.300 RUM + 240 SMK loads using US869?

[yote bomber]

Just picked up a pound of US869 and a box of the 240 Sierra Match Kings... I've seen a little bit of data on here for this combo, but most of it seems like it was shot in custom rifles. I'll be running them out of a stock Sendero in .300 RUM...

I'm thinking starting somwhere in the 93 grain range and working up? I'm thinking 2850 should be an acceptable velocity, as long as the accuracy/consistency are there. Anyone got any suggestions on where the velocity should be?

 

[jmatson]

My "Quick Load" v3.4 93.0g of US 869 2678fps 54,145psi and 99.0g at 2858 at 67,908psi out of a 26'' barrel. You should find an accurate load some where in between if the 1 in 10 twist will stablize those 240g MK's.

Hope this helps!

 

[Jon A]

Something isn't right with those numbers. Quickload shows me only 62.2 KSI at 99 grains with a velocity of 2893. That's with the weighting factor at the default of .5--it should be lowered to more accurately represent this case. At .4 it shows only 59.7 KSI at 2914 fps, which is closer to what I've seen in reality.

 

[yote bomber]

2900 fps with a 240... at under 60k psi would be an awesome load. Especially with the current availability of .300 RUM brass.

 

[jmatson]

Jon you are correct! my weighting factor was set at .7, I don't have a 300
RUM to compair any data. How do you like yours? I have been thinking about betting a Rem Sendoro.

 

[Jon A]

.7! Ouch! That'll do it! I'm glad we figured out the discrepancy though.

I still like it a lot. It's a great round.

 

[Varmint Hunter]

Stupid Question

.7! Ouch! That'll do it! I'm glad we figured out the discrepancy though.
I still like it a lot. It's a great round.

I'm sure this is a stupid question, but for the slow-of-mind; what is the weighting factor in Quickload? How (or why) is it applied to your input?

 

[Jon A]

It's a measure of the percent of powder/gases that go "down the bore with the bullet." For example, a straight walled case has a relatively small case capacity and large bore capacity. By the time the bullet exits the muzzle there's only a very small percentage of gas left in the case—most of it is in the bore. On the contrary, for an "overbore" case, with a relativley large case capacity/small bore capacity, when the bullet exits there's still a large amount of gas left in the case itself, a much smaller percentage will be traveling down the bore with the bullet.