DIY - custom breech seal

[vijaycool]

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.

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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.

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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.

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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

[tirths]

[vijaycool]

Tirtha.. I know what you are smiling for .. I have devised a method for custom silicon seal hope I can try on your gun .
In the last pic you can see I have made some changes in the pellet seating area.This gave me almost consistent performance and grouping. I dont have chrono or other proof to show this mod improved the performance.

[Basu]

dear vijaycool,
your idea is geat and executed properly too. yet i wonder wheather or not it is going to last as much as leather seal does normally.this feedback can be received from you only. hope to get the same once you are through with some thousands shots.

Basu

[tirths]

Dear Basu, I am sure it will not last as long as leather seal. But also it will also not let the air out as much as leather seal do.

[Mark]

Nice idea and implementation Vijay!

[vijaycool]

Feedback Time: After the mod, I have used around 1000 shots it is just perfect. There is no sign of wear and no leak what so ever. The material is soft butyl tube.It still has the cushioning effect when locking. My gun is not a regular mod 35 model. Now it has new spring and the increased swept volume. The trigger has some 10 paisa mod in it. Its crisp and relatively light. Try yourself it does not cost a fortune. You dont need to buy a new hose cut 1 inch from the existing tube from the stove end. If the breech seal depth in your barrel is less than 3mm use rubber sealant similar to cycle puncture repair solution while fixing.
Provide your feedback after the mod.

Cheers,
Vijay

[tirths]

Excellent

[noblekumar]

Nice one... I tried this on my IHP 35 and it just working great. Thanks