View Full Version : Heaspacing brass to correct headspace or SAAMI spec
I have once fired brass from someone else and I need to resize it. I got rid of all my fired brass so I don't know my headspace measurement. I have the Hornady head spacing kit but from what I understand the bushings don't exactly sit at a known point or to a known measurement if that makes sense. In other words the way I understand is I'd need a factory round to measure where the bushing sits on the shoulder then size my brass down until it mics the same at the bushing.
I don't want to have to buy a whole box of expensive ammo especially if this is easier than I'm making it :)
Why size all the way to SAAMI? It overworks the brass. I don't even size my semi auto brass that much.
Normally I would agree but I don't have any of my fired brass to measure and bump the shoulder back .002". I can't know how far to bump it back and have it reliably chamber unless I go back to SAAMI spec can I? Plus I'll be shooting some of the ammo in a different gun as well.
eightmillimeter
06-18-13, 03:27
Just screw in the sizing die until it touches the shell holder then back off 1/4 turn. Size and turn it in in little tiny increments until it easily chambers in both rifles.
Once you have them fired you can use the tools to measure like you normally do.
When I am dealing with setting up dies for resizing brass for many rifles, I use a case gauge.
Dillon makes them pretty cheap, but I like the quality of the L.E. Wilson brand myself.
Had a few "hiccups" long ago trying to feed 3 FAL's, started using case gauges and saved myself a lot of headaches.
Just screw in the sizing die until it touches the shell holder then back off 1/4 turn. Size and turn it in in little tiny increments until it easily chambers in both rifles.
Once you have them fired you can use the tools to measure like you normally do.
^This is the best and cheapest way without having to buy extra gages.
I also got a trick from a reloader on 68forums that once you get the shoulder bumped back enough for the bolt to close, then add a small piece of printer paper (which is usually about .004" thick) to the end of the case. Then turn the die and size until the bolt closes so you have reliable feeding in most rifles.
I think the recommended shoulder bump is .002-.004
For AR ammo, I always size back to a case guage. I have no use for ammo that will choke up one gun but run in another.
I've never really found there to be a huge variance in headspace on ARs like you'll find on a 308 bolt gun for example.
AR brass will ALMOST ALWAYS croak from loose primer pockets before it separates due to sizing.... assuming you're not bumping the shoulder too far back.
Nightvisionary
06-18-13, 09:20
I always set my die until it touches the shell holder, drop the ram then give another 1/4 turn before setting per the RCBS instructions. Is there another series of steps that I am missing that will produce more accurate ammunition? What about going a full 1/3 turn as is also mentioned in the instructions?
Case guage is the only way I set up an Auto Loader ammo die.
It depends. Do you want reliable feeding in any AR or do you want to maximize your brass life? If you want more brass life and don't plan on using your ammo in multiple rifles then I would custom headspace by taking a fired case and bumping the shoulder back .002" by using a Hornady head space gage set. Probably a good idea to keep an eye on the headspace as it grows with thousands of rounds.
If you want it to reliably shoot in all ARs then use the case gage because relying on one rifle's headspace can become a problem after a lot of rounds even though like Mark said the chambers in AR 5.56 may have less variance than other calibers or actions.
I've choked guns by pushing the upper limit on sizing brass. It's no fun. Brass isn't rare enough to be worrying about extending the life in my opinion.
I've choked guns by pushing the upper limit on sizing brass. It's no fun. Brass isn't rare enough to be worrying about extending the life in my opinion.
Depends on the caliber ;)
AR brass will ALMOST ALWAYS croak from loose primer pockets before it separates due to sizing.... assuming you're not bumping the shoulder too far back.How many firings does it take to do that, generally?
How many firings does it take to do that, generally?
Depends on the Brass and how hot you load it. LC10 brass for example... with NO NATO cross will often only get me one firing because the pocket is already blode out.
It really varies though... A full powered .223 load can go 5-7 times usually. A full powered 5.56 pressure load will only go maybe 2-4 loadings.
I cull my brass when priming it. I use the Sinclair primer and get a good feel. So the real loose ones go into a batch for their last firing before the scrap bucket.
I cull my brass when priming it. I use the Sinclair primer and get a good feel. So the real loose ones go into a batch for their last firing before the scrap bucket.
Very good practice and I do the same. The loose ones get seperated and loaded as "plinkers" then scrapped.
Very good practice and I do the same. The loose ones get seperated and loaded as "plinkers" then scrapped.
Same here. I put two stripes with a sharpie on the case body so I can spot them and scrap them when I get home.
I always set my die until it touches the shell holder, drop the ram then give another 1/4 turn before setting per the RCBS instructions. Is there another series of steps that I am missing that will produce more accurate ammunition? What about going a full 1/3 turn as is also mentioned in the instructions?
If you size with the directions listed in rcbs dies you are probably sizing down to saami specs. Rcbs rifle dies bump the shoulder back .006-.008. I have 5 sets of rcbs rifle dies that when set by directions bump the shoulder back to +-.001-.002 of saami dimensions.
My 223 brass when sized by rcbs directions it falls below the bottom step of the dillon and with the hornady headspace tool it measures out within a couple thousandths of all my factory ammo.
My rcbs dies just make contact with the shell holder and sizing is perfect right at .003 shoulder bump. If your adjusting your dies with a good bit of cam over you may be sizing to much. I do like markm does all headspace is done with the case guage so I dont have to segregate ammo an only use it in one gun.
I tend to lose AR brass before it wears out.
The only problem I've had with bumping the shoulder too far back (over sizing) is with my bolt gun.
Two years ago I started shooting and loading .308 and just used my case guage technique for bolt gun. I was wearing my brass out WAY TOO fast. Case separations up the ass with nice Lapua brass. :(
If you want to squeeze out every last bit of accuracy close headspace and overall length is something to consider. This is why guys with bolt guns do minimal resizing as possible and load long enough the bullets get at or damn near the lands. A long jump for the bullet to the lands won't be as accurate.
ETA:
And as mark said less sizing gives you longer brass life.
A long jump for the bullet to the lands won't be as accurate.
With most factory barrels this is unavoidable. But if you shoot Sierra Matchkings, they jump far and still shoot outstanding.
^This is the best and cheapest way without having to buy extra gages.
I also got a trick from a reloader on 68forums that once you get the shoulder bumped back enough for the bolt to close, then add a small piece of printer paper (which is usually about .004" thick) to the end of the case. Then turn the die and size until the bolt closes so you have reliable feeding in most rifles.
I think the recommended shoulder bump is .002-.004
If it's brass from and AR and you are sizing for another AR it could easily chamber with no sizing at all, so it might not be a good test.
If, just for example, it's brass from a 7.62 and you are going to use it in a .308; it's a whole different story.
Simple solution is load a few using the sizer die setting instructions; then after firing, the Hornady Cartridge HS tool will make sense. .002 should run fine in a 5.56 chamber, but I would go a minimum of .003+ for a semi (mine are ~.004 for .223.5.56). As the brass gets older they won't set back as much upon resizing and will end up one or two thou less.
As a side note, my SCAR-17 brass, with the shoulder set back .0045 - .0050" won't chamber without some effort in my Rem 700 .308.
It's 6.8 ammo so shouldn't be much different than 5.56.
eightmillimeter
06-19-13, 00:27
The only problem I've had with bumping the shoulder too far back (over sizing) is with my bolt gun.
Two years ago I started shooting and loading .308 and just used my case guage technique for bolt gun. I was wearing my brass out WAY TOO fast. Case separations up the ass with nice Lapua brass. :(
I feel your pain. My general rule of thumb is bumping the shoulder back .003 regardless if it is a bolt gun or an AR. .003 is more than enough for reliable feeding and case separations become a thing of the past.
eightmillimeter
06-19-13, 00:28
With most factory barrels this is unavoidable. But if you shoot Sierra Matchkings, they jump far and still shoot outstanding.
I will add that the factory throat on my Savage 10 .308 is short short short. Loading the 175 SMK to 2.80" (like the manual says and what GMM is loaded to) actually seats the bullet about .005 into the rifling in that Savage. I have heard of other Savage rifles with short throats as well.
Only way to know for sure is to buy the correct tools and measure. Sierras are very tolerant of jump as you said.
If it's brass from and AR and you are sizing for another AR it could easily chamber with no sizing at all, so it might not be a good test.
If, just for example, it's brass from a 7.62 and you are going to use it in a .308; it's a whole different story.
Simple solution is load a few using the sizer die setting instructions; then after firing, the Hornady Cartridge HS tool will make sense. .002 should run fine in a 5.56 chamber, but I would go a minimum of .003+ for a semi (mine are ~.004 for .223.5.56). As the brass gets older they won't set back as much upon resizing and will end up one or two thou less.
As a side note, my SCAR-17 brass, with the shoulder set back .0045 - .0050" won't chamber without some effort in my Rem 700 .308.
I set up all my dies qccording to rcbs directions and whas getting .006-.008 shoulder setback. Measured with the hornady heae space set up. The brass would also fall well below the low shoulder on the dillon headspace guage.
All my fired brass will load in any of my ars. I have run neck sized brass through all mine as a way to see how it worked. With multiple ars the best way is a simple headspace guage. When my brass is guaged using the dillon guage it is set back .003 from all my chambers. .003 setback has run in everything I have shot.
I still stand by the fact that when setting a die to rcbs directions the brass is being oversized. I have measured brass sized by rcbs directions and set back fell within .006-.008 that is over sized. After multiple firings and the brass work hardens you definately have to adjust the die, but I have never had to run the die so far in that I had much cam over. My brass ussuall only loaded 5-6 time.
I set up all my dies qccording to rcbs directions and whas getting .006-.008 shoulder setback. Measured with the hornady heae space set up. The brass would also fall well below the low shoulder on the dillon headspace guage.
All my fired brass will load in any of my ars. I have run neck sized brass through all mine as a way to see how it worked. With multiple ars the best way is a simple headspace guage. When my brass is guaged using the dillon guage it is set back .003 from all my chambers. .003 setback has run in everything I have shot.
I still stand by the fact that when setting a die to rcbs directions the brass is being oversized. I have measured brass sized by rcbs directions and set back fell within .006-.008 that is over sized. After multiple firings and the brass work hardens you definately have to adjust the die, but I have never had to run the die so far in that I had much cam over. My brass ussuall only loaded 5-6 time.
When set up per RCBS specs, my RCBS FL sizing die appears to size to the spec of my headspace case guage... hmm
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.