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Adjusting the power on your BT65

How to adjust the power on your BT65.

How to adjust the power on your BT65.

Adjusting the power on your BT65

It’s a question that I get asked quite often, “how do I adjust the power on my BT65?”  It’s extremely simple to do and I’ll walk you through the process here.  Before I start I need to say the following:

WARNING, working on your own airgun can be very dangerous.  It will also likely void any and all warranties on your product.  Repairs and maintenance should only be performed by qualified, factory trained technicians.  By working on your airgun, or modifying your airgun, you assume all responsibilities for any and all damages that may be caused to your airgun, person or persons, and property.

In other words.. “don’t do this at home…”

How I adjust the power on my BT65:

Step 1 – Secure and prep the airgun.

The first thing that I’ll do is secure the airgun in a proper gun rest.  This acts as my third hand and helps prevent things from moving when I don’t want them to.  I also remove the air cylinder so there is no chance of an accidental discharge.

Step 2 – Remove the stock

Removing the stock is easy.  Simply turn the rifle upside down and secure the action in the gun rest so that it won’t drop out of the stock once all the screws are loose.  Remove the three screws holding the stock with a #2 phillips screwdriver.  ONLY USE PROPERLY SIZED TOOLS.  Using the wrong size screwdriver will almost certainly damage the screws.   The three screws are located at the front by the barrel band support, in the middle in front of the trigger guard, and the rearmost screw in the trigger guard.  Do NOT unscrew the front trigger guard screw as that only holds the trigger guard to the stock.  Once the screws are removed, gently pull the stock upward, paying close attention to the spacer for the middle stock screw.  It fits in the stock and provides support for the main stock screw.

Step 3 – locate and loosen the hammer tensioner set screw

On the left side of the rifle, opposite the bolt, you’ll find a small allen screw protruding out the side of the action.  This screw helps hold the trigger group in place and should not be fiddled with.  Directly next to this screw is a little hole.  Inside that hole is a 2 mm allen set screw that secures the hammer tensioner.  Loosen that a couple of turns to allow free movement of the hammer tensioner.

Step 4 – adjust the hammer tension

In the rear of the lower assembly there is a 6mm allen screw.  This is what provides the tension to the hammer spring.  Rotating this clockwise adds tension to the hammer, counterclockwise reduces the tension.  I set the average velocity for my airguns using this adjustment.  It’s critical to have plenty of air, a chronograph, and a lot of patience.   Once I find my desired setting, I refer to step 3 and re-secure the hammer tensioner set screw to lock in my setting.   Now it’s time to put it all back together.

But wait there’s more!

Now that I have this all apart, I’m going to make sure that my top half never comes loose from the lower half. Given enough time, and due to the very heavy cocking action of the BT65 platform, there have been rare occasions where these two parts will want to loosen up.  To prevent this, I need to check and secure the 2 contact points.

Securing the top and bottom receiver components

Step 1 – Remove and Loctite the front screw

The front screw is located in the magazine area.  This is a 2.5 mm allen screw that should be extremely tight and hard to remove.  Once removed, I add a drop of Loctite to the screw and replace it, being sure to really tighten it into place.  It’s critical to only use the proper sized tools or the screw may be damaged.

Step 2 – Remove and Loctite the rear screw

The rear screw is located in the end of the action behind the hammer adjustment nut.  This is a 3mm allen screw and it is accessed through the underside of the action via a small hole directly behind the trigger group.  Once loose it usually takes a few shakes and then it will come out the rear of the rifle.   I apply a drop of Loctite to the screw and usually use small plyers to drop it back in its home.  Then it’s time to tighten it down and provide enough torque to really secure it to the action.

Step 3 – Let the Loctite cure

It’s best to let the Loctite cure overnight before doing any more work on the rifle.  Once cured, it’s time to put the newly adjusted action back into the stock.

Back to the first set of instructions…

Step 5 – replace the stock

To replace the stock, I’ll remove the action from my gun rest and replace it with the stock, being sure to properly secure it to the rest.  I’ll find my little spacer and place it in the recessed center stock screw hole.  Now it’s time to simply place the action back into the stock.  Everything should line right up.  Carefully release the stock from the gun rest and, while holding the two halve together, rotate it upside down, placing the action back into the gun rest.   I’ll replace the main center stock screw first, and then move on to the front and rear screws after that is secure.  It’s best to not fully tighten down any of the screws until they are all started as sometimes it takes a bit of wiggling to get them all lined up.  Once they are all started I carefully tighten them down with my #2 phillips screwdriver.

Step 6 – Replace the air tank and test.

Once everything is back together, it’s time to test the results.  Again, this process takes a lot of time, patience, and the proper equipment and experience.  If I find that it’s not quite where I want it to be for power output, shot count, or shot curve, then I’ll start over and keep adjusting and testing till I find my optimal setting.

I do hope this has been helpful.  Please refer to the following video if you’d like to see this process in action.  And again, this is what I do on MY guns.  Having performed service and repairs on airguns for many years, I’m well aware of how things can go wrong and I take full responsibilities for MY actions when working on them.  Please DO NOT work on your own airguns unless you are 1000% comfortable doing the same, holding only yourself to blame if you muck it all up.

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