Improved Mod D bayonet latch plunger

[Roundshot]

A mate inherited grandfather's brown patina'd 5th Batch 'BSA Air Rifle' No1 bore made 1906-7 and I offered to service it. Never touched one before.

So impressed was I with superb manufacture and lovely handling, I picked up a 1910 Improved Mod D for myself in .22".

Both needed tap levers straightening and a few other things. They're now in good fettle and shoot quite well.

Got piston seal, etc., from usual suppliers (tap cover screw provided needed head filing down to fit flush).

Anybody who has a spare bayonet latch plunger for a 1910 Mod D underlever lying about they'd consider selling, I'd naturally be delighted to hear from you. Or perhaps there's a good DIY alternative known that works a bit better than mine!

What super guns.

[micky2]

Welcome to the wonderfull world of the BSA underlever. you might find you have caught the collecting bug with these.

[micky2]

l forgot to say, l have had lots of these over the years and still have quite a few, but not one of them ever had a bent tap lever. one wonders what someone did to cause this as they are quite robust.

[Roundshot]

Welcome to the wonderful world of the BSA underlever. you might find you have caught the collecting bug with these.

Thank you and yes, this has occurred to me as I admire mint examples with aperture sights!

Re:tap lever, if dropped onto hard surface, perhaps more than once and possibly with tap open, I think it's possible for the lever to be bent inwards a bit, as evidenced by witness marks on compression tube where grinds on closing, possibly affecting alignment. Sorted out on wooden block with wooden mallett.

So easy to work on compared to modern guns. Good old British craftsmanship.

[Roundshot]

This Mod D came with cut down spring + Diana green seal. Now got well sized, run in Knibbs leather one. With new Chambers Airsporter (MS012) spring (recommended by some) + extra preload, wouldn’t top 8.9 ft lbs with blue tin Wasps.


I suspect original springs were much stiffer to give higher power claimed?


Cut down spring is same length as Chambers (240mm), similar gauge wire and ID (14mm) but 27 coils vs. 33 - more open coiled and can accommodate heavier preload so I stuck it back in. With a .22” Mk2 TX piston weight + metal slip washer + 14mm of metal washers on guide, spring sticks out 32mm.


583fps / 10.6ft lbs with Wasps – still nice to shoot - best groups <1 inch at 25yds table rested. I realise it’s not a power thing these old treasures but should a rabbit or squirrel turn up!

[Shed tuner]

Yeah, the pre-war underlevers are all real quality... BSA's best days for sure.

[martin bingham]

the tap arm clearance/gap on mine is exactly even/parallel with the tube when closed,mine [gwo] is a good sliding fit with a bank card used as a gauge between the arm/tube,
good luck.
M.B

[GMballistic]

Love my Imp Model D and other antique BSA's as you know Roundshot.