I recently shot a fair amount of factory ammo in several different rifles, and didn't seperate it according to the specific rifles it was fired in. I was benchmarking performance with the factory fodder to see if it might luckily be just right for one of the 3 rifles, and just 'fireforming' the brass--obviously not just for one rifle.

When resizing the brass, one of the rifles had a shoulder of the chamber about 15 thousandths longer than the other 2 which were virtually identical. Said another way, the brass from 2 of the rifles measured say; 3.388 with my calipers with the Stoney Point headspace gauge attached. The third rifle measured something like 3.400.

What is confusing me is that when I set up my die to set the shoulder back to 3.886, it worked fine on the brass that started with a measurement of approx. 3.388 to 3.389, but the longer shouldered brass would only 'bump back' from the 3.400 measurement to 3.890.

This ammo was all from the same caseof 10 boxes, and the only difference is that it was fired in different rifles to start with.

I am wondering if the brass will only size back to a certain amount--I have screwed the die in further on the longer shouldered brass, and can get it to size down to the 3.886 size, but if I leave the die there and size a piece of the shorter shouldered brass, it ends up at around 3.380

Thoughts/recommendations?? --I know--don't mix up the brass next time--I could still figure out which rifle has the longer shouldered chamber, but I'm just trying to figure why it won't all size to the same spec????

quote:

Originally posted by Fish30114:
...the brass from 2 of the rifles measured say; 3.388 with my calipers with the Stoney Point headspace gauge attached. The third rifle measured something like 3.400.

What is confusing me is that when I set up my die to set the shoulder back to 3.886, it worked fine on the brass that started with a measurement of approx. 3.388 to 3.389, but the longer shouldered brass would only 'bump back' from the 3.340 measurement to 3.890.

I am wondering if the brass will only size back to a certain amount--I have screwed the die in further on the longer shouldered brass, and can get it to size down to the 3.886 size, but if I leave the die there and size a piece of the shorter shouldered brass, it ends up at around 3.380

Don, here is my take on what you are seeing.

When you FL size a piece of brass, and even more so when you partial FL size them - as you are really doing when you attempt to set back the shoulder only .002" - the actual amount you manage to change the head-shoulder dimensions is a result of multiple factors.

In particular, the effect of sizing the brass in the case walls will generally cause the head-shoulder dimension to increase. You'll see this effect as you set up your die for partial FL resizing. As you screw down your die, but before you hit the adjustment where you achieve the required shoulder set-back, if you take readings at every intermediate setting, you will notice the head-shoulder dimension suddenly increasing, as opposed to being reduced. This effect comes from sizing the case walls, since the brass only has one way to go, it moves upward towards the case shoulder.

By setting your die deeper, you'll eventually achieve the required shoulder set-back - the shoulder of the die finally pushes enough to set back the shoulder, including whatever brass has flowed forward during the sizing operation. So I conclude, that where the die needs to be set for brass fired in a particular chamber, will be where the combined effect of head-shoulder dimension increase and head-shoulder dimension reduction adds up to the required dimension.

I'm guessing that the chamber producing the "long sized" cases will be quite a bit wider, and therfore the case wall sizing - and resultant head-shoulder dimension increase - will be more pronounced. To overcome this effect, the die needs to be set deeper to achieve the head-shoulder dimension you are after.

Does that make sense??

I think it really illustrates, that we normally need to keep FL dies separate for the various rifles we shoot. You did well in quantifying the effects on sizing on your brass. If you had not done so, and by chance had set the die up to size the "longer" brass, you might have created a headspace problem with the "shorter" brass.

It is a pain in the posterior, but we really need to keep brass separated by the gun it has been fired in, and size with a die set up specifically for this particular brass/chamber combination.

- mike

I`ll add spring back to your problem. The longer brass has been worked more and wants to return to its static state. The die bumps it back but the brass resistes the movement and tries to return to its original lenght. Try as suggested, and set your die a bit deeper.

quote:

Originally posted by Fish30114:
...the brass from 2 of the rifles measured say; 3.388 with my calipers with the Stoney Point headspace gauge attached. The third rifle measured something like 3.400.

--I know--don't mix up the brass next time...

Hey Fish, That 0.012" diffference can result in a real problem called Insipient Case head Separation(ICHS) "if" you continue to try and make them all conform to the shorter length. Just had a guy blow-up his rifle as reported on this Board because of it a couple of weeks ago.

Apparently you do have the ability to go back and "Segregate" the longer cases from the shorter cases if your Stoney Point thingy will give you some believeable info. So, go do that to start with.

Then either buy a second set of Dies, or face reality and realize you will be readjusting your current set all the time. I prefer a set of Dies for each rifle, even if I have multiple rifles in the same caliber.

Both the above posters gave good advice. And I sure don't want to see you blow-up a rifle. So, you might want to make an " L " shaped wire Feeler Gauge and check inside the cases to see if they have the ICHS Groove where the Pressure Ring is located. Nip off the end of the wire with a set of Side Cutters before you bend it to create a small Chisel Tip on the end of it.

If you begin feeling the Groove after a couple of Full Length Reloads, you need to just go on and Trash them. Of course, P-FLRing eliminates this as an issue in most Action types.

Best of luck to you.

Thanks guys, that confirms some thoughts I had, and I am planning on one sizing die per rifle, more stuff to buy--yoohoo!

I have gone ahead and segregated the 'longer shouldered' brass Hot Core, I will do the ICHS feeler gauge test for sure.

Mike that does make a lot of sense of the 'longer' brass having a wider chamber as well and causing more forward movement of the shoulder. I had been thinking what Ol Joe said, I was trying to get all this brass set up for the 'shorter chambered rifles' but I'll take the long stuff and get a die set up for that rifle only.

Thanks again guys--Don