Neck Size vs Full Size - Difference in optimum powder load

Hi Everyone
I used to only full size brass before reloading. I am considering changing to neck sizing. My question is : Will I have to rework all my optimum powder loads for my rifles or will the same amount of powder still produce the same speed and therfor be on the accuracy node.
Anybody outhere had a look at this and have some advice ?

My lone foray into neck resizing was for my 7mm mag. Perhaps because I was using full power loads or it was hot outside or both, but it didn't go well. Opening the bolt after firing required a fair amount of effort. Have not done it since.

But, I have learned to only resize just enough to bump the shoulder back to give about 0.002" of headspace. That's not exactly neck sizing, but it isn't full length resizing either. Whether it be reloads using this type brass or using brand new brass with presumably more headspacing, I've not noticed a difference in accuracy. I can't say that I've taken the time to chrono the two at the same time however.

What Phil just described is partial full length sizing. In my opinion the best way to obtain the most accuracy and repeatability from your handloads and the longest brass life.

When only neck sizing eventually your brass will become too tight for your chamber and the shoulder will needt to be pushed back and you will start the whole process over again, with work hardened brass to boot. Using PFL resizing your brass is the same size every time you fire it after the first fireforming shot. Accuracy is nothing but repeatability.......

To answer your question about changing the load? Maybe? A bit. But with PFL, never again.

I never changed my powder load, but can say without a doubt that my accuracy improved when I started neck sizing. You also don't need to go out an buy a neck sizer. You can simply set your full length die to only size the neck.
Personally I have not found that the cases get too tight for the chamber. I just keep reloading them, and they go.

JTEX said:

What Phil just described is partial full length sizing. In my opinion the best way to obtain the most accuracy and repeatability from your handloads and the longest brass life.

When only neck sizing eventually your brass will become too tight for your chamber and the shoulder will needt to be pushed back and you will start the whole process over again, with work hardened brass to boot. Using PFL resizing your brass is the same size every time you fire it after the first fireforming shot. Accuracy is nothing but repeatability.......

To answer your question about changing the load? Maybe? A bit. But with PFL, never again.

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Over the years, just about everything that I've heard or read about neck sizing has said that it is the most accurate. The case is fireformed to the exact dimension of the inside of your rifles chamber. Partial full length sizing still slightly re-sizes the sides of the case so the sized case will be slightly smaller than the chamber.

I have been partial full length sizing my rifle brass for at least 40 years. To assure that I would PFL the same at every reloading session, I made a 0.030" thick washer to put between my FL size die and my press.

Neck sizing only sizes the case necks. This die does not touch the shoulder or sides of the case, so they are not work hardened. Work hardening occurs when a case is repeatedly fired and expanded to the chamber dimension, then sized smaller.

A couple of years ago I bought a neck size die for my .300 Weatherby. I am up to 5 reloadings with full power loads on one box of brass, and the cases still chamber easily. To counter the work hardening of the case necks, I anneal the case necks after each 3rd firing.

Neck and partial full length sizing does not size the sides of the case as much as full length sizing, so a neck or PFL sized case would actually have a greater capacity than a FL sized case, so with the same powder charge, the internal case pressure would theoretically be less. Once I work up a load, I don't change it if I change sizing methods. I'll leave that degree of reloading to the one hole bench rest shooters.

Ok, I'm going to stir the pot a bit.

In your typical hunting rifle, under field conditions, the accuracy difference between neck and FL sizing will be completely wiped-out by other factors (assuming you take the time to optimize your FLS or new-brass loads).

I would be much more concerned about the reliability of the ammo, for big game hunting (varmints, especially small ones, is another story).

I have hunted with neck-sized only ammo...but any more, I will at least PFLS, if not FLS, if not use new brass.

If I can hold MOA off the bench with new brass, who cares if fire-formed and neck-sized shoot .6 inches? In the field, that will not matter. I want reliability. For the record, I don't shoot at animals past 300 yards.

I will be hunting in May with new cases...well worth the couple tenths off the bench!

As always, just my $0.02!

tarbe said:

Ok, I'm going to stir the pot a bit.

In your typical hunting rifle, under field conditions, the accuracy difference between neck and FL sizing will be completely wiped-out by other factors (assuming you take the time to optimize your FLS or new-brass loads).

I would be much more concerned about the reliability of the ammo, for big game hunting (varmints, especially small ones, is another story).

I have hunted with neck-sized only ammo...but any more, I will at least PFLS, if not FLS, if not use new brass.

If I can hold MOA off the bench with new brass, who cares if fire-formed and neck-sized shoot .6 inches? In the field, that will not matter. I want reliability. For the record, I don't shoot at animals past 300 yards.

I will be hunting in May with new cases...well worth the couple tenths off the bench!

As always, just my $0.02!

Click to expand...

+1 with Tarbe on this topic.

The only serious experience I have had with neck only resizing was when I was shooting a lot of ground squirrels with a .220 Swift and my brass never became too tight to chamber easily.

I did however make sure all my cases were kept trimmed to the same length (as JTex said, repeatability is accuracy - or words to that affect).

The necks would split eventually but that was after quite a few reloadings.

Aside from that cartridge, I did not mess around with neck sizing very much, only a little here and there, enough to know that most of my other rifles did not seem to "care" one way or the other.

I know this is blasphemy but many of my hunting rifles over the years would only keep 3 shots into about 1.5 inches or some only into 2 inches at 100 yds and yet, I nonetheless managed to shoot critters with them just fine.

Never went home after missing something, while crying that I wish that so and so rifle would put five bullets into less than an inch! (my Swift would do about half an inch but that was a very special purpose rifle, not a deer and oinker rifle generally speaking).

Cheers.

I agree with you @tarbe but then I've been fortunate enough to not have any significant shifts in accuracy between new brass and the reloaded stuff. But the one thing I will give for PFLS is brass life. The only reason I started to PFLS was due to a case head separation in my M70 .300WM. Full length resizing resulted in too much headspace and the brass just wouldn't last.

Thanks for the valuable input. I was thinking of neck sizing only as I bought a 3 die set for my .375 H&H. It consisted of a FLS, NS and seating die. The rifle as is is grouping under an inch over 100 meters with Swift 300 gr A frames. I am satisfied with the grouping but was hoping to spare the brass.

Alchemist said:

Thanks for the valuable input. I was thinking of neck sizing only as I bought a 3 die set for my .375 H&H. It consisted of a FLS, NS and seating die. The rifle as is is grouping under an inch over 100 meters with Swift 300 gr A frames. I am satisfied with the grouping but was hoping to spare the brass.

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There's no tricky method to the way I PFLS, quite simple.

1) With your the arm of your press all the way down and thus the ram all the way up and the shell holder in place, screw your FL die down until it contacts the shell holder. Then back it out a couple of turns.

2) Lower the ram and place a piece of fired brass in the shell holder (appropriately lubed of course) and run it through the normal resizing process.

3) Take a close look at the neck of the now partially resized brass. It should be evident where the die stopped when the ram was fully up. You'll see a "clean" area on the neck starting at the top and working it's way partially down but not all the way down the neck.

4) Now screw the die in a bit further and run the brass through the die again. Repeat steps 2-4 until the "clean" area just gets to/on the shoulder.

5) Place the brass in your rifle and close the bolt. It will probably still just a bit tight on closing the bolt. If so, now just slightly turn the FL die in and resize the brass yet again. Once again place the brass in your rifle and close the bolt. You're now just tweaking the position of the die until the bolt closes easily. Once the bolt closes easily, stop moving the die in. You'll now be bumping the shoulder in just enough to create enough headspace to easily chamber your reloads but without excessive headspace that shortens brass life.

I like the LEE collet die for some of my rifles. It basically only sizes the neck by squeezing it down, not pulling a plug thru which tends to stretch the case. In a .300 H&H I was shooting some time back I noticed after several go's with the LEE that chambering was more difficult. I FL sized the brass back to spec and no more problem. I think it depends to some degree on the case design, pressure levels etc as to whether or not neck sizing will cause any issues, but again, if it does, just FL size. The LEE collet die does produce really nice ammo and it will be accurate all things being equal.

Neck sizing, regardless of accuracy improvement will extend the life of brass, particularly belted magnums. i use both Hornady neck size dies and Lee's collet die. Both work great, BUT! There is no free ride.....brass expands when fired and springs back slightly allowing it to be ejected from the chamber. Generally after several "neck sizings" you will notice it starting to get tight when chambering.

The solution is to use the partial FL sizing method posted earlier. Once you do this, you can go back to neck sizing and repeat the process.

My 257 Weatherby used to eat brass. This method has me getting 6 reloads out of a case, along with annealing the necks occasionally.

I would never hunt dangerous game with neck sized ammo. In fact I'd use only new brass reloads or factory premium ammo as I want to minimize all risk of head separations, etc. Always check every round you intend to bring along for easy chambering. This applies to factory ammo as well. Surprises do happen and Murphy is a prick when you are 6 hours from a gunshop.

PHOENIX PHIL said:

I agree with you @tarbe but then I've been fortunate enough to not have any significant shifts in accuracy between new brass and the reloaded stuff. But the one thing I will give for PFLS is brass life. The only reason I started to PFLS was due to a case head separation in my M70 .300WM. Full length resizing resulted in too much headspace and the brass just wouldn't last.

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Yes, when FLS, one must be certain to avoid pushing shoulders back to where excess headspace is created.

KMG Hunting Safaris said:

I never changed my powder load, but can say without a doubt that my accuracy improved when I started neck sizing. You also don't need to go out an buy a neck sizer. You can simply set your full length die to only size the neck.
Personally I have not found that the cases get too tight for the chamber. I just keep reloading them, and they go.

Click to expand...

tarbe said:

Yes, when FLS, one must be certain to avoid pushing shoulders back to where excess headspace is created.

Click to expand...

That's the whole point of PFL sizing. I set up all my accuracy stuff for .02 clearance on the shoulder.

PHOENIX PHIL said:

5) Place the brass in your rifle and close the bolt. It will probably still just a bit tight on closing the bolt. If so, now just slightly turn the FL die in and resize the brass yet again. Once again place the brass in your rifle and close the bolt. You're now just tweaking the position of the die until the bolt closes easily. Once the bolt closes easily, stop moving the die in. You'll now be bumping the shoulder in just enough to create enough headspace to easily chamber your reloads but without excessive headspace that shortens brass life.

Click to expand...

Great step by step explanation.

One thing I notice when using this method is that right before I get to "zero" headspace is that the bolt gets a bit harder to close due to the base of the die pushing the shoulder up as it squeezes the base of the case. That's a good indicator that you are almost there and to screw the die down in tiny fractions of a turn until the bolt drops easily.

Hornady makes a set of headspace guages that makes this very easy also.