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

[Mram10us]

no advantage to neck size only.. hurts feed reliability, why do it?

I wish these videos had been around 15 years ago! I started neck sizing only. Learned the hard way. Galled some lugs and has velocity issues in my edge that I blamed on a new lot of powder.

 

[J E Custom]

How much does a case expand when fired but before the bullet starts moving down the bore? Does it fill the chamber at all? How much does the case fit matter if the case fills the chamber , self centering in the chamber, before bullet release?

The reason some like to neck size only is that the case already fills the chamber and there is no head space so the case cannot move even with the firing pin strike.
The only change in the case, is the neck and it expands to release the bullet that is already centered.

Another example that zero case movement is a benefit is in the AI cases. they actually have .004 thousandths compression In the chamber. This prevents any case movement and enhances the quality of the fire forming process. The biggest advantage is the accuracy when done this way. Most AI's (Ackley improved)cartridges are very accurate while fire forming and many will shoot 1/2 MOA while fire forming. All are plenty good to hunt with at reasonable ranges before with the parent case If set up right.

J E CUSTOM

 

[Huntz]

The simple answer is use a Forester seating die when first assembling new brass.Use quality brass(your choice).You will have little to no runout with your bullet or neck.Use a Forester bushing die to neck size the fire formed brass there after.FL size when it will not chamber.Use a body die to FL size your brass then run through the bushing die to align the neck.You can do all kinds of case prep if you are into wasting your time.Case prep is good if you are shooting F Class.Shooting a hunting rifle.Redundt.JMHO,Huntz

 

[Mram10us]

Hear is my take on this.
All necks should have a minimum of .004 thousandths clearance to the neck chamber to allow the bullet to be released without pressure going up. Tight neck to chamber dimensions can work if you load down. This will help align the bullet but cost lots of velocity. Also when running a tight neck chamber the case necks must be turned.

So if the neck clearance is .004 and the necks have been turned, the bullet will have to rely on case fit. the better it fits the chamber, the better the bullet will align with the bore.

I started loading buy just full length sizing and about the best I could get was 1/2 MOA. Wanting/needing better accuracy, I started full length sizing just enough to feed well. Accuracy improved again. When I joined this group, I went all out and used/tried everything I knew and what I was told about loading accurate and consistent ammo.

That is when I realized that i couldn't miss a single step. Some have had better luck than I apparently with full length and no neck turning, but not me. I also really found out what my ammo quality was when I bought a concentricity tool from Sinclair. that tool made me re evaluate my dies, press and technique.

Some have questioned why some others are not satisfied with 1/4 MOA, and I cant answer for others, but that's just what I want. I want to get where I can stay well below that consistently if possible. don't know if I can do it but for sure I can't if I don't try.

J E CUSTOM

I listed .002" for the neck because that is standard saami. Regarding the "satisfied with 1/4 moa", most of us on this site are probably very happy with consistent 1/4 moa, but I doubt many stop there. I think we are all about squeezing every last drop of accuracy. That's why it seems to take so many sessions to find that perfect load.

 

[Bart B]

The reason some like to neck size only is that the case already fills the chamber and there is no head space so the case cannot move even with the firing pin strike.

Are you referring to the distance from the case head to the bolt face as "head space?"

I thought the correct term was "head clearance."

Isn't rimless bottleneck head space a shoulder to back end (case head or bolt face) dimension?

 

[Beluebow]

Yes. Bullets are least deformed when entering the chamber throat as straight as possible. That said, even crooked ones indexed the same in the chamber can be very accurate.

7.62 NATO M118 match ammo was notorious for its 7 to 8 thousandths bullet runout. Best accuracy in bolt action test barrels was around 12 inches at 600 yards; near 16 inches in match grade service rifles. Indexing bullet runout high point repeatable down to about 12 inches in M1 and M14 match grade versions.

Too bad they used 3 or 4 different lots of bullets in each lot of M118 ammo.

I believe you would be hard pressed to find a die that produced .007-.008 run out...but not impossible. From my own testing runout is way down the ladder when it comes accuracy.

 

[J E Custom]

Are you referring to the distance from the case head to the bolt face as "head space?"

I thought the correct term was "head clearance."

Isn't rimless bottleneck head space a shoulder to back end (case head or bolt face) dimension?

The correct term Is head space. The gauges used are called head space gauges. Clearance can mean basically the same thing but it means that there is no mechanical lock up and The dimension is undefined. The most widely used term Is and has been called head space and this space has a specific Dimension.

Head space is the dimension from the case head to the bolt face with the case pushed forward towards the belt, shoulder, case rim, front of the case head, ETC.

Head space allows you to insert the cartridge. The amount of head space required normally is .000 to .006 any more than that and the weapon can become unsafe.

Some people call a barrel a tube or a pipe, but it is still a barrel.

J E CUSTOM

 

[Bart B]

From SAAMI's glossary...

HEAD CLEARANCE

The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.

HEADSPACE

The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats. 1. BELT: A type of chamber design in which the cartridge seats in the chamber on an enlarged band ahead of the extractor groove of the cartridge body. 2. MOUTH: A type of chamber design in which the cartridge seats in the chamber on the mouth of the cartridge case. 3. RIMLESS: A type of chamber design in which the cartridge seats in the chamber on the shoulder of the cartridge case. 4. RIMMED: A type of chamber design in which the cartridge seats in the chamber on the rim or flange of the cartridge case.

 

[Edd]

From SAAMI's glossary...

HEAD CLEARANCE

The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.

HEADSPACE

The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats. 1. BELT: A type of chamber design in which the cartridge seats in the chamber on an enlarged band ahead of the extractor groove of the cartridge body. 2. MOUTH: A type of chamber design in which the cartridge seats in the chamber on the mouth of the cartridge case. 3. RIMLESS: A type of chamber design in which the cartridge seats in the chamber on the shoulder of the cartridge case. 4. RIMMED: A type of chamber design in which the cartridge seats in the chamber on the rim or flange of the cartridge case.

Don't wast your effort ........https://www.longrangehunting.com/threads/300-win-mag-headspace.208001/page-2

 

[J E Custom]

I listed .002" for the neck because that is standard saami. Regarding the "satisfied with 1/4 moa", most of us on this site are probably very happy with consistent 1/4 moa, but I doubt many stop there. I think we are all about squeezing every last drop of accuracy. That's why it seems to take so many sessions to find that perfect load.

I don't understand the .002 thousandths neck clearance unless you are talking about each side of the neck and then I agree with you. Having first hand experiences with tight neck cartridges I found pressure if the loaded round had .003 (.0015 per side)or less clearance between the neck and the neck chamber. I consider the minimum to be .004 total and more if the necks are not turned, if the load is for dangerous game, it is recommended that dangerous game rifles have .008 total clearance.

I also agree that many would like to shoot below 1/4 MOA but when anyone wants to share how they do It, The non believers descend on them and state that It is impossible and that it's not worth the effort. I know people that are happy with one minute of deer and a pie plate at 100 yards is OK as long as you can hit it.

I will keep trying to make suggestions, and leave the convincing to others.

J E CUSTOM

 

[Bart B]

I listed .002" for the neck because that is standandard SAAMI.

Where in SAAMI cartridge documents below is that standard stated?

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

 

[Dean2]

I don't understand the .002 thousandths neck clearance unless you are talking about each side of the neck and then I agree with you. Having first hand experiences with tight neck cartridges I found pressure if the loaded round had .003 (.0015 per side)or less clearance between the neck and the neck chamber. I consider the minimum to be .004 total and more if the necks are not turned, if the load is for dangerous game, it is recommended that dangerous game rifles have .008 total clearance.

I also agree that many would like to shoot below 1/4 MOA but when anyone wants to share how they do It, The non believers descend on them and state that It is impossible and that it's not worth the effort. I know people that are happy with one minute of deer and a pie plate at 100 yards is OK as long as you can hit it.

I will keep trying to make suggestions, and leave the convincing to others.

J E CUSTOM

Spot on as usual.

 

[wbm]

Some people call a barrel a tube or a pipe, but it is still a barrel.

and bullets are called "pills"...have to say "thou", "pills", "tubes" etc. so folks will think you are in the know about the shooting disciplines.

 

[Bart B]

I listed .002" for the neck because that is standandard SAAMI.

Where in these SAAMI cartridge documents is that specification stated?

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