Lincoln Jeffries won't cock

[Vernal]

In an effort to subdue a rather nasty twang, I took my LJ apart and fitted a piston liner. I didn't do anything else, and all the same parts were reinstalled, but now it won't cock safely. Most of the time, as I try to cock it I can feel the sear trying to engage and failing, but occasionally it catches and stays cocked, but is then liable to go off with a slight jar, obviously very unsafe. The trigger blade is not catching on the guard, and the adjustment screw is backed off so far that it doesn't even contact he blade. The trigger is so basic, with no intermediate sears (it has always been heavy), that it is hard to think of anything that could go wrong.
I wonder if anyone else has had, and solved, a similar problem?

[DCL_dave]

I don't know but...

Is it possible that, upon reassembly, the latch rod has twisted slightly to a different position than it was before the stripdown and so not catching properly?

...or is the new piston sleeve interfering with the spring and forcing the piston/latch rod into a slightly different position?

[Vernal]

I don't know but...

Is it possible that, upon reassembly, the latch rod has twisted slightly to a different position than it was before the stripdown and so not catching properly?

...or is the new piston sleeve interfering with the spring and forcing the piston/latch rod into a slightly different position?

I don't think the latch rod could twist, but I agree that the sleeve may be part of the problem. It occurred to me as I typed the OP that maybe the sleeve prevents the sear from engaging fully, and I will check that soon. Thanks for the suggestion.

[ggggr]

In an effort to subdue a rather nasty twang, I took my LJ apart and fitted a piston liner. I didn't do anything else, and all the same parts were reinstalled, but now it won't cock safely. Most of the time, as I try to cock it I can feel the sear trying to engage and failing, but occasionally it catches and stays cocked, but is then liable to go off with a slight jar, obviously very unsafe. The trigger blade is not catching on the guard, and the adjustment screw is backed off so far that it doesn't even contact he blade. The trigger is so basic, with no intermediate sears (it has always been heavy), that it is hard to think of anything that could go wrong.
I wonder if anyone else has had, and solved, a similar problem?

Simplest thing to do is to remove the piston liner. If you still have the same problem then it is just unlucky it surfaced when you did the liner, but it rules the liner out. There is no point looking for anything else until you have tried this.

[Phil Russell]

If you added a liner and it is held in place by tabs at the base of the piston and maybe a slip washer in there as well (always a good idea with a liner) then maybe the spring is on the verge of being coil bound?
As above, remove liner and try again.
Cheers, Phil

[Vernal]

Simplest thing to do is to remove the piston liner. If you still have the same problem then it is just unlucky it surfaced when you did the liner, but it rules the liner out. There is no point looking for anything else until you have tried this.

That is a very sensible idea, thank you. I must be pretty dim not to have thought of that myself!

[Vernal]

If you added a liner and it is held in place by tabs at the base of the piston and maybe a slip washer in there as well (always a good idea with a liner) then maybe the spring is on the verge of being coil bound?
As above, remove liner and try again.
Cheers, Phil

I have checked, and it is definitely not coil bound. The piston comes back far enough, as I can feel the sear trying to engage.

[ggggr]

I have checked, and it is definitely not coil bound. The piston comes back far enough, as I can feel the sear trying to engage.

Ok--remove the mainspring and piston, then just push the rod of the piston into the trigger block. If it engages properly and you can pull the piston and the sear holds until you pull the trigger, then that would suggest all is well with the trigger.
Look at the cocking slot on the piston for any wear, then put the piston and the complete trigger block back on the cylinder but remove the cocking arm. Now if you slide the piston back with a rod/ screwdriver etc and it engages ok and holds with some forwards pressure , until you pull the trigger and releases, refit the cocking arm and see if it cocks then. If it doesn't then it would suggest either the cocking arm is bent or worn on the bit that pushes the piston , or the slot on the piston is worn. If all seems ok then refit the mainspring and try it.
Sometimes the cocking arm can bend a little and you can put the ends on some hard wood and give the back of the cocking arm a sharp tap with a block of wood and a hammer etc.

[Vernal]

Ok--remove the mainspring and piston, then just push the rod of the piston into the trigger block. If it engages properly and you can pull the piston and the sear holds until you pull the trigger, then that would suggest all is well with the trigger.
Look at the cocking slot on the piston for any wear, then put the piston and the complete trigger block back on the cylinder but remove the cocking arm. Now if you slide the piston back with a rod/ screwdriver etc and it engages ok and holds with some forwards pressure , until you pull the trigger and releases, refit the cocking arm and see if it cocks then. If it doesn't then it would suggest either the cocking arm is bent or worn on the bit that pushes the piston , or the slot on the piston is worn. If all seems ok then refit the mainspring and try it.
Sometimes the cocking arm can bend a little and you can put the ends on some hard wood and give the back of the cocking arm a sharp tap with a block of wood and a hammer etc.

That incredibly helpful reply must lead me to a solution, and I will run through it in the next day or two, thank you. I still rather fancy the sleeve as an influence, as wear or bending on components would presumably have been apparent before I fitted the sleeve?

[Garvin]

Top advice, Guy. Anyone would think you'd been inside a non-working vintage airgun before.

[Vernal]

Well, sorted at last, and I am left feeling a bit silly after not thinking of something obvious right from the start.
I worked very carefully through all the steps suggested by ggggr (and I have kept a note of them in case I encounter a similar problem in the future) I found it passed every test, but when I put the spring back in once again it failed to cock fully. On the umpteenth attempt, and about to give up and have a pint of lunch, I noticed that the trigger was not going quite as far forward as it did on the tests without the mainspring, but could be pushed a tiny bit further forward by hand to complete cocking. I then remembered that a long time ago I had fitted a slightly weaker trigger spring to try and alleviate the very high pull weight. This weaker spring worked perfectly for a time but for some reason must have given up now as refitting the original trigger spring completely cured the problem. Relief, and may thanks to those who helped. it is very reassuring to have a competent gunsmith standing behind you while you are sorting out unfamiliar problems.
Incidentally, the usual post interference chrono check showed its normal 7.4 fpe. Is this about right for a .177 LJ please?

[johnbaz]

Glad you got the old girl going again!!

I was given this 1906 BSA Air Rifle as a freebie (The chap was good enough to drop it at my door all the way from Wales! He was actually passing en route to a friends house!!)

The piston rod had snapped back in the mid 70's and had been in the back of his wardrobe ever since, He had an engineer friend that made a new one but it wouldn't cock!, It latched when I pushed it in to the trigger block and released when I pulled the trigger, Turned out the rod to the hook was a few thou too short, I used a diamond needle file to remove a little material and it works fine now!!




The gun came with a hex bolt instead of a screw to hold the piston, I think I machined the bolt to fit but can't remember how I did it for sure, I'd found some leather parachute washers on fleabay!!



The muzzle energy is very low due to soft mainsprings, I have a pair of unused ones for it somewhere but need to get some iron sights for it too! (No idea why people remove them )

The original screw from the cocking link was snapped in, I extracted the stub of thread and could only find a brass one to fit so if the springs are powerful enough it may end up shearing the soft brass screw too!



EDIT- It's only temporary though!!


John

[kamyonsofor]

Hi Gents interesting post, here's one for you ,as I have a Lincolns,Bsa's and a Haenal of the same type, how easy is it to just remove the stock from them to refurb stocks on a couple but nothing mechanical as a guy at my club said you need a special tool to insert into the rear of the stock ( he being a engineer has made one but not for lending) thanks.

[Phil Russell]

Hi Gents interesting post, here's one for you ,as I have a Lincolns,Bsa's and a Haenal of the same type, how easy is it to just remove the stock from them to refurb stocks on a couple but nothing mechanical as a guy at my club said you need a special tool to insert into the rear of the stock ( he being a engineer has made one but not for lending) thanks.

Quite easy. Not sure about the tool being special though. I have seen two arrangements to hold stock on, both basically the same though. First job is remove butt plate or other access point to get at the bolt holding stock to action. On some rifles you now need a long broad blade screwdriver to reach down the hole to undo the bolt. On others I have seen it is a standard hex head bolt that needs undoing. On some the bolt is set way down the hole, on others not so far. If you can't see it try a torch. A long screwdriver tends to be easy to get but a bolt head can be a bit more tricky. I have used a standard socket on an extension bar or at times a box socket, sometimes building up the length by fitting one box socket inside another. If stock has never been off since new you may need to squirt a bit of lubrication onto the bolt to help free it. But generally they rarely give trouble. Interestingly on some rifles you can find a manufacture date under the but plate or even a name, maybe of the guy who assembled the rifle? On reassembly I now tend to add a slip of paper indicating the date and what I did.
Good luck.
Cheers, Phil

[Vernal]

[QUOTE=johnbaz;7657015]Glad you got the old girl going again!!

I was given this 1906 BSA Air Rifle as a freebie (The chap was good enough to drop it at my door all the way from Wales! He was actually passing en route to a friends house!!)

The piston rod had snapped back in the mid 70's and had been in the back of his wardrobe ever since, He had an engineer friend that made a new one but it wouldn't cock!, It latched when I pushed it in to the trigger block and released when I pulled the trigger, Turned out the rod to the hook was a few thou too short, I used a diamond needle file to remove a little material and it works fine now!!

I assume my latch rod is original, and it certainly isn't too short - there is about 2mm further backward travel after the gun has cocked. Anyone is welcome to drop a nice free vintage rifle at my door anytime they feel like it.