Signs of Pressure vs COAL Question

[Shooter Fred]

Hello all,

I went to the range this morning and shot some new loads for my 300 RUM. I made a few adjustments to the OAL and the signs of pressure seemed to go away. I moved the bullet .012 closer to the lands than where I had it with my first test load (total overall length is 3.60" and 2.98" to ogive)...I thought making a longer COAL would have made my signs of pressure increase? For instance, I am not seeing any ejector marks now and virtually no flattening of the primer.

The odd thing is my velocities are all consistently in line with what was shot in my first test batch.

Can anyone comment if this is typical with the 300 RUM?

[Reloader222]

To increase the OAL would not have much increase in pressure for as long as you stay safe from the lands. One usually would look for the best grouping with batches of various OAL. Should you go too near to the lands (and specifically with maximum or near maximum loads) it is advisable to decrease the load and see what it does to the grouping. If there is no flattened primers I would say you are still on the safe side.

[Shooter Fred]

Thanks Reloader...I guess I was just trying to ask if its normal to see pressure signs decrease while increasing the OAL? I am a long way from the lands as my 300 RUM has a long throat.

The signs of pressure definitely decreased as there was no case that was hard to open the bolt after firing and there was no ejector marks and virtually no signs of primer flattening. Whereas when I fired the same load before there was definite signs of pressure (the only difference was a longer OAL).

Also, does outside temp have anything to do with pressure signs? The temp was a good 15 degrees cooler this morning than last time I shot.

Thanks,
Fred

[Tikkamike]

What powder are you using? and yes the out side temp will affect pressure and you will see it on a max or near max load the most usually.

[Shooter Fred]

Originally Posted by Tikkamike

What powder are you using? and yes the out side temp will affect pressure and you will see it on a max or near max load the most usually.

I was using Retumbo and the load was 98.4 grains...last time I used 98 and 99 grains and both showed high pressure signs but this time with 98.4 it showed virtually no pressure signs.

This makes me wonder if I should bump it back up to 99 grains because the cartridge actually shot the best with 99 grains of powder but the presssure signs were definitely there. But with cooler temps and longer OAL the pressure signs went away (at least with the 98.4 grain load).

As you may know, I am just getting into reloading...this is a crazy world! So many variables.

[Tikkamike]

I have a 7mm that shoots 1 hole groups with over pressure loads of 160 AB's and IMR 4350 and when I bring it down to a safe load it shoots 1" groups. I reccomend testing your theory 1 or 2 more times try to prove it wrong. if it holds true I would leave it where its at because you are obviously right at the max. Then try adjusting your seating depth to increase accuracy. you may have to switch powders. Some times a combo just doesnt work out

[MTBULLET]

increase in oal changes interior case volume.