BSA BSA R10 - SSG

[SpiralGroove]

Hey Guys,
Made a SSG for my BSA R10 to improve efficiency, thus reducing wasted air caused by hammer bounce.
Was using a Blast Tamer since 2015 to help, but decided to go with a SSG.

This thing is turning out to tricky as you don't have much space between the hammer (1-3/4") and the end cap.
Hence, you got to get enough spring power ..... in that short space w/o coil bind, keeping the end off the hammer (no pre-load),

Got 880 fps with JSB 10.34's but looking for 910/925 or maybe more power for JSB 13.43's.

All porting already 13/64" and valve throat already 5.5 mm, shouldn't be a problem ...... as shown by OEM spring at 946 fps using JSB 10.34's.

Likely going to add a second, smaller spring to get a "wee" more power.

 

[Motorhead]

Be sure the typical RED poly buffer is taken out, buys you @ 1/8" of spring stroke. Also allow the spring within end cap to bear against the factory HST adjustable collar. If you take collar all the way out towards the end cap it buys you additional distance for the spring.
Generally found .050 to .055 wire size to be ideal. Start with a spring too long at a higher spring rate & trim coils to settle at power wanted is my general way to get there. In a .177 caliber, reg only needs @ 120 bar IIRC

 

[SpiralGroove]

Thanks Scott,
Already took Red poly buffer out, but thought if I took out HST collar all the spring force would be on the aluminum end-cap (threads look wimpy).
OEM was .055 wire and just put in .059 wire to get 880 fps. May also reduce aluminum hammer length.

Not sure what the regulator pressure is, I dropped the belleville washers on the ground when I rebuilt the reg. a couple of weeks ago.
However, otherwise past set-up was providing 946 fps at about 320 bar fill (bottle) to 125 bar on gauge. So I think were not set too high and were shooting pretty quietly.

 

[Motorhead]

By having the striker stem LONGER on your aluminum hammer core, you have reduced stroke of the hammer and lost strike to poppet energy in doing so.

I'm saying keep the HST collar, just back it out so it is against the screw on cover. Get spring rate close and adjust from there.

* You can keep shortening the striker tip to a point where the shoulder of the hammer core will start hitting the lower / bottom of the magazine.
Best to keep this @ 1/8" shy of contact so sufficient poppet lift is not compromised.

 

[SpiralGroove]

Yeah, it makes the most sense ..... to shorten the hammer. Especially if I want to shoot JSB 13.43's at 900 fps.

 

[SpiralGroove]

Shortened a little more than 1/4" - JB Weld drying.

 

[Motorhead]

Shortened a little more than 1/4" - JB Weld drying.

View attachment 412972

Did you check for contact interference with magazine at this reduced length ?

 

[oaks1450]

Yeah, it makes the most sense ..... to shorten the hammer. Especially if I want to shoot JSB 13.43's at 900 fps.

 

[SpiralGroove]

Scott, not quite sure what you mean ......

- except the plastic hammer holder can go in at least 3/8" more before it bottoms out (on something) .... this is when the hammer is touching the poppet stem. Hence, the stem can be knocked in at least 1/4" or more providing sufficient lift.

Does this make sense?

- There is a 1/32" gap between the SSG and the back of the hammer when the hammer tip is touching the valve stem.
I also added a 1" piece of smaller inner spring around my 10-32 cap bolt to help with hammer momentum .

 

[SpiralGroove]

Hey Guys,
Finally got the BSA R10 completely together with SSG installed. What a Pain ...............

The SSG's working fine, getting 950 max with JSB 10.34 ..... probably a little hot, 835 fps with JSB 13.43's ... good enough for now.

I'm putting the gun down for a bit, but will likely fine sand the thumb rest area (drilled hole) on the pistol grip to allow for the SSG to retract.
The cap screw of the SSG sticks out about 1/4" beyond the stock and kinda breaks the lines of the gun when cocked.

I guess, you can't have it all .......... pics to follow.

 

[Motorhead]

In ALL the BSA "Scorpion" architecture PCP's the hammer core typically extends out the front of the black acetal body.
As assembled generally it is the core that will contact an inserted magazine before the body as the strike nose is shortened for more hammer stroke.

Yes there a PITA to get all fabricated & set up, but there functional improvement in shot cycle & air savings is very real.

 

[SpiralGroove]

Finally done, here is a few pics of the completed job .

 

[SpiralGroove]

Thanks Scott,
Your guidance certainly helps ........... .

 

[Ranchibi]

Nice work as always!

 

[SpiralGroove]

Thanks Guys,
This is my most Beautiful Airgun.

 

[beerthief]

great looking gun , thanks for posting .