Pushing it or not?

[Tesoro]

I got my first 6BR and working on a load for 85 Sierra BTHP, which I want to use for hunting. I have a 22in Shilen ultra match on a Rem7 action.

I am jumping .02 off the kiss and using unfired Lapua cases, 450m and .001 tension for load development.

I tried Varget ( think better for heavier bullets) and H322 and IMR3031. Looking for speed + accuracy combo. I couldnt get Varget or 322 to shoot better than .4 in. Some of it could have been me. And then today I tried 3031. Sierra manual v5 has MAX at 29.3g at 2950 in a 26in bbl. I got 2900 with a 22in bbl and primers/base looked fine. So I snuck up a little to 29.7, 0.4 grain over their max, and bingo! found the sweet spot. 4 shots in .18. It felt right too. And I'm up to 2950 with SD of 10, ES of 24. I got a SD of 1, ES of 3, with 4 shots at 29.5 but one shot 2 one holers, 1/2 inch apart. Weird.

Bolt lift normal and I could feel a bit more recoil.

I measured the web above extractor groove with my flat jaw mic. New brass is 4685. under max load 1x with plump mushroom primers are 4695 and all the rest around max or over +.4g are 4700.

What ya all think?
Pics of the +.4 gr case bases

 

[Bill Norris]

Primers don't look bad to me.

 

[Lone Hunter]

Looks like an ejector mark starting on bottom right brass at 7 o’clock where the L is. Primers look good. Interested in your use of the 85 grain Sierra. Tired of trying to find Bergers so looking at Sierra 85 HPBT and Hornady 100 gr. Interlock. Are you using yours as a repeater or single shot? Going to use these in 6BR and 6XC.

 

[Tesoro]

Yeah I saw that but its light and the primer is a doughnut! I’m just learning this round. Cases are little tanks and I had bolt bushed for small rifle so wondering.. maybe with small lapua flash hole the primer is the last to show pressure.
That 85gr gk is a proven deer killler in 243. But Sierra machine is off line that makes it. I have a few boxes of Sierra 100gr GK and look great. .516 bc to boot.
I wanted speed for trajectory out to 300 so thats why I scrounged up a pile of 85’s

 

[Evan]

How did the bolt lift feel? In my Bordens it is useless to look at primers for signs, but bolt lift goes from glass smooth to a little stiff with hitches in the lift, telling me that pressure is sky high. The brass will then require significantly more force to resize in the press.

If your primary extraction and trigger timing is good, and the the bolt is bushed, then you'll probably need to use bolt lift and how the brass feels when you resize it as a gauge for pressure.

 

[Tesoro]

To tell you the truth I didnt pay much attention to the bolt lift because I didnt feel anything as not used to it. Plus its a mod7 action! New rifle only shot 50x and new cartridge. But I definitely didnt feel any extra friction that brought attention.
I just went into loading room and f/l sized 2 of the +.4 over cases and compared to a couple shot within book pressure. Yup noticeable diff on the wilson die! The +.4 fit when re-chambered, maybe with a bit harder bolt close but not excessive.

I think the best thing to do would be to keep this laser load for deer, as I wont shoot many rounds. And then find a sweet spot within specs for general shooting.

Here's a pic of my bolt head with a nice bushing job.

Thx!