Options to Make a Mold PB

[Uncle Grinch]

Theoretically, which is the "best" option to make a GC mold a plain base, assuming it's iron/steel.

1. Mill the top down to remove the gas check shank

2. Open up the gas check shank enough create a plain base


Since the idea is to shoot a boolit without a GC, you will need to limit velocity to a tolerable level, based on the alloy requirements. My thoughts are a heavier boolit, of a given cailber, is more efficient PB boolit than a lighter boolit, i.e, 250 gn PB vs. a 220 gn boolit of the same caliber.

That being the case, would not option #2 above be a better choice.

The other side is cost (since I will have to pay or trade out the expense). Which of the two are more economical to get done?

And then, which option is mechanically easier to do? First thought would be #1, but would this also not necessitate drilling the sprue plate screw hole deeper and then tapping it


There is probably another option and that is to buy another mold that is already plain base, assuming you can find one that matches your desired weight and configuration.

Is this like my mother used to say "too much sugar for a dime"?

[fcvan]

I have the Lee C501-440 mold that I will likely plain base. Although I don't own the gun, my neighbor wants to have boolits to run at 1000-1200 fps and gas checks should not be warranted. Even so, I would rather get a 50 PB gas check make from Pat than buy 1k gas checks for $50.

When I plain base the mold I will use a drill press and a proper sized bit and ensure the block is centered in the press. I can't help but think one could do the same with any other caliber using a bit of the correct dimension. Frank

[Buckshot]

...........I suppose it's a matter of 'Druthers'. If you wanted, or could live with a lighter boolit then milling the blocks to remove the GC chank would be the way to go. Especially if a lighter weight was wanted. If doing this, there are 2 things to consider. One is, will the resulting base band be wide enough and secondly via milling, ....................



...................ALL the cavities must be done.



Boring the GC shank out will give a slightly heavier slug, which may also be beneficial. But it's about the only option if only one cavity is to be done in multi cavity blocks.

...............Buckshot

[Shuz]

Another thing to consider is lube carrying capacity of the modified design. I have tinkered with moulds modified with both methods (that were modified by others) and have found some carry enuf lube and some don't. The Lee 310 comes to mind. The one I have with the shank milled out doesn't carry enuf lube for my guns. The Lee 310 that was scalped to a 270 works beautifully in my guns. The Lyman 429649 scalped to become a 300g works fine, as does the LBT WFN280 that had the gas check shanks milled out.

[Uncle Grinch]

If you have to pay a shop to open out a gas check, what is the typical charge?

[GLL]

Send it to Buckshot and have him open up the base ! He has done several for me and the workmanship is outstanding.

Jerry

[Ben]

Ditto ! !

You'll be well pleased with Buckshot's work !

Here is Rick's work done on an RCBS mold of mine :

http://castboolits.gunloads.com/showthread.php?t=56055

[BOOM BOOM]

HI,
LEFTEYE ALSO DOES REAL GOOD MOLD WORK, HE HAS BOTH MADE MOLDS & HOLLOW POINTED MOLDS FOR ME.

[EDK]

MILL, REAM OR BUY. I've done the first two with varying degrees of success, BUT I'd recommend buying another mould rather than either one. BESIDES, then you'd have TWO moulds!

Eric at hollowpoints will also re-do the base band. There ain't a shortage of well qualified guys to do the work, BUT there ain't no going back after you modify the mould. The price of the work...and I'm not complaining about paying for good work by a craftsman!...would cover a fair part of the second mould.

Put this in the same context as selling a gun. Can you say SELLER'S REMORSE.

[paul h]

As others have said, either mill the base for a lighter bullet, or ream/bore the gas check shank out to full dia.

As far as cost, it's pretty much a wash. The setup time for milling the mold is less as you just have to square the base to the table. But, more material is removed so there is more machining time. To bore the mold out you have to zero the cavity on either a lather or mill, then take a few light cuts working your way up to bullet dia. Very little metal is removed, but more time spent checking and re-checking to make sure the dia of the resulting cut.

I'd say of the two options milling the base requires a less experienced machinist and it's very simple operation. Boring out the gc has multiple chances of screwing up the mold, but it will result in a bullet of nearly the same weight as the gc version.

I used to charge $20 to remove the gc shanks on a 2 cavity mold, adding shipping both ways it was around a $30 job. Odds are you can sell the mold and buy a plainbase version for less money.

If you have a drill press and are carefull you order a chucking reamer from a machine shop supply house in increments of 0.001" so exactly the size you want for about $20 shipped. Zero the mold in a vice and take a careful cut. You might get some slight chatter marks, but they'll clean up when running the bullet through the lube sizer.

[Buckshot]

.............I charge $15/cavity + rtn shipping to bore a GC shank, and $20 + rtn shipping to flycut a mould, regardless the number of cavities.

.............Buckshot

[Uncle Grinch]

Buckshot,

I'm curious if when reaming the gas check, can you not completely ream it out, thereby leaving another groove for lube where the GC shank was?

To put it another way.... if the gas check shank is 0.148 inches, can you ream the mold only half way (0.074) which would leave a 0.074 lube groove?

Would there be any benefit in creating another lube groove this way?

[Buckshot]

Buckshot,

I'm curious if when reaming the gas check, can you not completely ream it out, thereby leaving another groove for lube where the GC shank was?

To put it another way.... if the gas check shank is 0.148 inches, can you ream the mold only half way (0.074) which would leave a 0.074 lube groove?

Would there be any benefit in creating another lube groove this way?

................I can only say that yes you could partially ream out the GC shank to leave another (shallower) lube groove. As to whether it would be a positive I have no idea. I guess you could say, "It depends". Speaking of the 38 Special shooting 148gr WC's, I have a couple articles dealing with it, as to boolit design and also lube. How many ways can you design a 148gr WC?

Using the generic 2.7grs of BE in several revolvers it seems as if all it required was ONE lube groove filled with lube to be competitive. A further study using the same revolvers showed that ultimate accuracy occured when the one lube groove filled was the bottom lube groove. I would have guessed it would be the top LG as it leads the slug on it's way down the barrel? Just shows how valid assumptions are.

.............Buckshot

[yondering]

BUT I'd recommend buying another mould rather than either one. BESIDES, then you'd have TWO moulds!

An exception here is when the mold is only available in a bevel base, like some of the Lee 6 cavity molds.

I ream out the bevel base on all my Lee 2 or 6 cavity molds. I use a reamer, (NOT a drill bit!) in my drill press, and just hold the mold flat on the drill press table using the mold handles. This allows the reamer to self-center on each cavity. In rifle calibers, this may not be accurate enough, or may require some extra care, but works great in pistol calibers. Some calibers, like 9mm, are hard to find a reamer the correct size, so I use a larger reamer with a tapered tip (I'm sure there's a name for these?) and trim the tip back so that it cuts the right diameter at the depth I want.