Notes: Lee TL358-158-SWC Lapped for Testing, 700X & Variation / Issues, RCBS 38-150SWC Mention

A Lee TL358-158-SWC 6 cavity mould arrived the other day.  After buying & selling many moulds, I wanted to revisit this fine design, looking to refine the tumble lube process. Wow, this new mould dropped very small bullets. The .357 to .358 bullets are not what I expect.

Time to lap another mould.  To get each cavity to over .360 took a little longer.  Lapping it slowly and taking measurements often, now it's dropping these fully sized bullets.  Oh, this mould is casting great at 800-850 degrees.  I think the tumble lube grooves fill out easier then the grooves on a 358-429 mould.  The lack of deep squared off Keith grooves makes a difference:

 

They now weigh in at 163 grains when using 98% lead and 2% solder.  This newly-lapped mould has improved accuracy compared to the unlapped-one used originally.  When enough testing is complete the charts will get updated.

Early results using 5.3 grains of Unique look promising.  If it proves to be consistently accurate it will get added to the most accurate chart.

Now, info on 700X:  After loading many pounds of this powder, it finally has/had accuracy issues.  Just recently, 2 different canisters proved to vary quite a bit.  More than bumping the charge up or down 2-3 tenths of a grain.  Powders can vary 10% and still be in tolerance, but if you run into unexpected results, it could a bigger variation of the powder than usual.  There was no safety problem or concern, however groups opened up to the point of being horrible and at any charge - inaccurate.

I still have a 3 cannisters and will verify the third unopened cannister in the next few weeks.  In the mean time, further test will be with HP-38, H110 and Unique.  The first 2 are proven accuracy producers.  Unique is now at the top of the accurate powder poll.  In the past, it shot well, but wasn't one of the best.  I added it to the mix to revisit and see how it does.

As always, the results based on caliper-measured-groups will determine if it really does deserve to be on the Most Accurate Bullet Moulds and Loads Table.

In closing this update: Recently tests using the RCBS 38-150-SWC have shown it's a good shooter.  But so far not consistent enough to make the list.  It may work well in your revolver, but until it proves itself in my Taurus 66 it gets "try it if you'd like" mention, off-list.