US869, 200 Accubond, 300RUM starting charges?

[jmden]

Gonna play with this and see what happens even though I know folks are saying this powder is a bit slow for this combination.

What reccomendations for a starting powder charge to work up from? I was thinking starting at 95 or 96 grains and working up in .5 or .3 gr increments while fireforming and ladder testing at 600yds over a chrono.

This is the factory chamber, but I've done quite a bit of 'accurizing' to this rifle. With carefully prepped brass including neck turning to shine up 70-80% of neck and pushing the 180 Accubond at 3300, I'm consistently between .5 and .9 MOA out to 600 yds field shooting prone with the gun resting on my pack. Tend to average about .4 MOA off the bench with a few really nice groups with this load. I'm hoping to do similarly with the 200 Accu.

I'm also thinking of just neck sizing with this batch of brass and just waiting to FL size when chambering gets a little tight (I have been bumping the shoulder .002 using Redding comp shell holders and FL die) and waiting to anneal until I see a neck crack. Any thoughts?

Thank you.

 

[jmden]

I picked up 8lbs of US869 and played with it last week over in MT. So this is a follow up to let folks know what I found with this combination.

Essentially, I found that US869 is allowing me to get another 100fps or so out of this combination of powder, bullet and rifle. The max load that I am comfortable with is right above 3200fps with the 200g Accubond and I'm actually getting less in the way of pressure signs that I got at 3100 with Retumbo and RL-25. I'd started at 96 gr. and had loaded in .5g increments to 108.5. I quickly worked up to 108.5 and have settled on a load in the 109 to 109.5 range that's doing over 3200fps. I keep all the loaded ammo in the fridge overnight and in cooler at 40 degrees when shooting to try and simulate elk hunting conditions. A couple of the mornings I was shooting at ele., there was frost before the sun hit where I was shooting.

I had been using a low quality chrono this last week over in MT so that I'm not real confident of my ES, ave. etc., but I should be able to fly a few over the Oehler pretty soon and get a better idea of whats going on. I did shoot out to 700, but in bad conditions and w/o knowing my clicks because I didn't have a computer. So, I just worked it out by shooting a few and put in a few elk killers at that distance off a crappy rest and gusty winds, but I've still got quite a bit of testing and practice to do to feel comfortable shooting an animal at that distance with this load.

In terms of accuracy, things seem to be going quite well. I shot off a crappy rest most of the week and was getting sub MOA, but that was as good as I could hold as well. When I got to the Deep Creek range and had a real bench and shooting of shot bags, my groups plummeted into the .3s at 100yds. By the time I had a chance to reach out to 500+ there, gusty side winds kicked up and groups opened up to over MOA. So, I really haven't had the ideal conditions to see what this can do at some longer distances. I'd been worried that too slow a powder might make the pressure curve destroy accuracy, but at 100yds, this hasn't seemed to be the case anyway.

A couple of observations that I noted with this slower powder is that the entire barrel seemed to warm up after shooting 3-4 rounds. The heat from other powders I've shot seemed to be much more concentrated around the throat and a bit forward from there. Perhaps this is evidence of it's slowness? Cleaning was a cinch--seemed to clean up faster than other powders I've tried in this rifle. Meters very nicely, of course.

Edit: I don't know if others have found this to be the case with this powder, but so far there's and indication that the first 2-3 shots from a cold, clean barrel are really wild--much more so than any other powder I've dealt with and I'm not sure that this is the powder's fault, but am at a loss of how else to explain it. I did shoot nice groups to the same POI with a cold dirty barrel and this is how I hunt. After the first 3 or 4 with a clean barrel, groups and POI (full floated barrel) seemed very tight at 100yds.