.308 neck bumping question

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BIZERKO666

BIZERKO666

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New build for me, .308 AR10 platform. Aero Precision upper/lower, Wilson combat barrel and BCG.
Been gifted and range scrounged a bunch of .308 brass. Most of that brass measures between 1.637 - 1.626 on my Hornady Comparitor ( D400) before resizing. My rifle requires me to neck bump down to 1.622-1.621 minimum to reliably chamber. I'm looking at .004-.015. Not so worried about the .004 but everything beyond that bothers me. I am using an old Lee single stage press which requires me to turn the small base RCBS die down more than a half a turn, maybe 3/4 to achieve that dimension. I'm assuming both flex in the press and a very tight tolerance in the Wilson barrel.
Trying not to over work my brass. Have not tried a go-no go gauge yet, once fired brass yields about 1.622 form fire dimensions.
 
BIZERKO666 said:
Been gifted and range scrounged a bunch of .308 brass. Most of that brass measures between 1.637 - 1.626 on my Hornady Comparitor ( D400) before resizing. My rifle requires me to neck bump down to 1.622-1.621 minimum to reliably chamber. I'm looking at .004-.015. Not so worried about the .004 but everything beyond that bothers me.
Click to expand...

Its “free”, if it bothers you, don’t use it. You could always sell it and buy some smaller amount of brand new brass if you wanted to.
 
jmorris said:
Its “free”, if it bothers you, don’t use it. You could always sell it and buy some smaller amount of brand new brass if you wanted to.
Click to expand...
I I get that part, just never had to make such drastic adjustments with my .233, 30/30 or 300 win mag.
On a side note, I feel I lost the "cam over" effect on my old Lee press. Need an "O-press" or a new turret style for my single stage needs. My Dillon XL750 is still going strong on my pistol rounds after 27+ years.
 
Check your brass for head case separation on the longer ones, after sizing. If fired in a MG the brass will be overly stretched. If this is the case it's going to be hard to size without annealing it first. If MG fired I would toss them into the recycle bin and not put in the prep time. I have yet to need a SB die for any of my guns, including the early BAR's which were know to have really tight chambers.
 
BIZERKO666 said:
I I get that part, just never had to make such drastic adjustments with my .233, 30/30 or 300 win mag.
On a side note, I feel I lost the "cam over" effect on my old Lee press. Need an "O-press" or a new turret style for my single stage needs. My Dillon XL750 is still going strong on my pistol rounds after 27+ years.
Click to expand...

Adjustments as in have to change things or adjustment as having to turn the die past contact?

I have had die/shell holder combinations that couldn’t size the case enough, I have modified some case holders as well as faced the bottom of dies off, to allow them to close the distance from the shoulder to the head, so the case could be sized enough.

At some point the obstruction (contact between die and holder) will not allow the linkage to “cam over”, you might already be there, if you “lost” cam over but had it before.
 
BIZERKO666 said:
New build for me, .308 AR10 platform. Aero Precision upper/lower, Wilson combat barrel and BCG.
Been gifted and range scrounged a bunch of .308 brass. Most of that brass measures between 1.637 - 1.626 on my Hornady Comparitor ( D400) before resizing. My rifle requires me to neck bump down to 1.622-1.621 minimum to reliably chamber. I'm looking at .004-.015. Not so worried about the .004 but everything beyond that bothers me. I am using an old Lee single stage press which requires me to turn the small base RCBS die down more than a half a turn, maybe 3/4 to achieve that dimension. I'm assuming both flex in the press and a very tight tolerance in the Wilson barrel.
Trying not to over work my brass. Have not tried a go-no go gauge yet, once fired brass yields about 1.622 form fire dimensions.
Click to expand...
A thought or two if I may.
Firstly why bother with someone else's used mixed headstamp brass left in the dirt for your new build? You'll most likely have continued sizing problems /issues as you are already mention, additionally it may retard your load development time frame by constantly adjusting dies and presses, case volume is rarely the same so you just end up chasing your tail.
Of course buying a ( insert any number from $20 torch to a $1000 AMP) annealing machine to fix $ 50 worth of brass might help but might not either.
I would just order some fresh brass and move forward one time, it's not that expensive its just part of the build process.
 
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Sounds like you put together a great rifle.Probably the best thing to do is get it something good to eat.My suggestion is get some good brass when you can find some.$3000.00 rifle,spend another 100 for good Lapua brass.Or you could try shaving the bottom of the die or the shell holder.That rifle is going to have a tight chamber with minimal headspace,so you'll have no easy time making scroungy brass work well.Accuracy will be a lot better too.
 
jmorris said:
Adjustments as in have to change things or adjustment as having to turn the die past contact?

I have had die/shell holder combinations that couldn’t size the case enough, I have modified some case holders as well as faced the bottom of dies off, to allow them to close the distance from the shoulder to the head, so the case could be sized enough.

At some point the obstruction (contact between die and holder) will not allow the linkage to “cam over”, you might already be there, if you “lost” cam over but had it before.
Click to expand...
Could be the case, I can feel cam over on other cases, may be the die/shell holder combo or just asking too much from this little P.O.S. Lee single stage.

South Prairie Jim said:
A thought or two if I may.
Firstly why bother with someone else's used mixed headstamp brass left in the dirt for your new build? You'll most likely have continued sizing problems /issues as you are already mention, additionally it may retard your load development time frame by constantly adjusting dies and presses, case volume is rarely the same so you just end up chasing your tail.
Of course buying a ( insert any number from $20 torch to a $1000 AMP) annealing machine to fix $ 50 worth of brass might help but might not either.
I would just order some fresh brass and move forward one time, it's not that expensive its just part of the build process.
Click to expand...
Good points, Lapua brass is on my list. An annealer is definitely on my radar since I've been doing a lot more bottleneck rifle rounds lately. Most of my concerns were due to the fact that on .223, 30/30 and 300 W/M all that was required was to have the die make contact with the shell holder, give the die an 1/8 - 1/4 turn extra and I was golden. The .308 requires a half a turn or more to get me where I need to be. A bit to excessive in my eyes.

Appreciate all the suggestions guys
 
Don't worry over the fired brass you found that measures over your Rifle's fired brass. Resize it to fit your rifle's chamber. Load it 2-3 X and toss it. It was free. Segregate the long datum brass.

I Reload for 2- 308 gas guns, a SR-25 and GAP 10. On my Hornady .400 comparator insert, a reading of 1.621" = 1.630" SAAMI minimum. I used a 1.630" Go gauge and got the 1.621" measurement. What that told me is my Hornady .400 insert has a .009" chamfer on the edge. My SR-25 has a very tight chamber. Fired cases come out @ 1.622". My GAP 10 fired cases come out @ 1.625". I F/L my cases back to 1.621" and can use those cases in either rifle.

Take a few shoulder datum measurements off of some loaded factory ammo. You'll probably find the measurements around 1.620" or so. That will give you an idea of how near SAAMI minimum is.

Be aware that when using the Hornady comparator, you can get false readings off of fired brass that still has the primer in the case. Sometimes, the firing pin will crater the primer indent and it will raise a bit above the base of the case. To properly measure shoulder bump, decap the primer from the fired case. That will give a better measurement.

The proper terminology for the case shoulder datum measurement is datum length or the more common tern of "shoulder bump", not "neck bumping".
When I first saw your thread, I thought the topic may have been about neck bushing sizes.

This just helps being sure everyone is on the same page when discussing these different types of measurements.

I have a buddy who shoots a Les Baer 308 AR-10. For some reason, his fired cases come out + .009"-.010" (1.632") . I know his chamber isn't that big, I believe his rifle is over gassed. The cases come out a bit beaten up. He gives me his fired brass and I size it back down to 1.622", fire them 2-3 X and toss them.
 
FLIGHT762 said:
Don't worry over the fired brass you found that measures over your Rifle's fired brass. Resize it to fit your rifle's chamber. Load it 2-3 X and toss it. It was free. Segregate the long datum brass.
Click to expand...

That ^

If you are going to use the brass you don't have a choice , it needs to be sized down enough to fit your chamber . Keep in mind "you" are only doing this "extra large bump" once , after that you'll only need to bump a few thou . This is not to say the guy that left the brass at the range did not abuse the crap out of it before you picked it up .

I will add this , I was part of another thread recently where a guys was trying to bump his shoulders back and his Lee press was flexing to much to allow it ( leaving a gap between die and shell holder at top of stroke . I told him keep turning the die down until the gap went away and it sizes the case more , either you will size the case more or your press will break . I was wrong apparently both could happen , he turned the die down and did actually size the case down enough to chamber . Unfortunately he also snapped his Lee "C" type cast aluminum press in half . So keep that in mind when sizing your cases that much with a small base die . You will need good lube and a strong press to do so .

I get LC 308 brass from a local range that the military also uses so we can by there spent brass . That stuff is all kinds of blown out ( fat and long ) it's not uncommon for me to need to push the shoulders .010+ back not including needing the small base die . This results in needing to trim as much as .015+ after sizing . Really good long lasting brass once I get it small enough to fit in my chamber/s . I however have the benefit of knowing with 100% certainty that my brass is once fired . You do not , the brass you picked up could be fired once or thirty times you just don't know .
 
Last edited:
FLIGHT762 said:
Don't worry over the fired brass you found that measures over your Rifle's fired brass. Resize it to fit your rifle's chamber. Load it 2-3 X and toss it. It was free. Segregate the long datum brass.

I Reload for 2- 308 gas guns, a SR-25 and GAP 10. On my Hornady .400 comparator insert, a reading of 1.621" = 1.630" SAAMI minimum. I used a 1.630" Go gauge and got the 1.621" measurement. What that told me is my Hornady .400 insert has a .009" chamfer on the edge. My SR-25 has a very tight chamber. Fired cases come out @ 1.622". My GAP 10 fired cases come out @ 1.625". I F/L my cases back to 1.621" and can use those cases in either rifle.

Take a few shoulder datum measurements off of some loaded factory ammo. You'll probably find the measurements around 1.620" or so. That will give you an idea of how near SAAMI minimum is.

Be aware that when using the Hornady comparator, you can get false readings off of fired brass that still has the primer in the case. Sometimes, the firing pin will crater the primer indent and it will raise a bit above the base of the case. To properly measure shoulder bump, decap the primer from the fired case. That will give a better measurement.

The proper terminology for the case shoulder datum measurement is datum length or the more common tern of "shoulder bump", not "neck bumping".
When I first saw your thread, I thought the topic may have been about neck bushing sizes.

This just helps being sure everyone is on the same page when discussing these different types of measurements.

I have a buddy who shoots a Les Baer 308 AR-10. For some reason, his fired cases come out + .009"-.010" (1.632") . I know his chamber isn't that big, I believe his rifle is over gassed. The cases come out a bit beaten up. He gives me his fired brass and I size it back down to 1.622", fire them 2-3 X and toss them.
Click to expand...

Metal God said:
That ^

If you are going to use the brass you don't have a choice , it needs to be sized down enough to fit your chamber . Keep in mind "you" are only doing this "extra large bump" once , after that you'll only need to bump a few thou . This is not to say the guy that left the brass at the range did not abuse the crap out of it before you picked it up .

I will add this , I was part of another thread recently where a guys was trying to bump his shoulders back and his Lee press was flexing to much to allow it ( leaving a gap between die and shell holder at top of stroke . I told him keep turning the die down until the gap went away and it sizes the case more , either you will size the case more or your press will break . I was wrong apparently both could happen , he turned the die down and did actually size the case down enough to chamber . Unfortunately he also snapped his Lee "C" type cast aluminum press in half . So keep that in mind when sizing your cases that much with a small base die . You will need good lube and a strong press to do so .

I get LC 308 brass from a local range that the military also uses so we can by there spent brass . That stuff is all kinds of blown out ( fat and long ) it's not uncommon for me to need to push the shoulders .010+ back not including needing the small base die . This results in needing to trim as much as .015+ after sizing . Really good long lasting brass once I get it small enough to fit in my chamber/s . I however have the benefit of knowing with 100% certainty that my brass is once fired . You do not , the brass you picked up could be fired once or thirty times you just don't know .
Click to expand...
Thank you! These were the answers and explanations I needed to hear, makes perfect sense.
 
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