Excessive chamber neck clearance, how to fix?

[geargnasher]

It took me a long time to find a batch of brass for one of my Model 70, 30-'06s that came close to what I like for loaded chamber neck clearance, and I've about worn it all out.

What I'm dealing with is a .301" bore, .309" groove, and chamber neck right around .342" or a few tenths over. Even with a .312" boolit and brass in the .0145" range, I'm only at .341" loaded diameter. Most of my brass falls in the .0140" range, some thinner, and I'd MUCH prefer .311" or even .310" boolits. But a .310" boolit would require .0155"-thick necks to get to the .0006-8" neck clearance nirvana-land, and such is difficult to find.

Any tips, tricks, something I missed? Does anyone make un-necked basic brass with the .30-'06 head and body contour that might have some hope of sizing down thicker and maybe even have enough left to ream?

Gear

[frkelly74]

I get the impression that military brass is some times thicker. Lc 69 seems thicker than winchester commercial brass. That is my eyeball impression with no measurements to back it up.

[frkelly74]

I measured some of my loaded rounds LC69 and Winchester brass. they are both loaded with the lee 312-160 boolit sized at .311. The win brass measured .336 and the LC 69 varied from .337 to .339. Not as much difference as I was thinking it was.

[oneokie]

Neck down some 35 whelen brass? Set the barrel back and rechamber?

[Gtek]

I know it is not the easy way out, how about a new tube? Push feed or controlled? I have a few take offs laying around. Winnies have been a mixed bag swapping barrels because of the timing, but to far on is a good thing. You can re-cut chamber for a nice tight .002". Gtek

[btroj]

I read an article somewhere, Precision Shooting I think, where someone tested this. The guy made 22-250 cases from a case like 30-06 then neck turned the cases to get a snug neck fit in the chamber. It made absolutely no difference.
If you are seating the bullet into the lands does the neck diameter make a difference in a sporter type rifle? If you speaking of a true BR class rifle then it would be important but does it make a difference in this rifle?

[HangFireW8]

Gear,

Here's a link for Basic Brass. There is no guarantee it will be thick enough when necked down:
http://www.z-hat.com/Cylinder.htm

I'm totally with you on the advantages of a close-fitting neck in a bottleneck rifle chamber. However there are ways to compensate if you just don't have that.

One advantage is the accuracy of a self-centering cartridge. This can also be done by sizing so that the cone of the cartridge shoulder self-centers in the cone of the chamber, or as btroj said, seat the boolit into the lands.

Another advantage is case life. This can be extended by moderate and occasional case annealing. I know on another thread about revolver cases many don't bother with annealing, but if you have special brass reserved for your high power rifle, that's another matter altogether.

Minimising resizing stress by sizing to just below desired diameter and then minimal expanding is another tactic that will extend case life.

You probably know all of these tricks, but your thinking is stuck on the rifle not being what you want it to be. It's just not convenient to have one rifle that needs special treatment (at least, special beyond finding special brass for it).

I understand the frustation of a gun that just isn't what you want it to be. I have an FN 30-06 that just wouldn't shoot accurately. I glass bedded it, tried every reloading trick, nothing worked. It stayed at the back of the safe for a few years. It was only when I started casting 3.5 years ago that I slugged the bore and discovered it had a .3100" bore. Now it has its own set of brass and loads that work great in it, along with a j-word load that I discovered along the way when just burning up old reloads. That would have never happened if I hadn't had it at the range with cast boolit loads. I've come to accept it for what it is, but accepting it is a lot easier now that I have something accurate I can shoot out of it.

It basically comes down to two options, change the gun or change your preferred habits. If it is a pre-'68 Winchester, you may want to accept it as it is, or just trade it off for something more to your liking. If it's a modern push-feed, it already self-centers its cartridges. If it's a modern claw action type, there's not so much harm to the value in rebarreling, but is it really worth it?

HF

[runfiverun]

in many of my rifles i don't use an m-die.
okay,in none of my rifles. i don't even own one.
what i do is to bump the case mouth with the expander ball from the next size up.
i leave a little bit of flare on the mouth so the case slides down the chamber neck.
if the rifle won't feed the round that way for some reason, i go the other way and leave the base of the neck expanded.

your best bet might be to neck down some 35 whelen cases.
or the old make some 7.7 brass from 0-6 trick and wrap a piece of tape around the neck.

[geargnasher]

Thanks for all the replies, and the link to the basic brass. This particular rifle is a 2006-ish production CRF "Classic Sporter", and the best brass I found for it was some old Lake City stuff. I only FL sized once, during prep. After that the brass only sees a Lee Collet die and a Lyman "M" 30 die, essentally it only flares the mouth with a piloted spud since I turn back the Lee die to only size enough to grip the boolits. I only remove enough flare with the crimp shoulder to make it chamber, usually the mouth is the same diameter for a slight interference fit.

The weak link here is having 2-2.5 thousandths clearance all the way around the neck. There is a very noticeable difference in accuracy with this rifle and my other, push-feed Winchester '06 with typical factory brass, and it all can be traced back to neck fit. I actually tried using thin, clear packaging tape once before, it works great for one shot, and after about three rounds of heat it starts coming off in the gun, what a mess.

Gear

[felix]

It's the diameter of both the freebore and throat. "Tight neck" guns imply tight throat (including freebore, if any). Problems come with re-throating anything without regard for where the case is stationary. The rate and diameter of stepping either down (or up by accident) to meet the lands after the case ends is the typical accuracy killer location. ... felix

[rond]

The weak link here is having 2-2.5 thousandths clearance all the way around the neck. There is a very noticeable difference in accuracy with this rifle and my other, push-feed Winchester '06 with typical factory brass, and it all can be traced back to neck fit. I actually tried using thin, clear packaging tape once before, it works great for one shot, and after about three rounds of heat it starts coming off in the gun, what a mess.

Gear[/QUOTE]

Have you tried teflon plumber's tape? Cut off excess with a razor blade or knife.

[wallenba]

I have no experience with a problem of this type Gear, but...the first thing that came to mind was a paper patch around the neck. Could this be feasable? or would it just turn to ash?
It might warrant a look see just for giggles. Could it do harm? Maybe a wrap of teflon tape?

[HangFireW8]

I only remove enough flare with the crimp shoulder to make it chamber, usually the mouth is the same diameter for a slight interference fit.

The weak link here is having 2-2.5 thousandths clearance all the way around the neck.

Gear,

If the cartridge mouth is centered by its flare in the chamber neck, how do you explain the lower accuracy? The throat or freebore could make the difference, as Felix explained it, if so I don't see how thicker brass solves the problem.

If the problem is the length of the neck is holding the entire cartridge straight only with thicker brass, then you have to look at why the back of the cartridge is allowed to sit so crooked. It may be a bolt face issue or bolt/barrel alignment problem, such as a chamber reamed off-center.

HF

[geargnasher]

This rifle has about 20 thousandths freebore at .3115", then the throat tapers down from that into the rifling. The throat is not and has not been the issue with this barrel as one might think, the grossly oversized chamber neck is the only real issue. Well, that and the oversized bore and groove. Thicker necks makes all the difference on target.

Hangfire, the reason flaring the neck or using Run's trick of partial sizing and leaving a fireformed ring at the base of the neck doesn't work with thin brass in this gun is that the base can bend sideways under pressure along with the case neck as the case neck expands. Perhaps the base of the boolit "rivets" our swells some along with the neck, but whatever it's doing it's causing problems. A sized boolit literally rattles around inside a fireformed case neck. This causes some boolit deformation that is affecting my accuracy.

Tape helps, but isn't the solution, I was just hoping there was something I hadn't thought of to help make this work. I enjoy correcting rifle issues with just the ammo, but one day I might throw in the towel and get a real barrel for this rifle.

I guess I could just shoot .3135" boolits in it! Never tried that, but maybe with the right alloy and a Loverin boolit it wouldn't be too terrible. Gas checks might be an issue, though.

Gear