7BR with cast boolits

[PhilC]

Rifle data:

Savage PTA timed/trued by Fred
Target AccuTrigger @ 10oz
26" SS Shilen Select Match, heavy varmint contour, custom throated
Vintage B&L 24x
Bobby Hart LRT
Weighs 12.5lbs

Load data:

RCBS 168-SP, Lyman #2, gas checked and sized to .285"
WLL X-lox 2500+ in first lube groove only
Peterson fireformed brass
CCI400
N135

Removed the 6.5CM barreled action from the LRT and put it back in the factory stock, then fit the 7BR barreled action to the LRT. Loaded test rounds about 2 weeks ago and was just waiting for a good weather window which finally happened Friday.

Pulled my bench out and set up. Re-zeroed the 6.5CM then set up chronograph prior to shooting 7BR. Shilen recommends shoot 1 & clean for 5 rounds, which I did while getting scope dialed in. Fired up the chrono then proceeded to shoot 4ea 3-shot groups. Rounds 6, 7 & 8 produced the group circled in green, I forgot to adjust elevation before the first shot of the next group circled in red...



I use corrugated plastic for backers and they were quite wet from morning fog, so waited to measure after they dried, the three holes on left measured .712"...



The final group at 26.5gr openend up a bit, but still respectable with only 17 total rounds shot...



Disregard markings on targets, I save unused sighter targets for home practice. When I ran my borescope down the barrel afterward I found no lead fouling at all. Hats off to Shilen for a superb finish!

This is very promising and anxious to start a ladder test from 24.5 - 26gr. The 25gr load had avg vel 2048fps, ES 4.0, SD 2.0. :-)

[charlie b]

Nice start. What twist is that barrel?

I got my mold for the 6BR today (and sizing bushings). Will cast some up this weekend. It is also a Shilen barrel.

[PhilC]

It's 1:9, finished prepping remainder of my brass this afternoon. Back to waiting for another weather window as snow returns Thursday/Friday, then an arctic front moves in Sat night, highs drop to mid to upper teens and overnight lows near zero through at least middle of next week.

Good to hear your mold arrived, look forward to updates!

[charlie b]

You'll have the same problem with velocity that I will (1:8 twist). 2000fps will probably be fine. Will experiment a bit to see how fast it will hold up.

My 1:10 twist .308 holds up to just under 2100fps depending on powder being used (slower is better in it with heavy bullets).

[PhilC]

I spent a lot of time researching CBA match reports for 6BR & 30BR, powders, primers, molds, twist rates, charge weights, alloys, velocities, and resultant groups. I focused on the competitive averages and used that info in my decision process and in running variables in QuickLoad.

From that, I was "pretty sure" ~2000fps was going to be a sweet spot, sure seems to be so far. :-)

[charlie b]

I spent a lot of time researching CBA match reports for 6BR & 30BR, powders, primers, molds, twist rates, charge weights, alloys, velocities, and resultant groups. I focused on the competitive averages and used that info in my decision process and in running variables in QuickLoad.

From that, I was "pretty sure" ~2000fps was going to be a sweet spot, sure seems to be so far. :-)

I think the CBA website might be one of the most used resources I have. The other (for jacketed) is the International Benchrest site.

Yep, I find that my most accurate loads in the .308 are 1800-2000fps. My go to load right now with the 210gn bullet is 1950. The bonus is that long bullet is good for 500yd ranges. It is a little too slow for 600yd.

I'll be starting at 1900fps with the 6BR and work up until the groups enlarge, then back off 100 or 200 fps.