Bullet size question for fire lapping

[Mitch]

This is my first post here.I have been reading for a few weeks.I have found alot of great in fo here.

Just alittle about me.I am a Tool and Die Maker by trade for 30 + years.I am not new to loading just to casting and shooting cast boolits.I just got a new Lee pot Pro 20 and 2 new Lee molds 148 grn WC and 158GRN SWC.I have been trying my hand at sating some boolits mostly from the 148grn WC.So far i have remelted alot more than i have kept but getting betterLOL.likely more question to come about the casting.

Ok one point i am still a bit confused about is bullet size for fire lapping.I have the LBT kit and have read it.one place it reads "for most barrels bullets should be unsized".then a few lines later it reads."if a throat is already large and smooth with only the bore needing smoothing. For such special occasions,size .0015 to .002 inch smaller than desired final diameter,as application of the lap compound will increase diameter approximately .002 inch".

I have 2 357 mag S&W a 686 and 586 I want use cast boolits in.

I am Going to start with the 686. I believe it has more problems.

I have done some measuring and checking.
Muzzel slug checks .3565 to .357
I dropped a .346 gage pin in and it stops at the stamp on the barrel a .345 slides thru a .347 will not start in the muzzel
sluging the throats they are .358 to .3582
as far as cyinder alinement i have only shined a lite and looked dont see anything bad here but my eyesite it not what it use to be.i didnt think of checking with the gage pin befor. will have to bring the gage pin home from works again that check farther.

Now my new molds both make booltits at .360 to .361.I do not want to enlarge the throats just get rid of the constriction in the barrel.Here is my confusion with out ever fire lapping or even checking a gun this closely.It would seem to me my unsized boolit would have 2 things happening.1 it might make my throast larger.2 it seems with a smaller throat than boolit size it would rub off and break down the lap coumpound.

I have a used Lyman sizer I havent played with this yet.that is the plan for today.But from theboolits that came in the deal it has a.358 bushing in it.

So i am thinking that sizing to the .358 dia would be the thing to do for lapping my gun.Also should I lube the boolts with the sizer or try and run them thru the sizer with a bit of spray lube.I am thinking of useing the 148grn WC being it has more bearing area. Am i on the right track here?

Thank Bob

[truckboss]

Merry Christmas and welcome aboard.Have you fired you guns yet to see if you get leading,poor accuracy or what not?Maybe you don't need to fix anything.I had a model 629 that right out of the box shot lead great.Don't get caught up in the dimension thing,not saying ignore them.

[dragonrider]

Welcome to the forum, make a handlapping tool, nothing more than a rod smaller than bore diameter,longer than the barrel, drill a cross hole for a pin to use as a handle at one end drill and tap other end with a appropriate size, drill a thru hole in a boolit attach it to the rod with a screw, screw head needs to be smaller than bore diemeter, lapping compound on the boolit, stuff it into the bore and push and pull repeatedly.

[Az Rick]

Mich, I agree with truckboss. Make some bullets and shoot them in both guns. Lead isn't hard to get out of the barrel, if it leads them some.

A few strands of a Chore Boy PURE Copper scrubbing pad wrapped around your cleaning brush will take it out. Make sure and get all copper ones. They won't harm the barrel. It's difficult to get different guns to like the same bullets but you can get close.

Best,

[Mitch]

i guess i didnt give the reasons for wanting to lap my gun.
the 686 is 6 inch and the 586 is 8 3/8 inch

The 686 leads much more than the 586.with the leading condition of the 686 is didnt group well at all more like a pattern.Like allover a paper plate at 10 to 15 yards.

The 586 did much better with groups of 3 to 4 inches with the group growing as the leading got worse.

I am not all the great of shooter but no matter what i allways got better accurace with the 586 whit cast or Jwords.

I do beleve that maybe with the info i have read here on this site i have some problems with the 686 than need fixing.

And that with better lube and Boolits the 586 may shoot great.

I am still working on the casting to get it right.I need to get all my ducks in a row and the gun set up seem to be the place to start.

[truckboss]

Ok then,Me,I would use acww air cooled wheel weights,fire 30 shots unsized .360 if they will chamber.That would be 30 thru the barrel and 5 thru each throat.This will clean up the throats and maybe get rid of your constriction in the barrel.Clean after 6 rounds and check with your pin gauge.You will probably get quite a few different opinions here but this is how i would do it.Remember you can't ad the metal back.

[Piedmont]

Mitch, I have fire lapped a bunch of revolvers. If you can't feel a restriction at the barrel threads with a jag and enough paper towel folded over it to make a tight fit then I wouldn't even lap it unless you see lots of barrel roughness or it just won't shoot.

The thing is you talk of leading but are just now starting to cast. Your own cast loads if done right probably won't lead and will be sized and lubed properly so may well do better than the cast and jacketed loads you have already shot. You have not yet determined you have a gun that needs work so the old axiom 'if it ain't broke don't fix it' applies.

In specific answer to your question I would size the unlubed bullets .358" in my sizer and then get a light coat of the bore lap rubbed on. Any more and they probably won't chamber. In fact you could size them .357" and then lap. The .357 Magnum and .38 special revolvers I have messed with don't have loose chambers so being able to get your lapping loads in the gun is a factor. Don't run bullets that already have abrasive applied back through your sizer die. They will lap out your sizer, in fact that is how I personally open sizer dies when I want them larger.

[Mitch]

Ok getting cases ready now
may take a while to get things around like i said just getting casting to work out.also all i have for lube right now is a beeswax vasoline mix.I think i need better lube i am going to get something different maybe something from White Lable. I have win 231.bullseye and uneque for powders. still neew to work on getting good rounds from my 158 grn SWC mold.

thanks for the sugestions so far will post results when i get everything ready to go.i guees im just excited to get back to shooting and roll my own.again thanks for the reality check ill slow down a bit and get it done right.

[2 dogs]

Let me answer your original question and then make a couple of comments.

I wouldnt worry about enlarging my throats, I have not been able to measure any difference in mine and I have firelapped some revolvers quite a bit.

I would load a few firelap loads and see if your bullets will still go in the throats. If they are too big, and I have run into that as well, THEN you need to size them down. Otherwise you can just shoot them.

Rereading the dimensions you state, that revolver should shoot cast as it is. You dont have any restriction at the throat, which is where most problems are. If I decided to lap that one, I would proceed very slowly and carefully.

You dont say where in the barrel you are getting leading, but if it is all the way down it, perhaps your melt needs to be changed. You may have too much antimony in your lot of wheel weights.

You also do not mention if you have lube star on the muzzle of your sixgun. That lets you know your lube is making it all the way down the barrel and onto the muzzle. Get yourself some proper lube.

[tomme boy]

Every time I shot factory loaded lead, it leaded the barrels. CCI 38 special is really bad in my 38