FTR neck turning question?

[amlevin]

The issue of getting straight case necks on resized cases was mentioned.

'Tis my opinion that the straightest necks on resized bottleneck rounds happens when a gelded one-piece full length sizing die's used whose neck diameter is 1 or 2 thousandths smaller than a loaded round's neck diameter. Such die's neck axis is permanently and perfectly aligned with the die's shoulder and body axis'.

A very close second is a full bushing die such as the commercial ones made by Redding and RCBS. Their floating bushing doesn't perfectly align its hole to size case necks perfectly on the case axis as the case body's held by the die. But it's pretty close and these dies are popular with a lot of top ranked competitors.

By gelded, that's a die without a ball on its decapping rod; just the pin at the end to push out the fired primer. Expander balls tend to bend sized down case necks crooked as the case shoulder wall isn't uniform in thickness all the way around. The ball coming back up through the case neck bends the neck in the direction of the thin side of the shoulder wall. And it works the case neck brass a second time after the die's sized it down earlier. One sizing operation on case necks work hardens them a lot less.

Besides, bottleneck cases headspacing on their shoulder have their shoulders hard into and very well centered in the chamber shoulder when they're fired. Any off-center issue of the case neck on the case shoulder puts it off center in the chamber neck; doesn't matter how much clearance there is and there'll always be some. A well centered case neck on a .243 case shoulder will align its bullet dead center in a .308 Win chamber should the firing pin drive it hard into the chamber shoulder then fire the round.

You don't mention the freebore diameter. If one has a freebore dimention that's barely larger than the bullet itself, no a lot of chance that the bullet is going to start it's trip "cocked" in the bore. When you take into consideration the shoulder centering you mentioned, as well as the length of the case itself, it takes a pretty loose chamber to really allow things to not be pretty straight when the cartridge is chambered.

As for F/L sizing without the expander ball? I've tried Collet Dies, Body Dies followed by neck sizing dies, Shoulder bump bushing dies, and F/L dies. The straightest cases I get from the sizing operation is when I use a Forster F/L Benchrest die WITH the expander ball installed. Cases all measure < .0005" TIR when sized and I have the perfect neck tension for my bullet/powder combination in my .308 Win. In a non-Benchrest rifle I still am able to shoot groups in the low "20's" or high "teens" @100 Y.

Removing that expander ball isn't always necessary. I see it as a means of insuring the same neck tension even if there are minor variations in neck thickness. Or, as they say, "Works for me"

 

[Bart B.]

Has anyone measured the actual force needed to pull a bullet out of a case neck? "Release force" is the term arsenals use to measure neck tension.

In my own tests, a spread of 15% in release force about 10 pounds average across case necks that are unturned and have a .001" spread in wall thickness lets bullet fall inside 5 to 6 inches at 1000 yards and under 4 inches at 800.

Decades ago, when on a military rifle team, some lots of M118 7.62 NATO match ammo had a wide range of release force about a 40 pound average; at least 30% spread. That stuff shot good for windage at 600 yards but elevation stringing was almost a 3 MOA spread. We reseated the 173-gr. FMJBT match bullet with a Lyman 310 nutcracker tool pushing the bullet a few thousandths back into the case that broke the black asphultum seal. Release force was reduced to about 20 pounds and had under 15% spread. It held elevation as good as windage after that.

Regarding the bullet's clearance to the chamber throat and crooked bullets, I've not observed any accuracy problems with a .3082" diameter match bullets in a .3095" to .3100" diameter throat and .002" runout measured from the case axis running from case center at its pressure ring to center of the case shoulder.

 

[savageshooter86]

I am turning them to 14 thous. This will give 100% clean up on my brass that had neck wall thickness of 1 thous to 1/2 thous. The other brass that had 2 thous thickness variation I turned and will use those for load work and sighters. Not sure if that matters or not but probably could use them all for my match rounds

 

[Joe R]

savageshooter86 said: I am turning them to 14 thous. This will give 100% clean up on my brass that had neck wall thickness of 1 thous to 1/2 thous. The other brass that had 2 thous thickness variation I turned and will use those for load work and sighters. Not sure if that matters or not but probably could use them all for my match rounds

Smart move Andrew. I also turn my necks to .014 like many others and it works for me. Some go even thinner, but that's for those that have tight custom chambers.

 

[thefitter]

It's ball has been removed. Gelded; same thing with male horses.

I thought you were describing a LEE Collet die.