2240 SSG thread

[Blue]

I've been meaning to post a couple tips I came across.

The most difficult part (for me) making a SSG has been getting holes drilled centered and straight, especially the gap adjustment bolt that the spring guide rides through.

In another post someone suggested a couple products they found on Amazon.  Kind of pricey, each was around $8 for a two pack of bolts but they come pre drilled.  One was I think a motorsports product from Kuryakyn that was a 3/8x16 (I think) with a slightly larger than 3/16" hole bored through.  One of the bolts in the two pack is very well centered, the other is just slightly off.  The other product was a pair of banjo bolts 3/8x24.  These require you to finish drilling the bolt through the head and then enlarging the hole but much easier to finish than starting from scratch.  I am using one of these right now because I needed the 24 tpi thread for an existing stock adapter with an rva built in.

Also enlarging the hole on a crosman rva was easier than drilling out a stock rear plug.  Same idea, easier to work an existing hole than to start a new one.

[thelast88]

There is still a substantial amount of bounce there, I wonder how to reduce that more.

It looks like that but it's really a lot better and you can hear it just by the sound, there's no burp anymore.
As soon as the weather improves I'll test the entire string, now I'm getting 80+ shots at about 5.3 fpe avg, I hope to get around 90-100 when it gets warmer.

I've been thinking about combining a bstaley buffer with an SSG to (maybe) control the valve openning a little more.

Also (and I haven't watched the videos) the hammer may still bounce back and forth but my understanding is that after coming back and hitting the fixed, pre-loaded guide it doesn't have enough energy to pop open the valve anymore.  Although  Bob's results using a lighter hammer may suggest that reducing the mass might help.

That's the point, free flight reduces hammer bounce and increase efficiency. Reducing mass of hammer should help, but I don't think that the BSB with SSG would increase shot count.

[Blue]

Here's a picture of my last two attempts at drilling through the bolt using a drill press and vice.  To be fair, I may not have had the bolt exactly straight in the vice when I drilled it.




Here's a couple pictures of the pre drilled bolts.  Banjo bolt (hole finished and enlarged) on the left, fully pre-drilled bolt on the right.







Blue

[45Bravo]

I know it's better, but I wonder if it can be improved more.

Maybe A rebounding hammer that's attached to the shaft.

You know when you cock it, the shaft sticks out the back, put a slight cushion there so when the hammer is at rest, it's just slightly off the valve stem.
But when it's fired it compresses the cushion, impacts the stem,  then stops short..

Just a thought..

[sshewins]

I have a somewhat relevant question. With the SSG, can you still use a tipman stock? Or would that not be possible? Just curious. Thanks

[Blue]

I'm working on a 2400kt with a Mellon adapter for a tippmann stock right now.

I had to drill out the "buffer tube" at the end going into the adapter to give room for the SSG and spring guide.

If you make/use a completely internal SSG it wouldn't matter.

Blue

[sshewins]

Any progress and or pictures of that internal ssg?

[imadunatic]

Any progress and or pictures of that internal ssg?

Not sure about the other poster, but I did just start machining the components for my attempt at the internal 2240 SSG based upon the internal design Bob (rsterne) posted over on the behemoth SSG thread on page 24. I've got many posts to go before I can upload pics or post external links, so I figured I'd start here. I am guessing based upon my current workload that I'm at least a couple weeks away from testing and fitting the internal SSG; hopefully it works out as I need this to be kid and wife friendly, so pinch points, no matter how obscure they are, aren't an option for me. 

[David Mccann]

hey folks, whats up. been fiddling with the ssg . here is what i have so far. gotta get some springs.   

i have conjured up several of these and they work pretty good. does require modding rear tube plug or making a new one.

[Gerard]

Thought I'd posted my 2240 SSG here but it seems not. Ah well, here it is. Used a long spring with 1mm wire, 8mm diameter. It's pushing a carved down hammer with slightly drilled out core to allow the fatter than stock spring free movement. The parts with threading are delrin, with the spring going back to about 5mm shy of the rear small wrench flats. The whole thing screws into a larger delrin plug which acts as the mounting point for an aluminium tube stock. The rod is drill rod, threaded and with a nut peened onto the hammer end then turned down and polished. The carbine spits out about 43 shots from a 2,200psi fill of the HiPAC with an ES just under 2%, sufficient for my son to get in a full round of HFT targets before needing a refill.

[PBguns]

*subscribed to thread.

Wanting to build an SSG for a couple of my 2240s.....(on the back-burner right now though).

[imadunatic]

Finally have a working prototype for the 2240 SSG.... one question though: How are you guys setting your gap? I'm currently doing it by feel and slightly cocking the bolt and monitoring movement as a second check. This is a fully internal SSG, so that may add to the degree of difficulty in setting the gap, I've basically copied rsterne's version of an internal SSG so I'm hoping Bob can offer some advice on where he started with his as well.

I'm hoping to tune this afternoon and I'm thinking the place to start is just shy of coil bind and then back off the preload .100" at a time until I see the velocity start to drop dramatically. Near as I can tell, this is the "knee" that Bob refers to often in his posts and has been shown to be the best mix of power and efficiency, is that about right?

[imadunatic]

Well, still can't post pictures (at least I don't think... I believe I need 20 posts), but I managed to get 467.83 FPE out of one powerlet stopping when the first shot dropped below 300 FPS. Shot string was nice, but once I added the brass spring guide I started blasting gas again so I had to tune again after polishing the spring, guide and all other components. Once I hit my 20 posts I will take some pictures of my prototype, just ordered some material and springs for my final version. But I'm considering just putting it up for now and shooting while the season is still here; another month or 2 and the gas guns will get put up for good.

I'll save you having to scroll through the entire string, but here are the numbers:

Shot Count: 110
Hi   380.00
Lo   288.00
Standard Dev   17.16
Avg   358.08
ES   92.00

[Blue]

one question though: How are you guys setting your gap?

I use the cocking slot as a "window" to see the hammer pin.

When in the un-cocked position (with no pre-load on the hammer spring) the hammer should be fully forward resting on the valve stem, I use a slim sharpie to make a mark on the breech at that point.

After you've got a mark for where the hammer contacts the valve stem, start playing with the gap.  Add whatever amount of pre-load you are starting with then use something small to reach into the cocking slot "window" and push on the hammer pin until the hammer slides back until it stops.  You can make another mark and measure the distance between the two and that's your gap.  Each time I made an adjustment to the pre-load, I would have to readjust the gap.  Adding pre-load increases the gap and decreasing spring load decreases the gap.

I found that a gap of somewhere between 1/16" and 3/16" worked for the spring/tension setup in mine but I think each SSG is going to have a different sweet spot due to different tolerances and materials used in their fabrication.

Another thing to watch out for is to be conscious of where you are in relation to how full the CO2 cart is.  I have found that CO2 carts can have a "curve" of their own (a little low for the first few shots, then leveling out, then dropping off).  A lot of people who tune their pcp's will determine their "knee" then tune while the system is tethered at a regulated/set psi so that each test shot is showing them what they'll get at their particular sweet spot.  If you're doing a bunch of tuning and you finally find your "sweet spot" but you are at the end of the cart (pressure is a little low), when you pop in a fresh cart your numbers may be off from what you were seeing.  When I was testing my original setup I went through A LOT of carts and pellets.  I'd find a setting I liked then confirm it through a whole cart string.  I found similar velocities at the beginning of a cart would end up with fairly dissimilar shot counts sometimes, some settings would be very close to each other in initial velocities but one might start dropping off much faster than another.  I think it's easier to tune for either consistent velocity or a long shot count, nailing the sweet spot for BOTH takes more time, testing, and notes.

Blue

[imadunatic]

So I shamelessly copied Bob's idea for an internal SSG and implemented it on my 2240.

Apparently I didn't take any photos of it before I fully assembled and tuned it, but this was my basic design:




And this is how the prototype looks:



I'm going to tighten the entire package up and also replace the steel end cap with aluminum (this weighs about 3 oz and has definitely affected the manners of the gun). I think seeings as how my shooting season is drawing to a close I'm just going to leave this as is and spend some lathe time this winter making the final version. This one is definitely functional (I gained about 33% more shots at the same FPS as I was getting with just a clipped hammer spring).

[shed tuner UK]

Greatings from the UK.

Rather late to the party, I know, but I just did a Stopping Spring Guide for my 2250 and wow, completely takes out a load of hammer bounce; the fart noise has gone, and it now sounds more like a PCP.

Due to our UK power laws, I didn't want something poking out the back that could potentially be used for adjustment, so I went clean through the front of the hammer instead

Basically, drilled a 5mm hole though the centre of the hammer, then counterbored from the nose about 9mm, and 4mm deep, for the nut at the end of the spring-loaded bolt to sit in. I turned down the head of the 60mm long bolt so it sits easily in the recess for the spring in the end cap. Used bog std hammer spring, although it now has a bolt-head-thickness more preload now. Fine tuned the bolt length so it sits just about 1mm off the valve stem. The nut is a nylock, but I will probably use some strong threadlocker.

Cock the gun, and the hammer slides back, compressing the spring in the usual way, but the bolt and the nut at the end are now producing about 15mm (whatever the stroke is), through the front face of the piston...  Fire the gun and the hammer shoots forwards, collecting the spring guide (which is free to slide forwards out of the endcap) and the end of the bolt is hammered onto the valve stem. When the valve rebounds, the SSG principle now comes into play, as the preload in the spring loaded bolt is a good deal higher than stock - and of course there's the lack of direct contact between hammer and stem.

There a little inefficiency here, in as much as the hammer is slowed when it collects the guide bolt, but power with a 14" barrel is unchanged at just under 9 fpe. I guess the extra bolt-head-thickness preload compensates.

But it shoots so much sharper, less noisy, and I've got at least a dozen more shots. So it works. Best of all, nothing externally visible. I haven't seen one done like this, but I'm sure there are - it's too obvious for someone not to have tried it already, but it's defo the way to go for the UK with our laws.

Rgds - JB

[Gerard]

That's a great solution, really like it. Carbide to drill through the hammer face? The case hardening is quite difficult to get through on those things. I'd recommend pulling your guide bolt and hardening the business end before Loc-titing the fixing nut, as thousands of impacts on the valve stem are likely to eat into that end quite badly. Heating the striking end to bright orange and quenching in oil, then polishing to see the steel again, heating gradually with a low flame (a stovetop or a gentle torch) until you see a very feint straw colour on the steel will give a decent hardness, though actual RC values for hardness will vary quite a bit depending on the alloy. Of course case hardening would be ideal, but I've no idea how to do that.

[shed tuner UK]

Hi Gerard, yeah, hardening and a few other little improvements are definitely on the cards. This was really prototype #1, and it just so worked so well I'm not in a rush to change it, but I do think you are right about the bolt gradually getting bent out of shape. On the plus side, that section of the bolt is surrounded by the nut, so the metal won't move too far I'd also like to use a much longer bolt with a long smooth section, and then chop it down, so the threads are all inside the nut, and only the smooth section remains for the hammer to run on.

I just drilled the hammer from the inside, nice a slow with a bit of oil, and it was no big deal. A tiny bit more resistance just before I broke through, but nothing significant.

Thanks for the tips on hardening / tempering; will do that when I find my new (smoother) bolt...

Rgds- JB