Just did a little tune on my Standard...

[Shed tuner]

Bought it a kepton the time before last, put a comple of shots through and found it a bit hard and slammy, but never had chance to give it a once over before...

The piston was a bugger to remove - was a nice fit initially, then got really tight. realised the dint on the cylinder has actually bent the tube in a bit at that point, so some emery on a dowel was required to relieve the inside bump.
Leather seal was fair, so left alone - just a drop of neatsfoot
Piston weighs a ton - just way OTT - so I chopped 45 grams off the back. It's still too heavy, but a big improvement.
The transfer port is silly huge. 13mm long, and 5.5 mm dia (I'm sure they are reamed through the tap into the bore to sort the alignment) - so I made up a plug and installed to reduce it to 2.8mm. I'll probably end up reaming this out a bit to around 3.0 or 3.2, but easier to start small and ream.
Found a spring that was a tighter fit on the guide - still way too loose - but it wasn't rattling around. That guide is so skinny, I need to find some tube to sleave it up.
Made up a small top hat to centralise the spring in the piston. Will do a sleave later.

Spring is softish / weak, so nice easy cocking.

First few shots after the major dieseling subsided were very good. Much, much softer, less recoil, faster, but no slam; literally transformed the shot cycle. Chrono around 9FP but once it's bedded in I will ream the port a fraction and see what the affect is.

The big thing here is clearly the port (and the piston weight).

I'd probably not mess so much with a very nice condition gun, but as this was a bit untidy (I deliberately buy them that way, as I like to shoot them, not polish them) I'm very pleased with the results

[TonyL]

Sounds like a most positive transformation, Jon.

Are you coming to The Bash? If so, will you be bringing it along? I'd love to have a go with that, please.

[silva]

Great thread. Sounds interesting, various people have had a go at tuning the old Bsa underlevers, with mixed results. How did you sleeve the transfer port ?

[Shed tuner]

yup, will bring it to the bash tony..

silva, just made a 5.5 dia, 13mm long steel plug, slightly tapered, with a 2.8 mm centre hole, and tapped it in with a bit of glue ( not really needed for security due to the taper, but it fills the voids).

.Rgds - JB

[TonyL]

yup, will bring it to the bash tony..

.Rgds - JB

Marvellous; thanks JB.

[greenwayjames]

In an early 20th century article in a gun trade magazine (Arms and Explosives?) The factory described a series of experiments made developing these old rifles complete with results. Light pistons, heavy pistons et al. BSA also used to make a point, it could have been the same article, of saying that the barrel and cylinder were made in one piece and then rifled. This may explain the bore sized transfer port?

[slow_runner]

silva, just made a 5.5 dia, 13mm long steel plug, slightly tapered, with a 2.8 mm centre hole, and tapped it in with a bit of glue ( not really needed for security due to the taper, but it fills the voids).
.Rgds - JB

Hello JB. I assume that the insert is fitted from the cylinder with a stepped rod to guide it into position before tapping it home?
I will be interested to see what results follow as you alter the transfer port.

[Shed tuner]

Hello JB. I assume that the insert is fitted from the cylinder with a stepped rod to guide it into position before tapping it home?
I will be interested to see what results follow as you alter the transfer port.

exactly that.. just turned down a bit of rod with a ~2.5mm spigot left to stick into the inside of the insert, guided it home and then a couple of gentle wallops to seat. My guess is around 3.0mm will be optimal, as there is a fair bit of lost volume in the tap, behind the pellet