Seal Adapters for Tech Force Jet, AR2000 Jet, Beeman Mach12.5

[Paul68]

Since I am very fond of installing aftermarket JM seals in all of my rifles, I have a couple that are presenting problems. Most notably, my Beeman 1051(AR1000) and SAG AR2000 Jet, both of which use the well known screw on seal.

There just aren't many options besides a stock seal for these guns.

In this case, although the JET is great as is, I plan on installing a JM seal very soon, and Walther/Hatsan 29mm seals are a perfect fit. However, they have a "stepped" push on button design rather than the typical tapered push on button, so the fairly hard to find usual aftermarket adapter is a no go.

To fit the 29 mm Turkish seal to the SAG rifles something else is needed.

Basically what you have to do here is recreate the stepped button on the Hatsan/Walther piston and drill it to accept a screw. You don't have to have one of these pistons in hand to do this, just the seal. If you have a lathe, ignore me as you can whip up an adapter complete with an integral threaded stud in a hour. This is for us poor rubes with nothing better than a drill press

I came up with two ways of making these adapters. One is a solid one piece made from an automotive axle stud bolt which I used because the head is round and simply needs to be ground down to fit.I will describe this one only as it is in truth the best design. The other will work, but is unecessarily complicated.

I start with an axle stud bolt with a head larger than the diameter of the center of the seal the piston button will fit into.

I then drill a hole about 3/4" deep in the center of the stud head large enough to accept a 10x32x1/2 flathead countersink bolt.This is a PITA as you have to get the hole in the center of the stud and the bit can be finicky and want to off center itself even if you use a punch to make a starter divot. As you can see in the pics, I failed to get it properly centered but was able to drill the hole larger to salvage it. This one is workable, and a final version will hopefully be centered properly and cleaner. Then I take a drill bit slightly larger than the head on the 10x32 bolt and drill into the center of the previously drilled hole deep enough to allow the bolt head to sit flush when inserted into the stud. This chamfer cut combined with the slightly oversized bolt hole allows the bolt head to sit flush when installed and causes the seal to center itself automatically when installed, provided the chamfer cut is also centered. Again, A PITA when doing it with a drill press. Suffice to say, get your holes centered and you're good to go.

Then I chuck the stud up in the drill press and take my Dremel and a grinding stone to turn down the diameter of the stud head until it is nearly small enough to fit into the center of the seal. I then take a flat sided file to it until it is smoothed and ground down so the outer diameter is the right size. You want it to slip into the seal when pushed in from the top with a slightly tight fit so it solidly stops at the step in the seal, almost as if it "snaps" in. This takes a couple rounds of filing and test fitting until it's right.





You then need to smooth the shank of the stud. I use the Dremel and grinding stone with the bolt spinning in the drill press to make a few passes and remove the splines in the stud shank. I then use the flat sided file to finish smoothing it.Once that is done, I use a sharp edged triangle file to make all my ground edges  square and tight. I then take 220 grit, and with the bolt spinning in the press, simply polish everything up nice and smooth.

Once I have all that done it's time to cut the adapter off the stud. I leave the stud set up in the drill press and make a mark in the shank where I want to cut. I make it longer than it needs to be so I have material left for final grinding to fit it to the seal. Then with the stud spinning in the drill press I simply use a hacksaw and press the blade to the marked area on the stud and let the drill press do the work. Once it is almost cut through, I shut the press down and cut the adapter loose with a few quick strokes of the hacksaw.

You should end up with a little button that will drop into the seal and sit securely on the inner lip without being able to be pushed all the way through the seal.

The last part of this involves fitting the adapter to the seal.The face of the button should sit a couple thousandths below the edge of the seal face to prevent it from slamming into the bottom of the compression chamber during firing.

The bottom of the adapter where it comes out of the bottom of the seal should also be about a thousandth or so below the bottom of the seal to allow the adapter to compress itself into the seal and produce a tight fit with the piston when installed.Too deep and the adapter will distort the seal, not deep enough and the adapter wont hold the seal securely.

To achive the above, I simply lay out some 120 grit on a flat surface and proceed to hand grind the bottom and top of the adapter until I achieve the desired clearances as described.

Once fitted, you should end up with an adapter that fits tightly into the seal and centers itself once everything is tightend down on the piston. When installing, make sure the seal is not off center on the piston and put some blue locktite on the bolt threads for security.

The other adapter is made using a bronze bushing from Lowe's and an automotive drum brake spring seat. Same principles, just different approach. Both are shown and should be obvious which is which.

As usual with me, not beautiful precision work, but effective
 

[Bentong]

I was lucky to get mine with no problem from target tune for $2.00 for this adapter.

[Paul68]

I was lucky to get mine with no problem from target tune for $2.00 for this adapter.

That's the adapter I referred to. The 29mm Turkish seal uses a different button design that requires a step. Is there a 29 mm seal that works with that adapter? If so, this is a moot post

[Kailua]

I use a JM apex small that is oversized by 8 thou on a TF89 if that helps.

[Paul68]

The only thing I find a possible alternative to a custom button to fit aftermarket seals to AR2000's and variants are the aftermarket seals folks use on the Benjamin Np XLs, which as I understand it are JM Turkish seals as well. Since I have no idea exactly which seal, or whether the button on the XL's are stepped or just tapered, this is what I come up with since I do know the JM seals for Walther/Turkish are 29mm.

[Kailua]

Oh I missed something.  You want the screw for the JM seals.  Bentong's screw from Target Tune India is the one you want.  Shipping is hit or miss but fairly cheap with $3.00 shipping.  I had got two from them but the rest of the order never came.  India's postal service is really terrible.  Originally I had made an adapter which worked but can't find it being that I am using the TTI adapter.  What I had made was with a piece which was 3/16'' thick cut from a piece of channel iron.  Bought a tapered screw that matched the piston threaded hole and drilled and counter sunk the 3/16'' piece of metal.  Had to shape the flat piece on a bench grinder along with the taper it needed.  The taper measures .578'' OD to .510'' OD.  Not that hard to make.  Just some patience.  A 4 1/2'' grinder with a abrasive cutting disc would help also to get started with the cutting.  I hope this info can help.

[Paul68]

LOL. Guys, I don't need help making em or finding one, I already did.  I already know and knew about the adapter from TTI.

The point here is that the Turkish seal used here is not the type that works with the adapter from Target Tune.

Now, if there is a seal that is 29mm in outer diam, that will work with the Target Tune India part, that is another story. As I said, I don't know if the seal used on the NPXL's is the same or not. However, I also know that TTI has a bad reputation for failed deliveries, so perhaps making my own is still viable even if I could use their part.

[Paul68]

Still working to make these a bit better. Think I've about got it down. Made a larger radius on the lower portion of the adapter so it will fit the seal snugly both top and bottom. Went with some diamond tip shaping bits which really cleaned up the machining. Still a PITA to center the bolt hole properly, but doable with a lot of care. Think I will take this last version down to the machinist here and see if he can make several for me since it will be faster and I can get one or two out to members who've asked for one. Not bad for a drill press and Dremel part I'm thinking.

[Mr Fluffy Tail]

that is really looking good, i would love to get my hands on one of those setups

[Paul68]

that is really looking good, i would love to get my hands on one of those setups

You will within a week. Sorry for the delays, but I had too many misgivings about the rough versions. They worked, but I did not feel good about their fit. This last one seems on the money and I'll send it even if I can't get a run of em made. I'll install it in my Jet and make sure it performs well once I have the machinist sure he can reproduce it, then I'll send it. PM me your addy.

[Paul68]

Just an update for the heck of it. Finally installed the JM seal using my adapter. Also replaced the original Jet spring with a Hatsan 125 spring cut down to match the originals 43 coils. Original top, Hatsan bottom. The Hatsan spring is slightly larger at just a hair under .142, for all intents a .142" wire diam. Inner diam slightly smaller, which actually gave a better fit on the tophat and guides. BTW, note the monster tophat. That's one huge slug of metal.

Despite being Chinese made, the old spring is in great shape for nearing 2k shots. Only a slight cant on the end and still producing 27 FPE.

With the spring and new seal the gun is now hitting 28+ fpe. No noticeable difference in shot cycle, and only slightly harder to cock, which I imagine will ease up once the spring breaks in. Next step is to increase stroke a slight bit and see if it will hit 30 FPE.

Overall a cool little effort.

[Kailua]

Looks good to me.  Glad you got everything going in the right direction. Numbers looks killer.  LOL

[Paul68]

Looks good to me.  Glad you got everything going in the right direction. Numbers looks killer.  LOL

Thanks. The JET still impresses the heck out of me every time I shoot it. Very accurate and so reliable its almost weird. The deviation is on the order of 6 fps so far, which is also a significant improvement over the old seal. I'm working on another adapter for other members and hopefully can turn something out that wont embarrass me;)