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Old November 22, 2008, 08:45 PM   #1
stump shooter
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.308 headspace and sizing

I am starting to load for my FN PBR XP in .308 and everything is coming together nicely but I have a question regarding some headspace measurements I'm getting.

So far I am using some once fired (factory loaded) brass, fire formed to my chamber. Brass is from several, same lot boxes of Winchester and Hornady Match.

I am using a Redding F/L S bushing die and per Reddings instructions for the die, I have made adjustments to result in about 80-90% of the neck getting sized with the die body finally being only 1/4 turn from touching the shell holder.
Using a Hornady headspace comparator I am seeing absolutely no change in the shoulder position from the fired case to the sized case.
Case growth from new/unfired to fired is consistently .005".

The stripped bolt closes freely with just a faint amount of tension as the bolt is almost closed.

Am I safe to assume that the brass is still young and it will take another firing or two before the die really will work against the shoulder or am I not getting something? I am used to F/L sizing for a 30/30 lever gun and .45s and more precise loading is a little new to me.
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Old November 22, 2008, 09:48 PM   #2
rn22723
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First off you need to seperate the brass. Either use one brand or another for your reloading, but you can not mix brass in rifles. It is dangerous, because case capacity varies and thus a load developed in WW brass may not be safe in the Hornday.

To really set up your FL die, you need a RCBS Precision mic to measure fired cases from your chamber. Then you set the die to push the shoulder back about 2 to 3 thousandths. To me, I would neck sizing using a Type S die.

More then likely your going to need different bushings for each brand of brass.

I size my 308 brass in two passes. For Lapau I use a 339 bushing, and then a final pass with the 336. Whereas with WW brass I use 336 and then 331 bushing. This helps to minimize the work hardening of the brass.
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Old November 22, 2008, 09:58 PM   #3
Unclenick
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This is not the age of your brass. It will work harden with age and actually get more resistant to sizing. You just don't have the sizing portion of the die down far enough. Set the bushing and decapper back and adjust the sizing portion down until it sets the shoulder back 0.002". Then adjust the neck bushing and the decapper to give the desired neck sizing to remove primers without jamming the inside of the flash hole, respectively. It is normal for a sizing die to touch the shell holder plus a fraction of a turn to allow for press spring. Redding makes its competition shell holder with different lip thicknesses just for the purpose of achieving touchdown without over-sizing beyond that 0.002" setback.

0.002" is the difference in headspace between a SAAMI minimum headspace chamber and the SAAMI maximum headspace for a new piece of brass in cartridges that headspace on their shoulders. There may be exceptions, but this is generally enough difference to guarantee magazine feeding in most firearms.
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Old November 23, 2008, 12:30 AM   #4
stump shooter
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Unclenick, I was not aware that the competition shell holders had different thickness above the rim. If I can't get the set back with the die down farther than I have it I will pick up a set and work on getting the shoulder back .002" from the fired position. I just couldn't figure out how to get much farther down without die swaging issues

rn22723, I am very aware of separating the brass and working them up individually. I was just noting the consistencies I am getting in their fire formed size and trying to understand all the factors involved. I want to work with small quantities before I run with big lots. I bought a thousand new Winchester brass (all same lot) and from what I can tell, I am probably going to have to use the expander button and use a couple different bushings to straighten things out. Do you run the two different bushings to shape new brass only or do you use the same procedure on fire formed cases as well?
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Old November 23, 2008, 11:32 AM   #5
Slamfire
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Quote:
The stripped bolt closes freely with just a faint amount of tension as the bolt is almost closed.
This is a problem frequently encountered by people who use their rifle chambers as their only test of sizing. The leverage you get with the bolt handle and camming surfaces reduces your sensitivity. What you are feeling is your bolt sizing your case down. Obviously your cases are just a little oversized. And you need to increase the amount of case sizing.

The more times your brass is fired and sized it will work harden. Then you will notice even more difficulty in closing the bolt. I have measured changes in springback changes as brass work hardens.

I have a number of 308 rifles. Depending on the reamer used, the shoulder angle is a little different rifle to rifle. When you use a Comparator, it is basically measuring the diameter of a circle. The location of that circle will vary based on shoulder angle.

I really don't know if a comparator is a more "accurate" or "precise" way of measuring headspace than a cartridge headspace gage. I do know my Wilson gages correspond exactly to my chamber headspace gages, so they are calibrated to a standard. You cannot say that of a comparator.

I drop my sized cases in a Wilson gage, and size my cases to gage minimum. That works in most cases. It is functionally better to have a case with .002 or .003 shoulder clearance after sizing, than a case that is a crush fit. Someday the crush fit will require too much force to close the bolt. Accuracy difference between full length sizing and "neck" sizing is debateable. At least in rifles fired without a bench rest. Bench rest competition is a different game, people imitate their reloading technics, but things that show up in bench rest competition are in the noise level for hunting rifles or your PBR.
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Old November 23, 2008, 12:21 PM   #6
stump shooter
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Thanks for the additional info Slamfire1.

I have been waiting for a Wilson HS gauge that is on back order from Midway

I went ahead and turned the die down farther (bushing and decap assy removed) and was able to bump the shoulder back approximately .002" according the the comparator gauge. I still have about .005" between the holder and the die. I was just apprehensive about how far down the die should go

I realize that the bolt test is not an appropriate method, I just wanted to mention it as another diagnostic tid bit for you Pros. The bolt now does cam closed with absolutely no effort though.

I would still like to understand the need to run the necks through two different bushings though, if anyone could take the time to explain a little further it would be appreciated.

Thanks,
ss
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Old November 23, 2008, 12:53 PM   #7
F. Guffey
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Stump Shooter, I make gages if I need one, If I want to check head space I purchase cases that have been fired in a rifle with a long chamber, again I have a M 1917 that has a chamber that is .011 over a go gage (.016 thousands over SAMMI factory ammo), there should not be a problem finding 308 Winchester ammo that is once fired, and too long from the head of the case to the shoulder, and if I want to fire ammo in a 308 Winchester chamber with .000 head space, I form the 308 cases using 30/06 cases, when forming the 308 case control the amount the case is formed by controlling the amount of sizing with a feeler gage. The shoulder on the 30/06 is moved back .389 thousands, when forming the 30/06 to 308 Winchester the shoulder passes Japanese 7.7 at 1.782, the 8X57 at 1.819 and the 7X57 at 1.727, unless your press is not adjustable or as I am told some have 'springy presses, in that case crush the case with additional turn of the die or hesitate and let the (bind) spring of the press size the case.

If one turn of the die is .0714, 1/2 turn is .0357 and 1/4 turn is .0178, with these type adjustment, what is the difference is sizing between 1, 1/2 and 1/4 turn beyond contact, or as some choose to say, cam over, when the shell holder hits the shell holder any thing beyond that springs the press, the bottom or the top, if the case was not being sized when the ram is raised, the gap between the shell holder and bottom of the die could be measured, my philosophy, the shoulder sit back can be controlled, no gap, full length sizing, a gap, full length sizing less the gap, if the gap is .005, the press is prevented from full length sizing by .005.

Sizing: neck size, partial neck size and full length size, all can be controlled with the gap, a gap of 1/4 turn OFF is .017 thousand, that would mean the case was not full length sized by .017, this will be indicated on the neck, I prefer to adjust the die down and use a feeler gage to adjust the gap, on the M1917, I use a gap of .014 or .015.

A friend called and wanted to check 20 30/06 case, 5 did not fire, 13 were fired in the same rifle and 2 cases were fired in another rifle, the first thing we did was check effect the unfired cases had on head space, WITH A WILSON CASE LENGTH GAGE in thousands, .0025 under maximum, we then checked the 13 fired cases and the effect the chamber's head space had on the fired cases, there was .002 thousands difference between the fired and the unfired cases, the rifle was new and the ammo was factory, we pulled the primers and examined, we reinstalled the primers with a Lee hand primer (this same friend borrowed my RCBS and has not returned it), We chambered the primed cases in a reincarnated M1917 and fired the dented primed cases, all one after the other, nothing wrong with the primers, I ask my friend if he had contact information on the man that had the 'misfires' "no" it will happen again and Remington will get a call, another shooter at the range tried to shoot the 5 rounds, nothing. with the dented primers, that could be expected on a short stroking firing pin.

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Old November 23, 2008, 01:39 PM   #8
30Cal
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Quote:
I am using a Redding F/L S bushing die and per Reddings instructions for the die, I have made adjustments to result in about 80-90% of the neck getting sized with the die body finally being only 1/4 turn from touching the shell holder.
Using a Hornady headspace comparator I am seeing absolutely no change in the shoulder position from the fired case to the sized case.
Then you're not FL resizing. If you want to move the shoulder back, you'll need to thread the die down farther till the shoulder moves back.

The other possibility is that the case shoulder is being forward as you withdraw it from the die due to inadequate lube.
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