Lee Loader

I started working with my SMLE chambered in 303 British and noticed that as I started to chamber some test cartridges that I was getting some bullet slip as the bolt was rotated closed. With the short necked 303 British, the bullet was remaining stationary but the case was rotating and despite the positive crimp with the Factory Crimp Die the bullet would slide to the forward edge of the cannelure as the bolt was closed. Using cartridges dipped in mica, I was able to verify the movement.

I also thought that for this movement to be taking place within the confines of the chamber, the seated bullet might not be concentric with the longitudinal axis of the case thus making contact with chamber walls in the process of the bolt rotation. Pulling out the cartridge runout scale told the tale. The 303 British die set uses a .310" expander and the short neck of the cartridge was just not providing enough alignment and tension. Average runout is as indicated, .0027". Onc hit with the kinetic bullet puller would send the bullet sailing.



Lucky, I keep a stock of different expander diameters and the basic 30 caliber expander, a .307", provided great tension which eliminated the "slip" when chambering a cartridge and cut the average runout in half.



Will need to get a .002" undersized mandrell ordered for the collet die for use with jacketed bullets!

Very interesting. I've got that Sinclair concentricity gauge. I'll give the next batch a look see. Please keep us posted how the undersized mandrell works.

Glad to see you shooting mil surps. They are my joy and so dang fun to bring up to speed. I've got the lee mold and 2 others. I've only load cast bullets for my most of the mil surps collection, the exceptions are the M1 Carbines and the Garands.

I don't understand why you would dip them in mica?

62chevy wrote:I don't understand why you would dip them in mica?

The mica leaves a light delicate coating of powder on the cartridge and any contact with the chamber/throat will be noted. On the cartridges fed into the chamber from the magazine, I could see where the bullet ogive was making contact with one side of the chamber, the ogive would be rubbed clear at the contact and the mica left where at the point of contact. The contact isn't unusual especially with a staggered magazine. The maximum runout would be opposite the rubbed area on the on the .310" expanded cartridge. The contact was still being made with the .307" expanded cartridges but the runout didn't relate to the rubbed area. That runout was just the normal seen with any loaded cartridge. The above was all done slowly are carefully to see what was going on.

The slip on the cannelure could be identified by the mica on the cartridge case. There was a slight swirling pattern on the case.

RD so it's kinda like using bluing or a light smoking to find rub areas.

62chevy wrote:RD so it's kinda like using bluing or a light smoking to find rub areas.

Yeap!

Gonna have to do something similar on my .222 Rem project noted on RD's Rossi rifle site.

GasGuzzler wrote:Gonna have to do something similar on my .222 Rem project noted on RD's Rossi rifle site.

Haven't had time swing by it yet but I bet it is interesting.