Home Forums Hunting & Shooting Ask The Gunwriters Slow 257 Roy

I have a bump an jump model 70 that I've rebarreled to 257 WBY. I used a #4 Shilen 10" twist that I finished up at 26 inches. The chamber was the first one cut with a brand new a Clymer reamer. It's bedded full length into a wood stock from a classic and wears a Swaro 3-9 in Talleys.
The thing loves 100gr bullets and 7828, Barnes, Sierra, hornady, Herters, Speer, doesn't seem to matter insofar as accuracy is concerned. So far I've only shot paper, rocks, and one unlucky coyote but it is certainly accurate as long as the bullets are seated out and the gas pedal is down. 5/8" to 3/4" for 3 shots is the norm if I'm on my game behind the trigger.
And strangely the old Herters 100gr spitzers are it's favorite bullets, good thing I scored a 5lb bag at a gunshow a couple years ago for $10, wish I'd have bought the other 5lbs now that I'm running low.

Anyway, I've been shooting this thing for 2 years and have about 4-500 rounds down the tube. I neck size with RCBS dies and seat with a straight line seater, brass life is good. Last weekend I finally got some good weather to shoot a few over the chrono and was shocked to find that the average was 3320fps although the ES was in the single digits. With the bullets seated long, 3.310" I am still getting sooty cases when running the book max charge, the chrono results were with 69gr of 7828 which I believe is over Hodgdon's published maximum but is the point where I no longer get sooty cases and all of the traditional pressure signs are nonexistent.

I cut 2 other chambers in Lilja 3 groove barrels using the same reamer and gauges for two close friends and both of their rifles give speeds more in line with what the manuals have listed. What's going on with mine?

Hodgdon shows 73 grains of 7828 with a 100 grain bullet.

Guess that would explain it then. I was using an older hard bound Hodgdon's manual, apparently they've stepped it up since the 90's.

Check their online Data Center. It's pretty impressive...

Guy

In the 257s I have, 71 gr. 7828ssc will get you in the 3470-3500 range, 72 gr will get you in the 3550-3580 range. I have tried 73 gr but ran into pressure so backed off from that.This was with 100 grain NBT bullets at 3.340. Accuracy good with both.

Its good to check alot of sources on wby data. There is some terribly "weanie" data out there.

I just wonder if 7828 has changed any down through the years. My Hodgdon's manual from the 90's lists 68gr as max with the same speeds as the current Hodgdon manual has for it's max load of 73gr.

Bullets dont all have the same bearing surface either.