Mold sizes

Struggling to understand this concept, can someone please clarify?

If I want a .615 mold and run a 0.015 patch it's telling me I need a 0.600 mold which would not provide a great seal to my mind for a rifled bore.
Then taking into account shrinkage it just seems like I would get a tight fit.
(.615 x 1.007) - 0.015 = 0.604 mold

What am I missing?

For me if iI am using a .600 ball plus a .015 patch I get a total dameter of .630 into the barrel. Objective I believe is to place some patch material into the rifling. For me I call it compression as cotton will compress to a smaller diameter than at rest. So measuring your barrel diameter then you back into ball size. Others better schooled than me will chime in shortly.

Myself, I don't overthink it too much....

For a patched ball, I like my mold or ball diameter as close as possible to .020 shy of my measured bore size. With .020 under, I can use a .020 patch without the use of a short starter, without coning, and with no accuracy lost. I do use a felt OP wad for an added gas check/bore scrub.

Round ball molds are made to be used with pure lead, and are cut accordingly. Any other metals present in the lead will cause the ball to be larger.

Use the thinnest patch you need to.

There is no formula or computer program that is going to give you the perfect load that only happens from working with different loads actually shooting.

Where are you getting that screen-shot page you shared?
I'm wondering who and why they are posting that "calculation" information,(?)

For the most part, it's the fabric/thickness of patch size that is the variable for the individual user.
I've never seen recommendation of a stasis patch thickness being used to determine ball size, it's always the other way around.

Acquire "X" size mold, then experiment with the patch thickness/lube variable to find the accurate load for the individual rifle and user.

It's from Tamner Molds in the UK.

I've never seen anything like this either. A .61 or .615 mold is impossible to find here so I contacted him. He wants the calca done to determine what I actually need.

For my .54 I just bought a .535 mold and used pillow ticking, no great arithmetic required. Unsure why this is necessary if I just want a .615 mold to use with a .015 patch in a .62 mold.

@Bushfire

This guy also makes molds if you can't find what you need.


https://www.martysarms.com/products/round-ball-molds-inch-sizes

Dusty_Traveler said:

Myself, I don't overthink it too much....

Click to expand...

Yes, and a big "Amen, Bro". The size you need is the one that works best for you. The downside is that, for those of us who have been at this game a while, we usually have a substantial library of moulds we never use because of attempts to find that one that works best for us.

Rifleman1776 said:

The downside is that, for those of us who have been at this game a while, we usually have a substantial library of moulds…

Click to expand...

My library is growing lol. Today, two books were delivered from Tanners.

Dusty_Traveler said:

Myself, I don't overthink it too much....

For a patched ball, I like my mold or ball diameter as close as possible to .020 shy of my measured bore size. With .020 under, I can use a .020 patch without the use of a short starter, without coning, and with no accuracy lost. I do use a felt OP wad for an added gas check/bore scrub.

Click to expand...

You misunderstand me, I'm not trying to overcomplicate anything. I said I wanted a mold of X size and was asked to do these calcs before placing an order to determine what I actually need because if I want a .615 ball for e.g. I shouldn't necessarily be ordering a .615 mold. To me this doesn't make sense.

Could it possibly be because Tanner moulds are made of brass , not steel or aluminum?

I used a Tanner mould too pour several.642 roundballs.
They’re good moulds.

Ouch @smo , that makes sense, but makes my head hurt,,

Bushfire said:

It's from Tamner Molds in the UK.

Click to expand...

After reading all that, I feel your pain.
Maybe try asking/explaining to Tanner, that you just want a mold that will cast .615 as finished?
But there might be a reason why Lyman and Lee only offer the .600 (or the Lyman in .610)

It's easier to get a thicker patch, then it is to get a smaller cast ball,,

you have to account for shrinkage. if you want a pure lead ball of .615 from the mold you need it to be size .621

Remember that if you are using a 15 thou's thick patch, the patch will smash down slightly with the ball pressing on all sides against the lands. A 15 thou's patch and a tight ball your patch thickness might then end up at 13 or 14 thou's thick.
Ohio Rusty ><>

X 2 the patch is on both sides of the ball.

The OP and Tanner seem to be confusing ‘mould’, ‘ball’ and ‘bore’.
There’s really nothing complicated here.

Spillikins said:

The OP and Tanner seem to be confusing ‘mould’, ‘ball’ and ‘bore’.
There’s really nothing complicated here.

Click to expand...

This is what I was thinking too...
Thanks for stating it so succinctly.

In my 40 i use a .390 ball, my 45, i use a .440 ball, my 50 uses a .490, my 54 a .530, my 58 a .565.
I hope this helps.

Not sure this helps, but wouldn’t it be best to simply let the mold maker know what size ball you want to cast and the alloy you will be casting with? Mold maker then sizes the mold to make diameter ball with alloy you are using.

Patch thickness and bore size doesn’t matter to the mold maker, and you don’t care about the mold size as long as it produces the size ball you want with your chosen alloy, correct?

I have more molds than I can count, and honestly can’t tell you what the actual mold dimensions are. But I can tell you what size ball/bullet they will produce with pure lead, and with some, what sizes they will produce with different alloys.