GTS break barrel

[cooper_dan]

Think it's about time for an update!
So the break barrel was put on hold for a bit. The first prototype (up to about 10 ft-lb) finally let go and made a mess of its cocking linkage (due to a design oversight on my part!) And at the same time we had a baby so life changed a bit!

However in the last couple of weeks there has been some progress. A new cocking linkage has been designed which should be far superior to the first one. Parts for that are in production now and should be 3 weeks or so before I get them.
In the meantime I need to sort out a stock. I reckon you need all the leverage a stock provides to really test the limits of the cocking linkages.
Unfortunately my 'prototype stock' fund has just been wiped out by an unexpected car bill

So I've had a dig around and found my old TX200 frankenstock. With some modifications I think I can get the prototype to fit. Then do some major reshaping to get it looking sensible.

I've also re-worked the piston (in CAD only at this point) which brings the dynamic mass from 400g down to roughly 280g. This should really help give the spring an easier time and give an efficiency boost (400g was just too much to accelerate properly).

[cooper_dan]

Also I've designed a very simple but effective ABT. It's a ratcheting system that will lock the mechanism at any point, so if you cock the barrel halfway and your hand slips off (I'm sure everyone has seen this happen) the mechanism will lock and the barrel will stay where it is. Or if you accidentally pull the trigger when its fully cocked, nothing will happen. The mechanism doesn't unlock until the barrel is fully returned to the breech.
Not sure if any other break barrels out there have a 'true ABT' like this or just trigger blocks?

Pro's - 'true ABT' at any point in the cocking cycle. Additional layer of safety
Con's - Can't be de-cocked. Adds roughly 25mm to the overall length of the action.

[TonyL]

Cheers for the update, Dan.. Blimey! A new baby is life-changing enough, so huge congratulations to you both. And to contend with such a project too, with its various trials and tribulations. Well done. Keep those updates coming as things progress.

[Shed tuner]

sounds good Dan. Esp good news on the piston weight - with a shortish stroke, that 400g woudl just be too much...

[cooper_dan]

Minor update and a bit of a comparison to some other boingers. This is the P1/P2 prototype. The P3 will be about 20mm shorter in the action (distance from rear of trigger guard to breech face)

https://photos.app.goo.gl/2eEZcGLAhgPurdNH8

And a view of the underside. Nice short cutout for the articulated cocking linkage, and the front stock screw bolts directly into the action. So you could add a sling or bipod without putting any stress on the barrel/lockup

https://photos.app.goo.gl/wmd2FC24Qtp6xQf89

[charub]

I’m going to take a wild guess . . . . That stock looks like a butchered SR stock?

Hi Dan, great to see you are still at it.

[cooper_dan]

I’m going to take a wild guess . . . . That stock looks like a butchered SR stock?

Hi Dan, great to see you are still at it.

Close. Just a standard TX stock. But one that had been previously butchered by me to make an HFT stock.
The SR stock you are probably thinking of is next in line and I'll use that for another prototype.

[Shed tuner]

It's all progress Dan..

Howsabout a quick vid of it in use and some specs ?
The barrel looks shortish - 11" ? An option for 14-16" will give more efficiency.
Also when you talk about reducing the action length.... maybe also consider using the space saving for more spring room instead (helps with spring longevity and stress) as it doesn't look too long at present ?

Continued good luck on this mission !

[cooper_dan]

It's all progress Dan..

Howsabout a quick vid of it in use and some specs ?
The barrel looks shortish - 11" ? An option for 14-16" will give more efficiency.
Also when you talk about reducing the action length.... maybe also consider using the space saving for more spring room instead (helps with spring longevity and stress) as it doesn't look too long at present ?

Continued good luck on this mission !

I will get a proper video in a couple of weeks. I was going to make a floating rifle platform on a bed of ball bearings, and rig up a trigger pullerer that won't impart any rearward force.

Specs currently:
Stroke somewhere between 70-75mm
Bore = 28mm (using Diana piston seals ATM)
Weight = around 3900g, but P3 version should come down to 3600g (less than a HW35k)

The barrel is 10" .177. the plan is to do power development with this barrel, then I will know for sure that other calibres/lengths won't be a problem.

Length (not including barrel) is the same as an LGV which is about the biggest break barrel I could find (that wasn't super magnum). The aim is to get it down to HW80 length. It also saves a useful bit of weight. Good point about spring length through. I've taken most of the length off of the transfer port and the trigger block. Spring room is hovering around 200mm.

All excellent feedback, thank you

[Shed tuner]

thanks Dan, all sounds good

[BTDT]

...rig up a trigger pullerer that won't impart any rearward force.

A short length of windshield washer hose, with a loop of thin plastic coated wire though it, will do the trick, Dan.

[cooper_dan]

A short length of windshield washer hose, with a loop of thin plastic coated wire though it, will do the trick, Dan.

I don't have a trigger guard to pull it against but that does sound easier than what I was going to do.
I've got a couple of syringes at the moment. Plan was to have the body of one attached to the stock, with the plunger acting on the trigger. Then a hose to a second syringe in my hand.

[BTDT]

I don't have a trigger guard to pull it against but that does sound easier than what I was going to do.
I've got a couple of syringes at the moment. Plan was to have the body of one attached to the stock, with the plunger acting on the trigger. Then a hose to a second syringe in my hand.

If there isn't a rear trigger guard screw hole, a tapped hole with a bolt behind the trigger blade would be easier than faffing about with syringes.

[RustyBuzz]

This looks jolly exciting.

I know it took John Whiscombe a decade to bring his rifle to market, it’s remarkable how fast the world can work these days.

All the best with the project, loving the regular updates.

Richard

[cooper_dan]

If there isn't a rear trigger guard screw hole, a tapped hole with a bolt behind the trigger blade would be easier than faffing about with syringes.

There you go with your common sense again
Sounds good, I'll do just that!