group size when fire forming brass

[Shufisher]

What should expectations be for groups shot while fire forming brass; 257 Roberts to AI? I used 87 gr. Speer bullets seated to touch the rifling pushed by 37.5 grains of IMR 4895 straight from the hopper, weighing powder every 5th round. This load produced a 10 shot group of just over an inch at 100 yds. The barrel was scrubbed after the first 5.

The rifle is built on a virgin Sako Forester L579 with a Montan Rifleman stainless 26" heavy barrel (1/10 twist).

I hope my expectations arn't too high, but I am really looking forward to working up loads with a heavier bullet in my newly formed brass. I'll post the results once that operation is complete.

Thanks,

Jim

 

[41mag]

Sounds like it will be a shooter. Thats the way my Contender was when I worked up the loads in it. Fireformed under 1" and the final load is just plain boring to shoot at 100yds. After three or four shots you can't tell where you hit. LOL

 

[Shufisher]

Thanks Mike. I hope to participate in the same boredom you've had to endure...

 

[moosehunter]

I was fireforming 100 pcs. of .284 winchester to 6.5-284 in my 1K bench rifle a couple weeks ago. Load was 45gr. of H4831sc with Fed. 210M primers. 142gr. Sierra MK's jamed into the rifleing. 100yds over the chrony and near keeled over when I saw the groups. 5 shot holes measured in the .1 to .2 inch range. Of the 10 groups fired not one was over .3"

 

[Guest]

I have had good results fireforming a .243 Ackley/Lilja 3 groove 12 twist. Loads were with full power std.243 data and 87 gr Hornaday HPBT seated into the lands. accuracy was sub MOA.Plenty good for varmits.Velocity was in the 3200 range.After the brass was formed the loads were worked up to the 3400 to 3480 range using OLD H 4831 groups in the 2s to three"s.Cases are Lapua al match prept'd Fed 210 match.My experence with a std .257R is about 40 years and mu best load for a deer load was 49 gr H4831( old WW2 surplus) and a cci250 in Winchester cases.In Browning Safari 24" this load shoots at 2980fps.1" group at 200yd.
God luck Old Bear