Today Doug Wall covers Barra 1100z regulator installation in his Gen 1 model. He’s aiming for a high degree of consistency and a long shot count…
I’ll start this out by saying that this operation is not for inexperienced airgunsmiths. It will involve a lot more disassembly than changing the caliber as in Part 2.
Barra has put out a video on how to do this. It’s an excellent reference!
In this article, I’ll be doing the same thing, but I will add some details that should help to fill in any questions.
Barra 1100z Regulator Installation – Disassembly
For this Barra 1100z regulator installation we’re taking this gun pretty much all apart, including the pressure tube, so degassing is necessary as the first step. The degassing screw is included with the tools that come with the gun.
Insert the degassing screw into the fill probe, and screw it in with the appropriate Allen key, until the pressure is released, and the gauge reads zero. Make sure that you remove the degassing screw afterwards, so that all of the air doesn’t dump out when you gas it back up! Double check this by dry firing the gun in a safe direction, confirming that no air come out.
The next step is to remove the stock. Remove the safety by putting it on safe, and tapping the safety out, using a wooden dowel and a small hammer, from the side opposite the safety lever. After the safety is removed, remove the two stock screws, one in front of the trigger guard, and one in the forend.
After the stock is removed, remove the barrel shroud. Loosen the set screw in the top of the barrel band, and unscrew the shroud. Remove it by sliding it forward, over the barrel. If the air stripper comes off of the barrel, you may have to push the air stripper out of the shroud with a ¼” dowel.
Slide the barrel band off, over the front of the pressure tube. Remove the barrel and receiver by cocking the action, and removing the two screws holding it on.
Remove the front end tube plug, with the fill fitting. In my case, the front plug was pretty well stuck, and I had to improvise a tube clamp and pin/spanner wrench to get the plug out.
Remove the trigger group by removing the two screws holding it on. The front screw is a straight slot screw, and the back screw is a Phillips screw. Remove the lug in front of the trigger guard.
Remove the pressure gauge using an appropriate sized wrench.
Remove the screw at the bottom of the back end plug. At this point, the back end plug can be removed. Mine was a bit of a tight fit, and had to be wiggled out.
Remove the cocking pin screw. The hammer spring and hammer can be removed.
Remove the recessed, Allen head screws holding the valve in.
At this point, the valve, spacer block, and gauge block can be pushed out. I used a 24” piece of ½” PVC tube to do this. The tube will also be needed to re-install these parts.
With everything apart, I’ll mention that Barra has an excellent exploded diagram of the 1100Z, which can be an excellent resource for getting things back together.
Barra also offers a good selection of replacement parts, in case you need something.
Barra 1100z Regulator Installation – Reassembly
For all of the parts with o-rings, apply a liberal smear of silicone grease on the o-rings before reassembly. The picture below shows the proper relationship of the internal parts.
Insert the valve first, preferably from the front, to minimize chances of nicking an o-ring on a hole or cut out. Make sure to align the transfer port on the valve with the port in the tube. Secure the valve with the recessed Allen head screws, making sure that the screws are properly recessed and snug.
Next comes the gauge block. Some careful changes have to be made here. One end of the gauge block has a slot. This end will go towards the valve. The other end of the gauge block is smooth. This end will go towards the regulator.
Carefully remove the two o-rings from the smooth end of the gauge block. This change is necessary to give the regulator proper venting to atmospheric pressure, which is necessary as a reference pressure for the regulator.
Add some silicone grease to the o-rings, and making sure that the gauge port is aligned with the port opening in the tube, insert into the tube from the front. Adjust the alignment of the gauge port, and reinstall the gauge, lightly tightening the gauge with a wrench.
At this point, the pressure on the regulator can be easily adjusted, using a small screwdriver. I set mine to about 1700 PSI.
Any future pressure adjustments would require either a long screwdriver for adjustment, or removing the regulator, with a tool that would thread into the regulator.
Lightly grease the o-rings on the regulator and carefully insert it from the front of the tube. Seat it all the way in using the PVC tube.
Install the tube end plug with fill fitting. Lightly lubricate the o-ring with grease.
From the back end of the tube, insert the spacer block, making sure that the threaded holes are aligned top and bottom. Screw the stock lug into the spacer block from the bottom.
Insert the hammer and hammer spring into the back of the tube. Make sure that the cocking pin hole is aligned at the cocking slot on the tube top. Screw in the cocking pin.
Insert the end plug into the tube, making sure that the correct (they are different) screw holes are aligned top and bottom. Secure it with the bottom screw.
Install the trigger group. The Phillips head screw goes to the back of the trigger group.
Install the receiver on the top of the pressure tube. Make sure that the cocking pins a aligned and that cocking works properly.
Place the barrel band back over the pressure tube, and screw the barrel shroud back in.
At this point, it would be wise to pressurize the tube, make sure that everything is working properly. A 24 hour leak test is also a good idea.
After all is good, re-install the action into the stock, and re-install the safety.
The regulated Barra 1100Z is now finished. The gauge now only reads the regulated pressure. You will have to run some shot strings to determine how many regulated shots you can get before the pressure drops below the regulator pressure.
I did some quick experiments to check the performance of the newly modified gun.
As I mentioned in an earlier article, my goal is a gun that will shoot accurately at slightly less than 20 FPE, to make it reasonable for field target work.
Here are some preliminary results, using H&N Baracuda 8 pellets (8.44 gr), with various hammer spring adjustments.
– 3 turns in from flush (in fps); 955, 945,946, 945, 953
– 4 turns in from flush (in fps); 957, 954, 949, 945, 952
– 5 turns in from flush (in fps); 944, 945, 952, 953, 950
– 6 turns in from flush (in fps); 951, 944, 948, 946, 946
A velocity of 950 fps, with an 8.44 gr. pellet, calculates to about 19 Ft/Lbs of Muzzle Energy. Right where I want to be!
You may ask what’s going on here? If you go back to Part 3 of this series, and you look at the pressure curves for the three hammer spring settings, you will see that the velocity at about 1700 PSI, seems to be about 950 FPS for all three hammer settings.
The next part of this series will be to check, and optimize the air usage for the system.
When I had the gun apart, it seemed that hammer spring adjustments below about 5 turns in seemed to have some “hammer free flight” characteristics. We’ll explore this, and a little further down the road, we’ll explore a bit about hammer debounce.
Thanks Doug! Stay tuned for the next part of this series…
BUY FROM BARRA AIRGUNS:
Barra 1100z Air Rifle
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