Real world success lapping moulds?

[Canuck Bob]

What has been the real world success for green horns lapping moulds for larger bullets. I'm planning a LEE 429-200 RF mould for plinking with my micro groove 444. It seems universal that the rifle will require at least .432 after sizing. If I get a smaller mould can I expect decent results from lapping as a first timer? I am mechanically inclined and once was a lathe operator in a Timken Bearing factory tool room so this is not foreign ground at least.

For experienced casters would you lap or beagle for 2 or 3 thou.?

Sizing will be with a RCBS LAM.

[Kraschenbirn]

I've done both with Lee moulds and my usual procedure is to beagle first and, if that doesn't obtain the desired result, then I resort to lapping. My first project was to open up a Lee 312-185-2R to drop .316+ for my Longbranch Mk4#1. Using the lapping compounds from a Wheeler firelapping kit, I had to lap the cavities twice with coarse lapping compound and once with #600 polishing compound but mould now drops .3165 from my "rifle alloy" (4 parts Lyman #2 to 1 part straight lino).

"Slow and easy" seem to be the key ingredients. Make up your laps, do a finite number of turns in each cavity, clean the mould, and cast a few samples to measure. Don't try to hog it all out at once. Since doing that first Lee 185 grainer, I've also opened up a Lee .458 to drop .460 for my 45-70s, and a old Ohaus (iron?) from .378 to .381 for my .38-55.

Bill

[462]

My take is: If beagling gets the size you need, why lap?

[RobS]

My take is: If beagling gets the size you need, why lap?

If done correctly, then a boolit that has more potential of being rounder.

[stubshaft]

Unless there is someting drastically wrong with the mold a lapped mold WILL be rounder than a beagled one.

[GP100man]

Well , just to shine 1 up & clean burrs ya can use powdered comet cleaner & a soft boolit , but to actually lap it larger ya need a hard boolit & more agressive compounds .

Can`t remember exactly where but someone here used powdered diamonds "rolled into the driving bands to open a mold , patience is a must !!!

Beagling is a good way to see if a bigger boolit will help without permanetly altering a mold .
I Beagled a truely vintage Lachmiller mold to help with venting , as it has`nt any.

Personally I size everything so if Beagling makes em a little OOR the sizer takes care of it !

[btroj]

I will always beagle it first. I can quickly add 1 or 2 thousandths and KNOW I won't ruin a mould.
Lapping MAY give you a rounder projectile, it may also give you an egg shaped one. It may also round off bands and grooves. It is also very permanent.
Beagling moulds has been done around here long enough that the out of round argument has been shown to be a non issue. The sizer will round out the bullet, it will shoot fine.

My take- Beagle away and forget about it.

Brad

[462]

"Beagling moulds has been done around here long enough that the out of round argument has been shown to be a non issue. The sizer will round out the bullet, it will shoot fine."

Thank you, sir. I should have added the qualifier.

If beagled boolits are pan or tumble lubed, throats and forcing cones will see to it that they are made round.

[truckmsl]

Beagling has worked well for me, but does create flash at the tips of pointy boolits, which needs to be trimmed off.

[pdawg_shooter]

If done correctly, then a boolit that has more potential of being rounder.

I fail to see how a out of round bullet can be forced down a round bore with thousands of pounds of pressure behind it and have it exit any way BUT round.

[RobS]

I fail to see how a out of round bullet can be forced down a round bore with thousands of pounds of pressure behind it and have it exit any way BUT round.

That is true with the drive bands however the nose of the boolit that doesn't touch the bore will still be out of round; think of the longer nosed Keith's or similar boolits that have a front drive band that protrudes from the ogive. Does this create a huge accuracy problem.........no probably not but the boolit will still not be round never the less where it doesn't touch the sizer die or the barrel.

[Canuck Bob]

I should add that my question was prompted by the issue of round bullets.

I have no doubt that beagling works and is effective due to the verified reports that abound on here. If the mould throws small I'll beagle just to learn the technique.

If I can lap a nice round bullet it would be my preference though.

[btroj]

You can lap a mould to enlarge it. Beagling has the advantage of being faster, easier, and is reversible.
I have a Lyman 429421 that casts at .429. I need then at .433. Lapping out that much would be very difficult to do without a chance of altering other dimensions or potentially getting into an egg shaped cavity situation. A few pieces of tape and I instantly get bullets the size I want. Where is the real comparison?

Lapping is a good way to smooth cavities or to remove small burrs. Removal of large amounts of metal thru lapping is an iffy proposition in my opinion.

Brad

[fecmech]

Just because the nose of a bullet is out of round does not mean it's out of balance. The "fat" parts are opposite each other.

[btroj]

Yep, balance and round are not the same.

[RobS]

Just because the nose of a bullet is out of round does not mean it's out of balance. The "fat" parts are opposite each other.


Yep, balance and round are not the same.

I'm not saying that the boolits that are un-round can't be shot with good accuracy, but I can tell you that a round bullet has a greater likelihood of being more precise and balanced in all regards. You guys can't tell me that a person who beagles a mold or even laps one un-round is purposely doing it just so to make the boolit "balanced" or equal on opposing sides of the boolit. I don’t think anyone is that good.

[btroj]

Yes, I want a round bullet is possible. The key is this- can you guarantee a round bullet when removing, say 3 thousandths, in an iron mould? I did one, it remained largely round. I also rounded some edges I would have preferred stay sharp.

Beagleing works way betteer than I ever though it could. I was skeptical. How can it make bullets that can be accurate? They will be oval! I have yet to find a gun that seems to care. It defies all reason and logic.

I was with you, until I tried it. Damn it all, this idea works! This guy is a genius!

Just try beagleing your mould. You may well be amazed at the results. They certainly opened my eyes, and mind.

Brad

[Canuck Bob]

No doubt my first attempts will involve beagling. No sense looking a gift horse in the mouth so to speak. It would be nice to cast and shoot some decent bullets quicker.

[btroj]

I will admit to not using the Al tape that most others use. I have done stained glass work in the past and used the copper foil from that.
I think you will be amazed at how well is works.

[blackthorn]

If you decide to lap your mould, do a search for postings by our own "Longbow" I recall seeing a very good description of his procedure for enlarging a mould successfully! Have a great day.

[Canuck Bob]

Thanks, I believe it was Longbow's thread that convinced me it was doable. He talked about a soupy paste for easy cleaning to retest and some great tips on making the laps if my memory still works a little.

I checked some Al tape left over from installing my garage heater. It is .0015 it seems. It is no longer my aluminum tape but a partial roll of CB Beagling Self Adhesive Shim Stock.

edit-I checked and do have Longbow's thread in favs. The other thread that I saved is also referenced above from onandago, thanks to both guys.