Successful lapping

[JeffinNZ]

Team.

I decided to lap my 6.5mm Cruise Missile mould for two reasons.

1) The bullets needed a little persuasion to drop out of the cavities.
2) The front driving band cast at .2675 and all the others at .2705 in the alloy I am using. In my Carcano the throat is .269 so that's what I size to however the front band is unsupported so needed increased.

I made up a pair of laps per the instructions with the screw in the base and holding the mould in my hand and running my trusty old cordless drill in the other away I went. For those that have not done this the thought of such activity is a little nerve wrecking but rest assured the process is straight forward and lapping out even 1.5 thou takes longer than you might think.

I lapped out both cavities to throw the front band at a shade over .269 and gauged progress by cleaning the cavities then casting a sulphur/graphite impression from each. I kept lapping until the front band measurement was within 1 thou of the rear bands which gave me the correct girth for 'as cast'.269 band. Worked really well and nowhere near as tedious as cleaning and casting a lead bullet each time.

Now to see if the Carcano appreciates my efforts.

[303Guy]

Sounds great! I'm looking forward to your range results.

[swheeler]

Jeff; I'm guessing that little Italian is going to love you long time GI! har-har When you get to it post some results with pictures. I noticed another Lee 270 mold just sold on Ebay, 110 grainer this time, but I was too late. Scot

[lathesmith]

Jeff, glad to hear of your lapping success. Did the mold seem to release the slugs easier after you lapped it?

lathesmith

[JeffinNZ]

Jeff, glad to hear of your lapping success. Did the mold seem to release the slugs easier after you lapped it?

lathesmith

Yes, the rear cavity fulls freely without any assistance. The front cavity takes a tap but still heaps better. Good old "Lee-menting".

I gotta say; I take back all I said about Lee moulds. They are no CBE brass mould but still produce a dang good bullet. I would prefer a heavier sprue plate however.

[leftiye]

Yup, and that goofy shaped sprue plate on the 2 cavity molds purely sux.

[WHITETAIL]

Jeff, I think you have a winner there![smilie=w:

[lathesmith]

"Yes, the rear cavity fulls freely without any assistance. The front cavity takes a tap but still heaps better. Good old "Lee-menting."

Great! Yet another reason to give "Lee-menting" a go, especially with a mold that is reluctant to let go of its slugs. A sticky mold can be a frustrating tool; although you don't seem to remove much material when you do the lapping, it almost always seems to make the mold release better. Enjoy!

lathesmith

[JeffinNZ]

Just tested folks. 3 shots only at 50m/55y, round holes, 1800fps, spread of just over an inch.

I can feel the front driving band in the throat as I chamber the round now. Not much use for a speed match as the bolt takes a little effort to turn down but I have two Lee Enfields for that.

[6.5 mike]

Good thing you didn't get the one I have. Mine drops .268 on all the bands. It works just right for me, 2 swedes slug .266. I need to slug the other two now, & the 260, & the 6.5 jdj. Jeff, what does yours weight ? Mine is 175 gr with my mix.
Can you say damnifiknow ?

[JeffinNZ]

Good thing you didn't get the one I have. Mine drops .268 on all the bands. It works just right for me, 2 swedes slug .266. I need to slug the other two now, & the 260, & the 6.5 jdj. Jeff, what does yours weight ? Mine is 175 gr with my mix.
Can you say damnifiknow ?

175gr for mine also. Scrap, range alloy that is, air cooled, 14.5 BHN.

[6.5 mike]

My dad salmon fished off the coast in CA, they would use a #3 ball on a release. I had a bunch of these I've smelted down to ingots for boolits. I know some of it was ww's but don't have a clue what else he poured in them hence the damnifiknow. I haven't had a chance to shoot any yet, but have pp'ed a few. Should be fun.

[HORNET]

leftiye said
that goofy shaped sprue plate on the 2 cavity molds purely sux.
Um, you do realize that you can take that off, drill a small hole into the top of the mold, install a roll pin, and hacksaw/drill a new plate? I've done it on a couple of Lee's that had been damaged.

[montana_charlie]

I made up a pair of laps per the instructions
When you say "the instructions" are you referring to the sticky on Leementing, or some other set of instructions?

I want to open up an iron PP mould by two thousandths.
CM

[JeffinNZ]

When you say "the instructions" are you referring to the sticky on Leementing, or some other set of instructions?

I want to open up an iron PP mould by two thousandths.
CM

The Leementing 'sticky'.

[leftiye]

CM, - Straight sided design? Measure the cylindrical portion of the mold. Get a reamer two thou bigger than the measurement, and ream out the mold.

[montana_charlie]

Get a reamer two thou bigger than the measurement, and ream out the mold.
Are you talking about a 'chucking reamer'...with a cost of around forty bucks?
Does that require a lathe?
Are they produced in a size like .4558"?
CM

[longbow]

2 thou is easy to lap out. I have done two moulds recently, one 2 cavity and one 6 cavity opening both up by 0.003" to 0.004".

I did both by hand turning the laps as it is easy to get carried away using an electric drill. If you go slow and clean often you can avoid oval cavities.

The two cavity was a Lyman iron mould and the 6 cavity is aluminum. Both turned out well.

Longbow

[leftiye]

Long bow is correct, lapping would work and would be cheaper. And the results should be acceptable.

But there is no guarantee of a straight, uniform and concentric cavity in a hole as long as your paper patched mold probly has. Yes, a chucking reamer. As long as you are putting a chucking reamer into a hole smaller than its flute diameter, they center ( reads reamer flexes to cut hole concentric with old hole) quite well. It can and has been done with a vise in a drill press. Just align the reamer and mold as close as you can, run the rpms slowly, put a lot of oil on it and get 'er done. They can be had for less than 40 dollars. Believe it or not - try evil bay.

[lwknight]

I lapped out both cavities to throw the front band at a shade over .269 and gauged progress by cleaning the cavities then casting a sulphur/graphite impression from each
I would like to know more about the sulphur/graphite impression. How do you mix it and how do you use it?

[JeffinNZ]

Mix sulphur and graphite powder about 10-1 and carefully melt then pour into the cavity. Sets in about 30 seconds or less. Be aware that sulphur melts at a low temp so care should be taken not to over heat or it will ignition. Also, stay upwind as sulphur fumes are most unpleasant to breath.