How much to turn necks?

[Alan Griffith]

Have my 100 new Lapua 30-06 cases, FL sized on my Forster BR die and trimmed to SAAMI mins. Used my Sinclair Mic-4 neck thickness gage to get down to .0025" (gage reads to .001" but I can try to eyeball it to .0025"). Groups ran thusly.

.0000" to .0005 (6 cases)further referred to as .5 or less
.0006" to .001" (38 cases) referr as .6" to 1"
.001" to .0015" (29 cases) referr as 1" to 1.5"
.0016 to .002" (16 cases) referr as 1.6" to 2"
.002 and larger (11 cases) referr as 2" and larger

In playing with my worst 11 cases, the worst 2 being .003" neck wall variation. They are .0014" to .0017" and .0015" to .0018". Of all 100 cases, .0014" is the smallest and .0018" is the largest. What I'm trying to figure out is should I try and take all 100 cases down to .0014" so I aim for .0000" variation or maybe get .0015" at best.

Or, on my best 6 cases, the largest diamater is .0016"; should I try and take all 100 cases down to .0016"?

Thanks for the help!

 

[abinok]

Whats your neck diameter on the chamber?

 

[Alan Griffith]

Factory? SAAIM? I dunno /ubbthreads/images/graemlins/smirk.gif

1982 Rem 700 ADL.

Big Al

 

[abinok]

Just making sure on the decimal places.... youre saying your thinnest neck is .014", your thickest is .018" ? Saami is .340... so you will be right there. The easiest thing to do would be just hammer a round downrange, and slap a caliper on the fired neck. From that the answer is super easy. The whole goal of my tapdancing around giving an actual number revolves around wanting to keep expansion on firing as low as is practical to balance out sizing/work hardening the brass. Ive turned brass too thin to make it clean up before. worked great for all 3 firings /ubbthreads/images/graemlins/smile.gif before the necks split. Measuring a fired round will make everything clear.

 

[Alan Griffith]

Abinok,

I understand perfectly. I'd hate to ruin a bacth of new Lapuas.

Yes, my thinest neck was .014" and the thickest was .018".

 

[abinok]

The ones I toasted were norma (EEKS!!!)
taking the .018" to .014" adds .002" per side... and thats a lot if youve got a max dimension chamber. Im betting youve got .344-.346 or so... only one way to find out. Well, unless you want to cerrosafe it.

 

[Alan Griffith]

Ok, just to soothe everyone's curiosity, especially mine, before work this morning, I went and took 3 rounds and loaded them up with 57.5 gr H4350, WLR primers and stuck the bullets into the lands .005". Temp about 65 degrees. The brass I used was in the .0016" to .002" neck thickness variation pile (16 cases). Not the worst of the bunch, but next to it.

Here is what happened.

Case 1

.0015" to .0017" neck thickness variation. Loaded OD .338". Fired OD .341"

Case 2

.001425" to .001625". Loaded OD .337". Fired OD .341"

Case 3

.00155" to .00175". Loaded OD .337". Fired OD .341".

Seems to me, and I could be wrong, I'm getting, at most, .004" expansion. Actually, probably .005" because I'm getting .001" spring back after firing; probably! Right?

Would I be safe to surmise (that's my way of guessing) my chamber's neck is .342"?

Ok, now where to from here?

Big Al

PS. Isn't this Fun?!?!?! /ubbthreads/images/graemlins/grin.gif

 

[davewilson]

i agree that your chamber is probably 342. if your necks have .015 wall thicknes, your loaded rounds will be around 337-338. that's about .004 clearance with a loaded round. in my opinion that would be close to optimal for a hunting gun.you mentioned .016 for wall thicknes...too tight, only .002 TOTAL clearance. .014 would also work well. you'd size your brass a little more but you could use all of it and never have any "pinching in the neck" worries.

 

[Dan Carey]

Not to rain on your parade, but if you have a .342" chamber neck in a factory Remington I'd be surprised. (.3425 is SAAMI minimum spec.) and a .338 loaded round, your at the accepted sporting rifle chamber clearance already. If you cut the neck walls anything under .015 you'll have an undersize round for a factory chamber. I've seen Remington chambers run as high as .3450, the only to know is a chamber cast. Brass spring back cannot be used to figure the case neck size.

Match grade chambers usually like brass .002 under chamber neck size.

 

[davewilson]

i'm not sure what you mean but if you're saying that .0045 is considered something around standard clearance, i don't buy it.and if turning to .014 is too much clearance,i respectfully disagree.most factory ammo i've measured is at least .006 and usually more for a loaded round clearance.i think most would consider .004 clearance in the "tight neck" catagory.i do agree that measuring fired brass is not an exact thing for chamber diameter, but it will get you in the ballpark,probably within .001.

 

[Dan Carey]

Harvey Donaldson pioneered the so called tight neck cartridge around 1945 or so, it was carried over the 222 Remington when it came out around 1950 or so. The concept entails cutting a small neck chamber and cutting the case neck to the same size as the chamber neck, thus no clearance. AKA tight neck. The case was then able to be reloaded without using a sizing die.

Using 5 different brands of cases will yield 5 different case neck thickness dimensions. Also the cases will be of different temper or hardness, so they will never be even close as to figuring the chamber neck dimension from a fired case.

Factory ammo also varies in brass thickness, as measured loaded. So, just who is to say what is standard.

.004" will work in a hunting rifle, that's what I use when I can, never had a problem with it either. The more you cut the necks down the sloppier the cartridge fits in the chamber.

 

[davewilson]

measuring the neck on a fired case will get you close to the chamber size and more turning of the neck has little to do with how the cartridge fits into the chamber.

 

[abinok]

[ QUOTE ]
Harvey Donaldson pioneered the so called tight neck cartridge around 1945 or so, it was carried over the 222 Remington when it came out around 1950 or so. The concept entails cutting a small neck chamber and cutting the case neck to the same size as the chamber neck, thus no clearance. AKA tight neck. The case was then able to be reloaded without using a sizing die.

Using 5 different brands of cases will yield 5 different case neck thickness dimensions. Also the cases will be of different temper or hardness, so they will never be even close as to figuring the chamber neck dimension from a fired case.

Factory ammo also varies in brass thickness, as measured loaded. So, just who is to say what is standard.

.004" will work in a hunting rifle, that's what I use when I can, never had a problem with it either. The more you cut the necks down the sloppier the cartridge fits in the chamber.

[/ QUOTE ]

Well... Saami does... at least to a level of voluntary compliance from all US mfgs. I wasn't talking about .004"... I was talking about .004" more on top of whatever is already there. I do certanly agree that .004" is great for most applications... but you usually have to go to a custom reamer to get it. BR chambers are great for BR guns... but 99.9% of what the folks are shooting on this site is not a BR gun. Fortunately, we can stand a little more change in brass than the BR croud /ubbthreads/images/graemlins/smile.gifNo sizing requires under .001" per side... and closer to .001" total clerance. I personally can't put that much work into all the cases I put through my guns... hundreds of them...

 

[Alan Griffith]

Guys,

I'm away from my gun for a few days. Took the family to So Cal for a 4 day vacation and hospital visit. Still have internet when were not playing on the beach /ubbthreads/images/graemlins/smile.gifon puking on the roller coaster. /ubbthreads/images/graemlins/confused.gif

I'm going to try a little trick of placing a Hornady .350" lead muzzleloder ball just in the mouth of an old case. I'm going to lightly chamber it, not totally, to get the ball to swage down to the chamber neck dimensions. It should either stick in the mouth of the case and extract with it or I can simply pop it out via a cleaning rod.

I'm of the feeling I should get a minimum of .003" or maybe .004" clearance.

.342" minus .308" = .034" (assuming .034" is correct)

.034" minus .003" = .031" /2 = .0155"

or

.034" minus .004" = .030" /2 = .015"

Of course this is all academic until I get back home on Saturday and check the chamber neck diameter.