Help repairing an Original 75 needed.

[Mr.Fixit-Norm]

Hi,

I have an Original 75 action which won't cock ( the cocking lever only moves about 3 inches from its return position then it feels like something's stopping the springs and pinions from moving ) does anyone know how to remove the springs / pinions ?

I rebuilt an Original 65 about 3 years ago but once the screw cap is off, the end looks different, I have a tool which compressed and turned the 66's mechanism to release it but the 75 looks different under the end cap and the tool doesn't fit.

I've looked at a couple of online strip downs but they still don't look very clear, and the chambers exploded view isn't much help either.

Cheers,

Norm

[Rickenbacker]

This: http://www.network54.com/Forum/67020...+%28English%29 may be just the thing. Thanks to Garvin

[Mr.Fixit-Norm]

Hi,

Thanks for that, unfortunately I did look at that one but it gives me two problems, one, it says the trigger assembly has to be removed first, but the cocking lever needs to partly cocked - I can't do this as its jammed, secondly, it says when inserting the compression tool ( I don't have one of these but might be able to fashion something if I knew what it looked like ! ) it says when removing the compensation piston the gun needs to be fully cocked, something else I can't do

I'm really wondering if there's any other way I can unjam it, but I really need to try and release the compensation piston first.

Trouble is I suspect there's only one way it can be done, ie like in his tutorial.

Does anyone have any ideas.

Norm

[wonky donky]

My first move would be to remove the cog covers one at a time to inspect the cogs & then replace the covers. These will hold the pistons in place with the rear cap off If they are meshed with the pistons properly.

I would then just strip the trigger mechanism & the rest of the mechanicals out first, then remove the rear cap, put the action in a sash cramp or spring compressor taking a small amount of pressure off the rear piston.

Unscrew the two cog covers & remove the cogs with the action still in the spring compressor. Slowly release the spring pressure, expect lots of spring pre-load.

Rear piston out, cocking lever rearward until you can see the crosshead screw through the hole in the action, unscrew it, lever pulls out, rest of the internals follows. Easy peasy, much more so than this Bl**dy windows 8 I'm using!

[Big Seth]

Don't know about the 75 but beware the pinion wheels may not hold the pistons in place with the end cap removed. I learned this the hard way stripping a mod 6 pistol. On that pistol it was possible to take the pressure off the pinion wheels by adjusting the end cap in slightly, the wheels could then be lifted away . The trigger mech was already removed.

[Mr.Fixit-Norm]

Thanks for that, seems clearer the way you've put it! I've had a quick look at the cogs and they're ok but on both sides the very last tooth on the bottom ( rear ) piston has a chipped top

At least I can get the springs and pistons out to see what I can do, plus I'll need to try and find those chipped bits

Norm

[Mr.Fixit-Norm]

Right, I spent about an hour this afternoon taking the beastie apart, what a job, I can only surmise the trigger and ratchet mechanism for the cocking lever were designed by the Devil himself

It wasn't helped by the fact that the reason the mechanism was jammed was that a piece of the broken tooth had put a gouge in the rear compensation guide which was stopping the piston from moving backwards. I've removed the broken piece, and smoothed out the burr in the guide so it all works as it should. I don't think the damaged rack teeth are going to cause a problem as they are the two tiny lead in teeth, and it seems to work ok with out them

Interestingly, I was going to replace the piston washers but looking at the chambers website, my gun appears to have been modified Where there should be a washer on front of the main compression piston it seems to have been modified with a aluminium front piece and is now using an 'O' ring to form the seal with the cylinder. The rear piston has a plain aluminium 'washer' instead of the one shown in the exploded diagram.

The chap who gave it to me was a good friend and an excellent gunsmith, sadly he died last year ( only 66 ) so I can't get any info on the mod. I suspect he did the mod, as he has made several very good precharged target rifles ( two of which I own ) and a superb precharged target pistol running at 5.5ft lbs

When he made guns, he made pretty much every part other than the barrels , which he swore by BSA ones. He even made the air reservoir's on the first rifle and the pistol. which he pressure tested himself.

He was a very competent engineer, a coded welder and a superb machinist both on lathes and milling machines

Back to the 75....... Can anyone advise on what lubricants to use when reassembling the the Pistons and slides etc. I have the grey moly slip and the clear stuff as well if that's any use, the 'O' ring piston seal seems to have some sort of clear grease, possibly moly on it. I think I'll have to take a chance and leave the piston seal as it is as I don't know if it could be returned to the original design.

Sorry for the mega post !

Norm

[Mr.Fixit-Norm]

Back again,

Another couple of things I'm going to need to find out about, firstly I'd like to renovate the stock, how do I sort out the hammered parts, and is it best to just rub the plain parts down and oil it ?also the stock has the angled adjustable butt unit but is missing the pad, does anyone know where I can get one from ( Chambers don't list them ) or has anyone got one to sell?

I notice from Gavin's site from the link above, I have the later U T 01 stock version with the rounded forend, adjustable raised cheek piece and an accessory rail underneath.

ATB

Norm

[Benelli B76]

Well done on all your efforts. I have done repairs on these Giss mechanism rifles and pistols and found that the teeth normally chip when they are not exactly replaced in the correct tooth position (gear to rack relationship), giving a lot of stress during firing cycle. As you say they normally function OK after cleaning up and re-assembly.
On the rifles 66 and 75 the trigger mechanisms are much more complex and taking photos during stripping are helpfull, but you have done it before so you are OK. I found the best grease is bicycle grease from Halfords (in a tube, red colour grease) which has a Teflon additive. Gave very smooth cocking and no dieselling.

Baz

[18 Wheeler]

...firstly I'd like to renovate the stock, how do I sort out the hammered parts, and is it best to just rub the plain parts down and oil it ?
also the stock has the angled adjustable butt unit but is missing the pad, does anyone know where I can get one from ( Chambers don't list them ) or has anyone got one to sell?

Stock: Hammered parts = Stippling. It can be cleaned using an old toothbrush and white spirit.
Once the spirit has fully dried apply a small amount of boiled linseed oil , thinned with a little white spirit (I use 3 parts BLO to 1 part spirit) after about 10 minutes most of this will have penetrated the wood, remove any excess on the surface using paper kitchen roll pressed onto the stippling, don't rub you'll leave bits of paper adhering to the surface. Ugly .
Use Alkanet oil instead of the BLO if you want to darken it further.

For the remainder of the stock it depends on the condition and what you want to achieve.

Here's a simple method for a stock in reasonable condition:
1. Remove the action and all stock fittings, put them somewhere safe.
2. Lightly abrade the surface with 1000 grade paper. Use a suitable block when working on edges so as not to round them out. The aim is not to go down to bare wood, just remove the surface film.
3. Any dents or compression marks can be steamed out now.
4. Wipe down with a clean cloth and white spirit, allow to fully dry overnight.
5. Apply the finish. Trade Secrets Rapid Oil is nice and easy to work with (CCL stock conditioning oil is similar). Rub a small amount onto the stock, allow to go tacky (anywhere from 45mins-2 hours) wipe off the excess and give the wood a rub with your palm. Set the stock aside for a minimum of 24 hours, then repeat the "oiling" procedure. Given that this is just a refinish and you don't want a high gloss finish that may be sufficient.
6. Set the stock aside for at least a week in a warm dry area for the finish to fully harden.

Once this is all done I use a hair dryer to warm the stippling, if any oil has not dried the stock will sweat this out and it can be dabbed off the surface again. You end up with a well protected finish that remains grippy and won't sweat oil when used.

Adjustable pad: If you have no luck in sourcing a replacement (I can't find any at the usual spares retailers) then try the Wegu adjustable pad.
They come with an attached dovetail on pad, it may not be a direct fit (?) but should be the easiest by far to modify slightly if not.
My mod.66 pad measure 34mm at its widest and 134mm max. height, if that helps for sizing.

[Mr.Fixit-Norm]

Thanks for the replies guys, very useful info all round. I'm going to concentrate on the action first and if that all goes ok then 18Wheeler's stock refinishing methods look a good way to go ( handy links too ! )

Yes, the Wegu butt pad does look very similar to pictures of the original. Thinking about it, I have the same system on my 65 ( which has a 66 target stock fitted ) so I can probably use that for any measurement info.

I ordered a few small bits from Chambers last night but held off on the front piston washer, I'm still in a quandary as to wether or not to take a risk and try and remove the modified piston seal. Martin the original owner was a very clever inventive guy and wouldn't have changed it without giving it a lot of thought ! I know he knew all about working out the correct 'groove' for an O ring to allow it to expand under air pressure and create the seal so maybe this is what he did with the modified design?

He was skilled enough to make fiddly little things like firing valves and transfer ports, and even made his own trigger mechanisms !

The problem is I don't really want to have to take it all apart again to change the washers

Decisions, decisions....



Norm

[pegasus]

Thanks for the replies guys, very useful info all round. I'm going to concentrate on the action first and if that all goes ok then 18Wheeler's stock refinishing methods look a good way to go ( handy links too ! )

Yes, the Wegu butt pad does look very similar to pictures of the original. Thinking about it, I have the same system on my 65 ( which has a 66 target stock fitted ) so I can probably use that for any measurement info.

I ordered a few small bits from Chambers last night but held off on the front piston washer, I'm still in a quandary as to wether or not to take a risk and try and remove the modified piston seal. Martin the original owner was a very clever inventive guy and wouldn't have changed it without giving it a lot of thought ! I know he knew all about working out the correct 'groove' for an O ring to allow it to expand under air pressure and create the seal so maybe this is what he did with the modified design?

He was skilled enough to make fiddly little things like firing valves and transfer ports, and even made his own trigger mechanisms !

The problem is I don't really want to have to take it all apart again to change the washers

Decisions, decisions....



Norm

Hi Norm, a few years ago there was a step by step guide in one of the Airgun mags of a strip and re-build of the giss system that ran over two issues, I had a 66 at the time and kept the guide in case I needed it (I didn't ) sold the rifle but the but still have the guide, if it is any help to you I will dig it out and post it to you,send a pm with your address and I get looking for it. Regards John

[18 Wheeler]

I forgot to add that when you've oiled the stippling then mask it up. Otherwise you'll inevitably transfer some of the finishing oil to it when doing the remainder of the stock which is precisely what we are trying to avoid.

Here's one I've just put the final coat on, masked up and shiny due to the oil still being wet. HTH

[Mr.Fixit-Norm]

Hi Norm, a few years ago there was a step by step guide in one of the Airgun mags of a strip and re-build of the giss system that ran over two issues, I had a 66 at the time and kept the guide in case I needed it (I didn't ) sold the rifle but the but still have the guide, if it is any help to you I will dig it out and post it to you,send a pm with your address and I get looking for it. Regards John

Hi John,

That would be great if you can find it, I'll pm my address,

Many thanks,

Norm

[Mr.Fixit-Norm]

I forgot to add that when you've oiled the stippling then mask it up. Otherwise you'll inevitably transfer some of the finishing oil to it when doing the remainder of the stock which is precisely what we are trying to avoid.

Here's one I've just put the final coat on, masked up and shiny due to the oil still being wet. HTH

That looks really nice, I'd be really chuffed if I can get mine to look like that !

Norm