RCBS 50-350CM OAL info

[barkerwc4362]

Since I haven't seen a lot of information on the use of the RCBS 50-350CM bullet being used by members I though I would pass this info on.  I am using it since I originally purchased the mold for possible use as a projectile for use in a 12 gauge sabot loading experiment. The bullet weighs just above 350 grains cast out of my pistol alloy.  It has a crimp groove and a fairly substantial  lube groove.  It also has a very nice wide meplat, so no danger of primer activation.  I initially was crimping the bullet in it's crimping groove and that was giving me an OAL of about 1.545.  While it would feed sometimes it was not consistent.  Some times the first and/or the last rounds would jam trying to load from the magazine.  Moving the OAL out to about 1.575 helped but still an occasional cartridge would hang.  Moving the OAL out to 1.585 - 1.590 seems to allow all 7 cartridges to feed from the magazine.  I need to fire more rounds to make sure this length is the exact length.  Loading longer seems to cause a cartridge to fail to feed.  I have included a picture with the 1.585" OAL on the left, the bullet as cast in the center, and a cartridge with the case crimped in the crimp groove on the right.
Bill

[kendudley]

same problem and a great solution. I was loading at 1.61 and feeding the last round was iffy.   I'll put them through at 1.590 and try some.  thanks..Ken

[El Supremo]

Hello, and thanks:

Without a tight bullet fit in the case, OAL can shorten during cycling. 
Bullets should not be twistable in the case.
If so, check for a sized bullet OD that is not the same as case mouth's wall ID.
Often case mouths are expanded too much, and too deeply.  Then even with a slight amount of crimp, the bullet still spins and sets rearward during cycling.  Measuring a previously cycled, loose bullet, uncrimped round often presents a shortened OAL. Softer alloy bullets distort easily, and are more likely to be loose.

If the sized bullet OD is more than .001" larger than the case mouth ID, seating the over size bullet in the tight case mouth often "resizes" the sized OD below optimum.

Years ago, seasoned Spencer skirmishers said a SLIGHT amount of crimp helps feeding, but too much crimp can raise a doughnut that reduces bullet grip.  Tremendous trifles.

Smiles,
El Supremo/Kevin Tinny