I have .308 Lapua brass that has been fired 4 times. My lengths are from 2.005" to 2.010". Do I need to trim them all to the same length or are they good as long as they are within specs? I am loading some 175 smk for 1000 yards. I trimmed them to 2.005" last time I loaded them (only fired once since trimmed). Thanks
.308 case lenght
- Thread starter mattr25
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Re: .308 case lenght
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattr25</div><div class="ubbcode-body">I have .308 Lapua brass that has been fired 4 times. My lengths are from 2.005" to 2.010". Do I need to trim them all to the same length or are they good as long as they are within specs? I am loading some 175 smk for 1000 yards. I trimmed them to 2.005" last time I loaded them (only fired once since trimmed). Thanks </div></div>
This is a game of small improvements but I don't think you will see a lot of difference in POI with this small difference in case length.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattr25</div><div class="ubbcode-body">I have .308 Lapua brass that has been fired 4 times. My lengths are from 2.005" to 2.010". Do I need to trim them all to the same length or are they good as long as they are within specs? I am loading some 175 smk for 1000 yards. I trimmed them to 2.005" last time I loaded them (only fired once since trimmed). Thanks </div></div>
This is a game of small improvements but I don't think you will see a lot of difference in POI with this small difference in case length.
Re: .308 case lenght
What YAOG said, and more specifically from the 'Case Prep' stick in this forum:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">
Trim to length: upon firing of the loaded round the case greatly softens and inflates like a balloon to fill the chamber of the weapon. This seals the chamber and prevents gas leaks, etc. but with the brass nearing a liquid ("plastic") state it flows with the pressure of the propellant gas. Hence as stated before our primer pockets not staying uniform, the over all length of the case grows and the mouth of the case typically thins. Your reloading manual will give you the nominal "trim to length" measurement of a given cartridge case. So place said case in your case trimmer and trim it back correct? No.
NO!!! We are precision shooters for crying out loud. I have a friend that mows every case he get's his hands on back to minimum length and it gripes me to no end.
Historically & generally speaking the classic ultra accurate cartridges of the Bench Rest enviornment have longer than normal case necks. The typical case neck for a given cartridge is one caliber wide. Example: a 308 Winchester's bullet is a diameter of .308" so therefore the rule of thumb is the mouth of the case should be "about" .308" long minimum. This allows good bullet tension and support so our carefully assembled loaded round's bullet is sitting dead inline with the cases' centerline- which is inline with the centerline of the bore. All this leads to good shooting and smiles. The more we hack back the case mouth the less neck we have to make sure our bullet is held inline. And the benchrest cartridges I mentioned- they have caliber plus neck lengths for this reason.
So what do we do? If the case gets to long, it will engage the rifling at the same time the bullet tries to giving us a wild & very dangerous pressure spike. If we hack it back to bare minimum we may have given room for a little loss of accuracy, especially with rough handling of ammo in the field. But we HAVE TO maintain consistency from case to case for shot to shot.
The answer is to measure the chamber length in your individual rifle and stay trimmed back from that actual number. Small chamber plugs to get that measurement are sold by Sinclair and others.</div></div>
What YAOG said, and more specifically from the 'Case Prep' stick in this forum:
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TresMon</div><div class="ubbcode-body">
Trim to length: upon firing of the loaded round the case greatly softens and inflates like a balloon to fill the chamber of the weapon. This seals the chamber and prevents gas leaks, etc. but with the brass nearing a liquid ("plastic") state it flows with the pressure of the propellant gas. Hence as stated before our primer pockets not staying uniform, the over all length of the case grows and the mouth of the case typically thins. Your reloading manual will give you the nominal "trim to length" measurement of a given cartridge case. So place said case in your case trimmer and trim it back correct? No.
NO!!! We are precision shooters for crying out loud. I have a friend that mows every case he get's his hands on back to minimum length and it gripes me to no end.
Historically & generally speaking the classic ultra accurate cartridges of the Bench Rest enviornment have longer than normal case necks. The typical case neck for a given cartridge is one caliber wide. Example: a 308 Winchester's bullet is a diameter of .308" so therefore the rule of thumb is the mouth of the case should be "about" .308" long minimum. This allows good bullet tension and support so our carefully assembled loaded round's bullet is sitting dead inline with the cases' centerline- which is inline with the centerline of the bore. All this leads to good shooting and smiles. The more we hack back the case mouth the less neck we have to make sure our bullet is held inline. And the benchrest cartridges I mentioned- they have caliber plus neck lengths for this reason.
So what do we do? If the case gets to long, it will engage the rifling at the same time the bullet tries to giving us a wild & very dangerous pressure spike. If we hack it back to bare minimum we may have given room for a little loss of accuracy, especially with rough handling of ammo in the field. But we HAVE TO maintain consistency from case to case for shot to shot.
The answer is to measure the chamber length in your individual rifle and stay trimmed back from that actual number. Small chamber plugs to get that measurement are sold by Sinclair and others.</div></div>
Re: .308 case lenght
I have already read that post so I guess my question is, is .005" too much variation between case lengths? Will this be an issue with accuracy? Even if my lengths were 2.020", would 2.015" to 2.020" be acceptable tolerances? Or should they be within .002"? What's the tolerance?
I have already read that post so I guess my question is, is .005" too much variation between case lengths? Will this be an issue with accuracy? Even if my lengths were 2.020", would 2.015" to 2.020" be acceptable tolerances? Or should they be within .002"? What's the tolerance?
Re: .308 case lenght
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattr25</div><div class="ubbcode-body">I have already read that post so I guess my question is, is .005" too much variation between case lengths? Will this be an issue with accuracy? Even if my lengths were 2.020", would 2.015" to 2.020" be acceptable tolerances? Or should they be within .002"? What's the tolerance? </div></div>
I try to keep them within 0.005" which is why I said I don't think it makes much difference at this point. But I agree that you want to keep the cases at or near max. spec length for best support of the bullet. Some folks just let them grow a few thou less than their actual chamber length but this limits what you can use the loaded rounds in to your one rifle or rifle that has a similar length chamber.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mattr25</div><div class="ubbcode-body">I have already read that post so I guess my question is, is .005" too much variation between case lengths? Will this be an issue with accuracy? Even if my lengths were 2.020", would 2.015" to 2.020" be acceptable tolerances? Or should they be within .002"? What's the tolerance? </div></div>
I try to keep them within 0.005" which is why I said I don't think it makes much difference at this point. But I agree that you want to keep the cases at or near max. spec length for best support of the bullet. Some folks just let them grow a few thou less than their actual chamber length but this limits what you can use the loaded rounds in to your one rifle or rifle that has a similar length chamber.
Re: .308 case lenght
Get a Sinclair chamber plug and measure your chamber, will cost you less than $15 including shipping. Then you'll know your exact chamber size. My TRG is 2.044" or so, so cases at 2.020" wouldn't even be close to "trim time" in my rifle.
Get a Sinclair chamber plug and measure your chamber, will cost you less than $15 including shipping. Then you'll know your exact chamber size. My TRG is 2.044" or so, so cases at 2.020" wouldn't even be close to "trim time" in my rifle.
Re: .308 case lenght
I would think that you should be fine with shooting the rounds as is.
One thing you might want to consider doing,on a box of brand new brass trim them .005 right out of the gate.
I would think that you should be fine with shooting the rounds as is.
One thing you might want to consider doing,on a box of brand new brass trim them .005 right out of the gate.
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