How definitive is the "tissue test"?

[RedFeather]

This is the one in which you place a single layer of tissue over the breech and shoot to see if the tissue moves, indicating a leaky seal. I have an old, gnarly circa 1967 Milbro with what must be the original leather breech seal. The seal is flat as a board, yet the gun will shoot with some authority and the tissue is undisturbed. I can't see how the breech can be sealing. Does it have to be a big leak in order for this test to work?

[Gene_SC]

No, not really Red. I use toiliet tissue when I supect a bad breech seal. You can alos use a piece of wax paper by placing it between the breech seal and action. If when shot the hole is round, then that would indicate no leak but if the paper is blown out on one side you probably have a bad breech seal.

[daveshoot]

Now that's an interesting tip!

[RedFeather]

Well, it sure beats me. I think I've tried tissues on my old Haenel which, surely, has the original 1928 seal. That one shoots pretty slow, though, so it may not be producing a lot of blow by. These seals are the fat, wide style. O rings have gone a long way in improving things. (Plus they are a heck of a lot easier to replace!) Think I will give the wax paper test a try.

You know, thinking about it, I'm wondering if the old leather-sealed guns have as much problems with breech seals as do modern ones?

[Gene_SC]

I have seen flat breech seals that were flat,  nicked and gouged that did not leak on 800 fps guns. The ones I would see the worst was Gamo and Crosman breech seals. But they did not leak. But even if a springer shoots in the 500 fps range it will leak past the breech seal if it is bad enough.

[RedFeather]

Guess I will leave the seals alone then. On the Milbro, the gun was almost a basket case. Wrong stock screw (missing the other), cracked stock, lots of surface rust/pitting. The piston looks to have black dried grease on it and the spring is bare. However, it shoots with no twang whatsoever. I can't refinish it without pulling it completely apart. You watch. Clean it all up, put it back together and I will bet dollars to doughnuts it will ring like a bell with each shot. BTW, this is sort of an extension of the Diana 27 which Milbro Scotland got to produce following WWII. And it has a decent trigger, too. Came as part of a deal, thrown in for $20.

[gmh45345]

secrets away. Thanks for the tip Gene.
Gary

[itsnotom]

if it aint broke, dont fix it

[kiwi]

I use soapy water....but that has just changed since
I read Gene's wax paper trick...I now use wax paper..LOL

Pete

[bigbadwulff]

Isn't wax paper a little rough on your 'breech'

[davee1]

I've never had any luck with the tissue paper test. Probably because the leaks were slight, or they were leakingair on the bottom half. When I got a chrony, I replaced a bunch of breech seals on my guns which passed the tissue paper test. In most guns, I saw improvement in velocity, consistency, and grouping. It took me hours of patient work. Then when I started shimming the seals I saw more improvement. More hours of patient work. But in the end, I was fairly confident that I had squeezed more performance out of my guns. Thats one of the reasons why a chrony is an excellent tool.