Headspace one more time

[Bob Thompson]

I have an old Spanish Mauser in 7X57 I use as a trunk gun when traveling the backwoods of Utah. I have checked the headspace and it is barely acceptable. After test firing some rounds carefully I have checked the primers and they are protruding about .008 to .010. I am somewhat worried about a blown primer but they seem to have quite a bit of primer body left before exiting the case and no signs of excessive pressure. I am using the old Federal 175 g. RN. I would appreciate your take on this problem as it is a good do all rifle.

Information

Warning: This is a relatively older thread This discussion is older than 360 days. Some information contained in it may no longer be current.

[jmoore]

If the primers are protruding, then you have little worry. It's a sign that the ammo is low pressure. Not uncommon even in rifles with good headspace. The downside is if you reload. Since the cases aren't fully fireformed, brass life can be shortened.

[Bob Thompson]

Update: thanks to all who replied. I do not have go-nogo guages but after checking and measuring very accurately the fired and unfired cases I find with these Federal Blue box 175g. cartridges they are well under what four of my reloading manuals call on shell specs. Here is my findings:

From the manuals: OA length: 2.235 My cases both fired and unfired: 2.225
" " " Head to neck: 1.895 " " " " 1.875
" " " Base diameter: .471 " " " " .464
Naturally the neck is slightly bigger after firing.

Now my measurements are pretty accurate but even if I was off slightly they show a consistant difference and I believe Federal produces these cartridges well under reloading specs and pressure to chamber easily in the many different chambers of mass produced military rifles yet still be safe. I will be checking some other cartridges from Midway in the near future but I believe what is happening is when firing, with a fairly heavy firing pin spring in most military rifles, the case is moving forward the .010 I'm seeing in the primer extrusion. As you can see in my fired cases the base show no signs of high pressure but just the opposite, a case that feeds easily. With my AR and M1 Garand I'm reloading for I use RCBS small base dies to accomplish the very same thing. I believe I'm safe here but am I assuming too much and thanks again guys?

[lude92]

i have a friend that has one and i not a expert in spanish military rifles but is the bolt when pushed forward to close it is it a little hard to do that

[jmoore]

I will be checking some other cartridges from Midway in the near future but I believe what is happening is when firing, with a fairly heavy firing pin spring in most military rifles, the case is moving forward the .010 I'm seeing in the primer extrusion.

That's the likely culprit. Shoot what Federals you have and then find a better case. Seating the bullet to engage the rifling with new brass will produce the best results, but may be difficult or impossible to achieve with this rifle. Throat is likely quite long.

[budman46]

excess headspace can be addressed by necking the case up to create a false shoulder, sizing until the round will just chamber and firing it with a moderate load to blow the shoulder forward. from then on, segregate the brass for that gun and make sure not to push the new shoulder back during resizing.