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I am changing barrels to a CBI 308. I bought 200 pieces of new Lapua brass. I have a go gauge that measures 1.634 with my gauges. I measured a sampling of the brass. It all measured 1.618. Would it serve me well to set the barrel at 1.620? It is going to be a target only rifle. I figured if I did this it would keep me from having to fire form the brass before doing a load work up. Or would that extra case capacity be beneficial?
You need to measure to the datum line of the Go Gauge and the case to get a correct measurement not overall length. Not exactly sure how you would do that but if you want your headspace to fit your cases you can use one of your cases as the GO gauge then add a couple pieces of scotch tape to the back of the case as a NO GO.
Thanks. I guess what I was looking for is if the little bit of case space is worth the hassle of fire forming all the brass.Quote:
Originally Posted by stomp442
I don't how or what you're measuring but neither are anywhere even close to right. If you have a depth mic or caliper drop the Go in the chamber ( the barrel uninstalled) then measure it's protrusion then do the same with a couple sticks of brass. The brass will typically be in the neighborhood of .001"-.003" less.Quote:
Originally Posted by Kill N Grill
Bill
Ok lets see if I can do some pictures
This is from the Lee reloaders manual. Note it shows head space as 1.634
http://i1060.photobucket.com/albums/...-11_41_48.jpeg
This is a piece of new Lapua brass. As measured it is 1.618http://i1060.photobucket.com/albums/...-11_42_50.jpeg
This is a piece of FC brass that was fired from this rifle.
http://i1060.photobucket.com/albums/...-11_43_13.jpeg
So my question is. Should I or would it be advantageous to head space with this new Lapua brass or just leave well enough alone? For the size difference I would think that doing a load development with the new brass would be a waste of time.
I have a PT&G Go for 243,260,308 etc. It's marked as 1.630 but where my comparator touches it measures 1.620". My brass usually comes out fired around 1.621 and I size it down to 1.6195-1.620 as close as I can measure with these kind of tools. You're sure you measured everything with the same caliper and comparator setup, including the gauge? For NoGo I add a piece of blue scotch tape to the bottom of the Go gauge. As an aside my new Lapua 260 brass measures 1.619" so I doubt your brass is undersized. If it were me I would set the barrel headspace to the brass, 1.620 like you said. If you are stretching from 1.618 to 1.629 after firing your brass won't last very long being so worked. That's my 2 cents, take it with a grain of salt.
As shown in the pic head space is measured from the very back of the case to the center of the shoulder the difference between safe and non safe is only around 1-2 thousands of an inch you can head space it with your brass, but after you do I would still verify that it passes the NO-GO test either by using a NO-GO guage or a GO guage with a piece of cellophane tape taped to the back of it. I don't think its unsafe to have head space on the tight side you just might find your bolt hard to open after a fired round.
Your go/no-go gauges are precision tools.
Your comparator is not (at least comparatively speaking).
My personal recommendation would be to:
1. Set the headspace with your headspace gauge.
2. Find some fired brass that will not chamber in your rifle. Brass fired in a semi-auto will often work for this.
3. Adjust your full length sizing die to size this brass just enough to chamber "effortlessly".
4. Size, load, and fire your new (or any) brass.
You can then either full length re-size using the die as adjusted above or neck size it only.
Imagine this scenario: You assemble this rifle with an under-sized chamber to fit your brass. You get run over by a beer truck. Your wife sells all your toys. Some nimrod tries to load factory ammo in your rifle with the under-sized chamber and............................. Your wife is now obligated to compensate said nimrod for his injuries. Not a pleasant thought.
I recently put a 223 barrel on and used once fired brass that had been shot in the same barrel. I used a piece of tape on the brass and then confirmed it with go/no go gauges, worked well using the tape method. Just wanted to see if it would work.
I went back and measured some more. I have a Forster not PT&G Go gauge. My comparator has a ~.395 hole not .400 as is where the datum line is officially measured. So I'll have a smaller measurement than SAAMI. Having said that I measured my gauge and got 1.620" again. I also measured three separate brands of loaded factory 308 (Black Hills match, Hornady match, and Remington 150 SP. All three brands measured 1.618 to 1.6195 with the same comparator so they're just under what should fit into a min spec chamber. When I look at a SAAMI spec print I see the max cartridge headspace is 1.634 and the minimum chamber spec as 1.630 measured at .400 in the shoulder. Maybe your gauge is mismarked or the wrong one? Something is definitely not right. If you treat it nice and mail it back to me I'll loan you my Go gauge as a comparison.
I fixed my typo in the OP. I believe it was marked 1.634 and not 1.643. What I did was put this barrel on the action several months back. Then I mounted in a stock. I fired maybe 30 rounds from it. That was enough to know that I did not like the stock it was in. So I shelved it till hunting seasons were over and I had some funds for another stock. So I finally got my new stock. Fired another 30 or so from it and decided it was the one I would stay with. I then ordered up some new brass and bullets for it. I have looked for the gauge and can not find it. I may have since loaned that gauge out to someone and don't remember who. So in the OP I was going by memory of the markings on it.
I will use a piece of the new brass to set the head space with a piece of tape on it. Load a round and see how it measures after firing. If It comes out good all is swell. If not I may take you up on your offer, Alphapygmy. BTW that's a good screen name.
Here's a picture of the project
http://i1060.photobucket.com/albums/...-21-07-41.jpeg
Well 1.634 sounds in the ballpark compared to the 1.643 you had originally. If memory serves though I think a Go is 1.630, NoGo is 1.634, and a field gauge is 1.638. So you may still be using a NoGo. I still think if your brass is growing that much you need to re-headspace it. When you find the gauge measure it then your unfired Lapua brass, the brass should measure just under the Go if everything is correct. All the new Lapua I've ever bought in 308 and 260 has come sized ~.001 to .0015 under my Go gauge. I would definitely find or borrow a Go just to be sure though. Careful setting headspace with brass, it's not solid like a gauge.
It's for a pygmy goat that I had that was quite possibly insane. Best case was he thought he was a water buffalo, worst case possessed by the the devil!Quote:
Originally Posted by Kill N Grill
My wife always dressing him in costumes for holidays didn't help either. He was one of those pets that has so much personality you only find one once in a lifetime.
Woman do strange things when their motherly instincts are a little "off."
http://i759.photobucket.com/albums/x...pswbphkpdx.jpg
Better the goat than you, eh?
I think that would make for an awesome Halloween. Of course it could be a birthday. Other than that I am at a loss for a holiday for a pirate. Especially for a pet goat. I once worked on a house where the lady had a pet goat. That thing would jump into the bed of my truck as soon as I lowered the tail gate. Then onto the cab roof. He would challenge you to get him off of it. It was rather annoying working with the tail gate closed all day.Quote:
Originally Posted by alphapygmy
She dressed them up for Christmas, New Years, National Talk Like a Pirate Day, Halloween, Valentines, and more. I just sat back and watched as they tried to eat the costumes off each other. They liked to eat costumes almost as much as junk mail and poly tarps. Is this a record for thread drift or what.....:p
http://i759.photobucket.com/albums/x...psgmo4h0hv.jpg
http://i759.photobucket.com/albums/x...psgih5fg3x.jpg
http://i759.photobucket.com/albums/x...psxty4elwa.jpg
http://i759.photobucket.com/albums/x...pse04d3183.jpg
It has run down the exit ramp and jumped on another track.
If you put the CBI barrel on with a go and no go gage,shoot it. If after firing it springs back to 1.6295 and the new is 1.618 as new the shoulder of your chamber could be slightly different than the way lapua forms the case so it will form to any chamber. It is a difference of .011 thou, if you are really worried just seat the bullet to touch the lands to hold the case in position during ignition or redo the headspace. I think you got a false feel when you brought your barrel into touch the face of the bolt. I tighten by hand only the barrel to seat against the bolt face with the gage in the barrel and remove the ejector so it doesn't interfere with the base of the gage. I then try the no go and it wont close. Then I try a piece of new brass and I can feel just slight resistance when closing the bolt.I believe you did something wrong.