284 Shehane Neck Turning Question

[Craig McGowan]

Hello everyone,

I have been running a 284 Shehane since the beginning of the year. I had turned the necks on the Lapua cases (0.313 neck chamber) to 0.0125" which means I have about 4 thou expansion from a seated bullet.

Unfortunately I must have done something with the last lot of 60 cases that I have turned and the neck expansion has gone out to 5 thou. Apart from working the brass a bit more, does anyone know if accuracy is decreased with a greater neck expansion?

Regards

Craig

[ned kelly]

G'day Craig,
I doubt it, I NT W-W 22-250 cases for a standard factory Rem VS when I first started BR in the mid 90's and it shot less than .25moa with Berger 52gn Match bullets.
It would have had heaps of expansion by comparison your rifle.
Essentially and I think critically, provided ALL the cases measure the same neck wall thickness, shoot them until they are stuffed, and go turn some more.
There is a common line of thinking that fresh brass is also very important but it really comes down to the grip each case has on the bullet and with time this can vary.
Probably the only way to be truly sure is to measure the seating force for each round and batch them accordingly and load them just before use. This could be done by seating them long and reseating just prior to using them.
Personally, I just resize to 2 thou less than the loaded diameter and them seat 10 thou longer. This allows the bullet to align with the bore as the bolt closes and also the bullet WILL push back into the case for consistent neck tension AND consistent placement against the rifling which also compensates for wear during several days of shooting.
At the end of the day, a very good waterline is all I'm looking for, then finding time to practice in all weather is much more important for the scoreboard when the shooting is done.
Hope this helps
Cheerio Ned

[AlanF]

...does anyone know if accuracy is decreased with a greater neck expansion?

Accuracy might actually be increased! My understanding of neck clearance is that its a compromise between ensuring the chambered neck is not touching the sides, or on the other hand not over-working the brass. The first is an accuracy issue (preventing pressure spikes) and the second is not - its more of a brass life issue. My very first F-Open barrel was chambered for no turn 6.5-284. The Lapua brass at that time had quite bad neck thickness variation, so I tried turning it down by about 0.002", which would have given neck clearance of about 0.008"! That ammunition was very accurate. The only drawback was that I noticed more carbon on the outside of the neck after firing - and this tended to increase with the age of the brass - I didn't (still don't) anneal the necks. If you're only talking about 0.005" clearance, I wouldn't give it another thought, except as Ned suggests, keep it separate.

[pjifl]

I have seen neck turned brass with larger than intended clearance still shoot very well.

I think a few side benefits of thinner necks after turning is a lighter and more consistent neck tension and often better runout figures and feel that these may be at least as important.

I usually collet die when reloading so a bit of neck thickness variation is less important.

Peter Smith.

[williada]

Craig,

I am with Ned and Alan on this one. Did the experiment and used in them competition for a year after thinning neck wall thickness down from .014" to a minimum of .008". The best performers were the latter in the same chamber. Certainly no carbon problems. Some cases were culled after awhile, but generally lasted because I anneal. David.

[Craig McGowan]

Thanks everyone for your time.

I will turn down the other 40 in the batch to make a neat 100 and keep them seperate. I will see how it goes.


Just another question, with regards to turning necks. I have a club member who has decided to ream the insides of his necks instead of turning them down. Now he has access to some very top shelf machines and tooling to do it accuratly. His theory is that the outside of the chamber is smooth and any inconsistency in the brass will be moved to the inside after the first firing. Therefore by reaming the inside to get to his desired thickness provides a more accurate and consistent neck thickness.

My thought on this was, if it was better then the Benchrest guys and girls would be doing it, or would have tried it.

Any other thoughts?


Regards

Craig.

[williada]

Craig,

For what it’s worth, I neck size, then use a Sinclair mandrel to size the internal. Because I turn my necks in a lathe, I made a case holder out of brass which holds the case in the chuck. Then in my tailstock I attach an old RCBS case turner which cuts internally and externally at the same time and does not bog because I pre-sized with the Sinclair mandrel and use plenty of lube. On the odd occasion some internal fine scrapings appear. The main purpose of the RCBS tool is that it supports the neck for alignment purposes while turning the outside with the additional benefit of tidying up the inside. I then do a final external cut with a Sinclair neck turning tool that is piloted, with plenty of lubricant, holding by hand while spinning in the lathe. This a very fine cut. Then I re-neck size and use another mandrel to iron out any internal variances.
The danger with an internal ream by itself, is that you can roughen the internals too much due to variances of case hardness and sometimes the tool bogs on soft stuff and if done by hand it may have alignment issues which could lead to run out problems. It is vital to have a smooth internal surface for consistent neck tension.

Because brass is so malleable, I feel the brass flow can be ironed out with traditional methods which are quicker. So its not that big a deal, its depends on how much time you have and its so easy to bugger up a smooth natural case finish on the inside despite good equipment. That issue is more important than the brass flow.

David.

[Brad Y]

Craig

I have a 318nk chamber shehane and with a loaded round on necked up lapua brass .313 from my measurements, I have 5 thou clearance. For smaller cals I like having a tighter clearance (6 dasher I run 2-3 thou, 260 improved 4 thou). In the new maddco there has been no drama so far with accuracy. The old barrel was too hard to tell as it wasnt consistant with anything. Have seen comments on overseas forums about tight clearances suspected of causing producing vertical problems.

I also have a wilson case trimmer setup and the attachments to inside ream any donuts out. What I did was size with an intermediate bushing (315 I think) to get as much of the donut below the diameter of the cutter, then carefully cut out the material. I now do same as Alan and size the top half of the neck only to reduce any further interruption from the donut formed. I havent re measured to see if there has been a build up of donut material again but with a 220 freebore and trying to jump VLD's, I do find it hard to seat the projectile right down so possibly there is another donut.

Have been in discussion with Lee in regard to getting a collet die made up custom for what I want to do. But then I figured would probably want to run say a .315nk chamber so some cleanup is required to get the outsides all even and a slight cut into the shoulder to help deal with the donut after a few firings. Then I figured that after trimming, there is potential for the donut to keep growing and this would have to be done regularly- maybe passing the case over the expander mandrel to get the donut back onto the outside, then turn it off again.

In the end Ive come to the conclusion that I will keep to the way that Ive been doing it by sizing the top half of the neck. Much more user friendly. If Alans results are anything to go by, it works well. FWIW I dont anneal either but I do plan to experiment with it at some stage in my 1000yd BR gun to see if it helps tighten things up. If so I may apply it to a batch of cases and prepare them for long range shooting only.

[williada]

Annealing is another extra process you can master if you have time and it is not super critical. For me, I use it in case preparation after the case has its first 4 firings. This is when I do the major work on a case. Its the cases first service, like tightening the head bolts on a new motor before I put it to work. As I trim, turn both internal an external surfaces of the neck, I feel its important to have the same neck hardness to get consistency and ease of operation when turning off the brass. The use of the mandrel a couple of times in the process also work hardens the brass consistently and diminishes neck tension issues that sometimes can be associated with newly annealed brass.

[Craig McGowan]

David,

I started annealing about a month ago as I noticed some brass that had been fired about 15 times was becoming "less workable".

It has taken a bit to sort out a system but now I have a "app" on my ipad that is like a interval exercise timer that I have set up for the required time for the annealing.

I have also done what you said about the working the brass after annealing, to get more consistent next tension and I have to say, to me, it now feels more consistent now when seating projectiles using a Wilson arbor press.

Regards.

Craig.

[williada]

Craig,

Many people use every week as a championship and burn themselves out with reloading, looking at every nuance and doing everything at once, instead of using the weekly shoots for sorting components for bigger things to come in the longer timeframe. I sort bullets and keep good ones aside, I store cases based on how many times I have shot them, etc. So over time, I have ready made piles to go. I take the view, that you use club shoots as preparation, so all your components are cherry ripe and your testing is completed before a big event. In the final preparation, with the best ammo, retune your rifle. Unlike a good barrel you can set aside, the brass naturally hardens over time but a month or two won’t matter, particularly if it’s kept in an air tight container. This is another reason why annealing is relevant.

In terms of ammo, Ned has also made some astute observations here and on other posts that are pertinent to this thread. Firstly, he conditions his cases with lighter loads for a couple of rounds and this too work hardens the brass slowly and protects those valuable primer pockets (that I have been testing lately with the wife) before giving it full bottle. I know that a lot of people who fire-form, to make their own brass, give it full bottle on a jam setting to expand the brass evenly. This is ruinous to primer pockets if you want extended case life. You will be forced to select primers that are a tighter fit and some are, but they might not necessarily give the best ignition as you will see in a primer test.

The other thing I do, and mentioned before, and Ned has highlighted it again, is that if you have loaded and stored ammunition a bond between the case and the projectile forms through electrolysis as they are dissimilar metals. This is separate from the natural hardening of brass over time. This will cause neck tension to vary from your test ammo. Whether you soft load like Ned on a jam or the night before the big shoot, do a further seating to correct depth and you will break any bond caused by electrolysis starting so your loads will duplicate test results.

Peter also made a good point about the thinner necks, which I also endorse, about giving better neck tension and run out and if I was to re-chamber I would reduce the neck diameter on the reamer to be a closer fit with the brass to save overworking it. Brad is fairly on the mark with his figures; and the verticals related to tight necks, is exactly what I meant by having no carbon issues with the looser neck.

I am glad that you can feel the difference in seating after annealing by using a mandrel to work harden the brass a bit. Brass and bullet jackets are sensitive stuff and bullets also harden over time and are best used while fresh so they are a better interference fit for engraving forces to work on a sound gas seal. We know of many situations where the manufacturers have been blamed for hard jackets. Maybe the jackets were left in the bin too long after they were initially annealed. Proper storage as you do with your powder is important.

Cheers.

[Craig McGowan]

Hi Guys,

Sorry to bring this up again, but I am having a problem that is doing my head in......

I have a K&M neck tuner, and I am struggling to get it to give consistent neck turning. To the point that I am seeing 1/2 thou difference in case thickness when checking with a mitatoyo case thickness gauge.

My procedure is run the case through the K&M expander then onto the shell holder. I use redding sizing lube and only turn by hand, no drill.

I have noticed that the cases have a little wiggle on the mandrel when turning, so I put the shell holder in a vice and turned the cutter to keep everything a straight as possible, but this did not make any difference. Please tell me if I am wrong, but I would have thought that once you have a case on the mandrel, then the cutter would "pin" the case to the mandrel and cut to the required thickness.

I am slowly tearing out what hair I have left, and any help is greatly appreciated.


Also a little further information. The neck turning is being done after fire forming and ultra sonic cleaning.

[johnk]

Craig,

Stuart Elliott reckons 180 rpm is the speed to turn necks, so I use one of my cordless drills that runs around those revs.

I've found that the replacement carbide cutters K & M offers do a cleaner cut than the HSS ones.

Apart from lubing with Ideal lube, I store my cutter in a bath of water between cases. I use a Berger 100 round bullet box & fill it sufficient to have the mandrel & cutter covered when the adjustment nut is hooked over the edge of the box. The water acts as a coolant & lube, as I see it.

I also use a K & M Ergo holder (heat sink). Both the replacement parts can be sourced through BRT.

Cheers, John

[Craig McGowan]

Thanks John,

Just went down and tried it and it is much better now. I was doing it originally with the drill, but for reasons I cannot think of I decided to go back to doing by hand. Now I think of it this is when my problems started.........

[Cameron Mc]

Thanks John,

Just went down and tried it and it is much better now. I was doing it originally with the drill, but for reasons I cannot think of I decided to go back to doing by hand. Now I think of it this is when my problems started.........

Geez Craig, wait till you get to my age

Cam