100 fps deviation?

[bigsal5353]

Posting this for a friend so dont have all the details....

He's reloading for a 338 lapua, said he loaded 25 rounds of all the same charge, primer, oal, trimmed length etc.. he says this load will produce 1/2 moa groups at 100 yds.

When he shot these 25 rounds, his groups where close to 2 inches and his chronograph said his standard deviation was close to 100 fps.

What would cause this??? I'm thinking either something is screwed up with his scale, or his dies and not seating to the same depth??? He says he measures each load/oal

 

[Canadian Bushman]

I would think that if he measured all his C.O.A.L it has to be a deviation in powder charge. I know that there are many of things that can go wrong with scales.

 

[J E Custom]

Posting this for a friend so dont have all the details....

He's reloading for a 338 lapua, said he loaded 25 rounds of all the same charge, primer, oal, trimmed length etc.. he says this load will produce 1/2 moa groups at 100 yds.

When he shot these 25 rounds, his groups where close to 2 inches and his chronograph said his standard deviation was close to 100 fps.

What would cause this??? I'm thinking either something is screwed up with his scale, or his dies and not seating to the same depth??? He says he measures each load/oal

It sounds like a primer powder mismatch. It could also be his chroney. 30 to 40ft/sec is bad so
100 is terrible.

Just a thought.

J E CUSTOM