Setting up rifle dies

[Joefear7]

So I've just added .308 to the list of rifle calibers I reload and was setting up my full length sizing die. I'm using a rock chucker 4 , rcbs dies, and rcbs shell holder. I set the die per rcbs instructions and when I size the brass and put it in my lyman headspace length gauge it was too short. I backed the die off about 3/4 turn from contacting the shell plate and that got me about to just above minimum length. Am I doing something wrong?

I also put some factory rounds in my case gauge and they came out too short too. What gives?

[slamfire1]

So I've just added .308 to the list of rifle calibers I reload and was setting up my full length sizing die. I'm using a rock chucker 4 , rcbs dies, and rcbs shell holder. I set the die per rcbs instructions and when I size the brass and put it in my lyman headspace length gauge it was too short. I backed the die off about 3/4 turn from contacting the shell plate and that got me about to just above minimum length. Am I doing something wrong?

I also put some factory rounds in my case gauge and they came out too short too. What gives?

How much shorter? I have LE Wilson, three custom made cartridge headspace case gauges, and the Sheridan in 30-06 and 308.






I have plunked chamber head space gauges into these gauges and the No Go corresponded to the upper ledge, and the Go corresponded to the lower ledge. So these cartridge head space gauges calibrate to the chamber headspace gages.

And if they do so, than a sized case that is in between the Go and the No Go of the gauge, has been correctly sized for length.

I have found that on really tough cases, like 7.62 LC Match and 30-06 LC, I often have to adjust the die down closer to the shell holder. That is primarily due to the press springing. Brass reacts differently between brands and lots. Just how much you have to adjust the sizing die up and down to achieve brass sized between Go and No Go will depend on the brass.

The instructions that come with a die, size to the shell holder plus a quarter turn, if ever you get brass to size to the correct length following those instructions, go buy a lottery ticket, because, you are having a lucky streak.

Incidentally, cases that are fired and ejected out of a gas gun, you can't drop them in a chamber gauge and get the chamber head space of your rifle. You can only do that in mechanisms, like bolt guns, or single shot rifles, where you open the locking mechanism after pressure is zero. The cases in this picture, were fired in a M1a, where lubricated with Johnson Paste Wax and fired with Johnson paste wax on the cases, like the Pedersen Rifle wax lube, and as you can see, these cases lengthened on ejection.



This is because the bolt unlocks when there still is residual pressure in the barrel, the beginning of unlock is 1.4 milliseconds, the end of unlock is 2.3 milliseconds.





and the case shoulders are still sticking to the chamber as the case is withdrawn. The end result is that the case shoulders are moved during ejection. This is true for all gas guns.

Don't know if you are using a gas gun. The cartridge you are using is very popular in military service rifles.

[Joefear7]

I guess my real question is, is my gauge off?

[milw50717]

I guess my real question is, is my gauge off?

It is could be possible, but I would imagine highly unlikely as modern gauges are produced using automated CNC machinery that will process to very close tolerances.

Have you taken a micrometer to the cases and measured all dimensions, comparing them to the SAAMI specs ?

[Joefear7]

No but I did put the comparator on it and noticed I've only been bumping them back 2 thousandths to get them to fit the gauge right. The factory ammo was about 20 thousandths shorter than the fired cases.

[rsrocket1]

Compare your fully resized brass (die all the way down) in the gauge to a factory loaded cartridge that you say is 20 mils shorter in the gauge. Most likely both will have the bottom of the rim at the same depth on the gauge.

The factory ammo is probably sized to minimum SAAMI specs and the case gauge might be made to SAAMI max specs although I would guess that a case gauge ought to be made to SAAMI minimum spec because a cartridge that fits a max gauge won't necessarily fit in all rifle chambers.

[kcstott]

You need to remember full length dies size below minimum headspace.
Been reloading for close to thirty years never had a need for a case gauge.
Case guages are no representation of your actual chamber

[NorCalFocus]

[f4irder2]

I had the same problem with 223 brass and full length dies. I replaced my RCBS shell holder with a Hornady shell holder and it worked perfectly.

[tonyjr]

You have found the reason I use Lee hander loader. It is adjustable
and I use as a head space gauge / OAL .
When I was working / before I retired I had the machinist make some
for me . [ As an electrician , everyone want tape - etc ]
Since I / we use range brass , the spring back causes us to mainly use
go / no go .

[UclaPeon44]

Do yourself and buy Hornady headspace comparator. Die Gauges don't do much.

[OpenSightsOnly]

No but I did put the comparator on it and noticed I've only been bumping them back 2 thousandths to get them to fit the gauge right. The factory ammo was about 20 thousandths shorter than the fired cases.

Are you FL sizing the brass that was fired from your rifle?

If yes, use your cartridge headspace comparator to measure the brass length before and after FL sizing.

Did you also test-fit the sized brass into your chamber?

Were you able to chamber that sized brass?

If not, then you need to properly adjust your FL sizing die. Use the value of your cartridge headspace comparator as a guide.

Search and scroll down the thread post, there is a recent discussion about FL die set-ups.

[robert101]

I don't size per the manufacturer's instructions. On my 308 chamber I typically have to leave some space between dead bottom and about .01 to not under size or overwork my brass. Size the brass to your chamber.

[Joefear7]

Ok guys thanks for all the great info.

My next question is: if I want to make reloads that will work in my bolt gun my auto loaders and my friends guns how would I set the sizing? Just put my comparator on all the spent brass and size. .005 less than the smallest cases?

[FLIGHT762]

Set your F/L die to bump the shoulders of the case to be even at the bottom step of your case gauge. That should put you @ SAAMI minimum. Don't have the rim go below the bottom of the step as you show with the factory brass in your photo. That would be sizing way too much.

The ammo should have no issues chambering in any of the rifles.