Question for the .45 cal smokeless shooters

[Ridgeviewer]

Is pressure increased dramatically when going from a .50 cal barrel to a .45 barrel using the same bullet weight and powder charge.
Do you automatically drop your starting loads a prescribed amount to accommodate this?
What have you guys experienced?

As always, Thanks for your replies,
Ridge

 

[SW]

The pressure increases significantly. The efficiency is less also. Slower powders usually are needed . Slower powders are needed even with lighter bullets - ex: 44-45gs VV-110/250SST in 50 cal, vs 58g H-4198/200SST in 45 cal. If the same powders are used in 45 with same bullet wt as used in 50(by the way - what bullets would this be considering -?), powder wt needs to be dropped considerably.

 

[Ridgeviewer]

Thanks for the good information Steve. I didn't have specific bullet in mind. Basically, I was trying to gain a better understanding of proper adjustment between .50 & .45 caliber loads. Your help here, and DW's help at Dougs, have cleared things up tremendously.

I'm working on a couple smokeless conversion barrels, (one .50 one .45) and wanted to start sorting out my starting loads. Originally, I had planned on using H4198 but had been given some advice that IMR 4759 and AA 5744 were better choices in that they ignite easier. However, in reading RB's pressure trace info, I'm right back to H4198. I like the fact that the 4198 burns with slightly less pressure, and with the effective pressure lasting a bit longer in barrel, it just "might" be the ticket in my 28" .45 barrel.

 

[SW]

I like the fact that the 4198 burns with slightly less pressure, and with the effective pressure lasting a bit longer in barrel, it just "might" be the ticket in my 28" .45 barrel.

28" barrel. THAT really changes things. You will need to go slower yet. The extra 4" really is a major player. Consider H-322 and 2015. Start low and work up. I assume you are likely going to use 200SST,175 and 195 Barnes - I'd start 50gs max and work up to at least 2500-2600'/sec. If you don't have a chronograph, get one before this venture. If you try H-4198, which is ok to do, start low - no more than 48-50gs to start with.

 

[Ridgeviewer]

Steve,
Your assumption is absolutely correct. I'm hoping to push a 195 barnes in the neighborhood of 2600 fps from the 28" barrel. I know SB uses 2015 in his .45 28" #1 . That's a bit faster than i really need. Do you see any reason the 4198 would take a back seat to the H-322 or 2015?
How would the ignition of the h322 and 2015 compare to the 4198?

 

[SW]

H-4198 is a little fast. It would generate higher pressure at a lower loading. It would be fine to use if the fastest speed practical isn't desired. If say, you only wanted 2500-2600 just keep working up until you get that and stop there. If max velocity is desired, which the 28 will give more than a shorter barrel, then go with the slower powders that the 28 will allow and get up there without excessive pressure. 2800'/sec with 2015 will likely be even less pressure than 2600 with 4198 or 24oo with VV-110. The longer barel allows the effective usage of the slower powders with resultant higher velocities w/o higher pressures. The penality is a very heavy barrel. The longer barrel doesn't require that you shoot fast if you don't want to though.

 

[Ridgeviewer]

OK Steve...
Now you really have me looking forward to load testing!
More velocity, with less pressure . I really like the idea of that!
I can hardly wait to see what results I can get with the barnes 195. I picked the barnes 195 for a flat trajectory W/ low recoil, but I'm also thinking the bullet may hold together if a big corn fed deer shows up close. Time and some wet phone books will tell I guess.

I PM'ed you my thoughts on the long, heavy, 28" barrel... :wink:

Thanks again, for your help!
Ridge