I'm in the process of uniforming some of the factory brass I have laying around and wanted to "uniform" 'em up. I have noticed that through all my sorting I have found that the most excessive difference (aside from case weight alone) is the difference in neck wall thickness. I have case difference varing from .012"-.021" neck wall dimentions. I figured I'd hit the middle and neck turn to .015"- I have not spilt brass shavings as of yet, I wanted opinions of the hide members first. Let me know what you of your expertise and experience. Thank you in advance!
308 neck thickness?
- Thread starter Exhaust3
- Start date
Re: 308 neck thickness?
If you neck turn to that average, then all of your brass with thicknesses less than .015" will have different dimensions. Half of your necks will be too small.
Call me Mr. Money Bags, but I would toss the bottom 10% of neck sizes (or more correctly, I would put those aside for sighters and foulers) and then turn the rest to size. That size will probably be around .014".
If you turn to .012", you will be able to use a lot of brass, but now you are working your necks a lot as they expand to your relatively large chamber dimension and then are sized back every time you fire.
I don't know if you have measured necks in 3 or 4 different spots. You can identify brass with inconsistent neck wall thickness this way. If there is too much variation in a case, I would set aside brass that varies more than .001". The reason you do this is not to get consistent neck wall thickness, but the theory is that variation you spot at the neck will only increase as you get to the case head. Eventually, that brass will expand to become banana shaped... that is the theory at least. The reason I am bringing it up now is because if you plan on segregating brass this way, you need to do it before you turn the necks. Once you turn necks, you will have to measure at the case head to segregate, which requires an extra fancy tool and goes a little slower than measuring case necks the first time. It takes me an hour and a half or so to measure the necks at 4 places. Remember again, that you need to turn down to the smallest dimension. So if you measure case necks and get measurements of .0165", .0155", .0155", and .0140", you need to turn that case to at least .0140". If you turn to .015", you will now have a case with .001" neck variation... since you are turning to get rid of that in the first place, turning hasn't fixed your problem.
I put all of this in a spreadsheet and place each piece of brass in a labeled loading block, so I can look at piece # 307 and know what the wall thicknesses are at 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock. I then figure out how much brass I acutally want to cull based on how many I have to throw out. I cull based on 1) neck wall thickness variation and 2) minimum dimension. If the minimum measured dimension is too small, then I don't turn it for the above reasons.
But then, I am obviously incredibly anal about all of this.
If you neck turn to that average, then all of your brass with thicknesses less than .015" will have different dimensions. Half of your necks will be too small.
Call me Mr. Money Bags, but I would toss the bottom 10% of neck sizes (or more correctly, I would put those aside for sighters and foulers) and then turn the rest to size. That size will probably be around .014".
If you turn to .012", you will be able to use a lot of brass, but now you are working your necks a lot as they expand to your relatively large chamber dimension and then are sized back every time you fire.
I don't know if you have measured necks in 3 or 4 different spots. You can identify brass with inconsistent neck wall thickness this way. If there is too much variation in a case, I would set aside brass that varies more than .001". The reason you do this is not to get consistent neck wall thickness, but the theory is that variation you spot at the neck will only increase as you get to the case head. Eventually, that brass will expand to become banana shaped... that is the theory at least. The reason I am bringing it up now is because if you plan on segregating brass this way, you need to do it before you turn the necks. Once you turn necks, you will have to measure at the case head to segregate, which requires an extra fancy tool and goes a little slower than measuring case necks the first time. It takes me an hour and a half or so to measure the necks at 4 places. Remember again, that you need to turn down to the smallest dimension. So if you measure case necks and get measurements of .0165", .0155", .0155", and .0140", you need to turn that case to at least .0140". If you turn to .015", you will now have a case with .001" neck variation... since you are turning to get rid of that in the first place, turning hasn't fixed your problem.
I put all of this in a spreadsheet and place each piece of brass in a labeled loading block, so I can look at piece # 307 and know what the wall thicknesses are at 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock. I then figure out how much brass I acutally want to cull based on how many I have to throw out. I cull based on 1) neck wall thickness variation and 2) minimum dimension. If the minimum measured dimension is too small, then I don't turn it for the above reasons.
But then, I am obviously incredibly anal about all of this.
Re: 308 neck thickness?
I guess let me be more clear. I have segregated all the brass by mfg., then I have weight sorted between each lot (ie. lightest to heaviest; within each lot). I mentioned the neck wall thickness range, because that is the widest range I have in all lots combined. Most, and I say most, batches of same mfg. are quite close in dimentional tolerances, ie. WIN, FC, R-P etc. The range widens considerably when the LC, WCC, PMC etc. start to fit into the mix. I have my match brass and the average neck wall thickness is .015" and that is where I came up with the "middle." I was wondering what you guys turn you neck to? I also realize that each chamber is different, I have my chamber cut for FGMM ammo (on the small side of that tolerance) and load for that chamber. Oh, and I'll use the smaller neck brass for sighters and so on. Again thanks for all your imput.
I guess let me be more clear. I have segregated all the brass by mfg., then I have weight sorted between each lot (ie. lightest to heaviest; within each lot). I mentioned the neck wall thickness range, because that is the widest range I have in all lots combined. Most, and I say most, batches of same mfg. are quite close in dimentional tolerances, ie. WIN, FC, R-P etc. The range widens considerably when the LC, WCC, PMC etc. start to fit into the mix. I have my match brass and the average neck wall thickness is .015" and that is where I came up with the "middle." I was wondering what you guys turn you neck to? I also realize that each chamber is different, I have my chamber cut for FGMM ammo (on the small side of that tolerance) and load for that chamber. Oh, and I'll use the smaller neck brass for sighters and so on. Again thanks for all your imput.
Re: 308 neck thickness?
turn the necks depending on the neck dimension and how much you are willing to work the brass over at each sizing (as the other poster already mentioned) my reamer has a .341 neck, i turn my necks to .014 for .336 loaded rounds and use .334 bushing during sizing.
turn the necks depending on the neck dimension and how much you are willing to work the brass over at each sizing (as the other poster already mentioned) my reamer has a .341 neck, i turn my necks to .014 for .336 loaded rounds and use .334 bushing during sizing.
Re: 308 neck thickness?
Segregated by manufacturer? I don't think you have a need to turn necks.
Because of different internal dimensions, you will need to work up a different load for each brass manufacturer. That may or may not be worth it.
If you are turning necks, it needs to be to the SMALLEST dimension, not the average dimension. If yo uturn to the smallest dimension, you will end up with about half of your brass with .015", then some .014", some .013", and some .012".
If you are turning to one dimension to avoid having a different set up for each manufacturer, pick the smallest dimension if you don't want to toss any brass. If you decided to toss some brass (which there is good merit for, as the brass with the thinnest necks will likely be thin throughout than therefore have more case capacity than the rest of your brass), then turn to .013" or .014" and toss everything smaller (or use it for sighters and foulers).
Just to be clear you can't turn .013" brass to .015". It is not physically possible.
Now maybe you meant something else... like you want to go max spec on the necks for your chamber. If that is the case, measure the neck OD of a loaded round of FGMM, subtract the bullet diameter (the true bullet diameter) and divide by 2 and subtract .001". That will give you a nice tight neck diameter for your chamber. All of your brass will now fit. Some of it will fit differently that others because you are not turning all necks down to the same diameter, but if you are only turning because you want your ammo to fit, that method will work. I don't know why anyone would want to do it that way... you get all of the pleasure of turning necks with very little of the benefit, but it is a way for sure.
Segregated by manufacturer? I don't think you have a need to turn necks.
Because of different internal dimensions, you will need to work up a different load for each brass manufacturer. That may or may not be worth it.
If you are turning necks, it needs to be to the SMALLEST dimension, not the average dimension. If yo uturn to the smallest dimension, you will end up with about half of your brass with .015", then some .014", some .013", and some .012".
If you are turning to one dimension to avoid having a different set up for each manufacturer, pick the smallest dimension if you don't want to toss any brass. If you decided to toss some brass (which there is good merit for, as the brass with the thinnest necks will likely be thin throughout than therefore have more case capacity than the rest of your brass), then turn to .013" or .014" and toss everything smaller (or use it for sighters and foulers).
Just to be clear you can't turn .013" brass to .015". It is not physically possible.
Now maybe you meant something else... like you want to go max spec on the necks for your chamber. If that is the case, measure the neck OD of a loaded round of FGMM, subtract the bullet diameter (the true bullet diameter) and divide by 2 and subtract .001". That will give you a nice tight neck diameter for your chamber. All of your brass will now fit. Some of it will fit differently that others because you are not turning all necks down to the same diameter, but if you are only turning because you want your ammo to fit, that method will work. I don't know why anyone would want to do it that way... you get all of the pleasure of turning necks with very little of the benefit, but it is a way for sure.
Re: 308 neck thickness?
It sound like you have a factory chamber .
If I am correct then all the external neck diameters are within SAAMI 308 specs anyway.
So if you take each batch of casese as a seperate loading issue.
Then you can just neck turn each batch seperately to a convienient size that cleans up all the cases in that batch , about 75% around the case neck perimiter.
You don't clean up totally because that may leave the neck too thin.
As stated above any cases that are way undersize and don't clean up approx 75% you can stand aside for foulers and such.
The acual diameter of the turned neck in a factory chamber is not the issue like a tight neck chamber .
All we are looking for is some better neck thickness consistancy and try to save as much brass diameter as possible . Sizing can be an issue as different batches of cases will have a different diameter if no common size is persued across all cases.
If one common diameter is required of all cases then the whole lot has to be treated as one turning batch .
What is the big issue is how you then size the neck area in future to regain some of that increased gap between the case neck and chamber walls.
If you are interested in knowing this let me know because it's a lot of typing and I don't bother anymore unless someone actually shows some interest .
This is a good thread all the above advice is very useful indeed.
If you are talking a tight neck chamber then that's a different system.
It sound like you have a factory chamber .
If I am correct then all the external neck diameters are within SAAMI 308 specs anyway.
So if you take each batch of casese as a seperate loading issue.
Then you can just neck turn each batch seperately to a convienient size that cleans up all the cases in that batch , about 75% around the case neck perimiter.
You don't clean up totally because that may leave the neck too thin.
As stated above any cases that are way undersize and don't clean up approx 75% you can stand aside for foulers and such.
The acual diameter of the turned neck in a factory chamber is not the issue like a tight neck chamber .
All we are looking for is some better neck thickness consistancy and try to save as much brass diameter as possible . Sizing can be an issue as different batches of cases will have a different diameter if no common size is persued across all cases.
If one common diameter is required of all cases then the whole lot has to be treated as one turning batch .
What is the big issue is how you then size the neck area in future to regain some of that increased gap between the case neck and chamber walls.
If you are interested in knowing this let me know because it's a lot of typing and I don't bother anymore unless someone actually shows some interest .
This is a good thread all the above advice is very useful indeed.
If you are talking a tight neck chamber then that's a different system.
