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Neck Tension

I have been bench rest shooting for around 6 months and have noticed a fair amount of difference in the force needed to seat my bullets. I'm shooting a 6ppc .261 neck turned to .2593 loaded round. I have measured all my loaded ammo and don't see any between the cases. I have loaded my cases both sized and unsized. I started with new Lapua cases and only have a couple of hundred rounds shot. What am I doing wrong or what else should I be looking at.

Mike
 
The first entry in my reloading manual is April 9, 1965 with a .22 Hornet during my days as a University student. One of the first books I added to my shooting library was 'Principles and Practice of Loading Ammunition' by Lt. Col. Earl Naramore,ret), Stackpole, 1962. His in-depth scientific analysis of cartridge brass on the level of a U.S. military arsenal Exec Officer pretty well jibed with the more country boy observations of a Canadian gunsmith, Elwood Epps, who in the 1960`s gained recognition in P.O. Ackley`s dual set of 'Handbook for Shooters and Reloaders', Publishers Press, 1962.

Earl on a metallurgical level and Elwood on a practical level both said that given the variables in the chemical/mechanical mix of the components of cartridge brass, you ain`t never going to get it 100% right.

At the 2009 Ontario Fullbore Champs, one of Canada`s best benchrest / F Class shooters had three complete misses on a 300 yard target with a custom 6.5/284, Lapua brass, neckturned, sorted by weight, best reloading methods. You see commercially involved shooters standing proudly in front of perfect 1000 yard targets but you will never see the targets that have two complete misses.

After 50 years of competitive shooting, I am still in a quandry as to whether neck-turning is worth all the effort. But ain`t it great trying to figure it out!

Bushing dies, premium brass and micrometer neck-turning setups are the latest attempts to remove the variables but the guy at the smelting pot pouring the brass ingots while fighting a hangover has way more determinent effect than anything Sinclair can sell.

After 45 years of reloading, I have never felt two bullets in a row enter a case neck with 100%, completely identical seating force, but I have shot a lot of small groups and won firsts and seconds in F Class at 1000 yards. It is the results that matter, not the small variables along the way.
 
Not all pieces of brass from any given batch work-harden at the same rate. This is why many re-anneal every few firings to try to maintain consistant neck-tension.
 
1000yardstare said:
After 45 years of reloading, I have never felt two bullets in a row enter a case neck with identical seating force, but I have shot a lot of small groups and won firsts and seconds in F Class at 1000 yards. It is the results that matter, not the small variables along the way.


I load .222, 6 PPC, and 30 BR for short range BR, and can attest that with proper neck-turning and using chamber style seaters,Wilson) and custom Match bullets the seating force is very consistant for the first couple of firings.
 
I'm not a BR shooter so take what I offer with whatever grains,salt, propellant, BS...) you have a taste for.

Have you tried sizing cases / turning necks so there's little or no force necessary to seat your bullets?

I find, for my long-range pursuits,Palma, 1K, no rests or optics) I get the best ammo performance with just a hint of friction when seating; loaded vs. unloaded neck diameter is typically about .0015' - .002' & even with the Boron Nitride coated 6mm bullets for the 1K stuff,Palma's strictly uncoated .308) there's almost no force needed to seat bullets using my Harrell press.

I can't move loaded bullets by pressing on them with my fingers though, so it's not a slip fit. There's some case neck tension being exerted, but not much.

Same thing with gas-gun OTC ammo: 6HAGAR, .002' loaded vs. unloaded diameter, capable of shooting cleans at 600 if I consistently do what I'm supposed to.

One thing in common to all my shooting: I anneal the neck, shoulder & the adjacent 5 - 10 mm,cartridge length-dependent here) of the case body about every third firing.
 
Thanks for the input, I should have started by saying my gun shoots very well even with the uneven tension so can I conclude that neck tension is not that important. I have just read so much on the subject that it made me think that I must be doing something wrong.
 
twidle, As an old BR shooter,we never did any thing to the brass.Sized to.001 neck clearance and .001 at the shoulder and a .0005 at the base.this way you don't over work the brass. 50 pieces would wear out a barrel,this set up requires every thing to be straight and really good FL die. You are working the spring back in the brass.
These guns shot in the low 1's and zero's.........jim
 
I just wanted to say thank you for mentioning my Great Grandfathers book. LtCol Naramore is/was my Great Grandfather. I still look up to him today and try to learn something new about weapons and munitions every year.

Sincerely,
Shelley
 
Forster and Redding both now recommend .001 of neck tension for competitive shooters. And .002-3 for hunters or those with automatic weapons.

How you get consistent neck tension is dependent on.
1. Sizing (bushings or expander ball selection)
2. Neck thickens (turning fixes this)
3. Hardness (solvable by good annealing process)
4. How clean the inside of the mouth is (work with that brush or a good sonic cleaner here)

Did I missed anything?
 
i am obsessive and enjoy the heck out of this endevor. understanding neck tension and it's relationship to accuracy is a personal mission of mine. i may be wrong, again, but i suspect variation in neck tension will affect acuracy more if one jumps bullets, being that neck tension is the main factor keeping the bullet from entering the bore. this same variation seems less significant if one seats bullets so that they enter the lands .020 or more. now the resistence to movement is much greater and requires more pressure to move the bullet. jumped bullets can move early during pressure buildup, while "jammed" ones need much higher pressures. pressure to move a jumping bullet seem to vary over time as i suspect neck tension(bullet grip) seems to increase...the topic of "cold bonding".
 

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