Component Changes - Cast vs Swaged

[Hi-Speed]

Using Handloader Oct ‘16 edition as a basis, I developed a 38 Spl +P using a cast Lyman 358377 bullet.

Firearm: Ruger 4 5/8 NM Blackhawk
Load: 5.5 grs Longshot (RCBS Little Dandy #7)
Bullet: 155 gr SWC 358477 (crimped in groove using 3/4 turn Lee seat/crimp die)
Primer: CCI500
10 shot string:
Hi 974 fps
Lo 962 fps
Avg 968 fps
ES 12
SD 4

Amazing consistency and accurate.

However, I noticed a marked decrease using same charge, primer, cases, OAL (1.460”) but with swaged 158 gr bullets (only 3 grs heavier) from my usually “faster” 5 inch S&W Heavy Duty:

Bullet: Hornady 158 gr LSWC
Hi 898 fps
Lo 861 fps
Avg 880 fps
ES 37
SD 13

Nearly 90 fps slower compared with cast…there’s a reason reloading books state that when you change components start low and work up again. I have also seen this phenomenon using cast vs swaged with other powders in the same gun…I’m fortunate to have and use a chronograph!

I know that I’m not imparting much knowledge to other experienced handloaders on this wonderful site, but hopefully I can at least get through some regarding the importance of following your reloading manuals and obtaining a chronograph if you can…

Again, this data are provided for informational purposes only, and for use in my guns only. Always use a current reloading manual with its instructions before reloading any cartridge.

Best to everyone

[stubshaft]

You would normally see a difference in velocity and/or accuracy if you changed something as minor as the lube you use.

[rancher1913]

are the boolits sized to the same dimensions

[Hi-Speed]

Yes, both .358

[reddog81]

Different gun, different bullet, different crimp, probably a different OAL. Different velocities isn’t too surprising.

The amount of bullet inside the case can vary quite a bit depending on the length of the front driving band and size of bullet nose. This will cause pressure to vary.