The SSG - Finding Out For Myself

[CraigH]

The SSG device, as presented by Bob Sterne in the topic “A New Method for Increasing the Efficiency in a PCP – the SSG”, has been widely followed and implemented in single adjustment, dual adjustment, and internal versions.   This is my attempt at making one – in this case for a Crosman 2240 carbine.

The SSG in this topic is the dual adjustment version.  Spring pre-load is set with a 10-24 machine screw 3.5” long that runs through a 1” long  3/8”-24tpi bolt; that bolt controls the gap between the SSG/hammer and the valve stem.  I counter bored the threaded end of the 3/8”-24 bolt to receive the spring.   The SSG is screwed into a modified Discovery end cap.   Having had difficulty getting springs and machine screws desired, it took a while to make the device.

The SSG was first assembled with a 1.95” long, 0.265” diameter,  0.032” wire spring preloaded 0.45”.  The resulting performance was about 50 shots at an average of 509 fps before dropping 20 fps per shot.

I cut another spring (3.5” hardware store spring) to a longer length, 2.25", and added pre-load, now at 0.75".   I also shortened the head of the spring pre-load machine screw.
The combination;
      longer spring - less power
      more spring pre-load - more power
resulted in more power - the average velocity is now 518 fps for about 42 shots.

The 2240 into which it has been installed previously ran at about 527 fps average for 24 shots using a 0.042” wire, 1.5” long hammer spring.  The porting is 0.160” and the barrel is 14.25” long.  The temperature was 63 degrees F.

(The images of the pistol were taken prior to exchanging the o-ring for a flat rubber washer and the locking nuts for a nylock nut.)

Below are the graphic chronograph results of the SSG in this 2240 carbine.   It's a pretty good result; without the two excursions of 524.0 fps and 523.8 fps towards the middle of the string, it would be quite excellent.   This "finding out for myself" project worked out well.

I think a limiting factor here is springs with an internal diameter of approximately 0.195" to mate with the 10-24 (or 10-32) machine screw; and the external diameter of approximately 0.265" is about all that the counter bore of the 3/8"-24 bolt can take.   The counter bore is not strictly required, but it ensures the spring will not get near the 3/8"-24 threads of the tube end cap.   Of course, the guide surface of the #10 machine screw also helps equally as much or more.   I might consider using a #12 machine screw to enable use of Crosman stock diameter springs; this could be accomplished by eliminating the counter bore, or perhaps moving to a 7/16"-20 bolt - but that removes even more metal from the end cap that must hold the 8-32 screws for the grip frame and the breech.    All that to be considered in a future project.

[CraigH]

A more refined look now.

[triggertreat]

A more refined look now.

That SSG looks like it will work well at removing any preload off the hammer.  Although I prefer the internal SSG designs, I do like the threaded guide setup you have there.  I would run some strings to see if it is smooth and consistent without any hang-ups going on.

[CraigH]

I also like the other variations, like the internal version you mentioned and will at some point be trying that in another pistol.

This one has been good for over a hundred shots, but time will tell.   In the final version less than about 0.060" of thread enters the through bolt and that has a chamber at the entry.

Thanks!

[triggertreat]

I also like the other variations, like the internal version you mentioned and will at some point be trying that in another pistol.

This one has been good for over a hundred shots, but time will tell.   In the final version less than about 0.060" of thread enters the through bolt and that has a chamber at the entry.

Thanks!

Although the internal SSG versions are more esthetically pleasing, you won't find a better performing SSG design than one like yours that just lets the hammer free flight (assuming the SSG bolt is pushing against a hammer).