Breech Seal Removal & Replacement

[brihacharan]

Breech Seal Removal & Replacement

Hi Guys,
In Air Rifles more often than not, the breech seal is taken for granted, whereas attention is paid to parts such as the receiver, piston seal, spring, rear guide & top hat to maintain its power & accuracy.

It so happens that loss of power / velocity / accuracy is the result of either a worn out or ill fitting Breech Seal!
The breech seal is a small, rubber gasket that seals the joint between the breech and barrel of your air rifle, ensuring optimum delivery of compressed air through the transfer port to push the pellet through the barrel to attain the designed maximum velocity and power.

Over time, the breech seal can become worn, decreasing the overall efficiency of your rifle including decrease in velocity.
Replacement breech seals are inexpensive and commonly available and can dramatically increase your air rifle's performance.

Before you install a new breech seal, remove the old one. Correctly removing the existing seal will prevent damage to the gun as well as personal injury and will allow you to quickly and easily place the new seal.

To remove the breech seal cock the air gun and ensure that there is no accidental force on the trigger which may release the sear engagement and cause serious injury to you.

It’s advisable to keep the barrel after cocking pressed against a wall / table to avoid accidental firing of your air gun.
Now using a pin / small screwdriver slowly pry the old seal off the breech and pull it off with a pair of Pliers.

Clean the breech depression with a de-greasing agent such as alcohol or acetone. It is advisable to put in a 0.5mm metal shim first and then press fit the new breech seal. The shim offers a level surface to seat the breech seal properly.

The ideal breech seal should preferably made of an oil resistant rubber material – here synthetic rubber material such as neoprene is recommended. While leather seals can also perform efficiently, it needs to be kept moist with oil to maintain its fluffiness for its effective sealing quality / property.

Ensure that the top surface of the breech seal is a near ‘flush fit’ – this is important to prevent any air leakage when the air rifle is fired. This can be checked by applying ‘talcum powder’ around the breech surface & when the gun is fired - there should not be any puff spray of the powder, this means that the breech seal has a perfect fit.

Do not apply any oil / lubricant over the breech surface as this may cause dieseling. Apply a very thin film of oil and gently wipe it off with a soft cloth.

It is advisable to change the breech seal after 2500 to 3000 shots for maintaining optimum deliverance of compressed air through the transfer port to the pellet.
HAPPY SHOOTING!
Briha

[Suyash]

Briha Ji,
I'm in a bit of confusion.I was inspired by your article and decided to change a bit worn out leather breech seal by a new one. After searching many shops i finally got one which was WAY MORE BIGGER than the'slot' of the seal. I read few more articles on the topic and found that soaking it in oil would help . So I did the same for 12 h and finally went to do the job. I tried ways and means to some how Push the seal. But I didn't succeed. Neither hammer worked nor the scrapings. After an hour of sweat and tears I started loosing my mind.
I took the seal into MICROWAVE and boiled it for a couple of minutes. It was SWOLLEN and didn't look like a Ring. But I I took it out from the water and it became soft. Another 30 minutes of hammering and the seal was in it's place I oiled it and it looked fine . I don't think I need to post pics as after the job it looked like an ordinary leather seal.
But I am NOT happy with the results
•Velocity went around 50fps LOWER.
• it is not airtight as when I blow air in the muzzle I can feel that air is escaping

Now Questions
1 was my way right?( I know it wasn't)
2 I've seen people saying oil the leather seal...but how to do it? ( oil will go in the piston chamber)
3 I can't arrange a synthetic seal. So how to make a large leather seal fit in the place ( boiling it in water helped me... I'm thinking to fry it in oil next time )
Regards
Suyash

[brihacharan]

Hi Suyash,
Unfortunately the procedure you followed was not the right one
Always use an "O" ring as the breech seal - available at all hardware shops...

Measure the OD & ID of the breech before purchasing...
After removing the old breech seal....clean the area thoroughly with spirit or kerosene & dry the area...
Since the thickness of the 'O" ring may not be adequate...insert a fibre / metal washer & then insert the "O" ring...
Open & close the breech a couple of times (do not cock the gun fully) for the "O" ring to settle properly in the slot...
Good Luck
Briha

[Basu]

Please visit my thread in gunsmithing sec. "Breech seal- an easy solution".
This is the best DIY seal.

Basu

[Suyash]

IMG_20150403_144809.jpg

Briha Ji
I'm unable to get the o ring seal of the right size.... Only thing I could find was leather seals of improper sizes. Can you help me with your knowledge?
Regards
Suyash

[brihacharan]

IMG_20150403_144809.jpg

Briha Ji
I'm unable to get the o ring seal of the right size.... Only thing I could find was leather seals of improper sizes. Can you help me with your knowledge?
Regards
Suyash

One alternative is to cut the exact thickness from a LPG Gas Tube (Double walled) & sandpaper it to exact size & insert in the breech.....
This had worked well for me till I found a source to procure "O" rings...
Try it - it should work
IFGian Basu has done thuis successfully!!!!
Briha

[Suyash]

LPG gas tube?
Is it the pipe that connects the stove and the cylinder?
And I've had a hard time to cut the leather seal... Will the pipe be soft enough to cut?

Regards
Suyash

[Suyash]

Briha Ji , and all the experienced guys
I've been thinking about the idea of M seal as breech seal....I'm not sure about how will it work. But it is used to make things airtight. I can assure one thing ; I can remove it easily.
Please post your views
By the way I've successfully detached half of the breech seal and the screwdriver pierced my finger
at four spots ( better than last time)

[sa_ali]

Why M Seal, rubber or leather seal are fleixible material which seals the gap. M Seal is for permanent seal and once hardened it will over a time with rubbing againt metal loose the sealing capability

[Suyash]

I've finally done the experiment ( though experiments are meant to be done on useless rifles) M seal is drying and looks good. I'm gonna post results and pics tomorrow
Regards
Suyash

[Suyash]

hello guys
M seal has dried and is in a good shape ( while applying it I opened and closed the gun and it took the shape). Metal is not scraping the M seal as we expected. I've put a layer of transparent tape to prevent scraping.
Now about the results- I've not ‘ chronified ’( I like to make new terminology) the results but just to give you a rough idea
Loose leather breech seal - 230 pages of a hard cover book.
M seal. - 300 pages of the same hard cover book
I'll soon chronify and post the results

[brihacharan]

I've been thinking about the idea of M seal as breech seal -
Goodness Gracious!!!!! Of all the materials....why this??????
If you've made it work for you .....You deserve an equivalent of a "NOBEL PRIZE"
Briha
PS: Suyash, using a resilient material like rubber, neoprene, nitrile, nylon etc. had a purpose which is to create an effective sealing between breech & barrel - so that there is no air leak when the AR is fired. By using MSeal you have permanently damaged the breech as it would have hardened ....in the event you have to remove it, you probably have to use a hammer & chisel....Good Bye Breech - Adios AR!!!!

[Suyash]

I've been thinking about the idea of M seal as breech seal -
Goodness Gracious!!!!! Of all the materials....why this??????
If you've made it work for you .....You deserve an equivalent of a "NOBEL PRIZE"
Briha

I agree with Briha Ji that I deserve a Nobel prize

Well I forgot to mention the composition of the m seal - 3 parts of resign and 1.5 parts of hardner
The material after hardening is something kinda ' hard rubbish' material. Its working well till now. Added another extra 40 fps. Can't claim any thing about the durability of the seal......but seems to be working great!
Hope that the words of briha Ji about the nobel prize comes true ...
Regards
Suyash

[Basu]

Hmmm......
I am very curious to know what happens after 600 shots......
The idea is mind blowing........
I wonder what happens if the seal needs to be changed again....how you take care of the constipation....

Basu

[bennedose]

MSeal as breech seal is a bad idea Suyash. MSeal is rigid. You need flexible/compressible material for a seal. You need to take a small screwdriver and gently chip away the MSeal.

You may have damaged your air rifle forever. If I had seen this thread earlier I would have told you how to make a good leather seal from an old shoe or from a piece of thick leather obtained from any mochi/shoe repair man.

Never cut the leather into a ring shape. Cut it as a rectangle in such a way that when you bend the rectangle into a ring it forms a ring of exactly the same diameter as the breech seal. 1-2 mm extra is not a problem. You need a rectangle of leather 5 mm broad and length equal to the circumference of the ring. Leather should preferably be just thick enough to sit snugly in the breech seal groove.