I have checked for previous posts and there have been some comments on the matter, but they were more directed to adequate angle for the lead in the barrel.
I am probably having a 6,5 x284 built, the question is.. does a tight neck offer a truly big advantadge?
The rifle is not going to be heavy, and do not plan to use if for competition. I have neck turning tools, but I do not want to be pressed to neck turn if I do not want to ( let´s say I get lazy or want to shoot factory ammo some day) , unless the tight neck offers a real advantadge over a "normal" or saami dimensioned one. What is the real edge a tigh neck gives you, provided the gunsmithing job is good in both cases?
Tight necks do not offer a truly big advantage over saami specs, but to me would be desirable in a custom barrel.
Firstly i would describe tight necks as "any that are tighter than saami specs", and the ultra tight .001" to .0015" clearance necks on bench guns as "fitted necks".
Saami spec, necks are cut to provide ample clearance for all brands and maximum size deviations of factory ammo. This means that a neck cut to minimum saami spec. will still be bigger then a cartridge manufactured maximum spec and in an extreme case you could have a max spec saami chamber and neck and a minimum spec cartridge, giving you massive clearance as much as .040" has been recorded, [img]/ubbthreads/images/graemlins/shocked.gif[/img] not very productive towards accuracy and case life.
A tight neck in your 6.5-284 will help alignment of the cartridge in the chamber and aid straight bullet engagement into the rifling, thus increasing accuracy. Case life will also be extended.
Find out from your smith what size neck his reamer cuts and aim for a clearance of .003" to .004" for a tight neck, he may be able to cut you a neck which gives you the desired clearance, without you needing to outside neck turn your cases. Alternatively you could have minimum saami spec chamber cut and form your cases from 284 brass, which could also give you the desired clearance, with the very high quality Norma and Lapua brass available i would advise a tight neck as described above. Either way i think a bit of neck turning is in order. [img]/ubbthreads/images/graemlins/wink.gif[/img]
So I understand if I can get a chamber/neck cut to minimum saami tolerances, after a first fireforming shot the brass can be readily adjusted. is that what you suggest?
As said, I am already neck turnig for my 7 rem mag, but just becuase I want to.
Another thing I have heard is someone saying that neck turning in case of an ordinarty SAAMI chamber does not give you any benefits, and only makes brass move forward to the neck decreasing case life ??
I have just begun neck turning for the first time on my .222 Imp and immediately noticed a much lower velocity spread no doubt achieved from more uniform neck tension.
This is a major plus for long range work where velocity changes begin to affect the vertical strike.
My cases [Norma] were uneven in neck thichness and I have just taken a .0015 skim which averages a 85% clean up of the neck area.
This has been achieved without using neck bushing type dies as well altough that will be my intention when I can obtain custom dies.
I do not yet have a "tight neck" as such and intend having my reamer modified to a clearance of .002 after I turn off another .001 to fully uniform the necks.
My clearance now is .0055 after this first skim and with the current chamber so i don't want to take any more off before using a tighter neck chamber reamer.
It depends on how much you need size your necks in order to get sufficient neck tension, the use of neck bushing dies is probably the best way to accomplish this.
Seat a bullet in your chosen case (not turned) with adequate neck tension, about .002" to .003" and measure the neck diameter.
Compare this with the neck diameters your smith can cut for you. You can then decide if you want to neck turn based on the clearances that can acheived.
If you decide to shoot factory ammo make sure your new chamber is not to tight for the factory round, by also measuring the neck.
I suggest you arm yourself with all these measurements and decide whether or not to neck turn before having your new barrel chambered.