Neck clearance for body die

[Fast14riot]

I've got an extra FL die I'm going to open up to make a body die, how much clearance beyond fired neck diameter should I shoot for? Is +.004-.005 total too much? Would +.002-.003 be better? I know it's very easy to go too big and possibly create a strange donut formation at the neck/shoulder junction, but how far?

 

[Shynloco]

Personally. I've always noted (and liked) that Body Dies are "tighter" than other dies. So I'd opt for the lesser of the numbers you provided. Remember, you can always take more off, but once it 's off, you can't put it back. I wouldn't waste a die guessing on the the amount to shave.

Alex

 

[Brians356]

The only true body die I own is a Redding 223 Rem. The die's neck opening is .256", the fired neck ODs are .250" from a stock Rem 700 VS.

My other effectively body dies are Redding Type S bushing dies, I can measure some of those as well if you like.
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[Fast14riot]

My fired cases are measuring .340-.3405, so I'm thinking I'll shoot for .344"

The die I am modifying is a standard FL die, no bushing, and I don't care if it gets ruined, but that's unlikely.

 

[Brians356]

My fired cases are measuring .340-.3405, so I'm thinking I'll shoot for .344"

The die I am modifying is a standard FL die, no bushing, and I don't care if it gets ruined, but that's unlikely.

Your choice of diameter seems reasonable. How do you intend to enlarge the neck portion? Lapping? It'd be the devil to drill or bore out satisfactorily, being quite hardened.
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[Fast14riot]

It's a Lee die, so it isn't terribly hard to begin with, will probably try lapping with 220grit compound to start, may try it in the lathe as well. If it doesn't work out, I'll just go with a type-s and no bushing.

 

[Brians356]

Even a Lee will be awfully hard, it has to be. There's an article here or on one of the other shooting sites on lapping FL dies, but it's for reducing neck sizing a few thousandth, not removing as much as you contemplate.
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[Fast14riot]

I've lapped dies before, cutting the die will take a little longer, but isn't impossible. I'm well aware of possible issues.

 

[Brians356]

I've lapped dies before, cutting the die will take a little longer, but isn't impossible. I'm well aware of possible issues.

Then it'll turn out perfect!
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[Fast14riot]

Lol, hopefully so!

 

[Brians356]

PS

My Redding 270 Win Type S has a neck opening .318", and my fired cases measure .309" OD.

You want the die to clear the slight radius at the neck / shoulder transition. If you are not going to radius the die there after lapping / boring (leaving a sharp edge) it would be even more important not to leave it too tight.
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[Fast14riot]

Just an update to this, I got bored this evening and decided to modify that 30-06 die. I grabbed a good sharp 11/32 (.34375) and after indexing on the die I just ran up around 600rpm, gave a good squirt of cutting fluid and it ran through that die like butter. Assuming a couple thousandth run out on the drill press I opted for the 11/32 as opposed to 23/64. I measures 20 fired cases and referenced the reamer print, base of neck per print is .3425 and mouth is .3404, cases averaged .341". After confirming the die was not deforming the necks I polished it and softened the newly sharp transition to the neck.

New routine is to body size and shoulder bump, neck size with Lee collet neck die, seat with Wilson mic top chamber die. Fits my chamber like it should! Turned out exactly how I wanted and can't wait to get this new barrel dialed in.

 

[Erik Cortina]

I would make it about .001" smaller than brass neck diameter to provide neck support and minimize runout.

 

[Fast14riot]

I would make it about .001" smaller than brass neck diameter to provide neck support and minimize runout.

I had thought about this, but I did this on a drill press and didn't have the accuracy of using a lathe and boring bar, or mill. It fits with nearly zero play between die and brass at the neck now. I may just polish it up a tiny bit more to soften the shoulder to neck a little, but for first of all, a proof of concept and second a first attempt I'm quite pleased.