Got my custom .300 WSM finally, after an eleven month wait. Took it to the range with a whole host of loads to try.

The good news is it's practically a one-hole rifle regardless of load. The bad new is the load that shot the best chronoed excessively hot.

With 69 grains of Reloader 19, it pushed 180-grain Speer Grand Slams into one hole at a speed exceeding 3200 fps! The book says this load should shoot only around 3000 fps. Indeed, I only got around 2980 fps with 68 grains. Is it really possible to jump almost 250 fps with just an increase of one grain?

My gun does have a 26-inch barel, which accounts for some of the increase, but that seems a lot to me.

By the way, the bolt did not stick and the primers seemed find. There were no signs of too much pressure.

How many rounds did you chrono for each load.O ccaisional high or low readings do happen.

Did you step up your loads in .5gr increments? If so what was the 68.5 load's velocity?
The book's reporting a velocity from thier test gun, maybe you have a "fast" barrel in yours. If you absolutely see no high pressure problems, maybe that is the load for you.

I admit that velocity jump for 1gr does seem unusual though. Were the bullets all seated the same? Have you checked case expansion, compared to a factory load?

I chronoed 5 shots with an extreme spread of 32 fps.

No, I did not shoot the 68.5-grain loads, even though I had three in the box. The 68-grain load shot so good with no pressure signs that I went ahead and took the plunge. Not so bad when you consider that the book lists 69.5 as the max load.

I'm going to load up 10, 68.5-grain rounds and 10, 69-grain rounds and have a shoot off.

I'm telling you, this caliber is the best I've ever seen. I've yet to see a 300 WSM that doesn't shoot.

What your Chrono is telling you is that your load is too hot. One of the signs of excessive pressure is the sudden jump in velocity that you are seeing.

Those loads are at or over the max so as mentioned above the load is too hot.

What do the cases mike at just below the web? I read that you are having ejection problems also in another thread.

The rest of that big jump in velocity could be some measurement error. A velocity of about 3000 fps is all anyone is going to get out of a WSM anyway so back off on the loads. Now you know what max is for that load at that ambiant temperature and that lot of powder.

Don,

The ejection problem has nothing at all to do with the load being too hot. We discovered that the gunsmith had opened up the bolt face too much, which caused the ejection problem.

When I took the rifle back, he handed me another one that he had built up at the same time as mine for his personal use -- same set-up, McMillan stock and Kreiger ss barrel, but with engraving on the reciever and a muzzle break.

Bottom line is I've got to start the load work-up procedure and barrel break-in all over again in this new rifle. This time, I'll move up slowly and stop when I get to 3000 fps.

GA, sounds like the groups are terrific. So how can I get one of these from you smith?

GAHUNTER- Did the weather cond. change ie sunny to couldy?Just a thought.
I haven't been able to get the Velocity of the Load Data in the Winchester's I 've shot,at least not without going over the Max listed charges.No signs of high pressure yet an they shoot very well also.