A question about turning necks & dimensions

[SBS]

I seldom turn necks, not my favorite pasttime, so looking for some guidance. If I were to start with 6 BR brass that had been necked down to .22 BR and then neck turned to .011, how thick would the necks be if I were to then neck it up to .30 cal. ?

 

[Mike TackleBerry]

They'd probably tear, you're necking them up .083, I'd say they'd probably be around .006-.007 thick when done. I would neck them up in steps and anneal them each step.

 

[Killick]

.015"...because you bought new bass.

 

[Straightshooter1]

I seldom turn necks, not my favorite pasttime, so looking for some guidance. If I were to start with 6 BR brass that had been necked down to .22 BR and then neck turned to .011, how thick would the necks be if I were to then neck it up to .30 cal. ?

You'd definitely want to give the necks more annealing than usual and stepping up is a good idea as Mike suggests. The inside circumference of a .308 + .001 case neck is ~ .971" and for a .243 +.001 it's ~.766, which means there's a difference of .104" in circumference that it would expand. When I take a .277 case of mine +.001, the circumference is ~.874" and when I expand them to .308, I've moved the circumference .097". And when I did that I could not find much of any measurable difference in them that originally measured .0150 to .0159". To do what you suggest, you'll be moving the necks ~.007" more than I did with my .277 cases. I don't think you'll be thinning out the necks much more than I did with my .277 cases. . . certainly not near as much as Mike suggests to .006 - .007" of thickness, IMHO. I don't think you'd even lose a full .001 of thickness??? There's one good way to find out for sure; try one and see.

 

[SBS]

I understand about necking up (or down) in steps and annealing. I own a number of wildcats, and a lot of them involve changing neck size. I've made 30 BR from 6 BR before, but always turned the necks after expanding to .30 cal.. So I never thought to make notes on how much the neck dia. changed. Thought someone here may have done it and kept notes.

 

[SBS]

Well, Killick had the correct answer - except for the decimal point. Lost about .0015 at most by expanding to .30 cal. Sure surprised me, thought it would be more.

 

[BuffaloBill]

I went through the math. If I made no errors, the neck thickness would end up 8.09 thousandths.

Edit: I had made a math error.

Does this make sense? Please check my math.

Calculate the cross sectional area of existing neck dimensions:
ID 0.224
OD 0.224+0.011x2=0.246

Pi(0.246/2)^2 - Pi(0.224/2)^2 = A (the neck cross sectional area)
0.04752 - 0.39408 = 0.008112

This same area makes up the neck once expanded, so calculate the new OD for an ID of 0.308.

Pi(0.308/2)^2 + A = Pi( new OD/2)^2. Solve for the new OD, then wall thickness.

0.074506 + 0.008112 = 0.082618 = Pi( new OD/2)^2
(0.082618/Pi)^0.5 x 2 = 0.3243
(New OD - 0.308)/2 = new wall thickness
(0.3243 - 0.308)/2 = 0.00817

 

[ELR LVR]

.015"...because you bought new bass.

Heck, start over with forming them from .308 brass, that'll let him feel like neck turning aint no big deal

 

[Mike TackleBerry]

I don't think you'll be thinning out the necks much more than I did with my .277 cases. . . certainly not near as much as Mike suggests to .006 - .007" of thickness, IMHO. I don't think you'd even lose a full .001 of thickness??? There's one good way to find out for sure; try one and see.

That was just merely a guess on my part as i've never moved necks anywhere near as much as he's doing lol.