Improving a case, powder change??

[GasLight]

Wondering if there are any rules of thumb about improved cartridges? Do you typically use the same powders proven in the parent case just more of it, or do you move to something slower burning taking advantage of the increase in case capacity that way? Looking to get some ideas on how to increase velocity the best way in an improved case.

Thanks

Dave

 

[former naval person]

Re: Improving a case, powder change??

After chasing my tail over these IMPS for forty years or so...the main improvement is in case life. A typical improved case will give 6 to 10% increase in powder capacity. By the time you increase the charge to get the same velocity, and then try to load for increased velocity, you will only get 1 1/2 to 3 % improvement in velocity. If you have a tapered case like the .220 Swift that eats cases...then it is worth it for the improvement (by 5 or 6 times)in case life. If you have a cheap case like the .223 Win that has long case life anyway...the AI isn't worth it in my opinion. Other shooters experiences may vary.

 

[former naval person]

Re: Improving a case, powder change??

Oh...and I didn't answer the original question, as to the powder. I found with the .375 Whelen, that when I went to the .375 Scovill, I needed to go to IMR 4320 instead of 4895 for best performance. Not worth the trouble...although 4320 is a forgotten powder that is just now being rediscovered for 1000 yard competition. (Another non-answer) Expanding .35 Whelen to .375 and loading it is easy. Having to expand to .40 and neck down to a false shoulder, then fire form...lots of work for little gain. JMHO

 

[GasLight]

Re: Improving a case, powder change??

I am already sold on the improvement, have the gun chambered in it, a hydro-die made, and some brass formed. I am just about to start load development and was wondering if I should go with tried and true from the parent case, or move to a slower burning powder...

Eventually I guess I need to try them all and see what it does for myself, just didn't know if there was some type of rule of thumb for this stuff... never done much reloading or improving. I may well find the same thing, it isn't worth the effort, but at this point the effort is already in...

Dave

 

[former naval person]

Re: Improving a case, powder change??

Depends upon what the case is. And what the powder is. The original powder may be a trifle slow for the case and be just right for the IMP. Or, versy/vicey, it may have been on the fast side for the original and needs a slower powder. Parker O. Ackley's book helps...but that was long ago and far away as modern powders and primers and bullets go. Start low and carry a long string.

 

[GasLight]

Re: Improving a case, powder change??

I appreciate the input. What I have is the 6.5 Grendel improved to 40° and blown forward .075".

What seems to be enjoyed in the grendel is W748, AA2520, and some are trying IMR 8208 XBR.

I guess I will pick a couple of those and try them. Do you think moving to RL17 is too big of a change? I guess I can try it and see if I can stuff enough in there to get any kind of velocity.

Thanks again

Dave