What to do with a FWB Sport 124

[Vernal]

One thing with old Sports is the trigger sear spring, the one that goes between the sear and the safety. This can become bent and cause an unreliable trigger. Make sure you replace it when you strip the rifle, and if you are a perfectionist, machine up a tiny teeny little guide for it so it doesn't bend.

I wimped out and took the trigger block out with a couple of cable ties round it so that the safety slide and spring were kept in place. The spring looks straight as far as i can see, but it looks as though a length of suitable diameter rod with the ends tidied up could be dropped into the spring without further dismantling - would that make a useful guide?

[Hsing-ee]

I wimped out and took the trigger block out with a couple of cable ties round it so that the safety slide and spring were kept in place. The spring looks straight as far as i can see, but it looks as though a length of suitable diameter rod with the ends tidied up could be dropped into the spring without further dismantling - would that make a useful guide?

That is exactly the sort of thing; a tiny length of brass rod should do the trick.

Be careful putting the back block retaining bolt back in, it is VERY easy to misalign it slightly and cross-thread it - a hard steel bolt going into a softish alloy block wasn't one of FWB's best ideas...

According to popular myth, the mainspring can be replaced with one from a 77 if you have one kicking about.

[T 20]

According to popular myth, the mainspring can be replaced with one from a 77 if you have one kicking about.

Not a myth, Alistaire.

I fitted a very early 77 Spring (the one with 4" of preload ) to a mates .22" Sport, and it worked very nicely.



All the best Mick

[deejayuu]

Put this together and would appreciate some snagging. Pictures excepted

Feinwerkbau Sport 124/7
The Trigger Unit
The trigger unit, or block, is fully enclosed in the main cylinder and must be withdrawn to enable dismantling. The block is located and fixed in place by a threaded lug which also forms the rear stock locating/fixing dowel.
In original trim the mainspring pre load is around 100 mm so before unscrewing the fixing lug it is advisable to use some form of restraining clamp to control the force and reduce the risk of damaging the quite flimsy threads. A spacer is useful to avoid crushing the safety tab.

As the block travels out of the main cylinder the safety slide becomes exposed and is forced away from the block by the intermediate sear spring. The slide can be taped in place or simply held until fully exposed then removed.

The pre load now is almost completely removed at 100 mm with this standard spring from T W Chambers.

The trigger unit with fixed spring guide can now be safely removed for inspection/service.
Dismantling the trigger unit
The trigger assembly consists of a trigger blade with adjustment screw, safety slide, main sear, intermediate sear, and two springs, all located and fixed in position by two solid pins. The pins usually push out with little effort taking care that the springs don’t fly away. The front pin pivots the trigger blade and main sear. The rear pin pivots the intermediate sear.

The layouts above shows the parts in their relative positions. The smaller spring acts, between the front face of the trigger blade and the lower edge of the main sear, to turn the main sear clockwise. The larger spring acts, between the safety slide and the intermediate sear, to turn the intermediate sear anti clockwise.
On the right the mechanism is cocked, normally by the piston latch rod, with with the intermediate sear preventing the main sear turning to release the latch rod.
On the left the mechanism is uncocked, or triggered, by the blade turning anti clockwise which turns the intermediate sear clockwise to release the main sear.
It can be seen that the relative strength of the two springs is critical since the small horizontal spring is trying to force the blade to the triggered position and only prevented from doing so by the larger vertical spring pushing in the opposite direction via the inter mediate sear. This balance of geometry and spring forces is common in trigger devices.
May be worth mentioning that if non standard springs are used it can result in failure to cock. Same can apply if the vertical spring breaks since the horizontal spring will hold the blade in the triggered position.
Turning the adjuster screw clockwise will reduce the depth of engagement of the sears and slightly increase the trigger pull needed for release.
There is a small stop clip on the screw which should prevent the engagement being set dangerously shallow.