45ACP & mold question

[Jim Flinchbaugh]

I have this mold from LBT, I made a few dummy rounds to see if it would feed in my Sig P220. I had to seat the boolit very deep to get the radius back far enough to allow the case to headspace in the chamber. My question is, is this going to cause to high of a pressure -moving the slug back deep?
It does feed OK, at least manually cycling it.

propellant has been N340, shooting FMJ round nose,
Any ideas on starting point for this slug?

http://img.photobucket.com/albums/v313/James64/Web%20page/P1288773b.jpg

[NHlever]

You didn't say what the boolits weighed, but I'm guessing around 200 grains? I would look in the loading manuals, and see if I could find a similar shaped bullet / weight that is seated to an OAL that is as close to what you have to use as you can get it, or shorter, and start with their starting loads. Though I've been casting for 50 years, loading for semi auto pistols is a fairly new thing for me so I'm sure others with more experience than I will chime in.

[MtGun44]

Do some measuring of a standard .45 ACP boolit like .45 ACP, you should be able to see
where the base of the new boolit is relative to the base of the standard, well tested boolit.
If the combustion chamber is the same or larger, you are good to go. If the new boolit
intrudes farther, you should reduce your loads proportionally. Smaller combustion chamber
means higher pressure, so you may get the same velocity with a lower powder charge than
the book values. Use a chrono to set your load in these cases, or just stay low to stay safe.

Compare to similar or slightly heavier boolit loading data and try for the same or larger
combustion chamber volume. As, usual, start low and work up to avoid nasty surprises.
Make sure you TC the boolit in place, if it pushes into the case during feeding, the pressure
will skyrocket.

All said, I think that boolit is going to give you problems in feeding.

Bill

[fredj338]

Yes, that bullet seats deeper than most 200gr to achieve a proper OAL in most 45s. Seating deeper will raise pressures. Depending on your load, I would back the charge off 0.2gr for an equiv to say a 200grLSWC. Example: I run 5.6gr under a 200grLTC (Magma mold) @ 1.220"OAL for 825fps. With the Lee, they come in about 205gr & @ 1.175", they are rolling along at about 890fps in the same gun. SHorter OAL always produces higher pressures, how mcuh is powder & cartridge specific.