fast burning vs slower burning powders?

[flyfish]

I've been reloading for over 30 years but I never really got into the "science" of it. I have always been rather conserative in my reloading and it has served me well over the years. when it came time to choose a new load I would refer to the loading manual and pick one. I would go with a load that gave me the tightes groups. My question/request Can someone explain to me the advantages/disadvantages of a fast burning powder vs a slower burning one. Or maybe I should ask, how does one determine which powder should I pick and why.

I'm loading for a 257 Roberts.

Thanks

 

[FOTIS]

Man that really is a long winded subject if someone were to explain it thoroughly.

Let's put it this way. I usually go for the slowest powder that will give me close to 100% loading density. (Lack of unwanted air space in cartridge) This usually yields the best accuracy results for me.
That said you can go overboard. For example...lets say you're using a 100 gr bullet for your 257 BOB and you case capacity is 50 gr max
(NOT SURE OF THIS JUST GUESSING!!!)
You can load 30 gr of 3031 and have 35% air in that cartridge and reach max pressures fast---lack of max velocity--high pressure!

You can load 50 gr of H869 and have the charge 100%+ compressed with no air at all in the loaded round and you will probably get the same velocity as the 3031 load with very little pressure!

Or you can load the optimum powder (IE IMR 4350) about 45 gr and get good load density--no air -- and max velocity potential at acceptable pressures!

Again I do not have quickload in front of me, so all these powder charges, case capacities, powders are best guesses and to be used as examples only!!!!! They are not verified loads just best guesses from my experiences.

Honestly fellas if you can spare 150 bones get quickload. It is a wonderful tool and teaches you so much. You can sit there and simulate anything just for fun.

For example --again just for fun-- I simulated loading a 150 gr Ballistic tip in my 300 RUM with over 100 gr of Bullseye :shock:

Would you believe I got over 5500 fps? but pressures would knock me the gun and the scope into Nebraska or Utah pending on wind direction and how big the pieces of me or the gun were! :lol: :lol:


http://www.neconos.com/details3.htm

http://www.neconos.com/details3c.htm

 

[fredj338]

POP explained it pretty well. Slower powders build their pressure over a longer duration. You can often load the next slowest powder to 100%+ density, get slightly higher vel. & be operating at lower pressures.
When I start load dev. for a rifle round, I will usually pick the powder that fills the case & gives me the highest vel. Accuracy is often better too. Slower powders usually work best w/ heavier for caliber bullets. I have been using IMR7828ssc under 142gr SMK in my .260ai. The charge is compressed, accuracy is exc. & vel. is higher than I can get using H4350. In most cases you can have both great accuracy & higher vel. by using a powder on the slower side for that cartridge.

 

[flyfish]

Thanks guys.