Don't try it at home.
Contact Erik.
You'll be glad that you did.
Ben
I will back
@Ben 's wisdom with some "well-deserved" experience.
Full-disclosure - I knew better, but wanted to try it anyway.
I bough two 2C LEE C309113 moulds, used from Michael Reamy for cheap.
Somewhere, on this forum, I posted about my solution to the weird screws LEE uses to hold the 2C cavities to the handles. THAT worked out just fine, but I needed to solve THAT problem so I could do some "shade-tree machining" on the blocks.
On one mould, I followed
@Ben 's lead and removed the GC shanks and came up with an absolutely wonderful light bullet for my 30/30.
On the second mould, I aimed to make one of the two cavities a HP. I didn't tell anyone I was going to do it, because I knew they'd all tell me not to. Didn't ask because I knew the answer. Now that I did it, I am happy to share the experience.
My idea was to find a bushing slightly larger on the outside than the cavity on the inside, and slightly smaller on the inside than the outside of the drill I intended to use. I turned the OD of the bushing (on a drill-press) to be a snug fit within the cavity and opened the ID with the drill I wanted to use, which also became the donor for my HP pin.
I got everything set up to drill the first hole, which took WAY longer than actually drilling the hole. It LOOKED good and I thought I'd be OK. I made the HP pin and put a handle on it, using the base of the handle as a depth-stop. Cast a fair handful of bullets and they came out nice,... except that the HP hole was off-center - just barely, but it was off enough that you could see it.
Not to be discouraged, I figured I'd try the second cavity and end up with a 1C HP mould. Messed that cavity up too.
I'm not saying it can't be done, and I've pulled off a few feats using pretty basic tools, but the time I put into the project netted me experience I probably didn't need, because everyone here would have been able to tell me the outcome. I don't bemoan the loss of the time or the mould though. I gave it a shot and knew that at best, I'd have a very useful HP mould. I also knew that at worst, I'd be able to share with someone else that it ain't worth it. Not a huge loss for me, at least in my mind, but maybe it will save someone else a bigger loss.
My vote would be to ship it Eric or just buy a HP mould, unless you can afford to lose the mould and the time and your pride isn't easily bruised.