7.62x39 Cartridge Headspace Issue?

[impactco]

I have been reloading 1x or 2x fired Fiocchi 7.62x39 brass which I purchased as new factory ammo and I have noticed that the rim of many of the resized cases protrudes above my Wilson gage. If I smack the case on my bench while in the gage, it then seats in the gage correctly. I have tried adjusting my resizing die lower on the assumption that I am not pushing back the shoulder enough but I am already at the lower limit. I'm using a Rock Chucker press with RCBS resizing die and shell holder. I have checked for burrs on the edge of the gage and there are none. There is no lube or debris in the gage or on the cases. There are no burrs on the edge of the case rim. I have tried lightly running a file around the rim on one of these cases and the case then enters the gage correctly. The length of my resized cases are all within spec. The fresh factory Fiocchi ammo doesn't exhibit this behavior and enters the gage fully with no resistance. The rounds seem to chamber OK in my Vector AK and my DPMS AR upper but I am puzzled by this. Would the rim swell or become out-of-round after only a few firings? Any thoughts? Thanks.

This is correct:


This is not correct:


Factory round on the left, correct reload in the center, tight reload on the right. My reloads are crimped with a Lee Factory Crimp die:

[dardascastbullets]

Without a closeup photo of the case head or the rim my educated guess is an extractor problem. Then too it could be two problems in one: a somewhat heavy load causing an extractor problem. Your statement about 'running a file around the rim' leads me to believe that this may be your problem.

Matt

[impactco]

Interesting thought but my reloads so far have been the lowest powder charge listed in my Lyman manual for this powder and bullet weight. Now, the Fiocchi factory ammo might be hot but only 1 firing would cause this? I checked a factory case rim with a micrometer as compared to a fired and resized case and the rim on the fired case is as much as .0015 larger in diameter.

This is as close-up as I can get with my camera. Factory round on the right, good reload in the center and the tight rimmed reload on the left:

[WSM MAGNUM]

Your size die may be stretching the shoulders back out again. Did you check for that after you resized? Bushing size dies will correct that problem.

[mkl]

I checked a factory case rim with a micrometer as compared to a fired and resized case and the rim on the fired case is as much as .0015 larger in diameter.

Since you are using minimum loads, overpressure is probably not a problem, but it would not hurt to check.

Measure the rim or web of one of your "good" cases before firing. Take another measurement at the same place after firing. If you are getting any expansion, the pressure is too high.

Case to case manufacturing tolerances may vary .0015, but the rim or web should show no expansion in the same case before and after firing.

[steve4102]

The Wilson case gauge is a joke! It is set to Min SAAMI specs which your rifle or any other rifle for that matter clearly is NOT. Adjust your FL die to set the "head to shoulder" measurement specific to YOUR rifle and toss the Wilson in the "Purchased by Mistake" file.

If you want to know what your rifle needs and how to set up your FL dies correctly get one of these http://www.midwayusa.com/eproductpag...eitemid=479704
they are invaluable and work with just about every cartridge you can imagine.

Or you can set up your dies this way.



1. Put the Shell Holder in the press and raise the ram.

2. Screw the Full Length(FL) Die into the press so it is about a "nickle's thickness" above the Shell Holder.

3. Lube a "Fired" case (walls and inside the neck) and squash it.

4. Remove the Lube and try closing the bolt on it in the chamber.

5. If the bolt closes with no resistance, screw the FL Die into the press about 1/8-1/4 turn and repeat steps 3 & 4.

6. As you feel the resistance begin, slow down how much you screw the FL Die into the press so you are at about 1/16 of a turn, or "Fine Tuning". At some point you will not be able to close the bolt and you are extremely close to having the FL Die in the proper position.

NOTE: The reason for this is because the FL Die has begun Resizing the Case-walls down to the Pressure Ring. As it does so, the Case-body lengthens slightly which in turn moves the Case-shoulder slightly forward. Then as the "Fine Tuning" continues the Case-shoulder makes contact with the FL Die and is moved slightly reward(or slightly shortens the Case-head to Case-shoulder dimension).

7. Stop when there is a slight bit of resistance when closing the bolt on the empty case. You now have a "slight crush fit" for the case in that specific chamber, or Zero Headspace.

8. Once you get it where you want it, take some masking tape or a black marker and put a Witness Mark where the FL Die Lock Ring is positioned to hold the FL Die in this position. Loosen the FL Die and return the Lock Ring to align with the Witness Mark and sung up the Set-Screw.

Screw the FL Die back into the press and try squashing another case. It should have the same resistance as the previous one. If not, you need to re-adjust the Lock Ring so it does. But you are extremely close to where you want it, so make very small changes at this point.

Occasionally check the fit of the cases in the chamber, say every 5th firing just to make sure nothing has slipped. Checking more often won't hurt anything and give you confidence that the Set-Up is still proper.


The Wilson, waist of time and money!!

[impactco]

Thanks for the advice guys. I'll post followup when I figure this out.

[Armedmusician]

I'm a newcomer to reloading; early this month I finished setting up a Dillon RL 550 B progressive press. Among other calibers, I'm planning to reload 7.62 x 39 mm. for my (Chinese) SKS type 56 rifle. As Dillon does not make a case guage for this caliber, they are supplying me with a L.E. Wilson guage (backordered for about a month, thanks to the election!). Needless to say, I was alarmed and confused by the posting by Steve regarding the Wilson guage. 2 notes-the guages for pistol calibers I load (.380 ACP, .40 S & W, .44 Rem. Mag.) are supplied by Dillon, and appear to work just fine. The 7.62 Russian die set which I ordered from Dillon is made by Redding, as Dillon doesn't manufacture dies for this caliber. I realize that I'm responding to a thread from last summer, but as I'm new to this I figure I should learn as much as I can.

[impactco]

In my case the issue was that the violent cartridge handling of the AK is dinging up the circumference of the rim causing the reloaded cases not to enter the Wilson gauge.

[giz189]

Just get a small base sizing die. A lot of semi autos require this.

[impactco]

A small base die does not resize the rim.

[brickeyee]

If you are going to reload rimmed cases they will last longer if you change to using the shoulder to headspace.

If you full length size a rimmed case head separation is going to happen much sooner.

[impactco]

Nobody is talking about rimmed cases here.

[brickeyee]

Same thing applies to rimless.

If you full length size every time you will stretch the brass excessively and have case head separation sooner, especially if you chamber is at the long end of tolerance.

The 'standard' directions are so that the cartridge will be reduced to as close to minimum size as possible and chamber in any gun of the caliber.

If you are going to use the same case in the same gun there is no reason to work the brass this much.
While semi-autos are not as good as bolt guns at chambering an even slightly to large case, you still do not need to bring tham back to minimum size.

Making sure the shoulder gets pushed back 0.001 to 0.002 is more than enough.

[steve4102]

While semi-autos are not as good as bolt guns at chambering an even slightly to large case, you still do not need to bring tham back to minimum size.

Making sure the shoulder gets pushed back 0.001 to 0.002 is more than enough.

Bingo, That is why I stated that the Wilson gauge is a joke. There is absolutely no reason to size brass back to Min specs, unless Min is what your rifle happens to need. The best case gauge out there is the chamber itself. Size the brass to fit the actual chamber and not some Min spec gauge.