Springer spec. opinion please

[deejayuu]

Latest check. TP now 3.2 mm .Spring space 206 mm. Spring 256 mm plus 5 mm guide flange giving PL 55 mm at rate 32 lb.f/inch.
Forces acting. Uncocked 69 lb.f cocked force 170 lb.f
ME Hobby 8 fpe, SD 8 fpe, Exact 8.6 fpe, Bisley 7.5
Found a few Express 7.9gn giving 9 fpe.

Think we're there or thereabouts now. Cocking effort about 2/3 of original and feels good in hand.
More spring/pre load fiddles tomorrow hopefully.
Thanks again for input/looking.
P.S. Tempted to try FWB 124 spring for info.
What's the informed view on result of refitting original weight and/or spring? Massive "slam" and that which may not be discussed?

[Shed tuner]

do not refit the weight. What I'd do next, using your data above as a baseline, is add a couple of washers for preload, and see what happens.

if everything goes up uniformly (I expect it will), then you have a choice of leaving as is, or going further depending on your reqs.

If output falls, or it becomes unpleasant, report back - options in this situation would include a slightly shorter (stiffer) spring, reducing piston weight, etc. (or just leave as it was)

I know Jim will disagree due to a lack of scientific control on all the possible variables (Happy New Year JT ), but the Exact/Express comparison indicates to me that you could up preload a bit and not have a slammy cycle, with a useful power uplift to around 10 FP. If you wanted nearer 11, you'd probably need a slightly stiffer (but not longer) spring, rather than spacing this one, but the "add a little preload" test (say 3 -5mm) will inform that.

[BTDT]

And a happy new year to you, Jon (and Jules, David & Tony).

It's too early in the morning to start disagreeing. I'd certainly agree 100% on not refitting the piston weight; it's a lightweight rifle and the PW would increase recoil displacement (maybe approaching 30%).

What the rifle really needs is another 4" or so of barrel .

I'll have a think and maybe come back to this later.

[deejayuu]

Thanks again. Only curious about "going back" with internals to experience the "feel" changes in hand.
Will, time/chores permitting, continue the tinker later.

[TonyL]

I think we're all (remotely) enjoying this little tinkering journey of yours. Thank you for sharing. Going along with the general consensus, yes, re-fitting that very heavy piston weight wouldn't be desirable. A longer barrel would, most certainly, make things easier but would be slightly trickier to remedy! Keep playing with that preload (and spring rates if you have a few to go at) and we'll see where your happy place ends up being.

[deejayuu]

Thanks again for the suggested adjustments as shown below.
Recap of trial spring 255 mm x 36/38 lb/inch PL 50 Hobby 7 gn 7.6 fpe , SD 8.3 gn 7.8, Exact 8.5 gn 8.6, Bisley 10.2 gn 7
+3.5 mm Hobby 7 gn 8.7 fpe , SD 8.3 gn 8.5, Exact 8.5 gn 9, Bisley 10.2 gn 7.7
+6 total Hobby 7 gn 9.5 fpe , SD 8.3 gn 8.5, Exact 8.5 gn 9.3, Bisley 10.2 gn 8.2

Cut previous 268 mm spring to 260mm which stiffened rate a bit to near 40lb/inch

PL 59 Hobby 7 gn 10.2 fpe , SD 8.3 gn 10, Exact 8.5 gn 10.6, Bisley 10.2 gn 9.6
Also found Express 7.9 gn 11 fpe and FTT 8.7gn 11 fpe.
Really flat across the pellets but would like it to be as flat with Exact at 10 to 10.5 fpe
Quite tame in hand but some spring buzz due to slacker spring fit on guide methinks. Don't think cutting this spring will do it 'cos of stiffening.

[TonyL]

Good work.

I think I'd be happy to stick with that output if it were mine and you're generally happy with the overall manners? Maybe a little tweaking out of that spring buzz and job done?

[BTDT]

Cut previous 268 mm spring to 260mm which stiffened rate a bit to near 40lb/inch

PL 59 Hobby 7 gn 10.2 fpe , SD 8.3 gn 10, Exact 8.5 gn 10.6, Bisley 10.2 gn 9.6

From a previous post, with 3mm TP and the full 268mm spring;

268 x 36 lb/inch PL 67 Hobby 7 gn 10.8 fpe , SD 8.3 gn 10.3, Exact 8.5 gn 10.8, Bisley 10.2 gn 9.8

Have I got that right, Jules?

[Shed tuner]

If it's shooting nice I'd just go with that latter spring giving 10.5 to 11, find / make a better fitting guide (Tinners will do you one) and just shoot it

[deejayuu]

From a previous post, with 3mm TP and the full 268mm spring;

268 x 36 lb/inch PL 67 Hobby 7 gn 10.8 fpe , SD 8.3 gn 10.3, Exact 8.5 gn 10.8, Bisley 10.2 gn 9.8

Have I got that right, Jules?

Hello and thanks again Jim. Tricky being accurate, for me, but I think that data is correct except rate nearer 38 lb/inch.
Apologies to all for mixed dimensions. Just the way we're made

[BTDT]

Apologies to all for mixed dimensions. Just the way we're made

It would be nice if all measurements were either imperial or metric, but it's not a huge problem.

Did you test the full 286mm spring with the 3.2mm port before shortening it and, if so, what were the results?

[Shed tuner]

Did you test the full 286mm spring with the 3.2mm port before shortening it and, if so, what were the results?

I was thinking that should have been the perfect combo !

[BTDT]

I was thinking that should have been the perfect combo !

I'd expect very slightly gentler initial recoil acceleration, slightly better energy efficiency, and slightly less surge, Jon.

[deejayuu]

It would be nice if all measurements were either imperial or metric, but it's not a huge problem.

Did you test the full 286mm spring with the 3.2mm port before shortening it and, if so, what were the results?

Can't find definitive but fairly confident was above the 3mm TP values below.
268 x 36 lb/inch PL 67 Hobby 7 gn 10.8 fpe , SD 8.3 gn 10.3, Exact 8.5 gn 10.8, Bisley 10.2 gn 9.8.

For info. 268 spring now cut to 250 rate 40.6 lb/inch. Energy still near 11 with exact/express/FTT 9+ with Bisley.
Gone to owner for appraisal. His first shot rang 3/8" bell at 20 yds. standing unsupported.
Can't say shooter or rifle but promising.
Will report back after a bit of bedding in and try to be more diligent with recording data.
Many thanks to everyone.

[maximus]

Can't find definitive but fairly confident was above the 3mm TP values below.
268 x 36 lb/inch PL 67 Hobby 7 gn 10.8 fpe , SD 8.3 gn 10.3, Exact 8.5 gn 10.8, Bisley 10.2 gn 9.8.

For info. 268 spring now cut to 250 rate 40.6 lb/inch. Energy still near 11 with exact/express/FTT 9+ with Bisley.
Gone to owner for appraisal. His first shot rang 3/8" bell at 20 yds. standing unsupported.
Can't say shooter or rifle but promising.
Will report back after a bit of bedding in and try to be more diligent with recording data.
Many thanks to everyone.

Really interesting thread this, thanks for posting, Can I ask why you cut down the spring further, was it in the spirit of experimentation?? Also, I find it unusual that the FTT are giving high energy readings, in my experience they can be quite tight and thus drop the ME. Cheers Max