Neck Turning vs chamber clearence

C

Charles

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Hi guys

I need your opinion on this subject: neck turning vs chamber clearance on a factory chamber.

I ask the question because most of the .308w factory gun have a neck diameter of 0.344. The Lapua brass that i have receive have 0.013 to 0.015 of neck tightness.

If i want to neck turn them on the same neck tightness i have to remove 0.002 so the neck tightness will be the same at 0.013.

So with my lee collet die i will have a loaded cases to 0.331 at the neck.
Thats a clearance of 0.013 and i dont think this will help with accuracy.

What is the solution, bushing die or this type of clearence is not a big deal for accuracy.

Your opinion and knowledge will be welcome.

Thanks
 
With factory chambers, you would normally do an "80% turn", where not all of the neck on every case is touched by the cutter. This give you uniformity without materially increasing the gap between your loaded ammo neck OD and the chamber neck ID.
 
Neck turning for a factory chamber is a waste of time IMO since, as you have found out, they are of generous proportion.

BTW, if you turn your necks to .013" your loaded neck diameter should be .334".
 
Neck turning is about making your sizing uniform. Seating more consistent for less runout.

Chamber neck diameter does not affect accuracy ONLY neck life.

Skim all the necks to 12 to 13 thou and enjoy. Benefits are not huge but it doesn't hurt.

Jerry

PS 2 thou clearance per side is not large and will ensure safe functioning in the field.
 
Except if he turned to .013" then his clearance is .005" per side, .010" total when loaded round is .334 and chamber is .344
 
Whats the standard for clearance for a factory barrel for say hunting varmints and target plinking? Just curious because I have a .244 bushing coming for my .223. Case neck wall thickness is an average of 0.010 and a .224 bullet I figure .244 was the key. I have no idea what my chamber is though? I was looking for uniformity.
 
Wissem70 said:
Whats the standard for clearance for a factory barrel for say hunting varmints and target plinking? Just curious because I have a .244 bushing coming for my .223. Case neck wall thickness is an average of 0.010 and a .224 bullet I figure .244 was the key. I have no idea what my chamber is though? I was looking for uniformity.
Click to expand...

Your bushing should be 1 or 2 thou. smaller than your loaded round IE .243 or .242. You need some neck tension to hold the bullet in the case.

I don't know if there is a standard for factory chamber clearance. If there were it would be in SAAMI specs./definitions. Or maybe the Euro standards.

NormB
 
Thanks NormB. Sorry for the Hyjack Charles. Redding lists .244 to .252 for their .223 bushing range chart. Fired case was .254 so I figure the chamber would be close to that. I hear what you are saying NormB. These Redding dies just keep digging me deeper and deeper. I might just try the .244 when it gets here and go from there. If I hadn't screwed my Lee neck die I could measure what it was producing.
 
Budweiser360 said:
Except if he turned to .013" then his clearance is .005" per side, .010" total when loaded round is .334 and chamber is .344
Click to expand...

Nothing wrong with that and lots of good.

The bullet is on its way when the case is at bullet diameter - arguably sooner.

By the time the case has expanded to 1 thou over bullet diameter, the bullet is somewhere down the throat. It really doesn't matter what happens to the neck AFTER the bullet has left.

The only downside is that the large clearance may allow case splits to happen and/or to happen sooner then one with lower tolerance BUT the upside is that the chamber will never "jam' under normal useage due to fouling and/or moisture.

tight neck chambers are old tech and based on case neck thickness that have proven to not be ideal.

Keep neck tension 1 to 2 thou. Keep runout to as little as possible. Tune your powder charge properly and enjoy...

Jerry
 
Charles said:
I need your opinion on this subject: neck turning vs chamber clearance on a factory chamber.

I ask the question because most of the .308w factory gun have a neck diameter of 0.344. The Lapua brass that i have receive have 0.013 to 0.015 of neck tightness.

If i want to neck turn them on the same neck tightness i have to remove 0.002 so the neck tightness will be the same at 0.013.

So with my lee collet die i will have a loaded cases to 0.331 at the neck.
Thats a clearance of 0.013 and i dont think this will help with accuracy.

What is the solution, bushing die or this type of clearence is not a big deal for accuracy.
Click to expand...

When you say neck tightness, do you mean neck brass thickness? If so, I would just sort my brass by thickness, and not turn them.

Unfortunately many factory guns are going to have a loose chamber, and neck turning can only make it worse. A custom chamber will have about 0.0025"-0.0030" clearance. You really can't get that unless you cut a new chamber.

You can do something different about it though. Just resize 2/3 of the neck of your case instead of the full neck. Then you will have about a 0.001" clearance in the unsized portion. This helps get your cartridge centered in the chamber, even when the chamber is loose. The other trick is to use a slight jam of the bullet into the lands. Used together this can center your cartridge and the bullet, and minimize initial cant of the bullet.
 
Thanks guys many great infos here, very appreciate !!

Mystic Precision said:
Nothing wrong with that and lots of good.

The bullet is on its way when the case is at bullet diameter - arguably sooner.

By the time the case has expanded to 1 thou over bullet diameter, the bullet is somewhere down the throat. It really doesn't matter what happens to the neck AFTER the bullet has left.

The only downside is that the large clearance may allow case splits to happen and/or to happen sooner then one with lower tolerance BUT the upside is that the chamber will never "jam' under normal useage due to fouling and/or moisture.

tight neck chambers are old tech and based on case neck thickness that have proven to not be ideal.

Keep neck tension 1 to 2 thou. Keep runout to as little as possible. Tune your powder charge properly and enjoy...

Jerry
Click to expand...

Jerry can you alaborate on the tigh neck chambers when you say that is old tech. I was thinking to have one on a new barrel so i'm very interested to heard you on this.

Ron AKA said:
When you say neck tightness, do you mean neck brass thickness? If so, I would just sort my brass by thickness, and not turn them.

Unfortunately many factory guns are going to have a loose chamber, and neck turning can only make it worse. A custom chamber will have about 0.0025"-0.0030" clearance. You really can't get that unless you cut a new chamber.

You can do something different about it though. Just resize 2/3 of the neck of your case instead of the full neck. Then you will have about a 0.001" clearance in the unsized portion. This helps get your cartridge centered in the chamber, even when the chamber is loose. The other trick is to use a slight jam of the bullet into the lands. Used together this can center your cartridge and the bullet, and minimize initial cant of the bullet.
Click to expand...

Yes, i wanted to say thickness, sorry.

Thanks for the tips i will try this on another Lapua batch that i have.

I have just past 50 round on a sinclair concentricty gauge and after the neck sizing with the Lee collet die i have nothing up to 0.002. Same thing after i have seated this with a Forster ultra seater die, thanks Jerry for this one :)

I have obtained good results with this combinaison but you know what this is we always want to improve our results so this is was i have checked for neck turning. I have dome somes very nice grouping with my rifle but i have found that i have somes unexplained flyers. Maybe this where the factory barrel became a factor or something in my reloading.
 
Charles said:
Jerry can you alaborate on the tigh neck chambers when you say that is old tech. I was thinking to have one on a new barrel so i'm very interested to heard you on this.
.
Click to expand...

Back in the early days of SR BR, turning necks to make them even started but because of the very limited options in brass, you used what you could get.

Alot of factory brass was pretty wonky but were already fairly thin. Turning them made them really thin

It was not uncommon to see 10thou even 8 thou necks. That is paper thin and if there was much clearance around the case, the necks would split under firing.

So dimensions in the chamber were made to SUPPORT the necks. Somewhere along the line, tight necks became associated with accurate rifles and now it has become 'fact'.

Then of course light neck tension was used. Some as a by product of having no necks to offer any tension and because it reduced the chance of bullet runout during seating - again, limited options in dies in those days.

So light tension because the norm.

Today, we have so much to choose from and so many great tools. We have found that some of the practises aren't necessary and in some sports, don't work.

Heavier necks started showing up on longer distance venues with excellent success. Then heavier neck tensions followered. This has made things even more stable. Add in quality inline seaters and many problems simply dissappeared.

So what is needed to make an accurate rifle continues to evolve and develop. Unfortunately, many of the must-do's have lost their original purpose and some are using them unnecessarily or even inappropriately.

YMMV.

Jerry
 
Tight turned necks are somewhat falling out of favour, but they still offer the only real way to eliminating the variation in brass. However, with Lapua brass being so consistent, there is a trend to "No Turn" necks. They are still tight in the 0.0025" range, but sized so you don't have to turn a specific brand of brass -- most likely Lapua. The advantage of a tighter neck besides more accurate location of the case in the chamber is less expansion on firing. This means with a bushing die you size the neck much less. This reduces runout caused by sizing, and of course increases neck life.
 
The problem is the size of the chamber. Turn the necks to equal thickness and this will give you a more consistent neck tension, it is all you can do to increase accuracy. The tension is controlled by the diameter of the mandrel in your Lee die.
bb
 
bigbull said:
The problem is the size of the chamber. Turn the necks to equal thickness and this will give you a more consistent neck tension, it is all you can do to increase accuracy. The tension is controlled by the diameter of the mandrel in your Lee die.
bb
Click to expand...

Another problem with the large size factory chamber is with fired brass necks at .253/.254 and squeezing them into .243/242 bushings. This can be problematic as the bevel Redding puts on their bushing is minimal. I phoned their Engineer about that, and asked if they could increase the bevel. I got nowhere.


These bushings work best with tight SAAMI or BR chambers.

NormB
 
NormB said:
Another problem with the large size factory chamber is with fired brass necks at .253/.254 and squeezing them into .243/242 bushings. This can be problematic as the bevel Redding puts on their bushing is minimal. I phoned their Engineer about that, and asked if they could increase the bevel. I got nowhere.


These bushings work best with tight SAAMI or BR chambers.

NormB
Click to expand...

Norm, there is good reason for the small bevel, by doing so the neck can be sized to it's entirety otherwise the bushing will bump the shoulder before the whole neck is resized. I suggest neck sizing in two steps to get away from hanging up the neck on overexpanded necks. This problem also can apear on use of the Lee collet dies when the necks are balloned from over generous chamber neck dimensions. Certainly keeping runout becomes increasingly more difficult when so much rework is involved.
bb
 
Mystic Precision said:
Back in the early days of SR BR, turning necks to make them even started but because of the very limited options in brass, you used what you could get.

Alot of factory brass was pretty wonky but were already fairly thin. Turning them made them really thin

It was not uncommon to see 10thou even 8 thou necks. That is paper thin and if there was much clearance around the case, the necks would split under firing.

So dimensions in the chamber were made to SUPPORT the necks. Somewhere along the line, tight necks became associated with accurate rifles and now it has become 'fact'.

Then of course light neck tension was used. Some as a by product of having no necks to offer any tension and because it reduced the chance of bullet runout during seating - again, limited options in dies in those days.

So light tension because the norm.

Today, we have so much to choose from and so many great tools. We have found that some of the practises aren't necessary and in some sports, don't work.

Heavier necks started showing up on longer distance venues with excellent success. Then heavier neck tensions followered. This has made things even more stable. Add in quality inline seaters and many problems simply dissappeared.

So what is needed to make an accurate rifle continues to evolve and develop. Unfortunately, many of the must-do's have lost their original purpose and some are using them unnecessarily or even inappropriately.

YMMV.

Jerry
Click to expand...

Thanks Jerry your explanation seem to be very logic to me !!

I think i have to look for another reamer :)
 
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