If you’re like me and despise barrel nuts, you are left with two options: short chambered and deep chambered. My personal favorite is deep chambered because you don’t need to ream anything to set headspace. However, you will need a lathe and a set of go and no-go headspace gauges.
If you don’t have a lathe, you’re left with the “short chambered” option. That is the route I’m going to explain today. This method does require some more tools than the barrel nutted pre-fit barrels but nothing too advanced like a lathe. And the end result will look much cleaner and you won’t get made fun of at the range. (No offense to you barrel nut guys.)
The first tool you will need is a depth micrometer for some measurements. The first measurement you need to take is from the action face to the bolt face. In this case, the measurement was 0.966”. The action pictured by Defiance has an integral lug so no additional measurements will be needed. However if your action has a removable lug, you will have to add the thickness of the lug to your measurement.
The next measurement you will need to take is from the breech face to the shoulder of the barrel. This area is usually referred to the barrel tenon or barrel shank. The measurement I got on this particular barrel was 0.955”. This measurement tells us how far the barrel tenon will thread into the action.
Thanks to these two simple measurements, we can now calculate what I like to call “zero headspace.” This refers to how far the go-gauge must protrude out past the breech face to fill the gap between it and the bolt face. Thus, leaving zero space between the two. When subtracting the length of the barrel tenon from the action face to bolt face measurement I came up with a distance of 0.011”. This means the go-gauge needs to stick out 0.011” to be flush with the bolt face. Any longer and the bolt will not close but much shorter and gun could be unsafe,
These headspace gauges I’ve been referring are the second set of tools that are needed for the job. They can be purchased from places like Brownells Inc. or they can be rented from places like 4D Reamer Rentals. The go gauge is usually labeled with a painted green ring ground into the gauge body and the no-go gauge naturally had a red ring.
Now we need to determine how deep the manufacturer reamed the chamber. To figure this out, you need to insert the go-gauge into the chamber. Now rest the depth mic on the base of of the gauge and measure the distance to the breech face. You will then subtract your calculated “zero headspace” number from your current measurement. In my case the measurement was 0.013”. After subtracting my 0.011” from earlier, that left me with a calculation of 0.002”. Which means the chamber needs to be reamed that much deeper in order to achieve “zero headspace.” Though I’m not complaining, short chambered barrels aren’t usually this close to being headspaced. Keep in mind a sheet of paper measures around 0.003”. So technically this chamber needs reamed less than the thicknesses of a sheet of paper to achieve zero headpace.
Obviously, the next tool you’ll need in the process is the chamber reamer itself. Like the gauges, the reamer can either be purchased or rented. You will also need some kind of tap handle to turn the reamer and also some cutting oil.
Fill one or two flutes of the reamer with cutting oil and then insert it into the chamber. Begin to turn the reamer clockwise. Absolutely never turn a reamer the opposite direction than which it cuts. The amount of material needing to be removed will influence how much downward pressure you use as you turn the reamer. Check your progress with the go gauge and depth mic often until you reach the desired depth. Every time you remove the reamer, clean the cuttings off and re-oil. Also, blow any chips out of the chamber before re-inserting the gauge or reamer.
In my case, I barely used any pressure being that I was so close to the correct depth. I basically spun the reamer and let it clean things up under its own might. Due to what most refer to as “barrel crush”, you may need to ream the chamber slightly deeper than your calculated headspace. This can be determined by your TPI but generally is only an additional 0.001 or 0.002”.
The next items you will need is some sort of action wrench, a vise to secure the barrel and a torque wrench. Both my action wrench and barrel vise are home made but can be purchased from Brownells Inc.
Once you have the barrel secured, thread the action into the barrel by hand. Then insert or attach your action wrench and set your torque wrench to the desired pounds. There are different opinions on torque spec but I prefer an adequate torque of 75 ft lbs. Now tighten your action until your torque wrench clocks.
Now you’re ready to check the headspace but first you must disassemble the bolt. The firing pin assembly can be easily removed with the pictured tool attached to the bolt shroud. I have also used a smooth faced vise to clamp onto the cocking piece for removal. You just have to be careful not to mar the piece. The ejector also needs removed and can be done easily with a hammer and punch. It is not necessary to remove the extractor in this case and can actually help with holding your gauge when inserting into the chamber.
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