I am just starting to (try) loading pyrodex in the .45-70. It was my understanding that pyrodex was substitute for black powder and that the '70' was the amount of BP to cram into the case??

WELL!!  50gr of pyrodex fills the case to the point that there is not enough room for the 405gr cast bullet, and yes it is RS granulation.

What am I almost doing wrong. ??

Pyrodex is a volume for volume replacement for black powder.  It is considerably less dense.  I've never used Pyrodex so I really can't recommend a proper load.  You should also know that Pyrodex is actually more corrosive than black powder and will also react with any ammonia containing bore cleaner you might use to cause rust.  Try going to the Hodgdon web site and see what they list.

Jerry Liles

Thank y'all.   
I tried looking it up, but without success. Pyrodex is NOT going to be my main powder, just a short term experiment.

I put 50gr of that 'stinking'  pyrodex under a 300gr cast bullet. This is just a 'gee whiz' thing to experience the smoke. Besides, 2 cans of the stuff only cost $20.00.

Works great in my .50 Cal CVA Side by side double rifle. Have tried some in my .45-70 Trapdoor and accuracy was ok for my informal targed practice. Less corosive than black in my experience and a little easier to clean up. Hot soap and water works just like black powder.

I have used Hodgdon's Triple7 in cartridge guns with good results.
It is much easier to clean up than BP.
I tried Pyrodex in several muzzle loaders, with mostly indifferent results, so did not bother with it in cartridges.

Jack

Just use a MAg Primer and compress it a lot, about .375"works fine.Have used it in a 38-55 Ballard and a 50-70 and a 40-50SS  Rolling Block and others
which are foreign to this board, military bolt actions.It must be heavily compressed to burn good, not like Black powder in that regard. I would never use Triple 777 in a Ballard as it been proven to be HOT Stuff. Black powder is sold in a Gun Store only three miles from here, but by local fire codes they can get only 25# at a time, so it sells out in a hurry.I could buy #5 at a time by mail, but that would`cost me over $100, try selling that to the wife when my 15year old daughter needs a pair of $250 glasses, she needs them in a week-back to school time.
The only bad thing about Pyrodex is it MUST BE CLEANED WITHIN 24 hours, with water, or your rifle may be ruined. I have ruined a 40-50 SS
Hepburn barrel by not cleaning soon  enough, so i've been there.

I have no actual experience with Pyrodex so most of my information comes from the Mad Monk, one of the leading experts on black powder and substitutes.  According to him one of the combustion products of Pyrodex is, I believe (I need to find my discs) sal ammoniac.  This is hygroscopic and will cause pitting corrosion of steel and, according to the Mad Monk, is much worse than the corrosion caused by quality black powder.  If you shoot pyrodex and the humidity is sufficient you will have problems if you wait to clean.  It is also supposedly particularly hard on brass. Additionally combustion products of Pyrodex will react with ammonia containing bore solvents to cause almost instant rust.   Finally, unlike quality black powder, Pyrodex will deteriorate with time.

Pyrodex is certainly a lot better than nothing and I would use it if it were all I could get but I would clean like a fiend after shooting.

My 2 cents.

Jerry Liles

If you use black powder and do not clean for a year you are also going to have a major problem. Use what works for you. I have been using some turn of the century Dupont black powder and it works great. Have had no problem with Pyrodex or Tripple Seven. I have heard that Pyrodex degrades over time. Got some real old Pyrodex that I bought cheap a few years ago. Need to try it to see how it works. One of the problems with black is that it is difficult to get in some areas because of shipping and storage regulations. I bought several pounds a few years ago when it was available. The only problem is that some areas have limits as to how much black powder you can store in your home and how it should be stored.