Neck tension

[kestak]

Did a test....

Got me puzzled.

I loaded 20 rounds of 308.
10 rounds normally: set the Nosler bullet in, crimp with LFC die
10 rounds with Imperial wax inside the neck. The bullets slip in as easy as a suppository in what you know. Then crimp with LFC die.

I shot both groups. Both print at the same place and both have the same group size.

I really thought a difference in neck tension would have changed a group pattern.

I know I did not really changed the neck tension. I changed the neck friction.

Anyone ever tested "true" neck tension difference in POI?

 

[Blue68f100]

Why did you use Imperial Wax on the inside of the neck? The sizing wax should only be used on the outside of the case only. If I'm neck sizing only I may use the graphite lube every 5-10 cases at most.

 

[critter]

Some relatively slow burning handgun powders will change POI with a change in neck tension & crimp. Evidently, some powders NEED a good deal of resistance to get a good, complete, clean burn.

I have not personally noticed that in rifles, but that doesn't mean it doesn't happen.

 

[chrome_austex]

I believe POI is going to be mainly from muzzle velocity and barrel whip harmonics. Changing the neck tension (which wax don't do) will do little to change the barrel harmonics or the velocity of the projectile.

The neck sizing is important so that (wait for it) the bullet doesn't fall out of the case. Neck concentricity and thickness may be another matter (but I still think they won't influence POI much). I'm no expert so take this with a grain of salt.

The difference in neck friction with wax or no wax when the bullet is being pushed at 60,000 psi are probably negligible.

 

[rcmodel]

A better test would be both loads without the Lee FCD crimp.

The heavy crimp collet is making up for frictional differances.

rc

 

[brickeyee]

How tight a group can the rifle shoot?

Unless you are approaching one hole benchrest accuracy it can be very hard to detect minor changes.

 

[kestak]

I used the wax as a test. I don't use wax inside necks when i resize.
Group is 1/2 to 3/4 MOA depending on how crappy I am that day.

 

[USSR]

kestak,

You do know, that crimping has nothing to do with neck tension? Neck tension is a result of the ID of a resized neck. Absolutely no need to crimp a .308 cartridge.

Don

 

[kestak]

Ussr, i am not sure I follow you. Little neck tension with no cdimp = pushed bullet when chamberred and variance in oal.

I crimp my 308 because I use it in a m1a also.

 

[USSR]

Ussr, i am not sure I follow you. Little neck tension with no cdimp = pushed bullet when chamberred and variance in oal.

I crimp my 308 because I use it in a m1a also.

So, increase your neck tension and don't crimp. I load for 3 Garands and a FAL, and I have never crimped a bullet. I simply use a bushing that gives me .002" to .003" neck tension. If you don't have bushing dies, you can reduce the size of your expander ball by polishing it, which will reduce the size of your neck's ID. Hope that helps.

Don

 

[kestak]

Aaaaaaaaaaaaaah! Got you!

Thank you!