How does the breech seal on a fixed barrel springer work?
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How does the breech seal on a fixed barrel springer work?
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Topic: How does the breech seal on a fixed barrel springer work? (Read 1726 times))
Allen Rice
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How does the breech seal on a fixed barrel springer work?
«
on:
January 29, 2015, 10:26:36 PM »
Fixed barrel springers have a sliding compression chamber with the breech seal imbedded around the transfer port at the front of the chamber. When the rifle is cocked, the chamber is moved forward, closing the breech, but there does not seem to be an appreciable amount of pressure on the seal. Cocked and ready to fire, the spring is compressed and the piston remains to the rear, held in place by the trigger. At this point, the compression chamber and the breech seal are not influenced by any spring pressure at all. I am guessing that when the gun is fired, the compressed air inside the compression chamber exerts tremendous pressure on the chamber, forcing it forward against the receiver port in the barrel, thus providing a high compression seal just in time for "main event". As I said, I am just guessing and wiser, more experienced, opinions are more than welcome. I am also curious as to how well these fixed barrel breech seals stand up as compared to seals on break barrel rifles.
AR
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Clearwater, FL
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Re: How does the breech seal on a fixed barrel springer work?
«
Reply #1 on:
January 29, 2015, 11:21:38 PM »
Allen, it sounds as though you understand the concept. I have a TX 200. When the cocking arm is moved into the "home" position after pulling the compression cylinder forward it latches and thus applies the correct amount of force to hold the cylinder against the breech seal. When the breech seal becomes compressed over time the cylinder is no longer held snugly against the seal.
Replacing the seals will generally rectify that. Wear on the cocking shoe or linkage can also prevent the cylinder from homing properly.
To help prevent premature compression of the seal I do not latch the cocking arm when storing the gun.
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Near the Southern Coast of Washington State
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Allen Rice
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Re: How does the breech seal on a fixed barrel springer work?
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Reply #2 on:
January 30, 2015, 02:13:21 PM »
Thanks for the reply Thomas. What's the best way to test the breech seal? I tried blowing through the barrel with the gun un-cocked and the lever in the "home" position. I was able to detect a slight hissing from the breach, but the resistance to my blowing was significant. I'm not sure what is acceptable. Chrony numbers are not un usually low.
AR
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Clearwater, FL
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Re: How does the breech seal on a fixed barrel springer work?
«
Reply #3 on:
January 30, 2015, 02:19:48 PM »
Tissue test ....
Place a tissue paper/toilet tissue sheet over the breech area and safely discharge it with a pellet.
If Tissue blows off upon firing you have a leak ... No tissue movement your good to go
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Re: How does the breech seal on a fixed barrel springer work?
«
Reply #4 on:
January 30, 2015, 02:44:42 PM »
Allen - if you are using a TX 200, you may remove the latching block at the front of the barrel - 3 mm Allen if I recall. With the barrel down, gravity will move the lever toward the home position. If the lever hits the little rubber bumper on the barrel, the seal is not holding the cylinder. This can indicate a seal compressed out of tolerance. The seal consists of two O rings, one on top of the other.
It can also indicate wear or manufacturing tolerances cascading to cause the problem.
Scott's tissue test should tell the tale also. I just never thought to try it on a fixed barrel.
An individual going by Cloverleaf went into some detail on this issue on the Air Arms Owners' Club (AAOC)) website. You may check it out at
http://www.airgunforum.co.uk/forums/showthread.php/165327-The-TX200-cocking-shoe-cylinder-lock-up-issue
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Near the Southern Coast of Washington State
Real knowledge is knowing the extent of one's ignorance.
Allen Rice
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Posts: 386
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Real Name: Allen
Re: How does the breech seal on a fixed barrel springer work?
«
Reply #5 on:
January 30, 2015, 03:16:26 PM »
Thanks Scott and Thomas. I new I could count on you guys. Now to the "lab" for some scientific testing.
AR
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Clearwater, FL
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How does the breech seal on a fixed barrel springer work?