Does anybody have guidelines/useful tips/ or warnings on the use of Precision's Spherical Buffer (PSB) as a filler in cast bullet rifle loads?

Thinking of giving it a try.

DaMan, I can help you out as I've been using small amounts of PSB (.3cc to 1.0cc) with slow-burning milsurp powders, e.g., IMR 5010, and heavy CB's. You generally use PSB to improve the efficiency of slow powders (lower ES & SD + cleaner case necks and less unburned powder in the fired cases) because it increases pressure, though not dangerously if you stick to using 1cc or less of it. I've also found it made no difference when using it with WC 860 in both the .30-06 and 8mm Mau. However, it did improve efficiency quite noticeably in my 7.65 x 53mm with the same powder. In fact, I used a grain or two less WC 860 with PSB (and Ly. #314299).

Some rules of thumb: Don't even think about using 1/2 a case full of PSB (It's expensive!). Use it with slow milsurp powders, e.g., the very inexpensive, but very chunky IMR 5010 only. As noted above, it's not worth the extra reloading step with WC 860 except in the Arg. Mau. cartridge. Use only with a heavy bullet and enough slow powder to create a compressed load. Store your loads with the primer facing you since PSB may migrate if agitated. Since the addition of PSB raises pressure, drop the charge you normally use by 1 - 3gr. and chronograph your loads.

Loading data I: I use 47gr. IMR 5010 and CB's of 175gr. or more in the 7.5 Swiss, the .30-06 and 8mm Mau. The amount of PSB used with these loads is .7cc, 1.0cc and .3cc, respectively (Lee dippers).

Loading data II: I use 43gr. WC 860 + 1cc PSB in the Arg. Mau. with Lyman #314299 or a heavy CBE Loverin of the same weight.

Note: I don't generally use slow milsurp powders & CB's in cartridges smaller than the .270Win. because they're too erratic and there's a huge amount of unburned powder: It will dent your cartridges and necessitate frequent cleaning (every 5 shots or so).

Thanks, Paul! I can see how PSB would give more uniform combustion with those slower burning powders that don't have 100% loading density.

This article PSB filler suggested use of PSB with faster burning (IMR4198) powder.

I'm going to do some experimentation with PSB in .308 Win. with the IMR4198 with Bear Tooth 170gr. GC bullets sized .310".

Your opinion...... bad idea?!!

Thanks!

Don

A question.
How is this PSB different from the shotgun buffer Grex? Is it the same powdered poly as the Grex?
Jim

arkypete & DaMan, I've tried various versions of PSB and found they vary slightly in weight/density and color (some have a faint blue tint). If you can obtain a few different brands of PSB, just weigh say ten 1cc charges of each to see if they are all that different. In small doses, i.e. 1cc or less, I've not seen much difference in performance. As for H/IMR 4198 in the .308Win. or '06, 8mm Mau., etc. you don't need fillers at all as it burns quite efficiently by itself. Try 21-22gr. with the CB you mentioned, chronograph it and possibly increase the charge by 1gr. sans filler. Actually 4198 is one of my favorite CB powders, but AA XMP 5744 is even better (more consistent statistics in a number of different cartridges with CB's).

Slow Milsurp Powders: Although you didn't ask, I've used them primarily because of price. However, I think it's a false economy since you use a great deal more of them, e.g., 47-48gr. v. 22gr. 5744 or 24gr. 4198 in my '06 with >170gr. CB's. Moreover, there's a great deal of waste (unburned powder) as well as the added cost of using Mag. primers and inconvenience of using a filler. With AA 5744 or H/IMR 4198, you can avoid all of this and get excellent results to boot.