Service Guide for the FB Record Jumbo

In this article, for a change from writing historical pieces, I am going to write a guide that details how to disassemble a Record Jumbo. Why the change Jimmie? Well, I bought this pistol rather cheaply at a bring and buy sale some years ago. Bargain it was or so I thought. When I got it home when I soon realised it wasn’t such a good deal. It would not fire a pellet at all….

The naked Jumbo!

The Record Jumbo was made by Fritz Barthelmes KG in Germany, or to be historically correct, West Germany from 1982 to circa 1997. It is a very unique pistol that is sought after by keen collectors for it was the first pistol to have an oval-shaped piston. However, this uniqueness is also its Achilles heel.

Not only is the piston oval, but it is a concentric design where the barrel runs through the piston and mainspring. In such a design, there needs to be room for the air to travel back along the compression chamber, out of the breech at the rear, perform a U-turn and then travel back down the barrel. But where the U-turn would take place was an o-ring. Normally there is one o-ring at the breech and is located in a groove surrounding the transfer port. I assume that the previous owner also realised that the pistol would not fire a pellet and assumed that it was missing a breech seal. I removed this extraneous o-ring and tried again. Still no joy.

A strip down of the pistol revealed the true problem. The piston seal had deteriorated so badly through age that it was crumbling to pieces. Blast! No amount of searching would furnish me with a replacement seal and the company that made the pistol had closed its doors many moons ago. That was that I thought.

Not long after I bought this Jumbo, I sold another Jumbo along with a “project” Jumbo to a fellow collector and friend. Although I had not realised it at the time, that pistol also had a crumbling piston seal. I fully expected to refund my friend in full but he had other plans. As an experienced machinist, he insisted that he would manufacture a new piston seal and, as he was aware that I too was in need of a new seal, offered to make me one as well. True to his word, he did. But not until almost a year had passed. Meanwhile, my pistol had been sitting in pieces in a container feeling sorry for itself. Making the piston seal was by no means easy though. Being oval it required some special tools. Our heroin took the spare seal from the project pistol and measured it using a magical machine called a “Kemco” probe. Don’t ask me what that is, it’s magic remember. The seal was then cut from a block of PTFE using skills honed over many decades and acquired from fabled wizards.

However it was made, I am very grateful. For just a few days later, a package arrived containing a new seal for the Jumbo!

So, without further ado, here it is, a strip-down guide for the Record Jumbo…

tools for the job

You will need:

  1. A set of flat screwdrivers. Always use the widest screwdriver that fits the full length of the slot in the screw and one that reaches all the way to the bottom of the slot. Doing so prevents “nicks” in the slot and eliminates the risk of the screwdriver slipping and rounding off the top of the slot. The same is true for cross-head screws.
  2. A brass pin punch. A brass punch is soft and will not damage the finish of pins. A steel punch could be used for this pistol as its pins are not tapered and slide out with hardly any force.
  3. A small hammer for use with the punch.
  4. A small jeweller’s screwdriver.
  5. A pair of serrated needle-nose pliers.
  6. A modified dentist’s pick. This has flat smooth tips and can be bought from modeller or artist stores.
  7. A deep 14mm socket or other size depending on your toolkit.
  8. A sash clamp with soft-faced jaws.

I also used a toothbrush, a nylon brush, some wooden toothpicks and blue workshop paper towel to clean the pistol and its parts. An alternative to blue workshop paper towel is kitchen roll as it is practically lint-free. But beware the wrath of “she who must be obeyed”! I am also lucky to own an air compressor which I made good use of to ensure any remaining water from the cleaning and rinsing process was blown away.

Did you notice the chopsticks? These are handy items to have around. They are strong yet being bamboo they will not damage metalwork. I use them to push items out where necessary. They’re not strictly needed for this strip-down though.

It’s also a good idea to place the parts into a tub or even into separate zip lock bags so that you don’t lose them and keep sub-assemblies together. If you lose any parts for this pistol, you are unlikely to find any spares!

lubricants

Lubricants and conditioning oil

For reassembly, I used Bisley Gun Grease and Abbey SM50 gun lube. Bisley gun grease is a molybdenum disulphide based grease and was used very sparingly on the contact surfaces of the piston seal, sear contact points and screw threads. The Abbey SM50 gun lube was again used sparingly on pins and bushings. I do not apply grease anywhere else as it isn’t necessary, including the mainspring!

The brown box at the back is CCL Gunstock Conditioning oil. This was used to treat the grips and helps to prevent them from drying out and splitting.

Silicone grease for captive o-rings

Oh, I nearly forgot, silicone grease for o-rings. This is a tube I have spare from my scuba diving photography days. You can get a pot from any dive centre and it will last you a lifetime. Here is a tip for applying silicone grease to o-rings. First, make sure the o-ring is clean I use a piece of kitchen towel and pull the o-ring through it. I do this by placing the towel around part of the o-ring and in-between my finger and thumb. With the other hand turn the o-ring through the towel by pulling it. You may find that slightly wetting the towel helps the process. Place the o-ring on a clean piece of kitchen towel once it has been cleaned. It must be kitchen towel though. Don’t use any other kind of “bathroom towel”. Kitchen towel is almost lint-free.

Only a small amount is necessary

Place just a tiny amount of silicone grease onto your fingertip and then rub your thumb and fingertip together to spread the grease out evenly. Now rub the o-ring between your finger and thumb. That’s it! It applies just the smallest smear of silicon grease to the o-ring and that is all you need. Do not be tempted to plaster it on!

A very thin coating is applied

Having said that, you shouldn’t use silicone grease for all o-rings. It really depends on the application of the o-ring. If the o-ring is captive, i.e. it does not move, then silicone grease is ok. But, if it is going to be placed somewhere where it is likely to move then it’s not such a good idea to use silicone grease. Silicone grease can cause increased wear between moving metal to metal surfaces. If in doubt, use the grease recommended by the manufacturer. Or, try some Molykote 33 which is designed for moving metal to metal applications.

let’s get to work

Remove the cocking arm pivot pin

Stage 1: Remove the cocking arm pivot pin. For this, you may need two flat-bladed screwdrivers, a soft-faced vice or perhaps an extra pair of hands. Remove the smaller screw that secures the pin in place. Then, using a chopstick, push the pivot-pin out. If you use a screwdriver, you risk slipping and damaging the part or the finish of the pistol. I also removed the grips to save them from damage.

Remove the e-clips from the connecting pin

Stage 2: Remove one of the e-clips that is attached to the cocking arm link connecting pin. This might be underneath a rubber cap which can be levered off with the jeweller’s screwdriver. Next, lift off the cocking arm link and swing it slightly downwards towards the grip of the pistol.

 

Remove the connecting pin bushes

 

 

Stage 3: Remove the connecting pin bush. Then turn the pistol over and repeat the process for the other e-clip and bush. The connecting pin should then slide out.

 

 

Slide the arm down and then forwards to remove

 

Stage 4: Remove the cocking arm. This is best achieved by sliding the front of the arm downwards to disengage from the pivot recess. Then slide the whole arm forwards.

 

 

Remove the trigger module retaining screw

 

 

Stage 5a: Remove the trigger module retaining screw and lock washer which is underneath and at the far front of the pistol.

 

 

Remove the trigger module retaining pin

 

 

Stage 5b: Remove the trigger module retaining pin. This pin can be found just below the safety catch. A very light tap with a hammer and brass pin punch is enough to remove this pin.

 

Pull the trigger module down from the frame

 

 

Stage 5c: The trigger module can now be pulled downwards to remove it from the frame of the pistol.

 

 

 

Remove the breech plug

Stage 6: Remove the compression chamber end plug breech assembly. This is held in place by two screws on the left-hand side towards the rear of the pistol. The easiest way to do this is to use a sash clamp with one end over the muzzle and the other end over the breech seal. The screws can then be removed without the end cap shooting off into your television, cooker or prized Royal Doulton crockery! It also prevents the screws from binding and chewing up the frame of the pistol due to the pressure of the mainspring. Trust me, it’s a lot easier this way and you won’t risk damaging the screws. You might also wish to remove the breech seal o-ring with a toothpick to save it from being deformed by the sash clamp.

Compress the mainspring with sash clamp and deep socket

Stage 7: Remove the cocking arm links. Just as with the previous step, the sash clamp will be used to make our lives so much easier. Place the 14mm deep socket into the compression chamber and onto the face of the piston. If the seal is broken, remove it and the screws that hold it in place. You may want to place a coin on the face of the seal or the piston to protect it from the pressure of the socket. Place the sash clamp over the muzzle and the end of the socket and compress the piston into the pistol. This will provide enough room for the connecting links to almost fall out of their own accord. They may require some encouragement with a toothpick or jeweller’s screwdriver.

IMPORTANT! Release the clamp carefully and slowly as the piston and socket are under considerable tension from the compressed mainspring. Point the breech somewhere safe such as a box of old blankets.

Remove the piston, mainspring and barrel

Stage 8: Remove the piston, mainspring and barrel. Push the barrel from the muzzle using a chopstick – it’s a handy tool to have. Then pull the barrel out from the breech once you can get a firm grip with your fingers. DO NOT use pliers as you could damage the rifling or barrel breech.

Remove the piston. If necessary, push the piston out from behind using a chopstick via the slot on the underside of the pistol. The mainspring can now be removed without effort.

Replace the piston seal

Stage 9: Replace the piston seal. Providing you are lucky enough to find one, and this was a one-off so please don’t ask for one, you can now replace the seal. You may be able to do this without removing the piston and connecting links from the pistol as the seal is held on by just two screws. I think you can work out how to do the rest of this part.

Sear lever removal

 

Stage 10a (optional): Strip the trigger module. The trigger module consists of a sear lever, trigger blade lever, a spring and two pivot pins. Remove the sear lever pin using the brass punch and hammer. The sear lever can then be removed from the top of the unit along with the spring.

 

Trigger blade removal

 

 

Stage 10b (optional): Push the trigger blade lever-pin out using the brass punch and hammer. The trigger blade lever must be removed through the top of the unit.

 

 

Pellet storage gate removal

Stage 11 (optional): Remove the spring-loaded pellet storage gate. That’s right, the cavity within the grip can be used to keep a handful of pellets. On the bottom of the grip is a spring-loaded gate that provides access to the storage cavity. This is held in by a pin that can be pushed out with the brass punch. A tip for refitting…. Put the spring onto the bush on the gate as shown. Then slide the gate into position from the bottom of the grip. This will compress the spring against the frame as you go and there will not be a need for any tools that could mar the frame.

Safety lever spring bar and plug

Stage 12 (optional): Safety lever. I chose not to remove the safety lever although I did try. It is held in by quite a strong piece of spring bar. To remove it, you need to lever it out from the end furthest away from the safety lever. It appears to be held in place by a plastic plug. I advise not to remove this unless absolutely necessary as it is likely to be exceptionally difficult to refit and there is a high probability of damaging the surrounding frame in the process.

Breech plug and o-rings

Stage 13: Breech plug o-rings. There are two o-rings on the breech plug. One is around the circumference of the plug which is shown at the bottom of this image. This o-ring is 21mm inner diameter with a 2.5mm cross-section. The other o-ring forms the seal between the rear of the pistol and the cocking lever. This one is 10mm inner diameter with a 1.8mm cross-section.

O-ring removal

Do not use anything sharp to remove o-rings. Use a toothpick or you can obtain a tool very similar to a dental pick. The ends of which have been flattened and the edges rounded. You can buy these from artist or model shops and they are part of a kit for sculpting clay. Makes sure you apply some silicone grease using the method I described earlier.

putting it back together

Putting it back together is simply the reversal of the above process. It’s worth giving the parts a clean first. Make sure you lubricate the piston seal with a thin smear of Bisley gun grease to the faces that contact the side of the compression tube and on the inside where it contacts the barrel. You only need a smear. None is necessary on the piston body.

Also, add some grease to the threads of the screws to prevent them corroding and to the pivot pins of the cocking lever. A drop and I do mean a pin drop of oil wouldn’t go amiss on the pins and a smear of grease on the trigger sear where it holds the piston back.

Fit the e-clips using the serrated needle nose pliers to pull the clip onto the cocking arm connecting pin.

You may wish to protect the finish with some Napier VP90. Spray the VP90 onto a lint-free cloth and then wipe the pistol over. Never spray it directly onto a gun. Or, some collectors use Renaissance Wax. I tend to use the VP90 spray. Don’t forget to condition the grips with some CCL Gunstock Conditioning Oil or something similar. Some people use Walnut Oil.

performance?

Power chart

Oh, hang on. Before you go, I ran it over the chronoscope. I found that Webley Accupells were a very, very loose fit in the barrel. In fact, some dropped halfway down the barrel when loading. So I switched to RWS Superdome 8.3gr knowing that they’re usually a larger size. I was right. They sat in the breech nicely. Despite the manual suggesting to cock the pistol and then load a pellet, I was less keen on the idea of losing a fingertip should it accidentally fire, snapping the lever down over my finger! Instead, I released the cocking lever, loaded a pellet and then cocked the pistol. That felt far more controlled and safer. Five shots later and the power was a whopping 0.62 ft/lbs average or 180 fps. Oh, the disappointment.

So, I unpacked my almost new Record Jumbo and compared. After five shots it yielded an average of 0.80 ft/lbs or 200 fps. In comparison, the veteran Jumbo had a weaker spring. This was clear from opening the breech as the cocking arm cleared the rear sight. Whereas with the less used pistol, the cocking arm barely passed the barrel. Also, the breech seal on the less used pistol was much tighter. Perhaps with a fresh spring, the old girl would fare better.

Typical power of the Jumbo is reported to be between 200 and 280 fps. This will depend a fair bit on the weight of the pellet perhaps. I think 180 fps is not so bad, considering the pistol is supposed to be low powered anyway. Especially when you take into account the weaker spring, not so efficient breech seal and a new piston seal made of a harder material than the original. I have been told that there might be a version 2 seal in the making. In the meantime, I shall try to find a replacement mainspring.

There you have it. One more Record Jumbo saved from the scrap heap…. job done!

Until next time, happy shooting!

Jimmie Dee

Leave a Reply

Proudly powered by WordPress | Theme: Baskerville 2 by Anders Noren.

Up ↑