300 RUM OAL effects

[Tarheelpwr]

Hi,

I'm looking to build a 338 or 300 RUM. my DBM will have max COAL of 3.74. I've seen much longer OAL cited for the 300 RUM. How much will it limit my velocity if I have to use 3.74 as my max COAL?

I'm looking to run the 215 Berger Hybrids in a 26-28" tube. Just wondering if I'm talking the difference in say 3200 FPS down to 3100 FPS or if it will be DRASTIC, say more than 150 FPS?

Chris

 

[kcebcj]

I don't think you will see a lot of difference in velocities from changing the COAL if you adjust the amount of powder. More important is the max COAL going to limit how close you can get to the lands. It would be a good idea to have a conversation with your smith about the chamber options and the max COAL.

I'm building a 300 WM and the magazine will allow 3.650 COAL and that will get me to within .010 +- of the lands using the 215gr Berger with a standard chamber. I ran both the 3.650 and the standard 3.340 COAL in Quick Load and maxed out the pressure equally and there was a 15fps difference the 3.650 being the fastest.

 

[Tarheelpwr]

I don't think you will see a lot of difference in velocities from changing the COAL if you adjust the amount of powder. More important is the max COAL going to limit how close you can get to the lands. It would be a good idea to have a conversation with your smith about the chamber options and the max COAL.

I'm building a 300 WM and the magazine will allow 3.650 COAL and that will get me to within .010 +- of the lands using the 215gr Berger with a standard chamber. I ran both the 3.650 and the standard 3.340 COAL in Quick Load and maxed out the pressure equally and there was a 15fps difference the 3.650 being the fastest.

Good point. That sort of popped into my head after I posted this. I can always have the smith chamber around that limitation. As long as I can get 3100 ish, I'll be happy. That should be pretty do-able.

Chris

 

[live2huntmt]

You should have no problems pushing a 215 Hybrid 3100 fps regardless of magazine or chamber dimensions. I have pushed 230 OTM's out of my stock Rem 700 at 3129 using the max magazine length of 3.660" with no signs of high pressure in RP brass. in my factory rifle though, a COAL of 3.660" is still a loooong way from the lands though!

 

[Edd]

A seating depth change of .054" on a 30 cal bullet will make about a 1 gr change in the volume behind the bullet.

 

[Tarheelpwr]

A seating depth change of .054" on a 30 cal bullet will make about a 1 gr change in the volume behind the bullet.

Perfect ... that's exactly what I was after. So, basically, no difference on a RUM sized case.