A couple of different approaches to achieve the same goal

[CapitalBee]

I've just put together a project Beeman R1 in .22" calibre. At this stage, the internals are pretty standard apart from the spring, as I've dropped in a 14.5mm i/d spring with a bit more pre-load. Currently running at full stroke length, she's at 11.7ft/lb with FAP, but a bit harsh on cycle. The problem lies, I think, with the transfer port; measured at 4mm. I'm not sure if this was US spec' or if someone had previously tweaked it up. So, I'm thinking of a tp reduction to 3mm. Do I:

A) drill out the tp and tap it to add a drilled out grub screw and glue it in? I've done this before with an HW80 with good results.

B) get a sleeve made and drift it into the existing tp?

[Neil54]

Think I would be inclined to make a brass threaded sleeve and glue that in.

A bit in between.

[Black Beard]

You don't need to thread it. Close fitting and thread lock will be fine as they don't really get much force on them. You want the cylinder side to have a bit of a curve into the hole and the barrel side to be square (or slightly proud of the face of the breech.

[evert]

Full power HW80's have smaller ports than 4mm.
Could the 4mm port be an attempt at reducing bounce in a 12fpe gun?

[CapitalBee]

Full power HW80's have smaller ports than 4mm.
Could the 4mm port be an attempt at reducing bounce in a 12fpe gun?

Possibly, but as the rifle came in pieces, without a barrel, I can't say. The piston had been lightened

[ora8i]

I've used brass tube and red thread locker on a Diana 35 transfer port and I worked well.


Ora

[Shed tuner]

yeah, as BB said the forces relative to the area for glueing are very low.. so make the brass sleeve a tight fit and glue / loctite it in. Just be sure to degrease thoroughly first.

I'd go with 3.0 - 3.2 - I've just reamed my 80 TP to 3.1 and it shoots very nice at 11 fp - but this is going to be running near 16 when I export it. 4mm is too big for any power level.

[CapitalBee]

yeah, as BB said the forces relative to the area for glueing are very low.. so make the brass sleeve a tight fit and glue / loctite it in. Just be sure to degrease thoroughly first.

I'd go with 3.0 - 3.2 - I've just reamed my 80 TP to 3.1 and it shoots very nice at 11 fp - but this is going to be running near 16 when I export it. 4mm is too big for any power level.

Just sourced some 0.5mm wall thickness brass tube at 4.0mm outer diameter, so once it arrives, I should (in theory) have a pretty straightforward task.

[Steyr]

Yes thats the wonderful things about theroies. Often let down by reality

[NickG]

I sleeve and glue them, don't bank on the 4 mm hole being a very good one, I tend to open them up with a ream and make a sleeve to suit, as mentioned 4 mm way too big , had a 97 comp tube with a 4 mm port last week, I sleeve them back to standard 2.8 and go from there.

[CapitalBee]

Yes thats the wonderful things about theroies. Often let down by reality

It's a bit like the Harry Carpenter kiss of death (anyone who remembers Frank Bruno's fights will "know what I mean Harry ")