 250 yards from the prone. Poor thing had no rifling left in the first 10 inches of bore, tiny bit of a headspace issue too. Was shooting Reminton factory 180's and handloaded 150 seirra gmk. Start shooting 20+FPE airguns, they seem to disply this habit more than powder burners.