Hello, I have a new rifle (ARC CDG w/26" heavy barrel in 6BR) and I have fired virgin Lapua brass 1x. I have a Redding Instant Comparator and I'm getting readings of 0 to +.004 on the brass compared to the provided SAAMI headspace gauge. Anything above +.003 will not allow bolt to be closed. My understanding is new brass may need more that 1 firing to fully fire-form to the chamber so my plan is to neck size for the up to +.003 brass and shoulder bump the +.004 brass. I will full length size after the 2nd firing. As far as setting up my FL size die in advance, can I use a +.002 piece of brass of 1x fired brass that currently chambers, zero it on the comparator and then size so I get the -.001-002 bump on the future 2x fired brass? Thanks.
- Thread starter YamaS3rider
- Start date
As long as you have a piece of brass that’s fully formed I would use that to derive my shoulder bump number and just run them all through the full length die and skip neck sizing the short ones. If the brass is short you’re not going to bump the shoulder anyways.
What is the purpose of this rifle? .001” isn’t a lot IMO and I tend to favor minimum of .003” for any field use guns.
What is the purpose of this rifle? .001” isn’t a lot IMO and I tend to favor minimum of .003” for any field use guns.
Let the rifle tell you. Watch the video on sizing brass.
www.wheeleraccuracy.com
Videos | wheeleraccuracy
www.wheeleraccuracy.com 
Ignore gauges. Ignore internet guides. Ignore ultimate reloader. Ignore me. Ignore this forum.
Measure 2 or 3 pieces of fired brass, get an average. Size the brass 2 or 3 thou. Load and shoot. Repeat until barrel is worn out.
Dont get tied up in this. You are chasing ghosts.
Measure 2 or 3 pieces of fired brass, get an average. Size the brass 2 or 3 thou. Load and shoot. Repeat until barrel is worn out.
Dont get tied up in this. You are chasing ghosts.
Informal target shooting out to 1000 yards. No PRS or competition. I've measured 100 pieces and only one was negative SAAMI, most were +.001-003.
Good suggestion. There's almost too much information on the net. Everyone has an opinion...
Like stated above forget about SAAMI. Your chamber is your gauge. Find the largest piece that will chamber without resistance on a stripped bolt then bump it back .002-.003” and let her eat.
Huh?
If the bolt closes without resistance on a stripped bolt, WTF would you bump it another 2-3 thou?
Usually you bump it till the bolt closes without resistance, period. Done.
Lots of times that works out to 2-3 thou from fired, sure. What you're talking about is more like 4-6 thou.
I have too many rifles of the same caliber to bump necks for each. When I went to full length resizing I noticed no difference at all.
If you read my original post I prefer minimum .003” shoulder bump so shoot for .003-.004”. Just enough for bolt to close on a clean chamber is not enough IMO especially if it’s anything other than a benchrest rifle.
If he has brass that’s .001” different in length and one drops free and one doesn’t then it is pretty easy to determine chamber length. By taking that piece of brass that drops free and bumping .002”-.003” would net you .003”-.004” of bump.
I just find some fired brass that won't let a stripped bolt fall free and set up die to size it to fall free, with maybe another .001 or so to allow for some pieces springing back different or lube issues, etc. Then just run all the brass through the die. If the shoulders aren't fully fired enough then it's not going to matter as the die is setup to bump the long brass.
I've never seen a rifle that falls free on a stripped bolt have any issues, bet it dirty chamber or anything from the environment such as dirt or anything else to warrant purposely going another .003. There's also plenty of people with other opinions who size their hunting/field rifle brass to have resistance on closure and they almost never run into problems wither. Sometimes they will after repeated firings and their web gets too thick for the chamber, but it almost never renders the brass able to not be extracted even if it has a heavy lift or click at the top. I don't follow that opinion, but also realize that it still works out mostly fine for most people.
Though I also realize that having that extra .003 or so also won't really hurt much either.
I've never seen a rifle that falls free on a stripped bolt have any issues, bet it dirty chamber or anything from the environment such as dirt or anything else to warrant purposely going another .003. There's also plenty of people with other opinions who size their hunting/field rifle brass to have resistance on closure and they almost never run into problems wither. Sometimes they will after repeated firings and their web gets too thick for the chamber, but it almost never renders the brass able to not be extracted even if it has a heavy lift or click at the top. I don't follow that opinion, but also realize that it still works out mostly fine for most people.
Though I also realize that having that extra .003 or so also won't really hurt much either.
While you might be able to tell the difference between a case with the shoulder bumped one thou more than another with a stripped bolt... you're deluding yourself if you think it's going to be noticeable or make *any* difference with the bolt in its normal firing configuration. But hey, if it makes you happy, go for it
I think I'm seeing a spaghetti sandwich made sideways. 
It is absolutely noticeable to me when a case isn’t bumped back enough.While you might be able to tell the difference between a case with the shoulder bumped one thou more than another with a stripped bolt... you're deluding yourself if you think it's going to be noticeable or make *any* difference with the bolt in its normal firing configuration. But hey, if it makes you happy, go for it
You then add in some variables like spring back, dirt, debris and your asking for trouble. I’ve seen a dude lock up an action due to some debris during a stage. He was also a neck size only guy. Would have bumping a lil more solved the issue, maybe not, but it wouldn’t have hurt.
Will it make a difference shooting, most likely not, but when I’m competing or hunting don’t want any hiccups and pressure on chambering throws me off a bit.
If that means bumping a tad more I’m more than willing to take the safe bet.
If you feel comfortable the way you do things it’s ok too.
Normally takes 2-3 firings to get actual headspace unless you jammed the lands on the first firing. Like everyone said take the longest piece of brass if the bolt closes freely forget sizing load it and shoot it again. there will come a time when the bolt handle doesn’t drop on a fired case. Then you know your true headspace.
