245 Berger in 300 PRC vs 300 RUM

[jlphillips1]

I currently have a 300 PRC that I am pushing 245 Bergers at 2939 fps. It has a 26" barrel with a +P modification and I'm using 84 grains of N570 in ADG brass. I am building a new 30 caliber rifle and I also want to use 245 Bergers, but I'm having trouble deciding on whether I should build another 300 PRC or go with a 300 RUM or something else. I don't want to single feed rounds and I am going to use a 4" Wyatt box in the new gun. I would really like to push these 245 Bergers around 3100 fps, but that may not be possible without stepping up to the 338 Lapua case and necking it back down to a 30 caliber (aka 300 Terminator). For those people who are shooting the 245s in a RUM (or something else) can you help me with some data on what speeds you are getting?

1. What velocity can I expect to get with a COAL of 4" in the RUM with a 26" barrel?
2. Another dumb question, but since both the PRC can easily shoot rounds with a COAL over 4", why don't they make a mag box longer than 4" for setups like these?

 

[Shane Lindsey]

Your +P PRC (say that three times fast) is besting my 300 RUM with 245s. It is a SAAMI throat, but best I could get was 2929 FPS with 89gr N570. It was hard on brass, so backed it down. I have seen several PRCs with better velocity than I get, but again, just a SAAMI throat. If you do a custom reamer on a RUM, you may/may not be able to bes your PRC. If really wanting that velocity, may be better off with the Terminator. Probably wouldn't be pushing your cases as hard to get there.

I would imagine you start running out of metal if you went too much longer. An action would need to be designed that would make it longer, then stocks would follow, bottom metal, etc. Folks just figure it's logistically easier to single feed.

 

[Shane Lindsey]

PS, pay attention to your barrel life using N570. My RUM starting to get "loose" at about 700 rounds eating a healthy diet of N570.

 

[MagnumManiac]

Can't help with either cartridge velocity, sorry, but in my 30-416 Rigby Improved I can safely push 245's above 3200fps.
I believe you would be better off using the Norma Improved case due to not wanting to single feed.
I guess you can try running the RUM throated for the 245g and a 4.0" mag box. My 338 Edge needed a 4.0" mag box, but I still ended up single loading with certain bullets.
I run a 3.850" mag in my 300 RUM, but mine is a 10" twist and I haven't run heavies in it yet. I have 230's to use, but they run really well in my 9" twist rifle above too.

Cheers.

 

[Longtine88]

My rum runs them around 3,020 fps with a 4" box. My 30 nosler runs them around 2960. That being said I'd just run the 300 prc if you're getting those velocities. N570 is also the only way you can achieve those numbers. Barrels are cheap.

 

[haisardao]

I agree with above. In my 300 NM I capped around 2940 fps with N570 and 245s, those PRC numbers are excellent. I think it'll take a Lapua based case to get what you want.