A New Method for Increasing the Efficiency of a PCP - the SSG

[rsterne]

Please, let's not drag this thread off track, it's about the SSG....

Bob

[GarthThomas]

Here is my stab at it on the B50. I used a cap screw the same thread as the safety bolt but I turned the shank down to 3.6mm so it could slide from thread to head, it was a 2-1/2" M5x8
I didn't want to damage anything so I was able to make a sleeve from shim stock to protect the threads in the end cap where the safety attaches and slip it in the threaded part of the cap after I installed the screw, so far it hasn't moved but its long enough for me to flair the ends if I have to .




I used the original BAM spring

My new hammer

I haven't tested for efficiency yet but I finally got it to shoot, it took a bit of reading here to sift through everybody's stories but I like how I can control the power so easily.
I hope it stays where its set without adding set screws.

[rsterne]

Looks good, make sure the rear SSG cavity is vented.... the B-50/51s can pull a vacuum behind the hammer on firing which REALLY hurts the power and consistency of the hammer strike, even moreso with an SSG where the hammer is coasting the last part.... Venting it makes a huge difference.... (thanks Motorhead!)....

Bob

[Motorhead]

Thank Bob ...

What a B50 cap looks like vented ...


Hole is drilled on a slight angle to intersect the floor of spring cavity having placed a small pocket in the roof of the spring cavity.  In this way the spring or any shims in place do not obstruct air coming in as hammer falls from the cocked position.

* Position of drilled hole found best ( As viewed from rear of action )  at @ 7 to 8 O'clock being along side trigger housing yet Under the stock getting covered up.
There is wood inletting clearance at that position within the stock and venting is hidden and free of garbage getting into the hole.

[GarthThomas]

I have a different setup and I'm thinking of drilling holes in the tube just before the end cap starts beside the trigger housing.
I have made a sleeve spring guide bushing to help in the spring pocket where I drilled out for a previous MC spring.

Has anyone ever made a new end cap? I would but indexing the breech screw holes has me worried.

[Motorhead]

A new end cap could be done if one had a Lathe & mill.
Because the 2 rear receiver hold down screws are off center creating a radius surface a drill will walk on, Spot facing 2 flats om new cap would be best.  Then with new cap in rear of tube held with the side grup screws, transfer drilling threw the threaded holes in tube & then tapping the threads using the receivers threading as a guide would be necessary.

Enough here ... this is an SSG thread !!!
Take this B50 tech into it's own thread please 

[GarthThomas]

I have a lathe but I don't even have a drill press at the moment, not a lot of material there to try to time the theads for the new holes

[triggertreat]

Looks good.

[robertr]

 This my version of an internal SSG for the Disco, copy of the one I made for the Marauder, ( TSSG ).
Adjustable for spring preload and separate adjustment for the gap with the modified rear adjuster. Works as a SSG should, I also used fine threads so adjustments are not so touchy.

[Voltar1]

Intrigued by the SSG and really like the zero force on valve at rest.
Made a long throw hammer with a variation of the marauder setup for a B51 in 177cal.
Will shoot it more and gather some performance info. Currently doing around 720 with 7.3gr JSBs.
Very consistent and accurate so far.
Thanks Bob for your innovating and sharing.
Cheers

[skorec]

Which kind of system ( SSG, FFH, TSS )  can  improve my QB78D/.177/1500-1000PSI/5-shot PCP ?

In first step I had bean thinking to add adjusting M4 screw only but after  read-through  this thread  I am thinking to add also SSG  or FFH  or TSS system in one step .

[rsterne]

FFH is a commercial name for the SSG idea pioneered here on the GTA.... There are at least a half-dozen ways to make an SSG.... but not all of them are suitable for a QB.... The photo you show of two springs on a guide is not my understanding of a TSS, I believe they are two, concentric, counterwound springs, operating in parallel, not series as in your photo.... and without the stop on the spring guide.... but that idea may indeed work fine.... Anything you can do to prevent hammer bounce may increase your shot count.... from 5 to maybe 6, or even 7, it depends on how efficient the gun is now....

Bob

[Gerard]

Indeed the device shown in the photo at the bottom is my SSG, internally adjustable only, from my QB78D. I've opted to keep cock-on-close and so access to adjustment is strictly via disassembly, reassembly and testing. Works very well though. Just took more than 15 trial and error adjustments with various springs and lengths and rod lengths before nailing the power/efficiency. That picture isn't the final version - I got some new springs and use a single spring now instead of stacking two. This is the 'final' version (on the same vinyl stool):

[skorec]

Bob and Gerard,
Your answers are  absolutely short and absolutely understand In  another word excellent.
 
If I understand right If I add only adjusting  screw - my picture n.1 -  I have to take of "cockin pin"   to reach outside adjustment ?
Or what about to add bevel hole on QB78D  rear cap and use long screwdriver  from outside . Or add the long pin at rear of the guide which  will be going trough bevel hole in rear cap.

Disassembling gun for each adjustment is not acceptable for me at all. 

[Gerard]

Not sure I could adjust mine from outside. In fact no, it would be too difficult to access. My spring guide is secured by a pair of 10-32 nuts tightened against each other. I need two wrenches to loosen then adjust and re-lock them. The second nut is important to prevent gradually loosening and changing the depth of the probe. You would need to change your QB78 to cock-on-open, more like a Crosman 22xx for example, then drill the end cap and install your SSG to one side of the fixing bolt. I don't find that very practical, if that's even how it is done. A trapped, or internal SSG is fine for me. Just takes more time to get it set up correctly.

[skorec]

What disadvantage do you see  by changing it  to the  cock-on-close ?

sorry
What disadvantage do you see  by changing it  to the  cock-on-open ?

[Gerard]

Perhaps you mis-worded this question? I left it as stock, the factory method, which is cock-on-close. The drawing you attached shows a simple way (incomplete, perhaps?) of converting to cock-on-open. I suppose the most obvious reason is that without a safety (I remove safeties from my airguns as they are not entirely reliable, and I prefer to use my brain as a safety as it is more reliable than these flimsy mechanisms) it is easier/safer to de-cock the gun by simply opening the bolt. The spring pushes the bolt back, and the hammer spring is no longer in tension, so the gun is safe. A simple, effective action.

With the 22xx style of cock-on-open, the gun is ALWAYS ready to fire until I pull the trigger. The only way to de-cock one of these guns is to pull back the bolt, pull the trigger while holding the bolt back, then slowly release the bolt until the hammer spring is not in compression. This is far too easily fumbled. In fact, I had a 'negligent discharge' of my Brocock Atomic which is also cock-on-open for just this reason, firing a pellet into the kitchen floor tile between my feet and my wife's feet. She had called me from my workshop because a squirrel was on the porch, in the herb planters, making a mess. I grabbed the Atomic carbine (a conversion, scoped) and went to the kitchen window to see if there was a safe shot but the squirrel had gone. I went back towards the workshop, but as I held back the bolt to then press the trigger and slowly release it to de-cock... the bolt slipped from between finger and thumb and the gun fired, splattering both our bare feet with dozens of pieces of lead. It was fortunate that I ALWAYS point the gun in a safe direction, so it was pointed at plain tile, but those little bits of lead hurt. She was very startled. So was I. Seems my fingers had a bit of linseed oil on them, as I'd been polishing an ebony doublebass fingerboard, and that was enough to let me slip. I do not like this method of cocking mostly for that reason. It's unsafe, forcing the user to risk an accidental discharge of a pellet when making the gun safe if a shot has not been taken.

Another reason is that is slightly quicker to cock this way, compared to drawing a bolt back to compress it then pushing it forward and down to lock it. Sometimes a half-second is all the extra time a squirrel needs to get out of my sights. A small difference, but I've found it to be a small advantage with the QB78D's normal cock-on-close system.

I also find it a little bit quieter, as the sear does not *click* past the hammer when cocking, it is already in place ready to hold the hammer back. Small noises can likewise be enough to move a rodent out of the garden, so I have to waste more time waiting for it to return in a few minutes to do more damage to my garden or nut tree.

As for preferring cock-on-close in terms of using an SSG internally instead of protruding from the back, that would only be relevant if my setup showed the rear cap. It does not, as I use a delrin rear plug which serves as a mount for a tubular stock, so I have lots of room inside that tube for whatever shape and size of SSG type setup. If I used a traditional wooden stock I would probably not like that big thing hanging out the back, looking ugly and perhaps catching on my hand.

So not hugely important reasons except for the safety issue mentioned first, and that one alone is enough that I wish the rest of my airguns were cock-on-close type.

[skorec]

Thanks for  your investigating.
I accept lower safety and  noise differnces but most important not acceptable  what I see now is differnce from obviosly use  gun systems . 

[KnifeMaker]

Wow! glad no one was hurt from such a dangerous method.

Pointing the gun between you and your wife's feet is NOT as safe direction to uncock a gun. Shocked that you thought it was.

Never, ever uncock a bun by pinching the bolt between thumb and fingers. Why? I think you just learned WHY!

Wrap your index finger firmly around the bolt. No way for it to slip through when you are using this method. . Your method is extremely dangerous, as you have now learned. Even a tiny bit of lube or sweat, and the pinch method is a bombshell. Almost guaranteeing an accident. Had this been a HP PB, it could have been disastrous for the both of you. 

Now, all that is needed to cock a "to the rear" cocking system silently, is to pull the trigger on a non cocked gun, pull bolt fully to the rear, and release trigger then close the bolt. The gun is now cocked, without the click. 

As you say, the brain is the best safety, but you do have to engage brain in order for it to be safer than the mechanical safety. LOL

Knife

[Gerard]

The gun was pointed straight down at 1/2" thick ceramic tile over 1/2" of concrete, and was shooting with about 6fpe of energy. I was walking back to my workshop and was not expecting to let go of the bolt until getting to my shop door. Have you looked at a Brocock Atomic bolt knob? It's a tiny, shallow , round glossy thing sticking straight out the back of the upper. How exactly would you suggest grasping such a poorly thought out device if nit between thumb and finger? A pair of pliers, perhaps? But no, that would probably make it even easier to slip. I have since made a brass T handle because that incident demonstrated the inherent problem with Brocock's design. I have zero trouble de-cocking since.

Not trying to make excuses, and sure, it was a bit cavalier de-cocking as I walked, but I was very conscious of muzzle direction and the worst potential damage happened: minor momentary stinging from a sub-500fps pellet fragmenting as it splashed horizontally. I understand there's a tendency for knee-jerk harsh critiques whenever someone 'confesses' to an ND (hey, I've hung out on /k/ a little and seen how quickly those conversations descend into the absurd), but it was a heck of a lot safer than pointing the thing at a wall and there was zero potential for actual injury, not enough energy left after hitting that hard surface to draw blood from lower extremities. If you happen to be in the mood to attack someone so be it, doesn't hurt me, I'll just ignore any further attacks from you and move on.