6mm dasher .269 neck turn to what thickness?

[pressedRat]

currently i turn brass for 260 and 308 cases. I turn down to .014. my 260 and 308 both have saami chambers. the object of turning for these two rifles was simply to turn down to a consistent thickness that removed all variations in the case neck. in my new rifle, the issue is the same, but also making sure the result fits properly in the chamber of the new rifle. for these two rifles, i have neck dies for .001 and .002 reduction of neck prior to seating bullets.

example for .260.. .264 + .028 (which is 2x.014) = .292 so bought .291 and a .290 neck bushing.

i am in the process of buying dies for 6mm dasher. I plan to buy a redding bushing neck die and turn the necks. Issue is which bushings to order? and to do that i need some advice on the final thickness of the lappua necks on my new 6mm BR brass to determine which bushings to order.

i measured some of the brass it it varies, .012 to .013. i would like to turn the new brass down to x wall thickness use the bushings to then apply from .001 to .002 reduction.

example for .011 neck wall thickess.. .243 + .022 = .265 so i would purchase .264 and .263 bushings.

i use the titanium nitride bushes at around 25$ each so i dont want to purchase more than i will need.

the desired end result is a turned neck with .001 to .002 reduction via bushing that is the best fit in a .269 chamber.

thanks for any info

 

[Cigarcop]

If your desired bullet has a pressure ring you have to factor that into your measurement..... I guarantee its not going to be .243

 

[Link]

All that figuring makes me dizzy er. I have a 334 chamber so I buy a 328 bushing. I drop a bullet in the sized neck, take a measurement then return the neck until I have a measurement of 330 with the bullet seated. All measuring done with a micrometer. 004 neck clearance with .002 tension. Is this wrong?

thanks Link

 

[pressedRat]

All that figuring makes me dizzy er. I have a 334 chamber so I buy a 328 bushing. I drop a bullet in the sized neck, take a measurement then return the neck until I have a measurement of 330 with the bullet seated. All measuring done with a micrometer. 004 neck clearance with .002 tension. Is this wrong?

thanks Link

no, i think you are say something similar to me. i guess part of my question is 'how much neck clearance do i want in a .269 chamber'. from that and the diameter of the bullet at its widest point which gives me the thickness of the the neck i want then i need a bushing (or two or more to test with) to set the 'tension' down 1 to 2 thousands (or more)

so .269 - .003 = .266.. bullet plus neck should be .266.. a .001 tension requires a .265 bushing. a .002 tension requires a .264 bushing. if the bullet is .243 at its widest point (and its wider at the pressure point.. didnt know about that before, i have 200 berger vlds and they appear to be .2435 at the pressure ring.. more bergers of a different type to arrive tomorrow. will measure those) then the turned neck thickness should be .011 (approximately).

.2435 + (2 * .011) = .2655. .269 - .003 = .266.

so if i only shoot the vlds and the are always .2435 at the pressure ring and i only want to run .001 to .002 tension and i need .003 clearance then .265 and .264 would be a starting place.

take note that the titanium nitride bushings are 25$ a piece. i dont mind spending money for top shelf stuff but buying every bushing from .257 to .271 is 15 bushings for a total cost of 375.00...

using the smallest bushing in the list... .257 i will assume that for example that would be for a .001 tension setting of a .258 neck. so if the bullet is .243 wide and end thickness is .258, then .258 - .243 = .015 for a neck thickness of .0075 (.015/2)

one of the main issues for me is prior to ordering this rifle, i turned necks to provide concentric loads. i paid little attention to the chambers since they were saami and what i did was always less say.. than factory ammo in diameter. now, for the first time, i am paying attention to the chamber dimensions and the clearance of my loads within that chamber.. so im turning necks for both concentricity and clearance. and i have no idea what the min/max of 6mm dasher neck thickness should be for best results. thats a key question here.

prior to ordering the rifle, one recommendation was for a .272 'no turn neck'. if i had ended up with a rifle with that dimension, i probably would have simply looked at my brass, seen that .012 was what i could always turned down to for uniformity, decided that a .243 bullet + .024 wall thickness yielded .267 and ordered a .266 and a .265 bushing to start..

eta to say.. i tune computers (software and disk subsystems) for a living so i deal with endless 'makes me dizzy' calculations and information all the time. and this is not dissimilar in some ways.. after all i am tuning hardware to produce the best performance possible within a given range.

 

[tdogg]

I'm in the same boat as you. I have a supposed .269 neck dasher. I've been shooting the berger hybrids with moderate success (.3-.4 moa) consistently.

From what I have researched you may want to confirm your neck is actually .269 by taking a mold of the chamber then measuring the neck diameter. It's on my to do list of things I should be doing with my new toy.

That said I turn my necks to roughly 11.5 thou and end up with a total diameter of ~.265-.266. I think the pressure ring is right at the transition of the boat tail and thus the loaded diameter is not consistent the length of the neck.

From other research, you want fired brass to allow a new bullet just enough clearance to just slide into the case without any resistance. That will dictate your neck turn thickness. This in another item on my to do list with this new toy. I think I'm roughly at .004" clearance on my rig.

Loading up a dummy round and taking actual measurements is advised before you turn a bunch of fireformed brass. Ask me how I know that one.

Once you have the dummy cartridge dimensions you measured you can order additional bushings of the correct size. I'd start with a .264 bushing.

Cheers,
Toby