HW30 SR (semi recoilless)

[GTS_Dan]

Going to start a thread to keep my updates in (rather than spamming the springer section every few days ).

In the past I've designed and built a couple of fully recoilless break barrels, i.e piston motion cancelled out, like a park or Diana Giss. But they were complicated, heavy and very expensive. So I decided my next project would be the opposite end of the scale. Simple, light and cheap.
To that end I decided on a semi-recoiless sledge system (like a FWB300 or TX200 SR) that would accept a standard off the shelf actions.
I messed around with several iterations before settling on a design that I'm happy with. Which I'm now building using a HW30 as the base (although this same concept will also work with a 99 and 35).

In my mind there are a few key hurdles to overcome, in the following order, and I'll try to do a separate post for each of them:

1. The sliding action. Must be smooth and free running, but be resistant to excessive wear. Ideally cheap to repair if needed

2. The detent system. Required to lock the action in the forward position. Must be strong enough to resist trigger pull, but free enough to allow free movement of the sledge. Should be easily adjustable to account for different trigger weights and scope mass

3. Sledge reset system. Ideally the sledge should auto reset when cocking. Manually setting it could be easily forgotten

4. A stock to put it all in. Very unlikely to fit in a standard stock, so a new one will need to be made. I have some ideas on this.

 

[GTS_Dan]

Point 1 - the sledge system

For the current prototype there is no detent or auto reset system. This is focussed purely on getting the sledge working reliably.
The sledge is simple enough that this version is actually using mostly 3D printed components. The plan is to eventually upgrade to a mix of aluminium and SLS or MJF nylon, which will keep costs relatively low, but have the required mechanical properties.


To test it, I've been going out in the garage at night and firing around 50 pellets into paper targets (limited by time unfortunately). Most of these are rested, sometimes on my hand, sometimes on a bag, and sometimes with the stock directly on a table with no cushioning. So far it has held the same zero regardless of the surface.

This is 25 shots at about 12 yards. Not bad for something that's using 3d printed parts! However I have to remember to manually move the sledge forward, and the trigger is set very light so the sledge doesn't start moving too early.



Next step will be installing and adjusting the detent system. Then I'll be able to test shooting at angles and test with different trigger weights.

 

[Mr Bond]

Watching with interest, as I was the first time. Please bring this to market! BSA Lightning or cometa 400 please!

 

[GTS_Dan]

Watching with interest, as I was the first time. Please bring this to market! BSA Lightning or cometa 400 please!

Life has settled down a bit now so hopefully I should be able to see this through!

I've got a cometa galaxy fusion which I think is the same or similar action to the 400?
That will unfortunately have to wait for a version 2 due to the one piece cocking linkage. The current design will only work with an articulated linkage.

 

[GTS_Dan]

Problem 2 - detent system!

This is a tricky one. It needs to hold the sledge in the forward position and be strong enough to hold it there when pulling the trigger and/or aiming upwards. But light enough to allow the sledge to move as freely as possible.

By far the best solution is to trap a pin or bolt head between the back of the piston and the rear edge of the cocking slot (as per the TX200 SR). This effectively traps the sledge until the trigger is pulled, and the gives zero resistance afterwards.
Unfortunately this is very dependent on each model as some pistons get pushed beyond the cocking slot, leaving no room for a pin. It's also dependant on each individual action and state of tune. Choice of piston seal, spring guide, spring washers etc can all have an effect on this gap. As I want any action to be usable, this therefore isn't an option.

That leaves a ball detent design, as per the Diana Airking. A sprung ball bearing is pushed into a hole which locks the sledge in place. When the action is fired, the force of the recoil pushes the ball against the spring and allows it to retract out of the hole.
This means some small amount of recoil will be transmitted to the stock, but at least it's easy to adjust for each user. Bench rest users will want to set as light as possible. Field users will want it set heavier. This can be achieved by simply turning a grub screw which will increase or decrease spring tension.

This ball detent system raises an engineering problem though. The mating parts need to be hard enough to resist wear from the ball bearing. Any wear would elongate a slot and change the firing characteristics over time. But how to harden them? I could harden parts myself, but that would be inconsistent with the equipment I have, and what if any parts got missed? That could lead to rapid failures.
I could make the parts out of a tool steel or equivalent. But that would be relatively expensive in terms of material and machining, and I'm trying to keep this cost effective.

The solution is pleasingly simple. Use parts which are already hardened, in this case hardened dowel pins or needle rollers. These are made in their millions, are very cheap and all hardened to precise specifications. All I need to do is make a housing to hold them in place. Enter the 3D printer!
I have designed and printed a housing which will hold the pins as shown. The ball starts at the bottom of the vertical rails. Then when the action is moved forward the ball rolls up to the cross pins, goes over the first, and is pushed into the gap between them. This is the locked position.

Next step is to test different pin spacings until I get the right feel and amount of adjustability needed. The one shown holds the action up to about 70 degrees vertical, but annoyingly releases when returning the barrel after loading a pellet (cross pins are too close together). But would be brilliant for bench rest.
The next couple of weeks will be spent testing and tweaking this component. No point going any further until this is working properly!

 

[Tomdavies9]

Good to see you back on with this Dan, and will be nice to see the updates coming through

 

[GTS_Dan]

Quick update from today. I've found a pin spacing which seems to be working well. At one end of the adjustment is is the 'benchrest mode' I mentioned before. At the other end of the scale it managed to hold in the forward position whilst firing (i.e it locked the sledge and made it a recoiling gun again).
Somewhere in between there was a happy medium where it locked the sledge during loading and returning the barrel, and stayed locked when the gun was held vertically. But released easily enough during firing.

Next time I get it out I'll try to measure the sledge travel in that optimum position, and the travel with no detent at all, then I'll be able to say how much recoil the detent system transmits to the stock. Gut feeling is less than 5%, it's barely perceptible.

 

[GTS_Dan]

No more progress apart from putting some pellets through it. Probably 2/3 through the first tin of 500.
Made a short video showing two pellets balanced on the stock. It's only two because it turns out I'm not very good at balancing them, and my helper in the video hasn't got any thumbs.
I'll go through my pellet stash and see if I can find some easier to balance ones!

 

[P8X]

No more progress apart from putting some pellets through it. Probably 2/3 through the first tin of 500.
Made a short video showing two pellets balanced on the stock. It's only two because it turns out I'm not very good at balancing them, and my helper in the video hasn't got any thumbs.
I'll go through my pellet stash and see if I can find some easier to balance ones!

That looks brilliant Dan

 

[GTS_Dan]

That looks brilliant Dan

Thanks. The little HW30 arguably doesn't really need to be semi-recoiless, but it is fun to shoot!
The HW35/80/90 should hopefully be really good!

 

[P8X]

Thanks. The little HW30 arguably doesn't really need to be semi-recoiless, but it is fun to shoot!
The HW35/80/90 should hopefully be really good!

Don't forget the 85/95/98

 

[GTS_Dan]

Don't forget the 85/95/98

And the 57/77/97 too!

I've got one design for the articulated cocking linkages and another for the one piece cocking linkages.

Could even do a 55. That would be fun. A 'What could have been' type thing.

 

[Mr Bond]

I have a 97 Dan, just sayin'...

 

[P8X]

And the 57/77/97 too!

I've got one design for the articulated cocking linkages and another for the one piece cocking linkages.

Could even do a 55. That would be fun. A 'What could have been' type thing.

How far away are you from getting a chassis out for testing Dan (if you do intend to do that)?
Cheers Rob

 

[GTS_Dan]

How far away are you from getting a chassis out for testing Dan (if you do intend to do that)?
Cheers Rob

I would love to send some around for feedback, but realistically that is months away.
A couple of parts really need to be aluminium. I'm going to try and make those parts common across all the models if possible to reduce costs. So I need to make some more prototypes first to check that part will fit all actions.

Then I need to start making some stocks which will probably take a while! I'll try get one to you for Christmas

 

[P8X]

I would love to send some around for feedback, but realistically that is months away.
A couple of parts really need to be aluminium. I'm going to try and make those parts common across all the models if possible to reduce costs. So I need to make some more prototypes first to check that part will fit all actions.

Then I need to start making some stocks which will probably take a while! I'll try get one to you for Christmas

I'd be extremely interested in a 99 with recoilless ability
Be nice in a target style stock and thinking there should be enough meat to alter the stock for the necessary workings (though i have no idea of the design if you know what I mean)
After recently buying a Park RH91, I'm totally in awe of its recoilless cycle and for me, that's the way forward with springers

 

[GTS_Dan]

I'd be extremely interested in a 99 with recoilless ability
Be nice in a target style stock and thinking there should be enough meat to alter the stock for the necessary workings (though i have no idea of the design if you know what I mean)
After recently buying a Park RH91, I'm totally in awe of its recoilless cycle and for me, that's the way forward with springers

It definitely won't fit in a standard stock, the belly isn't deep enough. Although it might fit in a CS stock with modified inletting, so that's an option I could look into

 

[P8X]

It definitely won't fit in a standard stock, the belly isn't deep enough. Although it might fit in a CS stock with modified inletting, so that's an option I could look into

Thinking more a FWB300 stock variant

Do you still have that broken 300 stock and action we chatted about years ago?

 

[GTS_Dan]

Thinking more a FWB300 stock variant

Do you still have that broken 300 stock and action we chatted about years ago?

Haha yes. That's what this HW30 action is going to end up in I think. It's sat on my desk at home as I've been measuring the general dimensions to make a CAD model of a target stock

 

[Tomdavies9]

Thinking more a FWB300 stock variant

Do you still have that broken 300 stock and action we chatted about years ago?

I did chat with @GTS_Dan a while ago about dropping his system into wood stocks. I’m still up for it if he is