charlie brown

I just had a thought, and needed to put it down on paper (or electonically).

I reloaded some .30-06 the other night by neck sizing only (the first time I have done such a thing). I got to thinking today.

Is there a velocity difference between neck-sized and FL sized brass with identical loads?

Here is my theory behind this (not sure if it is valid or not, so feel free to correct me if I am wrong).
-When a round is fired it is "fireformed" to that chamber, so a certain amount of the pressure, or "energy" is used to change the dimensions of the case. This is for a FL sized case of course.
-When neck sized cases are used, they fit closer to the exact chamber dimensions of that peticular rifle, so upon firing, less "energy" is used in changing the dimensions of the case, there-fore allowing more "energy" to be used to push the bullet down the bore at a higher velocity.

So I ask -
Is this theory bunk, or does it have a valid point?

Now, I am sure even if it is valid, the benefits of a higher velocity would be quite minimal, probably within the extreme spread of the load, given the climatic conditions are exactly the same (ie: temp, humidity, elevation, etc.).

So, what do you all think?

bigcountry

Great question, and I find the anser to be yes to a point. I can get vel spreads say of 70fps with new brass. After neck sizing I see the velocity to be on the high side of the ones that are FL Sized but velocity spreads can go down as low as 15fps. If you can keep the necks straight, Neck sizing is great.

Virginia7

It's been many years since I did any reloading, but I got to admit this is one question that never came to mind in making up my reloads.
I'd be curious to know what capacity/volume each case holds - neck sized vs. full length.
Of course, would have to weigh the cases first to have two as near to identical as possible.
In theory, I think you may be right. Would be interesting to load up about twenty cases.
Load 10 neck sized only, and 10 full length sized. Test 'em by firing over a chrony, and
see what results you get - what the avg. for each bunch comes to.
If you do, please post and let us know how it comes out.

HighDesertWolf

good question i have some loads made up already which are identical except one batch is neck sized the others are FL sized i never thought of it but I think i will set out tomorow with the chrony and see if there are any real differences in velocity

mossy33oak

ok, i guess im just talking in theories here too, I have no actual data to prove any of this, but heres my opinion. I would think the differences between f/l and n/s casings would be so small, (probably talking in the .003-.001 range, or the thickness of a piece of paper) that other inconsistencies in your process (i.e. one grain of powder here or there or differences in primers from one to another) would probably make it very hard to tell. I just think there are so many things that are not able to be repeated every shell exactly that the difference would be unnoticable. Just my opinion, I guess the only way to tell is to try it!!

oldelkhunter

And if there were a minute difference in velocity between neck sized and FL sized who would be crazy enough to use necksized dies in a hunting situation? Target shooting fine Hunting No

charlie brown

Mossy- I was thinking of that also, but forgot to put that specificly in there, but more of an implication with everything being exactly the same.

I will try this in the next few days with my .223 and see if I can notice a difference, and I don't have any .30-06 shells loaded up right now that are full length sized. The ones I do have are loaded witha 165 grain Nosler Partition on top of 54-56 grains of IMR 4350 in .5 grain incriments at 5 rounds each to see which one will be a more accurate. I am going to go test those here in the next few hours after shooting some squirrels here in a bit.

RedAllison

oeh whats wrong with using necksized loads for hunting? I'm sure there are boatloads of answers for "what ifs" but in the real world I havent seen a problem. If proper care is taken to see that such loads are loaded specifically for a particular gun and all the finished rounds are cycled through the gun to assure proper feeding and loading, then what is wrong with it?

Neckloading can optimize accuracy and the main reason for it of course, to pro-long case life,
RA

Virginia7

RA
Amen! When I used to handload my ammo, I neck sized only for my Ruger 77 (308Win.), and never had a problem. Accuracy was great, and case life, if I recall
correctly, was somewhere in the range of 15x or more/case (150gr. bullets loaded to
approx. 2600-2700fps.).

bigcountry

Its that one time you do that counts. There has been trouble necksizing only by several shooters.


Mossy, i believe it has to do with the give of the case acually fireforming. That give is enough to slow it down some. Thats why I see spreads go way down with necksizing. With a fireformed case, there should be a slight pressure spike due to no give. It should go down quickly