LYMAN CAST BULLET HANDBOOK 3rd edition vs. 4th -- 38-40 loads

[downwind]

Can anyone tell me why there is such a big difference in the load data for Unique with the lyman 401043 bullet between the 3rd edition @ 7-10.5 grains and the 4th edition @ 6.2-7 grains.

I'm loading for a Winchester 1892 made in 1902.

I've shot 401043 with black powder = decent group @ 25yds for first 5 then opened right up. I have to attribute this to the pitting in the barrel.

Then shot both the Lyman 401043 and the RCBS 40-180cm on top of 6.5gr unique and got great groups (1 was 3/4"-5 shot group/ open iron sights)

Going to do some more loads and different distances but not sure how high to go.

THANKS
DOWNWIND

[TXGunNut]

Oops, neglected to write my loads down but the Unique load of 8grs came from MV's Shooting Lever Guns of the Old West.

[northmn]

Differences in loads may have a few sources.
1. Older data used to use the old CUP standards and have changed with the new piezo-electric measurements. CUP measurements were not consistant in PSI standards
2. Some say Winchester quit loading some of their hotter 92 loads for rifle like yours because some would use them in pistols and the older 73's. I have noticed my newer manuals do not list the hot 45 Colt loads for rifles or Ruger revolvers or at least some that are quite backed off. Again there are a few older Colt Peacemakers out there that may not be able to take these bombs.
Pitted barrels usually work well after fouling with black powder. Groups opening up are generally attributable to lube/powder brand combinations. One individual on another site used BP in his 44-40 and tried to match the claims that the 44-40 could go 30 shots without fouling out. He did so using Swiss powder and a lube I do not remember. It takes a bit of experimentation with BP to get there. When I shot BP competition some days the fouling was very hard and dry and others so wet I ahd to wipe moisture out of the pan on the flintlock.
Those things mentioned are why most like to use smokless for most shooting. I have learned to use the more moderate loads for my 32-20 as that is kind of what the rifle/cartridge is designed for. The old Winchester "92" loads were prety hot but whether you want to stress an older 1902 rifle is up to you.

DP

[Doc Highwall]

The powder manufactures have a +/- 10% on burning rate for their powders. The first loading data could have been a slower lot of powder with cases that weighed less giving a greater powder capacity also lowering pressures. The second set of loading data could have powder that is on the faster side with cases that weighed more giving less case capacity which will raise pressures.

This is why all the reloading books say to reduce starting loads then work up. Different components and different firearms do different things,...........start low and work your way up. This is one reason I like to buy powder and primers in larger lots to control this.