Home Forums Reloading Big Game Rifles Can I neck size with a full lenght size die?

I have an 7mm mag I am trying to load some ammo for. I will only be using cases that were fired from my gun. I have an RCBS full lenght size die. My question is can I use this die to neck size the brass only? If so how do I set it? Will neck sizing improve my accuracy?

Probably not but there are many who say, "Yes, just put a nickle - etc - between the sizer and shell holder", etc.

Consider that neck sizing means just that, exactly that and no more. Any die that contacts the case wall will change the case body and that will move the shoulder forward some amount..and that ain't neck sizing.

Cases with a lot of body taper; 22 Hornet, .30-30, .303, etc. can often be neck sized by backing the die out a little. But the straighter the case walls the less likely it is to work. And the actual dimensions of your chamber and die come into play; a smallish chamber and a largish die is most likely to work but the reverse isn't true.

Neck sizing is NOT likely to make a significant difference in your accuracy. It's only a tweak, not a quantum change so the results will be small if visible at all.

Neck sizing does have some helpful effects on case life IF it's done to best effect. Instead of cases dying from body splits they will die from neck splits! But two things can be done to increase neck life; neck annealing and correctly using either a bushing neck die OR the Lee Collet Neck die.

I prefer the Lee collet neck die because it works necks the absolute minimum and doesn't care about thickness variations. It works on a wholly different principal from all others, it isn't just a straight forward "push it in - pull it out" thing. Therefore, it requires a learning process but it's worth the effort. (Anyone who is a mechanical klutz or doesn't want to take the time to learn to use it correctly should stick to more conventional neck sizers.)

Are you presently setting your FL die to bump the shoulder only .002" or so? If not, then that's definitely something you should try.

How would I do that? Should I pull the handle all the way down and then screw the die in until it touches the case and then measure the case to see if it moves it .002"?

I'm at work so I can't type too much here.

Let me try to short cut things. How do you set up your die now?

I have had very good luck with the Lee Collet for my .30-06 and I am a mechanical klutz. I load cases ten times and then retire them. I have never had any chambering (or any other) problems within that framework. I appreciate not having to mess with lubing the cases (and cleaning the lube off). It also has freed me from trying to figure out exactly whatinhell "bumping" the shoulder is and how to go about only bumping it rather than going too light and just "tapping" it or getting heavy-handed and "bashing" it. If you do not want to spend money on a new die, there are those who worship the god "partial full-length sizing" and proclaim its superiority to neck-sizing.

I resized some once fired that I bought online. I set it up the way that RCBS said in the instructions. I lowered the press handle all the way down and screwed the die in until it touched. Then I screwed it in 1/4 turn more and then locked it in place and resised the brass. I have 120 rounds that were fired out of my gun, and I was wanting to try to bump it back .002" and see if it would increase accuracy or not.

Do you have one of the gadgets that you use with calipers to measure case head to shoulder length?

I have an RCBS presicion micrometer to measure the cases.

Deprime but don't resize a piece of your fired brass. Measure the head to shoulder distance. You may want to do this with several pieces of brass to see how consistent your number is.

Remove the expander ball assembly from the die. Put the die in the press and set it to touch the shell holder when the ram is up, the back the die out a half turn. Lube, size, wipe and measure a case. It probably won't be the right number. Turn the die in a small increment and lube, size, wipe and measure. Repeat until you have achieved the amount of bump you want. When the bump on that case reads right you aren't quite done. A case sized in one pass may not move as much as the one you just put through several die passes. So take another case and size/measure. If it's OK then you're done, otherwise you'll need to turn the die in a little more.

Reinstall the expander and you're off to the races.

Remember the threads on the die are 14 TPI. So a full turn of the die moves it 1/14 = .071". You can use fractions of this figure to determine how much you're moving the die. For example an eighth turn is 1/8 * 1/14 = .009". Note also that die movement doesn't necessarily correspond to brass movement because brass springs back somewhat.

There's definitely some cut and try involved, but really if I was there to show you we would have it up and running in less time than it took me to type this.

The way you have your die set up you are over working your brass which leads to short case life. Also the cartridge will be seating on the belt when the round is in battery which is not conductive to your best accuracy.
Without buying more gadgets, you might want to try this: Find a flat washer or a piece of flat stock about the thickness of a dime and make a hole in it big enough to fit around the threaded portion of your die. Put this around the die between the lock nut and the top of the press and resize your cases. You can tell by the resizing oil that is displaced that the shoulders are not touched. This is called "partial full length resizing". Using this method, your cartridges seat on the shoulders which means they are worked less when you resize. And your accuracy should be better. Over a period of time, your cases may become hard to chamber. Then remove the washer, full length resize the case, and start over. This is the method I have used for a lot of years and it works for me. If your accuracy increase is significant, you may decide to invest in a neck die but it is not the straight road to Jeruselum that folks would have you believe.

I neck size with a bushing die until the cases get tight to chamber then bump the shoulder back 1-2 thousants. Bumping the shoulder lets you chamber the case easier but I haven't seen it make any difference in accuracy. With belted mags you don't want to size the case to new dimentions after any firings. Measuring the shoulder is the way to be sure of your sizing procedure.Rick.

Would it be easier to just buy a neck sizer die? They are only 25 dollers from midway. Will I gain much accuracy from neck sizing verses full lenght sizing?

Again, I'll put forth the Lee Collet. You may or may not gain in accuracy, but you certainly gain in ease of resizing. As I said, within my self-imposed limit of 10 loads, I have never had a need to completely resize. Of course, this is just my experience.

To be clear, neck sizing and what I described are two different things. What I described is full length sizing, but "just enough" as opposed to producing "like new" case dimensions. It allows for smooth and easy chambering, consistent fit of the brass to the chamber from loading to loading, and doesn't excessively work the brass.

Neck sizing does not necessarily provide an accuracy increase. If you do want to neck size I'd recommend staying away from conventional neck dies. The Lee collet die and Redding bushing die are better ways to go.

1. Put the Shell Holder in the press and raise the ram.

2. Screw the Full Length(FL) Die into the press so it is about a "nickles thickness" above the Shell Holder.

3. Lube a "Fired" case (walls and inside the neck) and size it.

4. Remove the Lube and try closing the bolt on it in the chamber.

5. If the bolt closes with no resistance, screw the FL Die into the press about 1/8-1/4 turn and repeat steps 3 & 4.

6. As you feel the resistance begin, slow down how much you screw the FL Die into the press so you are at about 1/16 of a turn, or "Fine Tuning". At some point you will not be able to close the bolt and you are extremely close to having the FL Die in the proper position.

NOTE: The reason for this is because the FL Die has begun Resizing the Case-walls down to the Pressure Ring. As it does so, the Case-body lengthens slightly which in turn moves the Case-shoulder slightly forward. Then as the "Fine Tuning" continues the Case-shoulder makes contact with the FL Die and is moved slightly reward(or slightly shortens the Case-head to Case-shoulder dimension).

7. Stop when there is a slight bit of resistance when closing the bolt on the empty case. You now have a "slight crush fit" for the case in that specific chamber, or Zero Headspace.

8. Screw the die in just enough to eliminate the stiff bolt and "Crush" fit. That should be about .001-.002 shoulder bump.

Steve, don't you mean unscrew the die until resistance?

Similar to Steve's process, I would suggest you try PFLR or Partial Full Length Resizing.

Take your FL die, screw it in until it contacts the shell holder and unscrew the die one half turn. Lube a fired case, size it, clean the lube off, and chamber it in the rifle. If the bolt does not close or closes very stiff, turn the die in 1/16-1/8 of a turn and repeat the process until you have a snug bolt close. Not hard to close the bolt, but a alittle resistance.

That process will give you much longer case life than FLRing.

It's a very similar process to using a neck die as the brass will be more of a custom fit to your chamber. When I neck size brass, I eventually have to slightly bump the shoulder back with a Redding body die after a few firings, that is essentially PFLRing as well.

Good Luck

loder

No. The die is already set a nickles thickness high from the shell holder. It must be screwed in to come in contact with the shoulder.

Hmm, I must not be following your process. I feel we are talking the same thing(PFLR), just by a slightly different method.

My process is to start when the bolt will not close, and work until it will just close with slight resistance. It works like a champ and gives great case life.

Have a Good One,

loder

Simplify-Lee Collet Die is the answer-as many above are telling you.

Using a full length sizing die to neck size is counter productive as it OVER-WORKS the brass and has the potential to make non-concentric rounds. The expander ball in F/L sizing dies is capable of some horrible things that brass should not be exposed to. They can stretch necks. They can pull the neck off center if the rod that holds the ball is bent. They can trap dirt in the grease on top of the ball and put scratches inside the case neck. Too many reasons NOT to use expander balls. Many positive reasons to use Lee Collet Dies. I own one in every caliber I load for, and recently started buying the LEE Factory Crimp Dies as well. I think LEE has this stuff figured out.

What Reloader said about sizing cases to fit snug in the chamber is great advise as well that should be followed. Once you get a case to fit snugly in your chamber-use the Hornady Lock-N-Load comparator (or similar tool) to measure the case head to shoulder. Then record that measurement and use that as your target measurement (-.002" for springback) when bumping shoulders on brass FOR THAT CHAMBER in the future. Figuring out the measurements may take a little time, but once it's done, it's easy to re-size brass perfectly for your chamber and get the longest case life possible. Also, learn to anneal. The 7 Mag is not friendly to brass and will benefit from annealing.