06-17-2009, 10:16 AM
Join Date: Mar 2008
Location: Contra Costa County
incorrect headspace gun going boom in at the wrong end ..
Now I correct and adjust the head-spacing. I have to determine whether the current head-space is small, large or correct. There is no such thing as almost correct. I use an assortment of devices to accomplish this.
Assorted make (DUMMY) cartridges with no powder or primer
Head-spacing gauges (not a must if you have the above - That's right)
The variation between a Go Gauge( in specification) and No Go gauge ( out of specification - larger) is only .0045" to .005"
Assuming we don't have go - no go gauges, we can create out own.
Three layers of the scotch tape adds roughtly .005", to a regular cartridge making/representing a NOGo gauge.
The regular cartridges, without any tape on them will suffice for Go gauge.
So here is our NO GO gauge..
Inspect your chamber first to be certain it is clean. With all the metal shavings and chips around, you can not be sure.
1 - Using No go gauge - Action does NOT lock, bolt head does not seat and lock - This is normal, move on.
2 - Using No go gauge - Action DOES lock - Head Space is too great. Barrel needs to be pressed IN a little more, you are doing fine.
3 - Using GO gauge - Action does NOT lock, bolt head does not seat and lock - Head Space is TOO tight OOps. Reverse the press jig and press the barrel OUT some. You over pressed it.
4 - Using GO gauge - Action does lock - Beautiful. we have correct head space. Repeat steps 1 and 4 with recoil spring several times.
It is tight headspacing that is more dangerous. It results in the cartridge making a tight contact with the bolt head without the bolt head being locked in place. Pulling the trigger does set off the round, causing an explosion 8" from your eyes, having enough energy to shatter receiver, strip the magazine or rounds by blowing out the mag floor plate. And all sorts of stuff that make good stories and conversation pieces.
Here is great video checking/fixing headspace.
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Last edited by fredieusa; 07-07-2009 at 11:03 PM..