Bulldog Upgrades.2

Part 2

First page dedicated to Bulldog's upgrades had become way too long; so this one will be focused on drilling the TP and Valve, Spring Tension, and final results. This proceeding is for air-gun enthusiasts and if you think this task is not worth of your time and abilities, then seek a professional tuner. There are some around and they will charge you a common price ($) among them. If possible, check with more than one... and rest in peace.

This is what we did to our Benjamin Bulldog .357 in order to increase speed. See added pictures.

1- Drilled the barrel's TP up to 1/4 of an inch (6.35 millimeters). Polished inside / outside.
2- Drilled the TP, opening in the valve to 1/4 of an inch.
3- Added washer-shim behind the hammer spring.
4- Added some tape on reservoir's body and foam on grip and stock. Depinger was installed (Part 1).
5- Replaced the degassing bolt, as it was leaking air a little bit.
6- Added shims to the trigger in order to remove any lateral movement (to the sides) it had.
7- Replaced the factory o-ring in the barrel's breach.
8- Polished the hammer's body.
9- Replaced valve o-rings with HNBR ones.
10- Put back the factory valve's spring.

First we need to dissemble the Bulldog's body, including separating the barrel from the Receiver Assembly, removing Reservoir Tank with its adapter, Valve's Spring and Stem. The Benjamin Bulldog .357 caliber has a few screws and pins if you decide to dissemble the trigger assembly as well. For drilling-widening the TP you don't need to do that; however, do not get intimidated by the so many little things you see when doing your first dissembling of the rifle. You'll get used and will remember once you begin to put it back together. Just in case, you can take pictures before anything, and that way it can be used as a reference if something is forgotten.

Do not forget to first degas the rifle and bleed any remaining air in the reservoir.

We also had added before some foam to the inside's grip and back-stock + some tape around reservoir, and plastic rifle's body itself. The idea is to make it less 'plastic feeling.'

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html


After the barrel is separated from the Receiver, you can drill the size you determined in the TP, but first remove the o-ring you will see inside. We drilled 1/4 of an inch. The drilling operation must be done slow and with care. Do not rush and pay attention to what you are doing; but remember, you are just opening a hole, not drilling for gold in the Antarctica. Yes you can!

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Once that barrel is done you must polish outside and inside, removing burrs. After we polished inside noticed that the big bore pellets can sit there better off. Be careful not to 'grind' but slightly polish. Then finish with some fine sand paper.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

We took advantage and at this time once the barrel was ready and clean, also replaced the breach o-ring for a new one.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

You need to remove the Plastic Sleeve that is in the TP Channel going to the valve inside. Then from the top, with enough care also drill a 1/4 opening (or the size you decided, but never over 9/32 = 7.14 millimeters).

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

You can also remove the valve and inspect it if feeling good with that; and instead drill on it once outside. You do not need to do such; but if wanting, then remove hammer and spring, followed by unscrewing the Nut Valve Retainer (# 20 in Bulldog's diagram) with a long 8 mm hex key, and pushing the valve towards the other side of the Receiver. Thus from that side (see picture) you can reach to the valve. In this case (picture) it was already opened 1/4 on the up-side going towards the TP before I removed it for inspection.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

If you decide to pull it out, then drill it this way (I ordered more to try different sizes).

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Then, install the 'new' valve back from this side of the rifle with its hole facing up. Do not forget to put the two o-rings in the valve; as you see in this picture they are not yet in place.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

These green o-rings are HNBR (Hydrogenated Nitrile Butadiene Rubber), resist more temperatures and have more tensile strength; so will try if they are better than the regular factory ones in this part of the rifle, subjected to more pressure and high temperatures when filling up the reservoir. It has another one in the front, and we kept it as the one from factory. Add silicone grease to them.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Tighten it from the other side with that 8 mm hex key; and ready to keep assembling. As we decided to increase the hammer spring tension, I decided to put back the factory's spring valve, which I had replaced before for a lighter one.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Here the hammer and spring all together. We added a shim inside its cap, and re-polished the hammer. Also shortened the Spring Guide the same size of the shim, but it is not necessary unless you cannot cock the rifle or similar. I may later on replace the hammer-spring as well, with a heavier one if I notice it does not improve in fps right away as wanting, crying for more air.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Assemble the trigger if you had remove it. I needed to replace the sear with a new one, because I subjected it to a higher than needed pressure (unnecessarily) with an experiment I performed, and it did not pass the test, breaking in two pieces (# 17 in diagram); chopping off one corner. Also added a shim on both sides of the trigger as I do not like any lateral movement on triggers. 

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Also replaced the degassing screw, as the factory one was leaking a little, and this one once tightened all the way in, so far is working great. Also, as you see, in comparison with the factory one, its head is bigger, thus allowing you to tight it in with the necessary force, but nevertheless with care. The screw is a socket head cap 10-32 x 3/8".

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

After drilling you can apply some pressured air to the parts removing dust and dirt; beginning the process of cleaning the receiver as well.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

Begin the re-assembling.

http://www.drilldogbigborepellets.com/p/bulldog-upgrades2.html

If everything went smoothly in your Bulldog's TP job, then congratulations. If something went wrong, please, do not cry... felicitations anyway!, as you are trying to use your brain and hands. We learn from mistakes...all of us... Next time you will make it perfect, even if your wallet now had to go through a painful collision.

The good part about Crosman, is that you can order parts from them, and that's why they provide the rifle's Diagram [This is one good reason to look at Crosman]. It means you can always put your rifle back to the factory condition, or even have two different set-ups for the same airgun. Other manufacturers do not provide Diagram or parts, and thus lose a source of money in a dumb way; or they have such high prices for parts that no one tries to even bother to buy or play around with the device.

We'll keep you inform in the coming days if the Bulldog's tuning is worth over the factory condition. 

Of course, as we stated at the end of our page Bulldog Upgrades.1, we will need to play with the Hammer Spring tension as well, till we reach the necessary force hitting the valve to release the specific amount of air we need for the  kind of set up we would like after opening 1/4 of the TP and Valve.



May 2018.

For Part 3 of Bulldog upgrades go to:

For Part 4 of Bulldog's suppressor upgrades go to:

For Part 1 of Bulldog upgrades go to:




DrillDog ©