Now began one of the most frustrating, hair-pulling experiences I have ever had trying to handload for a rifle!
As I said, I had been looking for a 6mm Lee for quite awhile, so had accumulated quite a few 6mm moulds. I cast up samples from each, making up a batch of harder lino, & my usual softer scrap alloy. I decided upon an Ideal 245498. a 100gr g.c. with small flat point, and an Ideal 245497, a multigrooved roundnosed g.c. These were tumble moly-coated, & lubed with Lyman Super Moly.
Now you just can't stroll into your local gun shop & find 6mm Win.-Lee dies on the shelf, I had to special order thru Huntington for a 3 die RCBS set. Brass was ordered from Buffalo Arms Co. It is made from .25-06, and very high quality. I altered a Lyman "M" die expander for case-mouth expanding.
I found some loads in an early (1930) Ideal handbook for cast using IMR4227.
Once I had all the components ready...the fun began. No matter how tightly I sized the necks, the bullets were being pushed back..way back into case. I finally slugged throat and got a shock...The throat is VERY long..and tight! The smallest portion of throat is .0005"..(1/2 thou.) UNDER groove dia! Now with cast, I like to go .001" to .002" over groove dia. Not on this one! I ended up having to size bullet to groove dia., then, pushing bullet nose-first into .001" under groove dia. die, to size first band..this to allow chambering without bullet push-back. At least the gas-check spring-back was .001" over groove dia. I was hoping this would seal bore. I was still worried how a cast-bullet would take that fast 1 in 7 1/2" twist though.
Since the sights are an open "V" buckhorn rear with stepped elevator, and the front is a German silver blade, I did load development at only 50yds.
I started with low charges and gradually worked up. At 10.0gr. IMR4227, it was grouping in 3/4" to point of aim. Any heaver and groups opened up.
I wanted to try another powder..but what? Then I remembered a can of TrailBoss. I called Hodgdon & they gave me the start formula.. Interestingly, best accuracy with this powder was right at 10.0grs. also. Hitting to p.o.a. and 3/4" groups. I tried it off bench at 100yds. and managed a 1 1/4" group. The flat-nose proved better than the round-nose..just the opposite of what I had thought.
Now about the powder used...With every charge..even the heaver ones using IMR4227, the case necks were left blackened. With TrailBoss..even the start loads left them clean. Must be higher pressure...and yet..the muzzle blast & report seemed milder with the TB?
One thing about this little rifle..It is FUN! it is very light, yet recoil and report are about like a light sporter .222Rem. using 55gr. loads.
It took awhile to get the bugs worked out, and it nearly drove me crazy for awhile..but I learned alot. Oh about that fast twist? Even the heavest loads left no leading. I never did get around to using the hard cast..the softer worked so well.