Changing case brand ( 243 win )

John_R

Well-Known Member
I have decided to retire the Federal brass I have been using, and have a quantity of Geco once-fired.

The Geco is a heavier case, with slightly smaller internal volume than the FC. Actual figure measured was 3.337 cc in the Geco as opposed to 3.4408 in the Federal, a difference of 0.1037 cc ie 3%.

I am aware I will need to rework a load. By how much should I drop from my current data to be safe. and then work up from there?

At the moment I am using 37 grains of N140 under a 87 grain Hornady Interlock, which runs at just under 3100 FPS to be deer legal. I would be happy to run a little slower anyway, as these days I seldom use the 243 for deer.

TIA John
 

enfieldspares

Well-Known Member
The specific powder makers manuals recommendations are always best to follow on this. I can't quote them as I don't know what Vihtavouri advise. Some US powder manuals advise 5%. Other US powder makers advise other percentages.
 

paul o'

Well-Known Member
1st did you make a load chart for the FC brass if so start again using that , my pet load for hornady hp was 35gr n140 and 5 tho off in the RPA did't have a chrono back then but nowt walked away
 

John_R

Well-Known Member
I might struggle to find old notes as I did the load development perhaps 8 years ago. I was new to reloading and had generous help from one of the guys on SD and other boards.

One thing is for sure, Vhit data is now more conservative than it was back then, a subject that has arisen a number of times.
 

ashray

Well-Known Member
good morning,for foxing and stalking i have found very little difference with n140 loads in different cases,i use a 20"barrelled 243 and cases from fc/win/geco/sako/lapua and ppu,i do find sako split sooner than other cases but velocity with the same charge in various cases is within 50fps and at up to 250 yards makes very little difference on live quarry.i dont target shoot but do check the rifle zero when changing brass and its always within 1/2" so dont mess with any thing.others will have different finds i have no doubt !
 
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