Figured out what is wrong with the old 435

[lizzie]

The breech isn't closing well. 

It's not an affirmative *snap* shut, but has some sloppiness to it. Okay you German experts, or detente experts in general, how do I troubleshoot this problem? What is the mechanism that keeps the breech closure secure?

[bart the fart]

Well, Lizzie the first thing I would do is, cover the breech lock up area with a piece of tissue paper grasp it with your thumb and forefinger with your left hand and shoot it. Sounds goofy I know but if the tissue shreds and rips, well theres a good starting point. Sounds goofy but try a new breech seal, the slight difference in thickness might make all the difference.
  Second (if that didn't work), pop it out out of the stock and post some pic's of the cross bolt...hopefully its not a super odd ball head on the bolt.
  I know this is not an answer but hey...gotta start some wheres...LOL...Cheers Bart

[lizzie]

Thanks Bart- I tried replacing the seal, although the other one looked good. I call tell from the feel of the snap, and the slight off angle of the breech block, that it's not closing fully. Just not sure what to do about it except send it off, lol.

[bart the fart]

hehe yes I know what you mean. Try to tighten the cross bolt IF the cross bolt isn't to weird looking A lot of old rifles (especialy German) have some of the oddest bolt heads you will ever see good luck

[lizzie]

Sorry to show my ignorance, but I don't know what the cross bolt is. 

[bart the fart]

Oh I might have shown mine LOL. Im not sure the techincal name but the bolt that holds the barrel to the reciecer. Take the action out and post a couple of pic's.

[lizzie]

Dangit- I just put the action and barrel back in the stock just a couple of hours ago, lol. If I can't get back to it tonight, I'll try to tomorrow. Dang- I knew I should have taken pix, lol.

[Calmark]

Lizzie,

Those guns with a less-than-optimal breech lock up can be frustrating I know.     My older FWB 124 suffers from the same issues.  Even after I replaced the barrel pivot bolt last week and finally got it tightened, it still doesn't lock up quite right.  Its better, but still has a weird extra "bump" while closing that makes it feel clunky. 

Since I recently got another FWB 124 to compare it to, I definitely know something is wrong since the new one is extremely smooth closing and "snaps" shut.  For one, the accuracy on the old one isn't consistent like the newer one.  I also see the old one makes a semi-circle cut in the o-ring at the top and smashes it flatter.  you might look your breech seal over to see if its damaged from the lock up.

Also, really check things over on the face of the compression tube where the detent is.  Today I looked over both of my guns carefully trying to find the difference and I noticed where the old gun's transfer port was pressed into the end of the receiver, it sticks out slightly.  That seems to be the source of my o-ring damage and I'm thinking it could be something that pushes out the barrel so it doesn't latch quite right.  I think it sticks out maybe 1/64"more than the outside walls of the receiver.  I might even take the newer gun apart and look it over for more clues. 

I know you don't have another identical gun to compare your 435 with, but keep looking it over.  It could be something simple like worn shims or a breech seal that's too thick.  I sanded mine down this past week and it seems to have helped.  Good luck and if I think of anything else I'll let you know.

[lizzie]

Thanks Calmark. Whatever it is, it just happened within the past few days. This gun used to be an excellent shooter, and I'm really hoping I can get it to working well again. I'll just keep messing with it until I get frustrated enough to send it off, lol.

Thanks for all the info and suggestions.

[RedFeather]

Could be the ball detent - the part that locks it up.  Try a little penetrating oil applied to the ball and let it migrate behind it.  Sometimes the spring gets gooped up back there, especially after forty years of old oiling, etc.  That's the first place I would look with a loose lock up.  BTW, what are you using for a new breech seal, an O-ring?  How much does it stick up over the face of the breech?  (New gun term - "Proud - How high something stands, as in 'Someone refinished the stock and removed too much wood, so now the metal is proud.'"

[lizzie]

Could be the ball detent - the part that locks it up.  Try a little penetrating oil applied to the ball and let it migrate behind it.  Sometimes the spring gets gooped up back there, especially after forty years of old oiling, etc.  That's the first place I would look with a loose lock up.  BTW, what are you using for a new breech seal, an O-ring?  How much does it stick up over the face of the breech?  (New gun term - "Proud - How high something stands, as in 'Someone refinished the stock and removed too much wood, so now the metal is proud.'"

I really do suspect it's the ball detent. The seal is an o-ring, and it's flush with the breech face. I checked it yesterday with a high-quality level/ straight edge to make sure.

What kind of penetrating oil do you recommend?

[RedFeather]

Actually, something like a good shot of GunScrubber might work better.  It will evaporate.  DON'T shoot the gun until you are comfortable that it has, LOL!  (2,000 fps without PBA might be possible - once, LOL!)  Work the ball by pressing with something hard like an old fashioned clothespin head, now available only at craft shops it seems, until you ferl it has loosened up.  Then just a drop of a good grade gun oil.  I think your seal should stand a little bit proud of the groove and not lay flat in line with it.

This just in - that bit about your O-ring made me stop and think.  Some of these O-rings are rather soft and might, over time, blow out and not create a tight seal.  Do the tissue test.  If it puffs, then the lock up might not be your problem.  Even a 35 creates a good deal of pressure on that breech which may be enough over time to stretch or soften that O-ring.

[lizzie]

Yikes!
Sounds pretty scary.

The o-ring is new. Maybe my eyes and fingertips are lying to me, but it seems to be a perfect fit. I'll check that out as another possibility.

[Tom @ Buzzard Bluff]

Lizzie,
 If you're an airgunner ATF is your friend. Work some behind the detent ball to thin old hardened lubricants. I also use it to revive the seals in old CO2 guns that leak by injecting a few CCs where a new cartridge will force it into the valve, insert a new gas bulb and shoot the gun as rapidly as possible to distribute the CO2 and then just allow the gun to sit from a few hours to several days. It revives them in at least 50% of cases. Works on old multi-pumps too.
 Carefully inspect the part that hooks over the detent ball to complete the lock-up. If it has been distorted by wear or excessive force it too could be the problem.
 Without actually being able to see the gun analyzing the cause is mainly guesswork unless it is a problem common to the model so ALL of us except you are taking wild shots in the dark. If you don't figure it out soon send me a PM or e-mail and we'll talk further. I'd be happy to take a look at it rather than have you spend $ to pay a 'pro' that may have less experience than I!     Tom

[lizzie]

Thanks Tom.
I had to work today, and again tomorrow, so haven't had time to take it apart and take pix. I'll try to do so on Monday.

[lizzie]

Well, what the heck. I took the action and barrel back out of the stock, and the breech closed just fine. So I put it all back together, and now it's shooting well again. I must have had some little something out of good alignment when I put it back together the first time. I'll just watch and see how it goes for the next couple of weeks.

[Calmark]

Great news!  Glad your fix was something easy like that.  I guess something was just a bit out of alignment with how you put it together and something may have been binding up.  Gotta love the easy solutions like that.  Trouble is finding them is most of the battle sometimes. 

[lizzie]

Great news!  Glad your fix was something easy like that.  I guess something was just a bit out of alignment with how you put it together and something may have been binding up.  Gotta love the easy solutions like that.  Trouble is finding them is most of the battle sometimes. 

Yep- gotta admit I felt pretty silly, lol. I noticed when I took it back out of the stock that the stock screw on one side was definitely tighter than the other, so I'm thinking I may have tightened it way too much before starting on the other. It was binding somewhere, and that's my best guess.

[airnutz]

Yikes!
The o-ring is new. Maybe my eyes and fingertips are lying to me, but it seems to be a perfect fit. I'll check that out as another possibility.

I spoke directly with a Diana Technician last week, as my old 35 (leather o-ring) probably needs to be also replaced.  Nowadays the rings are only rubber.  Behind the o-ring a thin shim needs to be placed first, and according to Diana, the new o ring with shim in place should be 1/10 mm raised above the plane surface.

Just some info.

Greetings