lyman cartridge case gauge 7MM Rem Mag question?

R

ReloadKy

New member
I bought a lyman cartridge case gauge so I could check all of my brass to make sure it would still chamber correctly. I placed some neck sized brass and it would not go all the way into the case gauge. Is this because it is only neck sized and not full length sized or is my brass out of spec? The brass chambers fine in my rifle but I have not tried every piece of brass in the rifle.

This is the first time I have ever used a case gauge and I know it is pretty simple to use. I am thinking that because I neck size my brass I may have wasted my money on the gauge.
 
Think about it. A case gauge is going to be the max spec allowed.

Neck sizing your brass does not return it to industry spec dimensions, (intended to fit all rifles) it leaves it (the case body) "sized" to YOUR rifle's chamber.

that's the point of neck sizing, keeping the case body dimensions the way they came out of the rifle after firing (for a "better" fit of the reloaded ammo, and only sizing the neck to hold another bullet.

Case gauge is going to be spec'd for ammo to fit every rifle chambered for the round, and therefore at, or below max allowable INDUSTRY STANDARD size.

Now, if you were FL sizing your brass and it didn't fit the case gauge, THEN, you have an issue, somewhere....
 
This also depends on the gauge, but, yes, the gauge maker has no idea what your particular rifle's chamber has by way of headspace and diametric dimensions, so it isn't made to match your chamber; just the SAAMI minimum chamber.

The above is why some custom riflesmiths make a habit of taking a length of barrel blank and reaming it with the same reamer used to chamber a customer's rifle, thus to have it serve as the customer's matching gauge for that rifle alone. The commercial gauges, as 44 AMP said, are for guaranteeing the rounds will fit in any chamber that is within SAAMI standard dimensional limits.
 
I have not used Lyman gauges, but RCBS and Wilson gauges for belted cartridges are adjustable. Put a fired case in and adjust for the belt position, then tighten the lock screw. Neck sizer or full length, your die will not affect that lower portion of the case. But the case may very well have stretched upon firing, putting the belt in a different place than the original gauge set. Once the gauge is set for your rifle, all future measurements are valid.
 
The way the belted magnum rounds are made, they are supposed to headspace on the belt rather than the shoulder, so the SAAMI standard takes the belt location tolerance and sets the shoulder location tolerance so that even having the longest allowed shoulder will still let a case headspace on its belt without the shoulder reaching the end of the chamber. Once you have fireformed, the shoulder it is mirroring the actual chamber shoulder length, and there is no way a case that long can be guaranteed to headspace on the belt of all belted chambers of your caliber. So, quite by design, the gauge rejects it.
 
Not a foolish question. Your issue is the case gauge. Lyman's gauge is not adjustable. As Unclenick pointed out, it will reject any cartridge that will not fit in any SAAMI spec chamber. You only care about your rifle. RCBS, Wilson, and I'm sure others make case gauges for belted magnums that adjust for the as fired belt position. Once that is set, the gauge is useful for your rifle only.
 
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