338 RPM help

S

Shotzie43

New member
Hi everyone. I’m a newer reloader. I’m addicted, but definitely still learning. I have a 338 RPM and trying to load some 175 HH for my Backcountry TI 18” barrel. I’m struggling trying to figure out a searing depth. I played around with the Barnes 185 TTSX and actually got them shooting 5/8” groups at 3.373 OAL. I should just stay with that, but I want to try these. I called weatherby and they said to seat them at 3.370-3.380, but this is what they use for the 185 Barnes. The bullet profiles are very different. I measured the distance to the lands for both bullets with the Frankfort Arsenal gauges that clip on my cleaning rod (I had nothing else to go off of). For the Barnes it is 3.485, and the HH is 3.400. Can I use the total jump of the Barnes to calculate the OAL of the HH? It works out to .112 for the Barnes, which would give me 3.288 for the HH. Does this sound ok to anyone? The freebore on the weatherby’s has me a little nervous. It’s not quite as easy to figure out as most other non-weatherby calibers. Any advice would be greatly appreciated! A member named Fotis has this bullet at 3.995 on the load data page, and this does not seem right. The bullet has to be almost hanging out of the brass at that length. Thanks in advance!!
 
Don't know about the 338RPM, but the 2 Wbys I've fooled with had Enormous freebore@ like .400 freebore!
Good thing is Hammers don't mind jumping.!
In my personal rifles, i have jumps up to just over .200. They shoot fine.
My personal expectation is 0.50" groups. No problem getting them.
Most start at at least .020 jump
. 100-150 is not uncommon.
I think you'll be fine.
 
No experience with your cartridge, does seating in the top groove have at least.020” to the lands? Does it feed and function? If yes to both then try it there for starters. There are one or two guys here playing with that cartridge maybe they’ll see this.

Welcome from Saskatchewan!

Edit: looks like gl beat me to it posting while I was typing! Good to see you at it gl!
 
At the factory 3.370 OAL, the bullet is seated between the first and second grooves. It honestly doesn’t even look right. Thanks so much to both of you for the fast responses! And after gltaylors freebore comments, I feel safe to start test firing at 2.288, which would be the same jump as the Barnes. I’m going to wait a few more days and see what other responses I get before I go that route though. Thanks again
 
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