tight neck reamer? dies?

15 February 2002, 20:53

I have a .308 cal. barrel that I would like to have chambered to a 300WSM. I would like to order a reamer with a tighter neck. I do have the equipment for turning necks and I have been turning necks on my cases for factory chambers. I know I will most likely have to use bushing dies from Redding for a chamber with a tighter neck.
As you can see, I do not really have any experience with this aspect of reloading other than what I have read on these pages.
I would like to learn more about this and any suggestions on what I need to do to "get my ducks in a row" on this would be greatly appreciated.

Daryl

16 February 2002, 05:40

Robgunbuilder

Two schools of thought here. One- some people ,me included, believe that a properly cut chamber in a custom barrel fitted with a tight neck will shoot demonstrably better. This is demonstrably true in a benchrest gun designed to shoot off bags and rests with all the rest of the accuracy goodies. There is a second school of thought that can also prove that in a non-benchrest quality gun the differences are negligible and perhaps even detrimental.
You can get JGS to grind you nearly any dimension neck you want. The way to figure this out is to take bullet diameter (.308) and add to it the neck thickness of the brass you are going to use ( this assumes a fitted neck with brass of appropriate quality), usually about .010X2 to .015X2(depending on the brass) and a clearance factor of about .002 for brass expansion. This for example, would give a .330 neck and JGS would grind you a reamer to produce this neck diameter. You will also need to specify the neck length you want. You are correct in that you then will then need to buy bushing dies of about .326-.327 to properly necksize this thing.You may also have to bump the shoulder of the case to get it to fit-another story. Probably most important you will need to deceide what exact bullet you want to shoot and either have the reamer throat ground for it or buy a separate throater and do it yourself. In the above example you realize that you will have to turn your case necks to .010-.015 thickness and trim to a neck length about.002- .003 short of the chamber neck length. With this done, most likely,factory ammo will not chamber at all, Probably reducing the resale value of your gun. Also remember that with a fitted neck, that if you don't allow for that crutial .001-.002 case expansion on firing that your pressures will skyrocket and perhaps blow primers and even cases.Thus, you will constantly need to watch your necks and deal with trimming them often. remember this is great for a bench gun in 6mmppc for example, but frankly I'm not sure I'd want to live with it or that the accuracy gains would be worth it on a 300WSM.Remember, one reason that people use 6mmPPC brass is beacuse of its uniformity, which probably isn't true for 300WSM brass. In the end if this is what you desire, then go and do it and you will learn alot in the process. Hope this helps-Rob

16 February 2002, 16:24

Atkinson

It is not a good practice to turn cases for a factory chamber, nor is it necessary. All it does is over work your brass. Most dies are within specs for everything except target and some varmint shooting....A lot depends on what the rifle is used for.

I agree that a tight neck is desirable for accuracy and the best accuracy comes from a near 0 tolerance neck..I can reload my 6x45 with out resizing actually, but I have a hand sizer that I had made. It is extremely accurate...

I don't want a tight neck on a big game rifle where function is a more important issue than accuracy and double that on a dangerous game rifle...I want a case to waller in there..but I still want to get inch groups, and that hasn't been a problem.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

16 February 2002, 16:29

Bill Leeper

Daryl,
We got two WSM reamers one standard and one with a .334 neck. The tight neck is for the building of long range target rifles and even then I'm not sure it will make a significant difference in performance but brass will last longer!
I think it is always a good idea to buy the dies first then find out what the neck size is in the die. As long as the chamber neck is larger than the die you will be able to use the standard sizing die.
Of course, not following my own advice, I haven't checked a set of WSM dies yet! We should be fine though since this size seems to work well with most thirties. For the 30/06 improved for instance I cut the chambers with a 334 neck and the dies with a 330. Again for target use of course. Regards, Bill.

16 February 2002, 18:51

<Big50>

My brother had a barrel chambered for 338/378wby with a tight neck, they rented the reamer. He thought he would have to turn the necks, in fact we modified my Forester trimmer/turner for the job. We had to open up a collet and collet holder with a lathe and clearance the cutter head for the shoulder. Turned out it had .005" clearance with factoryloads and handloads. He just has to keep track of the thickness on new brass he gets. So I guess it was a "tighter neck" reamer is all. Holy cow that thing is accurate though, never over .5moa groups except at 1000yds was 9" in ten mph 10 o'clock wind. 32" Pacnor does it and 300gr SMK at 2975fps. Oh I forgot, groups were shot while working up from 115 to 120gr H870 and cleaned between every shot so far while breaking it in also. A good barrel? A tighter chamber? Both? 122gr groups opened up. First powder tested.

My father is rechambering his Rem.700 from 308 to 300WSM also. I would go with a "tighter neck" chamber for better case life too but how much without having to turn necks? These guys will have a better idea than I, my brothers works well with .005" that's all I know and am interested what everyone else has to say about this.

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Brent

[This message has been edited by Big50 (edited 02-16-2002).]