Another neck turning question

[nmkid]

I have read much on neck turning and I have a question. What is the process for determining how much to trim? Say I have 100 unturned cases, and I make 4 marks around the necks, (spaced evenly). Now I measure the necks at the 4 marks. OK. I get 2 different readings. Say I get, .013 and .014. Do I trim the necks down to .013 on all the cases? If so...What if in turning the cases I clean up the entire neck? (read that NOT to clean the entire neck because then the neck will be too thin and the case will be ruined). Hope I'm making sense.

 

[jcampbellsmith]

I have read much on neck turning and I have a question. What is the process for determining how much to trim? Say I have 100 unturned cases, and I make 4 marks around the necks, (spaced evenly). Now I measure the necks at the 4 marks. OK. I get 2 different readings. Say I get, .013 and .014. Do I trim the necks down to .013 on all the cases? If so...What if in turning the cases I clean up the entire neck? (read that NOT to clean the entire neck because then the neck will be too thin and the case will be ruined). Hope I'm making sense.

I neck turn a little at a time, because as in planing wood, you can't put metal back onto the necks. I have a Sinclairs neck turning tool and I have it set up for just my 6XC cases. Some necks it barely takes any metal off the neck, but it does remove material at the neck/shoulder junction. In due course, if the brass survives, I will crank the neck turner up a notch. I'm more interested in uniforming the necks, than an absolute neck thickness. I don't have the kit to make anything more than indicative measurements of the neck thickness.

Also having paid for a .274 necked 6XC, I don't want to be working the necks too much.

Have fun.

JCS

 

[Dusty Stevens]

Measure a bullet then do the math plus your desired clearance. Then measure over a loaded round to confirm.

 

[ShootDots]

I have read much on neck turning and I have a question. What is the process for determining how much to trim? Say I have 100 unturned cases, and I make 4 marks around the necks, (spaced evenly). Now I measure the necks at the 4 marks. OK. I get 2 different readings. Say I get, .013 and .014. Do I trim the necks down to .013 on all the cases? If so...What if in turning the cases I clean up the entire neck? (read that NOT to clean the entire neck because then the neck will be too thin and the case will be ruined). Hope I'm making sense.

If you have a "no-turn" neck, just "skim-turning" them is a good idea.. That is taking off the high spots which generally cleans up about 80 or so percent of the neck. But if you have a tight chamber you need to take off enough to allow for clearance between the neck walls of the brass and chamber. EXAMPLE: I have a .284 with a .313 neck. The new Norma brass had a neck wall thickness of 15.5 to 16.0 thousandths thick. If I tried to chamber a loaded round it would not go in. 16 + 16 + 284= .316. So I turn my necks down to 11.5-12.0 thousandths. That is 12 + 12 + 284= .308.. That gives me 5 thousandths clearance..

 

['Freak]

How reasonable is it to assume that a fired case neck OD plus .001” is fairly close to the chamber’s neck ID?

 

[ShootDots]

How reasonable is it to assume that a fired case neck OD plus .001” is fairly close to the chamber’s neck ID?

I don't know if that is possible to make an educated guess at.. Run a fired case into your sizing die, then seat a bullet. Measure the O.D. and see if it is 3 or more thousandths smaller than you chamber neck>> that is IF you know your chamber neck reamer size.. If you do and it is, your in good shape, unless you have a 7mm. For whatever reason they shoot better with 4+ clearance.

 

[P1ZombieKiller]

How reasonable is it to assume that a fired case neck OD plus .001” is fairly close to the chamber’s neck ID?

I think it is closer to + .002

My .330 neck 30br chamber has a fired case that measures .328 <at the neck> after firing.

added <at the neck> to original posting.

 

[aj300mag]

I have read much on neck turning and I have a question. What is the process for determining how much to trim? Say I have 100 unturned cases, and I make 4 marks around the necks, (spaced evenly). Now I measure the necks at the 4 marks. OK. I get 2 different readings. Say I get, .013 and .014. Do I trim the necks down to .013 on all the cases? If so...What if in turning the cases I clean up the entire neck? (read that NOT to clean the entire neck because then the neck will be too thin and the case will be ruined). Hope I'm making sense.

Turn them all down to .013" . That isn't close to be considered too thin. We run necks at .008" in benchrest...

 

[LHSmith]

If this is for a factory rifle, IMHO, I wouldn't waste time making the slop between the case neck and chamber neck sloppier.

 

[jcampbellsmith]

If this is for a factory rifle, IMHO, I wouldn't waste time making the slop between the case neck and chamber neck sloppier.

I don't agree. When I first started shooting Remington 260 Rem brass, the necks were all over the place. Neck turning made them much more usable. Neck turning has a role to play in my brass prep regardless of the quality of the chamber.

Regards

JCS

 

['Freak]

How reasonable is it to assume that a fired case neck OD plus .001” is fairly close to the chamber’s neck ID?

I think it is closer to + .002

My .330 neck 30br chamber has a fired case that measures .328 <at the neck> after firing.

added <at the neck> to original posting.

Thanks P1ZKiller- to you too ShootsDots

I’ve seen that .001” difference figure stated more than a few - but as a more or less ‘guesstiment’. My own guessing has been the more the case neck to chamber wall clearance so more neck expansion on firing, the more spring-back so more difference between the fired neck OD and the actual ID of the chamber’s neck.


Lack of case neck OD to chamber wall clearance is certainly not an issue with factory production line SAAMI spec. chambered rifles. Whatever’s turned off the neck’s OD is adding that much more to an already very generous neck wall to chamber wall clearance. Then when fired, the neck wall has to expand out that much more so also increasing the working of the brass as it’s blown out to and seals against the chamber wall.

I figger there are some redeeming qualities to turning necks that’ll be fired in SAAMI spec. chambers. The nearer to equal thickness neck walls will be work hardened more alike instead of having the thinner areas expanding more so worked more vs. the thicker areas opposite the thin that’ll expand less so are worked less. The more equal thickness so more equally worked and hardened neck wall ought to hang onto the seated projectile with nearer to equal tension all around, and then on firing, equally relinquish its grip all at once, or maybe more an all as one.

 

[Webster]

You didn't state what your rifle is used for. If it's for varmint hunting I would just do a minimum clean up cut. ~50-70% not cut. The quality of your barrel and bedding will probably be the determining things for accuracy. I have a right handed Rem 700 BDL Varmint rifle with a Kreiger 6BR barrel on it and glass bedded. I shoot it left handed usually without wind flags at the range and I consider any load over 0.400" a bad load. My biggest improvements have come from improving my bench skills.