proper neck tension for 6.5 accuracy

[gene so]

This gets a little involved. I am going to start shooting a 6.5 IHMSA (shortened .308 case )in a rifle with a 29 inch barrel. I enjoyed the challenge of creating this bunch of brass for this rifle from Lapua. I remember when just doing some basic prep work with this cartridge years ago that in firing strong loads even after reloading twice the case necks did not expand enough to bother with resizing them. The necks have been turned .010.
In that same vein I had read where a very successful benchrest shooter was providing more than the normal .002 of case neck clearance and his rifles are simply more accurate now.
I shall be taking some of my cases and turning them down an extra .001 on each side and see if this improves accuracy even though my old notes state I shot 1/2" groups with the older rifle at 200.
Is there someone out there who has dealt with shortened wildcat cases such as this in a bolt action rifle?
Also, I am wondering about annealing the necks to produce the consistent neck tension and also have these cases NOT split after all the work I have done on them. Thank you for your insight into this matter,

 

[mikecr]

I had read where a very successful benchrest shooter was providing more than the normal .002 of case neck clearance and his rifles are simply more accurate now.

To set a scale, was it more accurate than not accurate enough?

I shall be taking some of my cases and turning them down an extra .001 on each side and see if this improves accuracy

This will be a better basis for you.

Is there someone out there who has dealt with shortened wildcat cases such as this in a bolt action rifle?

I have, and with fitted necks, but short, long, what does this matter with neck clearances, or your thread title -proper neck tension?

Also, I am wondering about annealing the necks to produce the consistent neck tension and also have these cases NOT split after all the work I have done on them.

Annealing counters splitting instead of causing it. Why do you think you need to anneal?

 

[gene so]

Hello Mike,
I'll answer as many of your replies as possible. First of all the person writing the article is well known in the east and his family dominates the Williamsport 1,000 yard benchrest matches. I read that statement about clearances and remembered it for many years, and want to take advantage of it now that I will be shooting the Sporting rifle matches at Whittington NRA, which is dominated by mid sized 6.5 cartridges, even though nobody has shot it perfectly in 11 years.
I had this rifle built for competition at 600 yards when you could NOT get 6.5 x 47 Lapua here in the USA. Initially it worked well enough, but then my 30BR arrived and I won matches at 1-2-300, 500 meters and set both ends of the 600 yd worlds records(NBRSA) with it at 600, so this 6.5 has set all this while.

I noted the seating of the bullets required a little more pressure and never had encountered cases fired twice that did not need to be resized to form proper neck tension when reloading before. I used annealing religeously on the 30BR every third reloading, but in retiring from Seattle to northern New Mexico at 6,500 feet, It would appear I am going to have to buy a really good unit and do my own annealing.

Since the sporting rifle competition requires 60 shots at 60 targets from 230 to 875 yards with no sighters allowed; keeping that brass working a long time is a priority.

Since in the case making process and also turning with Neilsen pumpkin you would think that the proper neck tension would become a part of the process, yet I remember the seating as more difficult than normal and also the fact the cases never expanded enough to need to be resized. Thus, my concern about proper neck tension in the first place and also the possibility of necks splitting, secondarily.

 

[mikecr]

I'm probably misunderstanding the thread.
Seems like 3 questions going with decisions about em already made.

You should anneal before forming to reduce splitting issues.
With minimal neck clearances you can work brass less, keeping consistent tension, and so you can anneal less. Way less.
IMO, tighter clearances won't hurt a thing unless your ammo is crooked.
That is, ammo made with precision should be able to benefit reloading-wise from tighter neck clearances, without ill affects to accuracy. Right?
So if someone can't make their ammo shoot well enough with tight clearances, I'm thinking there is another issue, worked around with sloppy clearances as the 'fix'.

 

[searcher]

I think mikecr said it! If you stop to think about why a thinner neck may work better on one's load - my guess as to why is that he only needed lighter tension - and the need was great enough to show only by turning the necks a little thinner - rather than changing the tension by the alternate method with the neck sizing bushing/die. As we know - change anything and something else changes....

 

[madderg]

If you know the dimensions of your rifles cut chamber just make you case necks 3-4 thousands smaller, if you don't make a cast and get the measurements you need. Then get a neck sizing die with insert, choose the right one and use every time. Annealing the case necks is always a great idea that will give you both consistency and extended case life. Good shooting, Gary.

 

[Alex Wheeler]

I played with neck clearance on my dasher. I could not see a difference from .0005-.004''. I would not bother with a fitted neck. I see it as zero benefit. You want the lead centering the bullet, not the case neck. As good as we think we can load ammo, its very hard to do it perfectly. Most of us use bushing dies, that prevents the case neck from being concentric to the body.

 

[mikecr]

Your right zfastmalibu in that there is no isolated accuracy difference or detriment in tight to loose neck clearances(with no issues present).
But there is reloading benefit to tight clearances, like less sizing and therefore more stable tension without sacrificing the amount of it.
While you can anneal to get consistent tension, it is also less tension.

This isn't always best for a cartridge/load.
If I shot a 30br for instance, I'd want high bullet grip that is very consistent, at best seating(which might not be jammed), and this is easiest to maintain with tight neck clearances.
And since I would go tight, I'd turn to set it so, and my runout would drop.

Given that it doesn't hurt anything, for anyone intent on turning necks anyway, they might as well set tighter clearances.
I just don't see this as a bother.

 

[gene so]

Hello again Mike,

I value your insights, even though this time I do not agree with them. I used my 30 BR to set two different 600 yd. World's Records. (NBRSA) I used the absolutely minimally amount of neck tension, like .005 and set the BIB bullet +.030 into the lands. The consistency and accuracy was better than with any of my 6 PPC's and I shot some .0 groups with them at registered matches.

I shall be receiving the 6.5 IHMSA rifle back from the gunsmith so I can start real load testing and case prep finishing and I know the results will be superior thanks to the insights given me in this forum.

Gene so

 

[mikecr]

+30thou into the lands, takes neck tension out of it.
If your best seating were off the lands, tension would matter, and this is the scenario I tried to relay.
I don't know if your 6.5IHMSA will be jammed