Brand of brass, sizing, and accuracy - a question for experienced reloaders

[lte82]

Today I loaded and shot 18 rounds for my 338 Lapua, 9 rounds in RUAG brass, 9 rounds in Lapua brass. The load is below:

Lapua Scenar 300gr
3.680" OAL
Fed 215 mag primer
RL33 - 92, 93, and 94 grains

I sized all of the brass with the FL die set to the same position, but the RUAG brass fit a tiny bit snug when I closed the bolt, and the Lapua brass was not snug, ie, no resistance when I closed the bolt. Why would that happen if I left the die in the same position? More on this later.

My groups with RUAG brass were FAR superior to the Lapua brass. With the RUAG brass, groups were tight, and shot to shot vertical variation was non-existent. They were nearly all on the same plane. With the Lapua brass, I saw as much as 2 1/2" vertical variation at 200 yards, and all three groups did this to some extent, though the other two weren't as bad.

RUAG groups: .25moa - .75moa (yes, a legitimate 1/2" group at 200)
Lapua groups: .75moa - 1.5moa (most of the variation was in the vertical direction)

The RUAG is once fired brass, the Lapua is 2-3x fired purchased used from another shooter (or so he claimed).

All of the brass was prepped the same, loaded the same, etc.

What would cause the Lapua brass to shoot like that? Is that a sign of shot out brass? Could it because I didn't have any resistance on the bolt, ie, a bit too sized? I guess i will do more testing, but I'd like to see what the more experienced guys say.

 

[sic65stang]

Not 100% on this, but i would think that there would be different springback rates on those cases. Possibly the Lapua cases stayed where you sized them to, and the RUAG brass stretched back slightly increasing the headspace slightly. The reason I would suspect a tighter group would be possibly because the tighter headspace on the RUAG brass slightly increased load pressure and may have pushed that load to the sweet spot. Just a thought.

 

[ksthomas]

ite82,

Not to criticize your methods here, but 18 rounds does not a test make. What you have here are what would be considered an statisically insignificant amount of rounds, rendering any results obtained as little more than anecdotal. Most shooters are guilty of this, but yes, it takes a lot of rounds under controlled conditions to establish any real results that you can draw statistically valid conclusions from.

 

[lte82]

ite82,

Not to criticize your methods here, but 18 rounds does not a test make. What you have here are what would be considered an statisically insignificant amount of rounds, rendering any results obtained as little more than anecdotal. Most shooters are guilty of this, but yes, it takes a lot of rounds under controlled conditions to establish any real results that you can draw statistically valid conclusions from.

I shot a few more groups this morning at 6:30am. The huge vertical spread seemingly went away (though still not perfect, as there is still some vertical component there), and both lapua brass and ruag brass shot similar in terms of accuracy. .425 & .65 moa groups with lapua, and a .55 moa group, all at 200 yards. I agree, still not statistically significant yet, but at some point it will be.

Top group: Lapua brass slightly oversized (had resistance when closing bolt), left group: lapua brass FL sized, right group: Ruag brass FL sized.

 

[X-fan]

You have a trigger tripper problem