[Jaywalker]

As we neck-size rifle cartridges repeatedly, the cases stretch, even though not as fast as when we full-length resize. We don't want to either FL-resize too much (too much re-working of the case and resultant shortening the case life) or to do it too little (hard to chamber and excess lug/receiver wear leading to excess headspace issues, maybe).

How do you decide when to bump the shoulder back?

Jaywalker

[Jim Watson]

When the increase in effort to chamber a round is noticeably greater.

Actually, does neck sizing really add to the life of a case? I don't think I have ever had a bottleneck rifle case wear out by anything BUT a neck split, even if routinely full length sized.

[Black Snowman]

Jim, my understanding is it's for going for that last tiny bit of consistancy, not for case life. With the case fire-formed to the chamber then it won't move when fired because only the neck has anywhere to move to. The rest of the case has already expanded. At least that's how it was explained to me.

[ocabj]

I full length size for my Savage 10FP in .308 now, but I set my die up to set the shoulder back just enough so that when I chamber the brass, I can feel some tension. I look to get enough tension such that I can tell when there's a round in the chamber and when there isn't when I swing the bolt handle up and down.

After about 3-4 firings and neck sizes, the shoulder will be pretty far forward. Grab the fired brass and set the full length die and resize one. Check in the chamber and adjust the die as necessary, then resize another piece of brass and try to chamber. Repeat until you find a good die setting.

[Jim Watson]

Snowman, I didn't say it wasn't for consistency, JAY said it was for brass life and I was concentrating on that.

Me?
I neck size for bolt actions because it MIGHT help accuracy but mostly because I don't have to grease cases for it. I'm lazy.

I am mostly shooting BPCR Silhouette with a Winchester Single Shot (Highwall) these days. Talk about tedious loading. I full length size the .38-55s for it because it doesn't have the extraction power of a bolt. Slhouette is shot on a time limit and I don't want to have to wrestle a tight case out of the chamber while I should be blow tubing (to keep BP fouling soft) and checking the wind. They make little rammers to cram tight rounds into a single shot rifle and the guys who neck size or don't size need one every once in a while even with straight cases. I have one, but have never needed it and would consider it a failure if I did.

[Jaywalker]

My reason for neck-sizing is primarily laziness, too, but also for the accuracy. Also, it seems reasonable that less working of the case means longer case life, but I have no evidence to support it, and as Jim pointed out, it may make no practicable difference.

A recent small kb (pierced primer and frozen bolt) led me to have the chamber of my Ruger M77 MkII checked for headspace, and the results weren't great. After approximately 500 rounds through it, the bolt would close on the "No-Go" gauge (barely), but would not not close on the Field gauge. It's safe to shoot, but I got to wondering about the cause of the incipient headspace problem and its cause after so few rounds. The only thing that immediately sprang to mind was that the hard-chambering for a couple of reasons caused me to wear away the bolt lugs and receiver lug recesses. I could be wrong about this, however.

Not all of the hard-chambering was a result of case stretch, though. Some of it was me seating the bullet out close to, and in some cases touching the lands, in the search for that last 0.1" of accuracy. If I'm right about the wearing of lugs and recesses, though, there have been a lot more than 500 rounds through the action; I may have turned the bolt on 2,000 rounds, not just the 500 that I actually fired. If that's true, then I may have to redefine rifle wear - my wife will be delighted to hear that I'll need 2 - 3 new rifles each year!:D

So, in answer to my question, Jim bumps the shoulder when effort increases. Ocabj, do I understand that you do it on a schedule, like every four or so neck sizings?

Jaywalker

[JuniorG]

I have always full length sized NEW brass for the 1st loading. After the 1st ( fire forming) shot I set my die up so it just squeezes the mouth and appx. 1/2 the neck.
After the 2nd firing I remeasure my brass for length and usually get an average measurement that is closer to the max length for that given cartridge, this is the length i keep my cases trimmed at. By keeping my cases consistently trimmed to this length i have never had any problem with chambering rounds.

As far as brass life goes? My limited experience has taught me that brass life is based more on how hot a round is loaded than how many times it is sized.
I have 270 win. brass that has been loaded 10+ times with moderatly charged 'paper loads' and see no signs of wearing out, on the other hand I've loaded some full throttle 220 Swift cases that neck split on the 3rd shot. Then again brass gets brittle after getting real hot and being worked alot and a person can anneal thier brass if they so desire, personally I've never found a reason to do this.

I've never had any luck partial sizing straight wall cases.

[Black Snowman]

Sorry Jim, didn't mean to come off negative if I did. I have heard many rumors on neck sizing. Longer brass life because you're not resizing the whole thing and don't need to trim, shorter case life because it's harder on the neck (something I heard but can't figure out why that would be the case). But universally I've heard people say it should improve accuracy if done right, which is why I brought it up.

I don't have to grease cases for it.

This seems to me to be the best reason for neck sizing ;)

[Jaywalker]

Black Snowman: Longer brass life because you're not resizing the whole thing and don't need to trim, shorter case life because it's harder on the neck (something I heard but can't figure out why that would be the case).
My theory is that the FL die squeezes waaay down then the neck expander brings it waaay back up. The expander plug also stretches the case, adding to its length, and can pull it out of round, since the plug comes out when neither the neck nor the shoulder is in contact with the die.

I've experimented with FL-sizing without the decapper-expander plug, then running the whole thing through my Lee collet neck sizer to decap and resize the neck. Since the neck is so sqeezed, though, the neck die's plug has to work to get into the die; it appears to me I've just substituted unsupported pressure coming out for unsupported pressure going in. I don't think I'll do it again, and that's why I'm searchng for a strategy for when to bump the shoulder.

Jaywalker

[Jaywalker]

Black Snowman: Oops. Did I misread the intent? Do some people think the neck sizing [i]reduces[/ii] case life? If that's what you meant, I don't understand it either.

Tried to edit the previous with this comment, but it won't take.

Jaywalker

[30Cal]

I FL resize every round that I use for highpower rifle competition even if I'm shooting a bolt gun (pretty standard practice). Easy, positive chambering is the watchword for the rapidfire stages. I usually shoot a semi-auto, so case life isn't a concern (I toss them after 5 firings). Also, I buy brass in bulk and it's cheap.

I've seen a couple case head separations due to excess FL resizing after setting the die per mfgr recommendation--my advice is to get a case gage if you're going that route because the factory instructions aren't always a recipe for getting it right. The shoulders on mine were set back about 0.005" more than I would have liked them to be. The Stoney Point gage is nice because it's easier to get good quantitative numbers for both fired and resized cases (my Wilson case gage won't swallow a fired case and is difficult to get measurements off of).

As far as driving the cases out of round, you'd need to take some measurements with a concentricity gage. My dad has done some tinkering around in that area--the reloading press itself seems to be the biggest factor. I wish I had some numbers handy, but I do know that his new Harrell turret press gives him negligible runout whereas his old press gives him a small percentage (in the 5% neighborhood) that would be of concern.

Ty