They look like the cylinders for the RCBS measure.
NRA Benefactor Member NRA Golden Eagle
Thank you. I just found they are Uniflow parts.
They are, as you have discovered, for an RCBS Uniflow Powder Measure; the "Measuring Cylinder" Part #09004 (S) or #09005 (L) and "Crowned Measuring Screw" Part #09009. Could be (should be but might not be) an "S" for Small or "L" for Large stamped on one of the flat sides.
Rifle cartridges are routinely charged with the "L" cylinder and handgun cartridges with the "S", the depth of the measuring cylinder being the difference. An "L" cylinder will throw small charges. An "S" cylinder is more consistent for small charges but will not throw large charges.
If it was easy, anybody could do it.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |