Drop Free Lapping -- non-size changing
Drop Free Lapping -- non-size changing is done using comet powder. I still clean off the gas check shank on the lap bullet with a file (taking it way undersized) so it doesn't change anything in the mold around the gas check shank area.
http://photos.gunloads.com/images/Ol.../dscf0001x.jpg
Goal here is to get the bullets to drop free and to see if there are any restricted areas or if perhaps the cavities are different sizes. This form of lapping is very mild and will not change any sizes appreciably (not unless you do it like forever).
Being the world famed Wobbly Goblin Mold those two cavities are currently two different sizes -- I have PM'd Ric to ask him what size he wants both the cavities to be as our next step is doing the size change lapping.
Ack !! Thread hijacking in progress ....
Ack !! Thread hijacking in progress .... Hijacking a Sticky no less !!
Now I promised everyone I would post the statistical analysis of an entire LEE production run -- this one was the 7mm Soup Can run which was 50 molds long but I only got hands on to the first 25 molds for measurement purposes.
First, let me explain why a caliper was used instead of a micrometer -- the mike I had available had a clicker thimble on it and it would absolutely reliably crush all parting line irregularities flat as a pancake instead of measuring them and it put little bitty minute flat spots on thin ogive "max diameter" areas too (once you laboriously located them and tried to measure them). In other words the mike really wasn't working for me at all and the caliper did just dandy in both finding and measuring the "soft" parting line areas and them frail and downright tiny ogive maximum diameter points.
A caliper isn't an ideal statistical tool. First, it lacks fine division or discernation-- it will only discern to 5 tenth increments while a mike will discern to single tenths (and some good ones will do 50 millionths which is half again finer discernation). Second, a caliper can be "driven" by an operator to achieve a desired goal (conciously or unconciously) and a mike generally tends to be more impartial as well as being more accurate -- on solid steel parts anyway.
But, hey - when you are dealing with lead bullets the only reliable mike I have ever found that won't crush things is a Mitutoyo QuickMike with the "hands off" fast action low contact force slip-type thimble. But the silly things cost $450 and I don't own one personally. And my current company doesn't own one either.
So I used a Mitutoyo caliper for this study -- shame on me. At least I didn't "drive" it, I always recorded what I got and I took all measurements twice and I used two different bullets per mold to make sure I had some basis to call out an "off" number with some level of confidence.
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What can cause cast bullets to vary?
Many things, alloy - temperature - casting speed - head (pour distance) - open close variation on the alignment pins - closure force on the mold cavities - lordy, there are a lot of things. I tried to take some out just to keep things simple and keep things as neat as possible.
To attempt to be fair, all casting was done exactly as the molds were shipped using a Lee handle set to provide the clamping force and using a Lee 10 pound bottom pour pot allowing the nipple to rest in the sprue cone and using the nozzle as a forced pour arrangement. In short, I wanted as wrinkle free a first cast bullet as I could get and I wanted to reflect the size of the cut cavities in WW metal without any smoke or spray or other sorts of stuff that folks normally use on molds.
(smoke and spray all make mold cavities cast smaller, you know that, right?)
So, here is the raw data in picture format so you can see the organization of the rows and columns.
http://photos.gunloads.com/images/Ol...oppagedata.jpg
Once again, right click on the pics, hit copy then paste it into your favorite graphics program so you can expand it enough to acutally see the numbers.
http://photos.gunloads.com/images/Ol...ompagedata.jpg
Got to split this post in two -- list can't take the whole enchalada. This seems as good a spot as any ...