Just now saw this old topic of yours.
There are not that many enthusiasts taking the trouble to modify Streamline.
Some 1,5 year ago ‘uplifted’ a .25 Streamline to shoot 34 grain MKII at 100 yards.
Perhaps you may find something useful in what i ve experienced.
What i changed :
- Added DL power plenum
- Brass barrel inlet slightly enlarged to ‘squarish’ (with rounded corners) - the pellet probe i didn't touch
- After many testing sessions and longwinded trial and error with several hammer weights and several hammer spring combinations, today still using the (relatively heavy) factory hammer, on a somewhat shorter and heavier hammer spring
- Polished hammer housing, hammer weight + spring (and lightly sprayed weight and spring with teflon)
- Hammer travel set to max. (hammer spring adjuster almost all the way backed out)
- Blocked hammer spring adjuster up with (a slightly filed off) brass locknut (now sitting entirely flush with the back of the block)
- Added barrel band (“rather unlikely this will make any difference”, i thought at first, but imagine my surprise when establishing the entire opposite)
- Also added a DL barrel sleeve support (again thinking “even more unlikely this will make a difference”, but again i was mistaken).
- Added a (by FX) upgraded FX regulator with otherwise arranged cups (of slightly different shape)
- Regulator still set at 140bar
- Very slight adjustments in the diameter of the powerwheel transfer holes (but i don t by heart remember the exact measurements)
This SL .25 is now a 100 yard gun (with 34 grain MKII only).
At 100yrd (91m) regular groups are just outside 1 inch (3cm = 1.2”) and sometimes smaller.
At 70m (77yrd) one full magazine mostly leaves just one hole in the card, just big enough to put your finger through.
This .25 Streamline performs at its best at following velocities
- with 25 grains around 268-271m/s (880-890fps) ~ 60 joules
- with 34 grains around 260-262m/s (855-860fps) ~ 75 joules
Bullseye groups with (sorted) 25 grain Kings up to 60m (65yrd)
Bullseye groups with (sorted) 34 grain MKII up to slightly over 70m (77yrd)
As already indicated, about 1,2 inch groups with (sorted) 34 grain MKII at 100yrd target distance.
Shotcount with 25 grain (before modification) used to be 45-46 good shots from 230bar fill down to 140 reg pressure.
Before modification, ES over 45 shots used to be as high as 4-5 m/s. (13-16fps)
After modification, ES over the entire shotstring is always below 3 m/s (10fps), often barely 2,5 m/s (8fps)
Shotcount with 25 grain King today is 51-52 shots between 230bar and 140bar.
Shotcount with 34 grain MKII today is 39-40 shots between 230bar and 140bar.
Before anything else (i changed in the process), finding the ideal combination between hammer travel length, hammer weight, strength and length of the hammer spring, has proven crucial. The choice of the used (shorter) hammer spring, its combination with the ideally corresponding hammer weight, as well as the slightly increased hammer travel, in the first place made this .25 Streamline shooting as it does today.
Have a nice Sunday.
