chamber to barrel seal on a RWS 48 .22 cal

[bluetalon1]

I just need to know if there is suppose to be a seal, o-ring on the chamber side.
Looks like there should be one.

[melloroadman]

http://www.umarexusa.com/images/PartsDrawings/48-52-1.jpg

[bluetalon1]

I can not open that link.

[davee1]

BlueTalon, there should be a seal...yes. I don't have a 48, but I have a B21 which is a chinese copy of the 48...and it has a seal. Its not an oring though...its more like a "cup" with a cone shape in it, to mate up with the loading port cone. I just cut some fuel hose and put that in the seal cavity. The OEM seal was cracked and hard...not good. You can always buy a seal from Umarex, or just make one out of a short length of tubing/hose.

I was able to open the parts diagram and it shows a seal and I believe a shim. There can be one shim, more than one shim or none at all...just depends on your particular seal cavity/seal/loading porttolerances.

[bluetalon1]

Thanks davee1
So it kinda looks like the breech seals on the b3 but smaller. I knew there had to something missing.
The power level on the 48 really dropped out a while back so I stopped using it. I figured it was a broken spring.
Last night I decided to take it apart and Everything on the inside looked good. I cleaned it up, the thing was nearly dry on the inside, then I lubed it up.
No more twang.
I know it should be shooting harder than it is now.
I decided to work on the 48 since I finished the 350M. It was also dry, very little oil on the internals. The 350M went from my favorite gun not to shoot, to my favorite to shoot
I have taken 3 rabbits with the 350m this week alone. Last week I choped the 350's barrel 3.75" recrowned it and ofcource thats when I did the complete tear down. I love the way it behaves now.
I am shooting the cabella's outfitter series ultra mag 10.5 gr pellets. Looks just like crossman premiers to me without the oil on them.
Anyway thanks for the info, I will try to make one out of a short length of tubing/hose before I order one.

[davee1]

I can tell that you are having a good time!!! Right on!!! Gotta love those 350s...

Yes, the seals are like those of the B3 breech seal...need something to mate up with that cone.

I checked my records and the seal that I made was from vinyl tubing 1/2" OD, 5/16" ID, 17/64~9/32" length.I have also used fuel hose...but what works betteris forgotten now....too many pellets have passed. Don't know if the seal size of a B21 and Diana 48 are the same, but I figure that they must be close. When making the seal, you want "firm but squishy" material, if that makes any sense. Firm enough not to curl, and squishy enough to conform to the cone and cavity. Don't want to make it seem difficult though...its not. Just a matter of finding tubing/hose with the right OD/ID and start experimenting with the length. There should be a slight resistance as the breech closes up...thats the sealing taking place.

The breech seal for the 48 is not a cone shaped piece as described above. It is more of a flat section O-ring/washer type of a deal. I have replaced a few. There also has never been a shim under the seal , even though is does show one in that link. I asked a gunsmith at Umarex about this one time, and was told that it is not necessary as, breech seal fit /headspace is adjustable via the treaded cocking rod. You would be advised to order a couple from Umarex. If I have time I will measure the couple I have here, and will post the measurments. Maybe McMaster Carr has something that will work, and would be cheaper.

Just looked at the breech seals I have. They have a  recess in the center ,but are not cone shaped as the ones in the  B-3's and the Chinese cleaning kit are. They are not a flat o-ring. I was thinking of something else ,sorry!  The measurments are .414 in daimeter, .140 high(thick),.166 (#19 drill will just pass) hole in the center of the seal. They are made of a hard  blackmaterial, almost like teflon(?). The recess in the center of the seal has a slight bevel and is 9/32" in dia. It extends about half the depth of the seal. On another forum a guy tried to use a modified faucet washer for these and while it worked well for a few shots it failed early. It does sort of look like some of the faucet washers I've replaced in my line of work. I think you could turn one out on a lathe if you have some suitable material. BTW, It can be hard to remove the old seal, and you want to make sure it is seated in the piston all the way , before firing the gun. I pushed mine in with a plastic rod to make sure it was fully seated in the piston. Damage to the seal will result otherwise. Hope this helps ,sorry for the typo above. Robert

[bluetalon1]

Thank You    Bobber

Thats good to know i will have to order some.
I double checked last night and the seal is gone, all i see is metal, there was a small poece of lead smashed in there I removed it.
I can't wait to get a new seal for it so I can get my knock down power back
I have to say It does look like the the right sized fuel line can work. I was able to find a oring that fit but I don't think it will last very long.
Thanks Guys for the info.

Glad to help. The part # for the breech seal is 303621, and it is described as "breech seal 3.5(square x-section) on  an invoice I have from Umarex from  this past August. They cost me  $4.75 each, but the cost to put just one in an envolope was five bucks more! Might want to order a couple extra. BTW, this part # was for the .22, but I think the .177 is the same. My current 48 in .22 is getting 820fps with RWS super H points, after I lube tuned it.It's a real hammer! Take care , Robert

[mikeiniowa]

if you can give me an exact measurement of the opening it fits in I may be able to send you one, have a number of different sizes and as usual I didn't label them as to what they go to....