New 8mm Rem Mag & Range Report

Well, today is revealing indeed all accept me changing my OAL and opening up my group to over twice the size it was Friday. You know, sometimes I need to leave somethings a lone. Now that said, here are my velocities from two different groups this morning and they are not over max (you can see by looking at my brass). I am going to adjust my OAL back to were it was 3.600" and continue to work up one tenth of a grain at a time till I get near or at max for my rifle.

Here are pictures of my chronograph readings, brass fired for highest velocity average and my group that needs the OAL adjusted back to where it was. This is very significant, considering I have a 24" barrel, and a greater cross section of my 200gr bullet than a 200gr bullet out of a 300Rum.

Competition Electronics ProChrono Digital Chronograph with Competition Electronics Digital USB Interface , hooks up to my laptop

Today was an interesting morning but you talk about hot and humid. Once again to remind everyone, this is an out of the box rifle with no glass bedding or pillar bedding and this rifle uses a pressure point up close to the end of the for end. No, I do not have any intention of changing it at the moment. But today was a very good day of discovery. First, 200gr Accubonds give me great velocities but the accuracy is very poor. I have tried now different loads with RL-25, RL-22, MRP, Magnum and IMR7828 and the groups are embarrassing to say the least. My rifle simply does not like them. I have 100 200gr Accubonds left and will trade them for some 200gr Partitions if someone is willing to do so, and if you are willing please pm me about trading.

Magnum powder preformed well, my barrel did not get as hot to the touch as with the other powders and accuracy was fair to good but average velocities were 2951fps with the 220gr and that was disappointing. Now IMR7828 did very well in velocity with the 220gr SBT and accuracy was good and this was with one grain under book max. I am very please with this powder and the Sierra SBT. I will be soon testing 250gr bullets and also some 200gr (forgive me for even using these words and don't remind me of my dislike for terminal results I get with the :mrgreen: - Barnes TSX).


220gr SBT, 83.0grs IMR7828, Rem brass, Rem 9 1/2M primers, 3016fps, OAL 3.600" .964 minus first round which was first round out of a clean barrel. After ten shoots this group should tighten up a little more once the barrel is fouled good.

Man, this 250gr Barnes orginial in 8mm sure makes the Sierra 220gr SBT look anemic. :shock: Can't wait to work with this bullet, but that will be when the weather get just a little cooler. :mrgreen:

What a cool looking beast and if I can get around 2800fps (hopfully) WOW!

Well, I did some more range work with my 8mm Rem Mag and I have discovered that my rifle does not like 200gr Accubonds or Partitions, but does like 220gr Sierra and 250gr Barnes Originals.
First: The 200gr Accubonds will give me 3154fps and the Partitions will give me 3137fps. These are awesome velocities but accuracy is not acceptable to me running 1 ¾” at best to 3 ¼” for most groups.



Second: The 220gr Sierra SBT gave me last time I was at the range working with this bullet 3016fps on the average. This time 3018fps on the average with 21 Extreme Spread and 9 Deviation and a three shot group size of .487” – This was the seventh and last group I fired and still had this level of accuracy after all that recoil. The first group I fried was after one fouling round from a clean barrel and it was a three shot group that was .849” and it had an Extreme Spread of 20 and a Deviation of 9 giving me 3017fps.
Three shot group .487", 220gr Sierra SBT, 3018fps average

Three shot group .849", 220gr Sierra SBT, 3017fps

Third: There were the two groups I fired using the 250gr Barnes and was 5% with below published max with one group and 4% below max with the other group, giving me from 2701 – 2720fps as I was testing in the margin of safety to make sure I did not get close to max pressures with this very soft bullet. Of course I will now increase my charges moving toward max hoping to be over 2750 – 2800fps with an accurate load. Group sizes were as follows as I increased the powder charge from 5% to 4% below max. Best group was .447” with Extreme Spread of 22 and Deviation of 11, and worst group was .8485” with Extreme Spread of 22 and Deviation of 11.
Three shot group .447", 250gr Barnes Original 2720fps

Three shot group .8485" , 250gr Barnes Original 2701fps

Today I decided to test my extended load work with my hunting load for my 8mm Rem mag and also looking for better velocities for my 250gr Barnes Original. My average today with the 220gr Sierra was 3003fps and this is due to me using after I full sized my brass an expander mandrel expanding the diamater of the neck .002 and then using the regular mandrel for my Sinclair neck turner. This reduced the neck tension which also reduced my pressures and velocities from 3018fps on average to 3003fps but group is much tighter. Was able to get the 250gr Barnes Original to 2749fps and what was amazing today was all three of the rounds were 2749fps.