What type of improvement should a person hope to gain in accuracy by going to a tight necked chamber and turning necks. I am in the late stages of a custom .308 win and am wondering if it will be worth going away from a standard chamber. I am hopeing for 1/2 moa @ 100.

I don't like turning necks if I can help it. What I usually do for my custom chambers is find some brass and bullets in that chambering and assemble some dummy cartridges, then I mic the loaded round's necks and get the chamber cut to the next whole number between .003" -.004" larger than that diameter.

In my 6.5mmX284 the SMK's in Lapua brass measured .2926" so I had my chamber neck cut to .296". That gave me a good fit in the chamber without have ing to do a lot of brass prep and that gun will shoot under 1/2MOA

Don't think in terms of tight neck. Think in terms of knowing chamber neck diameter. The "tight neck" allows you to clean up the imperfections of the factory brass.

quote:

Originally posted by Buliwyf:
Don't think in terms of tight neck. Think in terms of knowing chamber neck diameter. The "tight neck" allows you to clean up the imperfections of the factory brass.

Match grade chamber with tight neck .335 (standard neck is .346). This is what is being considered for my rifle. It is still up in the air on wether I will do it or go with a standard chambering

I think a tight neck will help accuracy if this is a true bench rifle. That said I have owned exactly one rifle with a tight neck and will NEVER own another.

I hate turning necks and I hate the idea if one that isn't turned gets shot in the rifle something VERY bad could happen.

Terry

Not knowing who is doing the work I have to encourage chambering,throat and crown all must be dead nuts on with the center of the bore.
So starting from that point accuracy comes from
the play one has when the bullet leaves the case and engauges the rifling. So you can have all kinds of neck diameters. The smaller is better and your benchrest neck will have a neck very tight so that they must turn the case neck so both match each other exactly. Note: one must have a slight oversize case to neck so the case can expand and let the bullet loose. Mine are .003 for case swell. The critical issue however is the throat or that area in front of the case neck that holds the bullet prior to firing. All of mine are .0002-.0003 over bullet diameter. I also cut the throat length according to what bullet I am going to shoot and the depth or lack there of based on the bullet length. As a comparison, a standard factory barrel chamber will be 4-6 times greater than the above mentioned numbers and nothing in the rules say that the chamber must be concentric with the bore.
Hope this helps and good luck.

Neal

My 308 tight neck rifle has a neck dia of .330 and I turn neck to .010. I have some IMI 308 brass that has neck thickness .015 to .016, Laupa is .014 to .015. I would thing any tight neck 308 with the right twist and bullet combination should be able to groups less than 1/2" provide the shooter can shoot those size groups.

If it was my project, I would settle on which brass to use - e.g. Lapua. I would then establish the loaded neck diameter of that brass. I would have a reamer cut which produced a chamber inside neck diameter .002" over loaded round neck diameter. That would mean you will not HAVE to turn, unless you want to. Should you decide turning is a fun thing to do, you could then set up for a skim turn of .001". That will just clean off any potential high spots on your case necks. Yet, you'd still work your brass as little as possible.

Personally, I would not bother to turn. Instead, I'd sort my brass for neck wall variation. .5 MOA (even at ranges beyond 100 yds) should be achievable without turning. If not, the reamer setup described above will allow a minimal turn.

Neck turning is still widely used in competitive BR. But when you look closer, you'll see a lot of people moving to either less turning, or to no-turn chambers. Brass has become a lot better these days, and that takes away part of the incentive to turn.

- mike

Mho, I have settled on Nosler Brass, but do have a hundred or so new Lapua around from my other .308 Win

Ncooper, I have a local gunsmith doing the work. He has been in business for some time ( 35 yrs) and I have seen alot of his benchrest work.

Tc1, Point taken ...I hung your warning on the wall here so as not to forget it as decision time nears.

Guys I posted my project below. You will see it is not a benchrest rifle, but was meant to be a paper punching fun gun that my nephews can hunt deer with.

Action: Nesika Bay “T†1.350 Diameter with the following options: Right bolt, Right port, Repeater cut, Nesika recoil plate, Mag box, Mag spring, Follower, Plunger Ejector, Drop bolt

SS Trigger Guard

Barrel: Shilen Select Match SS #5 Silhouette #5 1/2 weight. 25†length, 10 twist, Match 11 degree crown, Match grade chamber with tight neck .335 (standard neck is .346).

Trigger: Jewell

Stock: High Tech Specialities, Pillar bedded, Classic sporter style, with Marsh Paint , Pachmayr Decellerator Pad , Nickle Uncle Mikes studs and Swivle

Scope / Mounts: Nikon Titanium 5.5 16 AO, Talley SS Rings and SS Talley bases.

Cornerstone a number of years back I had the good folks at Hart Rifle Barrels in NY do a (308Sako) and the reamer was a .340 neck. This was ideal to use without turning and still not overworking the brass. Most factory rounds and reload brass tend to fall between .338 and .334 on the thin side in my experience.

Now for all that is worth, my Remington VSSF .308 Win with the sloppy chamber will hold under 1/2 MOA when I do.

want a cheap test...? Buy some good quality 30-06 brass, like Norma or RWS and just slap the Imperial Sizing Die Wax to it. Ease it into the FL die and make some "fat neck" cases. You should add .003-.006" to loaded diameter that way. I did this on some rifle tests for Precision Shooting Magazine about fifteen years ago. Made 22-250 out of 250 Savage and 308W. Even made six out of 30-06 military stuff, LC match. Made 308 carefully, then 7-08, then 250 Savage, then the 22-250. Saw nearly 1/4" at 100yds reduction is size with the military cases, shooting one case and reloading it at the range.

Rich
DRSS

Rich
How far away from Jordan Valey are you at?

In additon to the above information- I went the anal benchrest route many years ago. Got tired of everything and quit making chambers so as requiring me to turn them. I do not own a gun today that shoots over a half inch and I do not turn brass any more.

Just like what Ed is building, nice light skinny rifle barrels and a proper chambering job and they shoot into one hole. Just heat up faster which is not a point for hunting.
Neal

quote:

Originally posted by CORNERSTONE:
What type of improvement should a person hope to gain in accuracy by going to a tight necked chamber and turning necks. I am in the late stages of a custom .308 win and am wondering if it will be worth going away from a standard chamber. I am hopeing for 1/2 moa @ 100.

One of the best shooting rifles I've ever had (& I've had a bunch) is a 222 with a tight neck match chamber I turn the necks once inside after sizing but not expanding and that's it. No trouble at all (Forster turning tool) and you only do it once about every 10 firings. By then it's probably time to get new cases anyway. It's my coyote gun.

ncooper,

about an hour, give or take. I am in Nampa.

Rich
DRSS

quote:

Originally posted by ncooper:
Just like what Ed is building, nice light skinny rifle barrels and a proper chambering job and they shoot into one hole. Just heat up faster which is not a point for hunting.
Neal

Mine all shoot into one hole too... on the first shot . I hear a lot of these tiny groups with pencil barrels but they never seem to be at the range when I am ...

quote:

Originally posted by brayhaven:

quote:

Originally posted by ncooper:
Just like what Ed is building, nice light skinny rifle barrels and a proper chambering job and they shoot into one hole. Just heat up faster which is not a point for hunting.
Neal

Mine all shoot into one hole too... on the first shot . I hear a lot of these tiny groups with pencil barrels but they never seem to be at the range when I am ...

#5 Silhouette #5 1/2 weight is not what I would consider a light weight or skinny barrel, but it is all I would want to carry around

The older I get the heavier things seam, but I was wanting something in the light varmit range to help with accuracy.