neck sizing for proper bullet seating without a crimp

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frank2003

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Ive tried the search feature but couldent seem to find the proper keywords to find my answer.

Im currently reloading my first batch of .308 win for target shooting with my bolt action. Im currently using winchester brass and 168gr hornady Match tips that have NO crimping sleeve. The Dies I use to resize is the Deluxe LEE reloading set and as I shot my own brass from only one firearm, im only using the resizing neck die right now. MY problem is that by adjusting this die, I can actually modify my ID measurement of the top part of the neck where the bullet seats from approx 0.302-0.309.

As mentionned, this ammo is for target shooting on a bolt action only so I am not crimping. Right now my die is resizing the ID of the neck at 0.303 and they seem very tight after they are seated. Is this too tight to seat the bullet? What do you guys recommend and how tight are you sizing your brass to seat the bullets? I dont want the bullet to move at all after seating but I also dont wanna spike the pressures due to having the bullet squeezed too much by the brass.

Thanks all!!
 
Interesting! So in this particular example, you would have an inside dimension at the mouth of the case of .305" to .306" ?
I am currently using almost the same setup, 168 grn Hornady Match & fire formed Win brass, bolt action Rem 700 .308 but I've been using a Lee collet neck sizing die. I sure do like not having to deal with lubing cases!! I use a similar setup on my .223. I'll have to measure to see what the collet die is actually doing for the ID at the case mouth and how consistent it is. Might explain the occasional flyer I get with 223. Results/accuracy with the 308 using this setup have been stellar but I'll measure out of curiosity.
 
Neck tension is self-limiting by the yield strength of the brass, i.e., it can only be so springy. You cannot undersize the neck such that the tension would create overpressure. Seating a bullet in a case mouth that has been sufficiently undersized will just expand it back to whatever corresponds to maximum neck tension.
 
Neck tension is self-limiting by the yield strength of the brass, i.e., it can only be so springy. You cannot undersize the neck such that the tension would create overpressure. Seating a bullet in a case mouth that has been sufficiently undersized will just expand it back to whatever corresponds to maximum neck tension.
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Interesting, I didn't think of this. Although, I think that before reaching that maximum strength point,I think that minute adjustments could affect bullet flight due to pressure variations. Unfortunately, I have 3 reloading manuals and none talk directly about mouth tension.... Unless I missed that part three times haha
 
I ran a test once with light neck tension vs maximum neck tension in 308. Two 10 shot groups of each type. 40 rounds. The high neck tension groups were almost half the size. My theory was that it helped uniform ignition. I use a 3 thou bushing neck sizer now.
 
I did a similar test using a Lee factory crimp die in 308. Through the course of my test (about 500 rounds, with three bullet weights; 168,175,190). In that particular combination of rifle and loads, the crimping die helped cut down on group size in just over two thirds of the loads. More with the lighter bullets, less with the heavier. So in that case more neck tension helped. I don't think I would take it as a constant, however. - dan
 
frank2003 said:
Interesting, I didn't think of this. Although, I think that before reaching that maximum strength point,I think that minute adjustments could affect bullet flight due to pressure variations. Unfortunately, I have 3 reloading manuals and none talk directly about mouth tension.... Unless I missed that part three times haha
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Richard Lee touches on it in modern reloading Vol-2
 
Funny, I had a issue with my Lee neck sizing die yesterday doing 30.06. The neck size is determined by the decapping die. Upon decapping, the collet pinches the neck smaller than .300 and when you pull down the decap pin expands to a fixed size of .303. I suppose you could just neck size to .305 but I have found that my bullets are loose in the neck because less brass is on it. I have a factory crimp die but I feel it isnt really required especially if you want a clean bullet departure
 
I'm officially intrigued with the whole neck sizing deal and will be trying out partial sizing on brass for my milsurp bolt guns since I dont have the actual neck size only dies. Figure this way I can get the best of both worlds. Thanks OP and other fellow reloaders for the inspiration to add an other level of interest to this already very interesting hobby.
 
I am a relatively new shooter and reloader but I am learning so much as this hobby continues. For those of you who have never heard of neck sizing it is the way to go. I started out full length resizing 30.06 and found that when you do that your brass actually grows and you need to trim your cases back down to spec. Full length resize is not needed if you are gonna used the same brass in same gun. Once a new cartridge is fired from your gun the brass is fire formed to your gun. That is where neck sizing is perfect - neck sizing increases life of your brass and does not need full case lube. After neck sizing my brass is at the most .002 over 30.06 spec length. However, you should use a bit of lube on the inside and outside of the neck or this will happen

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Not enuff lube inside this case and my shell plate tore the rim right off. So now my case was stuck in the neck sizing die - in order to remove I loosened and removed the decapping collar and hammered the decapping pin down to push the case out. To remove the decapping pin I used a pair of tube cutters to cut open the case - now my decapping pin was flared so I grinded it back down to fit back in the collar.
 
Well I got home and checked it out. I have 20 Win .308 cases I just recently collet neck sized and they were all .305" with some .306" ID at the case mouth so right in the 2 to 3 thou spread tending towards .003" undersize. Pretty cool info & handy to know down the road. Thanks guys! As Myth Busters would say .... Confirmed!
 
VLD Deburring Tool by RCBS or Lyman assists in making the seating process easier.
The Lee Collett die makes neck sizing and decapping easy to and while you may not have to lube, it is a good time to clean the outside of the neck with some steel wool and solvent.
 
Agree with Hotwheels. Richard Lee says (as I recall) that seating the bullet will just expand the neck if the neck is too small. In other words, there is a limit as to how small the neck dia. can be once the bullet is seated.
BE AWARE that insufficient neck tension is very dangerous. The issue is that recoil from a previous round can cause the bullet to set back into the case. This can cause overpressure, and destroy your rifle and your face. Test each loaded round by pressing firmly on the bullet by hand. If it moves, DO NOT SHOOT IT. To protect the bullet tips on pointed bullets I drilled a 3/16 hole in a block of wood. I put the point in the hole and press firmly on the case.
 
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