Full Length or Neck Only; What's Best Resizing for Accuracy?

[J E Custom]

I've been trying to understand everyone's recommendations and apply them to my situation (factory barrel/chamber). I full length resize and normal case prep but I don't neck turn. In a factory rifle/chamber, will some degree of neck turning make any difference for bullet alignment? My bullet runout is normally <.002 without neck turning.

Think about it this way, If the chamber is perfectly aligned with the bore, and the case perfectly fits the chamber And the loaded ammo Is perfectly concentric, even though the bullet is not touching anything, It will be aligned with the bore and when fired will have a better chance of concentric engraving in the rifling. This is purely a mechanical alignment. Loading ammo that perfectly fits the chamber and perfectly aligns the bullet with the bore is the goal.

Placing Prussian blue on a bullet will not tell you it is touching the neck wall but that it is not feeding correctly, The marks shone on one picture are from contacting the chamber edge at the back as it is fed in by the bolt, but with mag tuning it can be eliminated and prevent damage to the bullet. Ideally, The bullet never touches anything while being chambered until the last as it is going into battery when the bolt is closed.

Factory chambers and rifles are seldom perfectly aligned with each other so full length sizing is probably the best route for you. Anything you can do to load better ammo will help.

J E CUSTOM

 

[Bart B]

There is on my SAAMI drawing and it is the same as what is shown on that posted chart. It isn't very long but it is the tightest part of the chamber.

Is the drawing you have from the Rifle document listed in

https://saami.org/technical-information/cartridge-chamber-drawings/

There are no 5.56 NATO case and chamber drawings in SAAMI documents.

 

[Tree Farmer]

Thanks all! I'll try adding some amount of neck turning to my routine and see what it does. I've got some new brass to fire form before getting serious about an accuracy load. I'll do some comparisons.

 

[Orange Dust]

Thanks all! I'll try adding some amount of neck turning to my routine and see what it does. I've got some new brass to fire form before getting serious about an accuracy load. I'll do some comparisons.

Please don't do them @100yds. Try midrange of 500.

 

[Orange Dust]

Think of it this way on neck turning when the neck doesn't need it for safety. All cases will have a varying neck wall thickness, and there is also usually a taper added to the mix. When you size the neck the die makes it round on the outside. What's on the inside holding the bullet? Then you expand the neck. It stands to reason that the thinner side will give more than the thicker side. Add the taper in and the bullet is seated crooked. That being said, I also have a theory, that is wholly conjecture, but makes sense to me. Remember, I am just a country redneck and not an engineer. What happens when you fire this thing? The bullet travels a short distance and stops briefly at the lands. The case neck expands as the bullet is released. Even if you manually straightened the round perfectly after loading, the pressure has to be released unevenly as the case lets go of the bullet. Seems almost like dealing with a bad crown on the other end. Truing the necks has to help this. I believe it does with all my heart, and don't have the education to prove it.

 

[Edd]

Is the drawing you have from the Rifle document listed in

https://saami.org/technical-information/cartridge-chamber-drawings/

There are no 5.56 NATO case and chamber drawings in SAAMI documents.

Quit shuffling, you said 223 Remington.

 

[Tree Farmer]

Good advice. I am not satisfied with my load consistency. I'll definitely test this at 500 yds.

 

[Orange Dust]

Good advice. I am not satisfied with my load consistency. I'll definitely test this at 500 yds.

Remember, after turning the necks, resize them before loading.

 

[Bart B]

Quit shuffling, you said 223 Remington.

Your drawing 223 data is different than SAAMI's 223
Remington.

Don't try stacking your deck of false cards again.

 

[Orange Dust]

Your drawing 223 data is different than SAAMI's 223
Remington.

Don't try stacking your deck of false cards again.

How is this helpful to the thread?

 

[Bart B]

Think about it this way, If the chamber is perfectly aligned with the bore, and the case perfectly fits the chamber And the loaded ammo Is perfectly concentric, even though the bullet is not touching anything, It will be aligned with the bore and when fired will have a better chance of concentric engraving in the rifling. This is purely a mechanical alignment. Loading ammo that perfectly fits the chamber and perfectly aligns the bullet with the bore is the goal.

Well stated.

After the cartridge is driven into the chamber shoulder then fired, the bullet has the straightest path to bore center.

 

[Bart B]

How is this helpful to the thread?

Ask the guy who posted false chamber dimensions and made snide remarks about me.

 

[Bart B]

What happens when you fire this thing? The bullet travels a short distance and stops briefly at the lands. The case neck expands as the bullet is released.

I doubt the case neck expands much behind the bullet as it travels to the lands. If a 30 caliber bullet needs 5 pounds of force to push it forward in the case neck, about 65 psi will move it.

I don't think it'll stop, just slow down until pressure gets up to several hundred psi to get the bullet fully engraved by the lands.

 

[Orange Dust]

I doubt the case neck expands much behind the bullet as it travels to the lands. If a 30 caliber bullet needed 5 pounds of force to push it in the case neck, about 65 psi will move it.

I don't think it'll stop, just slow down until pressure gets up to several hundred psi to get the bullet fully engraved by the lands.

It must expand fully at some point before the bearing surface of the bullet leaves the case mouth or it would not seal. You haven't proven me wrong yet.