DIY - custom breech seal
Posted: Wed Jan 06, 2010 3:29 pm
Hi Guys,
My experiment with my new airgun continues. The factory breech was leaking badly and I lost much of the power. I tried to use O ring but it often fells down and the sealing is not quite effective. The problem with the standard O-rings is either with the thickness or the depth which we wanted. The breech groove depth of my airgun varies from 6~7mm. This mod is very simple but very effective using household material. I have tried more than 500 shots before posting here so it is quite reliable. I made this mod before the short sear mod. It takes less than 30 mins of my time to do this mod.
You need to dismantle the barrel before this mod.
What all you need?
LPG Gas tube , fine file, knife and mallet.
I prefer Suraksha tube as it as two layers. The inner layer is the perfect fit for the breech.
Cut open the outer layer by knife. Its a shielded cable so beware there is some steel Gauss between the layer. 1.5 cm is enough for this mod.
I didnt take any pics during the mod as I am not sure whether it will work or not. Once cut place on top of the breech and slowly hit by a Nylon or wooden mallet. The tube will expand and fit into the breech space. Take care the tube doesnt break in between else you need to remove the broken tube and start again. Once fully in cut the excess tube. Let the tube protrude from the barrel by 3 ~ 4mm in excess. This is important as it takes the shape between the breeches.
Now assemble back. Note: you will find barrel drooping initial 30 ~ 40 open-close cycles.
When you close the barrel shut down with moderate force so that excess rubber will cut off. You find the barrel drooping. Now open the barrel and start filing slowly.
Important: The filing angle must be exactly parallel with the barrel face. Normally the barrel face for the mod 35 guns will be angled. File little by little and try to close it . You should not find any bumpyness while closing. Remember do not file down too much. Just little is enough. Try to get the feel after 40 odd shots if you still feel locking hard you can file a bit. Once done try with some talcum power around the breech and fire. If its sprayed you need to make a new tube again.
As you see in this pic the top side of the barrel the seal is sunken deep inside and the bottom side the tube protrudes. This is due to the angle of the barrel end.
Note: Never polish the transfer port side and also the tube. It needs to be rough for airtight sealing.
Comments welcome.
Happy modding,
Vijay
My experiment with my new airgun continues. The factory breech was leaking badly and I lost much of the power. I tried to use O ring but it often fells down and the sealing is not quite effective. The problem with the standard O-rings is either with the thickness or the depth which we wanted. The breech groove depth of my airgun varies from 6~7mm. This mod is very simple but very effective using household material. I have tried more than 500 shots before posting here so it is quite reliable. I made this mod before the short sear mod. It takes less than 30 mins of my time to do this mod.
You need to dismantle the barrel before this mod.
What all you need?
LPG Gas tube , fine file, knife and mallet.
I prefer Suraksha tube as it as two layers. The inner layer is the perfect fit for the breech.
Cut open the outer layer by knife. Its a shielded cable so beware there is some steel Gauss between the layer. 1.5 cm is enough for this mod.
I didnt take any pics during the mod as I am not sure whether it will work or not. Once cut place on top of the breech and slowly hit by a Nylon or wooden mallet. The tube will expand and fit into the breech space. Take care the tube doesnt break in between else you need to remove the broken tube and start again. Once fully in cut the excess tube. Let the tube protrude from the barrel by 3 ~ 4mm in excess. This is important as it takes the shape between the breeches.
Now assemble back. Note: you will find barrel drooping initial 30 ~ 40 open-close cycles.
When you close the barrel shut down with moderate force so that excess rubber will cut off. You find the barrel drooping. Now open the barrel and start filing slowly.
Important: The filing angle must be exactly parallel with the barrel face. Normally the barrel face for the mod 35 guns will be angled. File little by little and try to close it . You should not find any bumpyness while closing. Remember do not file down too much. Just little is enough. Try to get the feel after 40 odd shots if you still feel locking hard you can file a bit. Once done try with some talcum power around the breech and fire. If its sprayed you need to make a new tube again.
As you see in this pic the top side of the barrel the seal is sunken deep inside and the bottom side the tube protrudes. This is due to the angle of the barrel end.
Note: Never polish the transfer port side and also the tube. It needs to be rough for airtight sealing.
Comments welcome.
Happy modding,
Vijay
