Hi all,

TLDR, - Can the lee collet neck sizing die Undersize the necks creating too much tension? If so, Is this caused by improper (too deep) die adjustment? Will too much neck tension spike pressure/degrade accuracy etc?

Full Story:

I've embarked on a rifle reloading project after laying off rifles for about 4 years. Anyway, I have a large quantity of primed Milsurp brass for my M96 Swedish mauser from which I have pulled the projectiles, dumped the powder, and then prepped the cases to reload with Sierra Match King 140 gr bullets. These are plinking loads as they have Berdan primers and I cannot reload them-- that's a different story - but I'd like to see if I can't make them as accurate a I can knowing I only get one shot each. I've encountered a number of challenges (how to pull the projectiles without damaging the case mouth (too much) with my Hornady Collet Puller), cleaning tarnished cases etc etc.

Anyway - I loaded and tested a number of rounds today using a Lee neck sizing die. On some test rounds I didn't resize the case at all - simply dropped powder and seated a bullet -- I labeled these my lazy loads- no case prep or neck sizing.

When neck sizing, I adjusted the die per the instructions (I think correctly) with a final toggle over/cam over of the ram using a single stage Hornady lock n load press. (I now think the collet die is set up to resize the neck too aggressively -- I had thought it just applied the same resizing force regardless of depth so long as you didn't crush the shoulder as shown in the directions). Note also - since I'm reloading berdan primed brass I removed the Neck Sizing Die's decapping pin (Might this contribute to undersizing the neck?). Mine is being resized by WAY more than .001 as I have it set up...:(

I dropped powder and seated using dillon 550.

Powder Reloader 22, 44.2gr from a Dillon Powder measure.

Anyway, results at the range were somewhat confusing -- my lazy loads had an ES of 42 fps. Others that were neck sized only had ES of 33 with another group of neck sized shots had an ES of 117.

Still more perplexing was the ES of 117 produced the best accuracy? (At 100 yrds with iron sights off sand bags - 3 shot groups of ~ 1" to 1.5in - nothing super).

Anyway, this led me to wonder about the necks as the sized ones I made seem to have an unusual "coke bottle" appearance where the seated bullet -- is expanding the neck as it is seated and the neck slims down before the shoulder. (The projectile is a Boat tail that seated at the recommended depth for the 140gr at OAL 3.050 and doesn't extend all the way into the neck.)

I know that powder variance is another potential cause of ES - but I found the drops to be surprisingly consistent from the Dillon despite it scattering grains of powder on my workbench (Dillons powder measure dislikes stick powders).

Anyway, a picture is worth more than these 1000 words so look at this -- is this the source of my ES variance and/or too much neck resizing from the lee collet dies? How does one know how much tension is correct?

As you can see the projectile is expanding the case neck as it is seated...



And all the Chrono Data for insomniacs:


Load Development Milsurp Ammo
1917 CG M96
140gr Sierra Match King HPBT (Seconds)
Reloader 22
Berdan Milsurp Primed Cases


PPU 139g SP Reference Load.
Series Shot Speed
6 1 2503 ft/sec
6 2 2516 ft/sec
---- ---- ---- ----
Series 7 Shots: 3 Hand trickled 45gr
Min 2600 Max 2676 Case Prep (Deburred inside/out), Bevel Cut Mouth
Avg 2640 S-D 38 Neck Sized w/Lee Collet Die
ES 76 No accuracy data (shot at 50yrds)
0.8gr additional yielded 80 fps increase in velocity

Series Shot Speed
7 1 2676 ft/sec
7 2 2644 ft/sec
7 3 2600 ft/sec
---- ---- ---- ----
Series 8 Shots: 3 Dillon Powder Measure Throw 44.2 +/-0.3
Min 2548 Max 2581 Very Consistent Checked at 44.2gr
Avg 2561 S-D 17 Case Prep (Deburred inside/out), Bevel Cut Mouth
ES 33 Neck Sized w/Lee Collet Die
No accuracy data recorded (shot at 50 yards)
Series Shot Speed
8 1 2548 ft/sec
8 2 2556 ft/sec
8 3 2581 ft/sec

---- ---- ---- ----
Series 9 Shots: 3 Dillon Powder Measure Throw 44.2 +/-0.3
Min 2543 Max 2610 Case Prep (Deburred inside/out), Bevel Cut Mouth
Avg 2575 S-D 33 NO Neck Sizing
ES 67

Series Shot Speed
9 1 2543 ft/sec
9 2 2610 ft/sec
9 3 2573 ft/sec
---- ---- ---- ----
Series 10 Shots: 3 Dillon Powder Measure Throw 44.2 +/-0.3
Min 2562 Max 2604 Lazy Load - No Case Prep, No Neck Sizing
Avg 2578 S-D 22
ES 42

Series Shot Speed
10 1 2562 ft/sec
10 2 2604 ft/sec
10 3 2568 ft/sec
---- ---- ---- ----
Series 11 Shots: 7 Dillon Powder Measure Throw 44.2 +/-0.3
Min 2532 Max 2649 No case prep
Avg 2585 S-D 43 Neck Sized
ES 117 BEST Accuracy despite WORST ES

Series Shot Speed
11 1 2532 ft/sec
11 2 2539 ft/sec
11 3 2649 ft/sec
11 4 2615 ft/sec
11 5 2602 ft/sec
11 6 2602 ft/sec
11 7 2557 ft/sec
---- ---- ---- ----
Series 12 Shots: 4 Dillon Powder Measure Throw 44.2 +/-0.3
Min 2556 Max 2593 Case Prep (Deburred inside/out), Bevel Cut Mouth
Avg 2574 S-D 18 NO Neck Sizing
ES 37

Series Shot Speed
12 1 2593 ft/sec
12 2 2586 ft/sec
12 3 2556 ft/sec
12 4 2561 ft/sec

Well, ok, after some more interweb research I've discovered that the "decapping pin" in the Lee neck sizer turns out to be an essential component of the resizing process! Who knew

Seems the problem most people have with this die is having an oversized pin which results in insufficient resizing by the collet...by removing the pin (mandrel) I sure solved that issue (!) and turned mine into some sort of Super Factory Crimp Die...which explains why I was getting the undersized necks which in turn looked like straight walled pistol cases after seating a boat tail bullet to the prescribed depth. (Not good, but apparently functional as demonstrated above?)

So now my problem -- I don't think I can adjust the lee neck resizing die high enough to prevent the decapping pin from bottoming out on the Berdan primer.

I suppose I could grind off the decapping pin's last 1/3rd of an inch or so, so I could use it exclusively on this Berdan project (I have 4000 more berdan cases!) but I am reluctant to permanently alter the die...

Or, I could just seat the new projectiles without neck sizing after pulling the wooden training bullets, or even - ironically - get a Lee Factory Crimp Die after seating.

Any thoughts on what might produce a better product -- (1) neck sizing with an altered die or (2) no neck sizing and then using a FCD or perhaps (3) no neck sizing, no crimping, just seating...

You need to covert the brass to boxer primed or buy some new boxer primed brass.

replacement mandrels are 4 bucks so grind away. Adjusting the lee neck sizing die is a matter of less is more go slowly in your adjustment and measure neck until you find what you are looking for.

Eyes, thanks - I ordered a replacement and snipped off the decapping pin. Looks like I'm in "Berdan" business.

For those who stumble upon this thread -- here's a very nice write up of how to use the Lee Collet Neck Sizing Die. http://benchrest.com/showthread.php?49899-Lee-Collet-Die-Adjustment

Apparently it's never intended to be used sans mandrel (duh) so I pioneered that application.

For those with any interest, the Swedish Mauser Milsurp rounds had a .250 case mouth opening after pulling bullets -- way under the .262 nominal. Without the mandrel I inadavertantly sized them down to .240 and resized them up to .264 during bullet seating. With the die properly adjusted I'm now resizing/expanding the case mouths out to .260 .

I suspect that the consistency of my reloads will dramatically increase with this. I hope so. Now to find that primer on neck tension...

I actually use LEE FL sizing dies with the mandrel removed. I turn the die in a lathe to open up the neck portion of the die so that it does not size any part/portion of the neck. I then use this die in this manner to bump shoulders, and re-size the case body. I size the necks separately on a Lee Collet die. I only do this on rifles I'm loading for accuracy and this has proven to produce more accurate ammo than just using the F/L sizing die as Lee intended. Plus, as you discovered, using the F/L die to re-size the neck portion over-works the brass by crushing it down to a much smaller ID, and then opening it back up as the case is pulled out of the die, when the mandrel is pulled through the neck. My method, the brass at the shoulder/neck junction is only worked one time during resizing. When I load for other, non-accuracy-essential rifles such as AR's for killing pigs, they go through a standard F/L sizing die, and then a neck crimper, and are good to go.

Using FL dies without the decapping rod its one thing, but trying to use the Lee Collet die without the mandrel is another.

One thing that should be understood about the Lee Collet neck sizer is that the mandrel will limit the reduction in neck diameter, and that turning the die in further will accomplish nothing but damage to the die cap, necessitating its replacement when its threads let go. Lee's instructions for the Collet neck sizer are crap.