Hello Guys

A few months ago (in the winter here) I developed a load of 117 gn Hornady, over 35 gns of IMR 4320 with Fed 210 primers in Win cases. I worked up to the load, which is listed as max in the Lyman Manual, no pressure signs at all back then. Velocity was 2770 from my 22" barrel, right on what Lyman predicted.

Anyhow I was checking the zero today, which was a warmish spring sort, and wow - lots of pretty sticky cases, bolt lift was definitely quite stiff (and that's in a Mauser 98) so pressure was up quite a bit!

I need to reduce my load by 0.4 to 0.5 of a grain I think, but how much do you think it would reduce the velocity - I don't have the chrony anymore to check . . . and it would be nice to have an idea.

Thanks

It really sounds like your reduction should be at least a grain maybe more. One grain reduction will give you about 2720 fps. in the winter roger .

Tentman: a generel rule with IMR powders is that for every change(percentage)in a load you will ge a equal change in speed but a double change in pressure. If you incease a load by 3% you will get a 3% change in fps but a 6% increase in pressure. If you decrease a load 5% you will get 5% less speed but 10% less pressure. With you load a 3% reduction (33.95gr) you should get about 2686fps. My balistic program shows your 35gr load at 47250 CUP and with a drop of 3% of powder you would get a 6% drop in pressure to about 44,415 CUP.
SAMMI pressure standars for a 250 Savage is 53,000PSI and 45,000CUP

While the SAAMI maximum is 45,000 cup, that is clearly too conservative for an M98 action which can be safely chambered for the .25-06 at 53,000 cup. My Lyman #48 shows a maximum charge of just 31.8 grains of IMR-4320, staying under SAAMI pressure. The OP's charge is well above that, probably closer to the 53,000 cup of the .25-06. He would not be seeing sticky bolt lift at under 48,000 cup...

The reason for the increase in observed pressure is probably the increase in ambient temperature. IMR powders are not Hodgdon "extreme" powders and will show definite pressure increases with increases in temperature. If the OP was close to maximum in cool winter temperatures, an increase of 10-15*C could be the reason for the sticky bolt lift now. Drop the charge at least a grain to be safe, the little velocity loss will never be noticed.



.

Gentlemen - thank you all for thoughtful and useful answers, I appreciate you taking the time to explain . . . .

One of the reasons I wanted to explore this is my rifle has a "dovetailed" receiver (it is factory Mauser but . . . ) so I am pretty wary of "hot-roding" it.

This is one reason I have never really liked 4320, especially when nearing maximum loads.

Hey Roger Bartsche - your estimate was a whole 8 fps out (over a 10 shot string), I got an average of 2712 !!
(34 gns 4320 behind a 117 Hornardy)
Thanks