Appropriate case fill levels for very fast powder

[toddpotiphar]

I've been working up a subsonic load for my 300 Wby using cast bullets and Trail Boss. The charge weight range I'd like to test at is 10 - 12 grains, which is only about 40% of case capacity (27 grains was a full case).

In my first round of test loads (testing for velocity only) I stuffed pieces of cotton ball into the cases to take up the empty space. Considering that I'd like to use the load for shooting gophers (among other things), I'd rather not spew cotton embers onto the dry prairie grass.

What would be the effects of leaving the cotton out of the case? Pressure issues seem unlikely to me considering the fast burn rate, but it's quite likely I don't know what I'm talking about. Inconsistent velocity seems like it could be a problem.

I read an article where the author described his load of 5 grains of Unique in a 300 Wby case with a 55 grain cast bullet; he didn't mention anything about using a filler for the extra case capacity. Does anybody else have experience with this kind of load?

 

[dirtybarry]

I loaded up a bunch of subsonic .223 rounds with 3.1 grains of Titegroup that looked positively lost in there and every single round went bang. Kind of fun too.

 

[Fargone4sure]

I'd really recommend against using cotton balls. Google "ringing" and you will see why. Basically it can cause a ring in the barrel. Anyway, most fast powders don't need to be held against the primer.

 

[saskgunowner101]

I googled Trailboss loads for 300 Wm (which I'll assume has a smaller case than 300 Wby), and even then, starting loads were around 18 grains. I think even if it pressures up without hangfires, you won't hit the broad side of a barn.

 

[toddpotiphar]

I googled Trailboss loads for 300 Wm (which I'll assume has a smaller case than 300 Wby), and even then, starting loads were around 18 grains. I think even if it pressures up without hangfires, you won't hit the broad side of a barn.

10, 11, and 12 grains gave me 950 fps, 1000, and 1050. All printed well at 30 yards.

 

[Andy]

I've used "fast" pistol powders from Bullseye to Unique with charges that filled less than 10% of the case, and never had a hangfire, nor any need to tip up the barrel or any such thing.

The only problem encountered was with bullets that didn't exit the bore, the solution to which was a minimum 25% increase in charge weight.

However, with pistol powders slower than Unique, e.g. H4227, problems ensued at the low end of charge weights.

 

[toddpotiphar]

I've used "fast" pistol powders from Bullseye to Unique with charges that filled less than 10% of the case, and never had a hangfire, nor any need to tip up the barrel or any such thing.

The only problem encountered was with bullets that didn't exit the bore, the solution to which was a minimum 25% increase in charge weight.

However, with pistol powders slower than Unique, e.g. H4227, problems ensued at the low end of charge weights.

Thanks, all. This is definitely the information I was looking for.

Hodgson's burn rate chart lists Trail Boss at 21, Unique at 31, and H4227 at 66.

I'll load my next batch of test rounds without the cotton.

 

[saskgunowner101]

10, 11, and 12 grains gave me 950 fps, 1000, and 1050. All printed well at 30 yards.

Well, if what you're doing works, all the power to you. I've stepped outside the lines quite often, and sometimes a little too far and it all goes to crap. I think one of my favorite failed experiments was a light load of Clays in 9mm. I couldn't believe the gun was actually still cycling, but the accuracy was comical. Best of luck.