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.
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
Last edited by Shed tuner; 02-06-2018 at 07:33 PM.
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
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.
THE BOINGER BASH AT QUIGLEY HOLLOW. MAKING GREAT MEMORIES SINCE 15th JUNE, 2013.
NEXT EVENT :- August 3/4, 2024.........BOING!!
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 ?
"helplessly they stare at his tracks......."
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
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
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?
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
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
final update on that port...
After about 50 or so shots, the power had settled down to around 8.3 FP and the spring had taken a small set.
Stripped it down carefully, and reamed the port out tapering 3.2 - 3.0 (parallel would have been fine, but I have a taper reamer). Upon reassembly, after a couple of dozen shots, it's now nudged up to 9.1 FP, so a worthwhile if not dramatic increase of 0.8 FP. This confirms my initial premise, and I think this is probably about optimal now, so I'll leave it alone. Firing cycle is a fraction better too, presumably because the piston is bouncing back a little less. So job done, very happy.
For those wondering, I've no doubt that with a slightly stronger spring or more preload, the power would come up very nicely, without wrecking the shot cycle, but with open sights at my eyesight-limited max range of about 25 yards, 9 FP is plenty, thanks
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.