Cast boolit size

[Gundogblue]

I had the thread up slugging a barrel, and you guys steered me in the right direction. But I have just one more question, since I didn’t know the real bore diameter of my Marlin but now I do, it’s 0.4305. I’ve been sizing my boolits to 0.434, is that too big? Would I be better off sizing the boolits to 0.433? I’m useing a Lyman #2 ally, and shooting very mild( under 1000 fps) loads.
Thanks
Paul

[Winger Ed.]

It probably wouldn't make a huge difference, but I'd try them as they are now.
I've found better results with the boolit being slightly over size compared to the bore dia. by a full .001".

If you want to save a buck or conserve your alloy ingredient 'goodies'- going that slow, a softer boolit might work well too.
For such slow speeds, I add just enough 'goodies' to pure Lead so that it casts well with good fill out.

I got that idea from looking at the more or less pure Lead handgun (factory) swaged Lead bullets Hornady & others make.
They're good up to around 1,000 fps or so with their published data.

[stubshaft]

I'd size to .432" and call it good.

[fredj338]

Never hurts to try. I heard all kinds of stuff about Glock 9s only being accurate with 0.358". I tried 0.356", 0357" & 0.358". All shot about the same but 0.358" cause chambering issues in mixed brass, so I settled on 0.357".

[Mk42gunner]

As long as it chambers freely, and has room for the brass to expand on firing, your 0.434" projectile should be fine. It wouldn't hurt to try the smaller size as long as you already have the sizing die.

Robert

[castmiester]

at that alloy yeah probably.. .002 to .003 is rule of thumb. If harder might spike pressures. I would gas check them though depending what bullet, and if they have a shoulder to put them, then use them. Typically at that velocity it's not critical, but you can load up without and see if your barrel leads up first with a few.

[243winxb]

Depends on type of rifling. Marlin has 2, i think? Micro or Ballard?

[Bazoo]

I’d try the same known “good” load with all sizes from .430 to .434. It’s worth testing before you go into full production.

[castmiester]

Depends on type of rifling. Marlin has 2, i think? Micro or Ballard?

be a bear to mic if it's micro

[Larry Gibson]

In rifles, I size the bullets to fit the throat in most cases.

[waksupi]

Slip a bullet into a fired case. There should be a bit of resistance. That most likely will fit the throat best.