I recall the RL-15 Alliant data, which has been repeated in this cartridge, even using magnum primers at the 59.5 gr. charge; the late Finn Aagaard used it in Handloader. Of course, he hit the published VELOCITY for the 250 gr. bullet.

In two particular 35's I've toyed with, 56gr. of RL-15 has been max over 3 lots and 15-20 lbs of that powder with 5 diff 250 gr bullets.

One should also note RL-22 charges for the 338 Win.and all bullets listed in that manual. I have hit those speeds, but NEVER those charges!

Agree with JB (big shock) use your chronograph. If you are getting speeds not published in ANY manual, better put on a welding mask when you shoot....the last imprint may not be on cartridge brass.

I was mostly reacting at first not to the exact charge the guy in quextion was using, but his muzzle velocity, close to 2700 fps with the Nosler Partition, which indicates WAY too warm a load for the .35 Whelen.

The Partition tends to create higher pressures than the Hornady Interlock of the same caliber and weight, mostly because of longer bearing surface but also because the Partition tends to "bump up" then the rear core is booted by expanding powder.

So I looked up Nosler's own data for the 250 Rl-15 in the .35 Whelen and found 53.0 grains as maximum, for a muzzle velocity of over 2500 fps. This is when I suggested the guy's load might be a little hot. It might not be with a Hornady Interlock.

57 grains should get around 2500.

We can usually predict what velocity a minor change in powder charge will bring by dividing the "new" charge by the old charge, then multiplying the original velocity with the result. Thus 57/59 = .996 x 2590 ("almost" 2600) = 2502.

This formula works very closely with single-based powders, not quite as well with double-based. But it is generally pretty close with minor charge variations.

One thing that may be going on is that all powders do vary somewhat from lot to lot. I went down to Charlie Sisk's shop in Texas a few years ago and we ran a bunch of pressure/velocity tests. One of the rifles we used was my CZ 9.3x62, and we tested some of the loads I normally use. At that time one of these was 62 grains of RL-15 and the 250-grain Nosler Ballistic Tip (now the 250 AccuBond). Everything was identical in the load we tested, except Charlie's lot of RL-15. It took two more grain of powder to equal the velocity I got with my batch of RL-15.

This sort of lot-to-lot variation isn't uncommon. Add that to using a different bullet that might very well create different pressures, and it's no wonder that sometimes data can vary 5 grains or more between different sources of data.

We did confirm, though, that velocity is the best predictor of pressure for the average handloader.