New 430L, is the Breech Seal damaged?

[Pavesi]

I’m hoping someone here has some experience with this and can give some advice. I think this may have happened when a loose pellet fell out of the breech as I was breaking it in. I have couple of questions.

1. looking at the 430 parts list it looks like the seal has two parts.
   
   1. P/n 30868000 is called the “ring”
   2. p/n 30439300 is called the “ring “F” controlled velocity”
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      [/LIST=1]
      
      Which of these parts is the rubber seal that needs replacing or do I need to order/replace both?
      
      1. Another question, can this job be done without disassembling the gun, or do I need to make a spring compressor to take it apart?
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         I have to say though that this air rifle so far appears to be outstanding in terms of trigger and accuracy. I only have about 100 rounds through it and it already groups far better than a Walther Terrus I had with 500 plus rounds through it. The trigger as delivered was a hair trigger, which I didn’t like, but with a little adjustment, it is the best trigger I’ve ever felt. The trigger now has a glass smooth light 1st stage, then a predictable wall at 2nd stage where it breaks clean with just a little more pressure. I couldn’t ask for better.
         
         
         
         Thanks,
         
         Marc

 

[bandg]

I've never had to change a Diana breech seal but I believe you can remove and replace from the front without disassembly. I would use a block mechanism (wooden dowel cut to length or something similar) and not just rely on the anti-bear trap mechanism while working on such. What you note happening seems very common. Others have noted loose breech fit and mine is the same. All should take care in loading to avoid this. I also had one fall part way down and got stuck in the cocking mechanism. Probably would have sheared away and cause no issues but it is something to watch closely for.

 

[Pavesi]

Thanks, great advice. I will definitely install something like that before working on it. As it is, the port is pretty far back in there when the rifle is cocked. I saw someone mention using a straitened out fishing hook as a method to spear the seal and hook it on the barb. I might try something like that to get it out once I find the replacement seal.

 

[bandg]

You could try Harbor Freight or look on Ebay for a set of picks. Often called "dental" picks but the tool places usually sell them. Also Joe Brancato sells a pick for just a few dollars for just such use.

 

[marflow]

the part number 13 is going to be a metal washer, spacer and would not need replacing but would be handy if you lost it

the dental picks but good ones the cheap ones that look like heavy wire with different ends are as soft as butter

 

[Bob-in-WV]

I bought a nice American made set of picks at True Value recently. I think 4 picks for about $6 or $7,and very well made. I have a longer Craftsman set too which are nice. I have tried the cheap stuff and they usually bend on the first use.

 

[smithfan4152]

I had a pellet fall into the chamber, I must have had 2 pellets and not realized it, I loaded the one, and when I closed and fired, I knew something was not right, I cocked it and looked and found my pellet as a piece of foil, I looked for damage on the breach face, which would have been far below the seal. I'm surprised at the location of your damage, and wonder if something else may have been in the air system itself. Also doesn't the Diana have the through slot, so a pellet may fall right out the bottom? 

 

[uglymike]

The 430L extremely loose breach results in pellets falling out if you don't hold the rifle horizontal when loading. Many others have had breach seal issues. This and the unreasonable cocking effort was why I sold mine with maybe a tin of pellets thru it.

 

[Pavesi]

Thank you all for your advice. I contacted AoA and they’re sending out a seal today, great customer service. I’ll fab a little wood dowel to go in there for safety for when I pull out the old one/install the new one. I’ll keep my eye out for that item 13 washer/spacer so I don’t lose it and can reuse it.



Smithfan4152, I’m kind of surprised at the damage as well, and I’m not sure a pellet did it. It’s hard to see, but the seal seems to be cut / damaged in the upper right 2 o’clock area. If a pellet fell out into the breech seal area as I was closing the breech I would think it would have become smashed down lower, but who knows. Either way, I’ll have to be more careful loading it.



All things said though, I really like this rifle. I’m not a good shot, but I was getting very discouraged when I couldn’t get another rifle to group well at all no matter what I tried. This gun with barely 100 pellets through it has already shown signs of being able to group really well. I’m sure this was mostly sheer luck, but I had one instance where 4 shots went into one hole at 15 yards. I had to stop and go inspect the backstop thinking something must be out of alignment and I probably had 3 extra holes in my garage. I was pleasantly surprised when I found no extra holes. If it has accuracy, I can forgive any idiosyncrasies it has.

 

[bandg]

"unreasonable cocking effort"

Many don't agree with you on this, me included. A little heavy for the power level, maybe. Unreasonable, not at all.

 

[makapili]

I have one of the low power ones{ 8fp} built de 2018. which yours looks like. The seal is very hard, I wasn't able to pick it out. I removed compression chamber and used a small screw driver as a chisel to cut seal. mine looked just like yours a call to AOA and they sent me a seal asap no questions asked. Excellent service, thankyou AOA

Also mine did not have the restrictor plate.

 

[Pavesi]

Thanks Makapili, though not what I was hoping to hear. Sounds like my next project will have to be rigging up some kind of spring compressor so I can take things apart and get the compression chamber out on a bench. I’ll give the picks a try first, but your experience is very good to know, so I don’t waste a lot of time trying to get it out while it’s still in the gun.

 

[Pavesi]

Here is a follow up on how I dealt with the breech seal problem, hopefully it helps someone else like me that doesn’t have experience with this. Makapili was right, there was no way to get the seal out without tearing things down. I didn’t even attempt it. I’ve never torn an airgun down before, but this gave me a good reason to do it. First thing was to build a spring compressor as I don’t think there is any safe way to take this gun apart without one. I put one together out of some scrap 2x4 I had in the garage along with some wood screws and an old gear puller I had, not pretty, but functional. The spring compressor needs to be able to accommodate about 3” of spring extension as it uncompresses on this gun, so keep that in mind if you build one. This video on a D460 spring replacement helps a lot https://www.youtube.com/watch?v=Y1MVRuEv4Vk

I tensioned up the compressor on the back notch in the T06 trigger group until I could drive out the two pins. I used some chop sticks I had lying around to drive the pins out without marring them. Once tension is off the spring, the T06 trigger group comes straight out. Next the spring and spring guide come out. After that the piston can be pulled out, but you still have to get the compression chamber out of the gun. To do that you need to disconnect it from the cocking arm. The first step here is to remove the pin nearest the compression chamber by removing the e-clip and dropping the pin out to disconnect the cocking handle. Be careful not to lose the compression chamber tensioning spring/clip as this is done. Next, you need to remove the cocking arm stud that is screwed into the compression chamber. There is a small 2.5mm Allen screw that you access from the front of the compression chamber. Remove that Allen screw and the cocking arm stud should come out. Now you can slide out the compression chamber from the gun. The seal in mine was totally trashed. It was blown out and pretty much in two parts. I tried to pick it out with a dental pick, but no go. I tried to pry it a bit with a screwdriver, again no go. I tried to drive a screw into it, but it was too damaged to bite, no go. I tried to heat it some with a lighter, no go. Thankfully Makapili gave me the idea that worked. I took a jewelers screwdriver and a small hammer and slowly chiseled a section out of the seal. Once it was cut through in one section it came right out with the dental pick. Also, there was a “controlled velocity” washer in there under the seal. I cleaned that port and washer up, and dropped in a seal that AOA gave me that said it was for a Diana 460. Part number on it is 3056100. Since I had things torn down already, I decided to debur things where I could and then to re-grease it. I also polished the spring ends while I had the chance with some 800 grit then 2000 grit sand paper. I’ll probably get flogged for what I used to lube things but it is what I could get quickly and I wanted to try a paste based on tungsten disulfide. I used a light amount of Silicone “dielectric” grease for the breech seal. I then used Lubri-Moly LM48 paste for the piston seal skirt, the piston, a light coat on the inside of the compression chamber, the spring and spring guide. I used TW-25B for the outside of the compression chamber and cocking arm pins and other places I didn’t want the color/staining of the LM-48 paste. I didn’t touch the T06 trigger unit since it is working so perfectly I could only make things worse. Re-assembly is as they say the reverse of disassembly. There was one catch though. On reassembly I discovered some binding as I moved the cocking arm through its travel (with no spring installed yet). I’ll discuss this and a fix for it in another post about 430L compression chamber binding up during cocking.



Here is a picture showing the spring being decompressed. Pins have already been pushed out and trigger group is almost all the way out of the tube.

Here is a picture of the cocking arm after the pin is driven out and it is disconnected from the compression chamber.

Here is a pic of the cocking arm stud on the compression chamber and the 2.5mm Allen head screw that needs to be removed to get it out.

Here’s a pic of the old seal after the compression chamber was removed.

Gun is now back together and I'm going through the cleaning process again. Accuracy seems to be as good as ever. Shooting cycle is very smooth and quiet. No dieseling from the very first shot. Hopefully this 460 seal will hold up in the 430.

 

[bandg]

Well done and nice write-up. I'll add a little modification I do that may not be helpful but shouldn't hurt anything. In your second picture above, at the lower right area you see the angled "foot" where the breech seal tensioning spring sits. On my 460 (same mechanism) and now my 430, I've added a second spring nested inside the larger stock spring to apply more pressure to the breech seal when latched closed. I have a large assortment of various springs purchased long ago from Brownells and I picked a revolver hammer spring that fit easily inside the stock Diana spring and cut it to the same length as the stock spring. Then, when the cocking arm is latched, more pressure is applied to the breech to keep it snugly closed. I'm certainly not sure that it helps but it might reduce any air loss at the breech seal and it is something I've done to both my Diana rifles after reading about such several years ago being done for a breech seal leaking issue. 

 

[Pavesi]

 

Thanks Bandg, I have a few springs I've saved from other projects, so I'll look through them and see if there is one I can tuck inside the main seal tensioning spring. I may need to get back into the breech again before too long. I took a look at the new seal with a borescope and it looks like its sitting a little off center, kind of like in the picture above of the original seal, but its off center in a different direction. When I put the seal in, I just pushed it in with a deep socket. Maybe there is a better way to install it than the way I did. AOA also sent me a seal for 48, but I chose the 460 seal as the 48 seal was a harder material and looked like it might end up getting cooked in the breech like the original did. I may pick up a few more 460 seals the next time I order pellets from AOA.