I have a custom 6.5/284 Norma with a 28" 1 in 8.5 twist barrel which has been melonited. The reamer used is a no turn one for the Lapua brass, but in a couple of instances a bullet wouldn't re-enter the case mouth after firing. Loaded rounds measure .2935" fired cases mike out at .2963"

I'm thinking I need to turn off about .001 to .002" to decrease the apparent pressure, or at least uniform it. I am not anywhere near published powder maximums, and velocity is below 2950 ft/secs with 142 grain Sierra MK's. Accuracy on the other hand is fantastic... hence the dilemma!

Your input is appreciated, where relevant!

I'd be inclined to not fix what ain't broke. Did you mike the bullets that were reluctant to enter the fired case mouth?
I don't think turning off a bit of neck would affect your accuracy but when you start talking about turning off .001-.002, you're talking about some pretty fine work.

Even Lapua brass can benefit from neck turning.
If you haven't done so, I'd take off the absolute minimum necessary to even out my neck to provide for a more uniform bullet release.

BTW those are some awsome groups. Keep up the good shooting.

The bullets which didn't enter the fired cases mouth were other loaded rounds that I declined to fire.

I agree that the small amount I am proposing to remove is perhaps not the answer, and a challenge to accomplish!

I had some exceptional conditions to shoot in, so I looked good that day!

Thanks for the responses.

The Norma rl guide shows 2920f/s for 140gr sierra.

I have built several 6,5X284s with 1-8.5 twist and have never gotten to 2950 fps with a Sierra 142 even with 29 inch barrel. I think that velocity is out of 31 inch and probably slower twist. Built one with a 1-8 twist and had to drop 4 grains in charge from the 1-8.5 twist loads. Looks like your gun is shooting pretty good especially if you have a suppressor on the end of the barrel.

quote:

Originally posted by srose:
I have built several 6,5X284s with 1-8.5 twist and have never gotten to 2950 fps with a Sierra 142 even with 29 inch barrel. I think that velocity is out of 31 inch and probably slower twist. Built one with a 1-8 twist and had to drop 4 grains in charge from the 1-8.5 twist loads. Looks like your gun is shooting pretty good especially if you have a suppressor on the end of the barrel.

I appreciate this comment as I was going by my previous 1 in 8 twist 27" Hart barrel which gave 3013 ft/secs with the same load, no pressure issues. This is a 28", but regardless I will be backing off and starting over for the individual rifle.