Sunday, August 10, 2014

Back to the Patriot

Got back to the Patriot the other day.  Wanted to reduce the airflow through the transfer port to create a slightly larger cushion of air in front of the piston.  The hope was that the "ping" from the piston hitting the front of the compression tube would go away.  Tore the gun down again and jumped in.

Didn't bother to go through pin gages to find the actual size, but a #20 drill bit (0.161") just fits.
So, the transfer port is huge--about 0.035" larger than "normal".  There are a lot of ways to reduce the port size.  Could've drilled it out even larger, threaded the hole and made up several set screws with various sizes of through holes.  Or made interchangeable sleeves that are secured with a perpendicular setscrew.  Could've done a bunch of work, but the gun's firing cycle was so harsh, and with the end result unknown, I couldn't find the motivation to spend the hours doing the machining.  The fastest, easiest way to see if this idea would work would be a simple reducing sleeve bonded into place.  I've done this very same fix in the past on a Haenel 303-Super.

Turned a piece of brass to 0.160" then drilled a 0.135" hole down the center.

Leaving a very thin walled sleeve.

Mixed up some quick setting JB epoxy...

and pressed the sleeve in just below flush.

I know.  Not much to it.

No protrusion to catch on the edge of the base block.

While it was apart, I removed the main pivot's locking bolt. 

And found a replacement socket head cap screw.  Just taking it to length.

Also reduced the head's diameter by a couple thou.  Here it is re-blued.

And installed.  Well, the pivot bolt looks a bit ragged.  Might need to turn a new one at some point.

The sleeve is a success!  The noise is gone and the rifle is producing just over 28 foot pounds with H&N Baracuda Hunter X-Treme pellets(670 fps).   H&N wadcutters are moving out at 740 fps. We'll call this a victory for the moment.  The gun still has a pile of recoil no doubt due to the sheer weight of the huge mainspring and the heavy walled piston.  Reducing the piston weight may just be on the list. 

Friday, July 18, 2014

Early Sheridan Model C, Part 4

Making the pump cup adapter.DSCF2923I turned down some free machining steel. Made it long in case I screwed up. Drilled it out a bit.DSCF2927Bored to the minor diameter.DSCF2929 Had “fun” boring it out so it would have a lip that retained the pump cup. The tool has to cut on three sides which means that it doesn’t cut that well.DSCF2933
But the pump cup snaps in!  DSCF2938Some chatter marks. I’m not perfect.  DSCF2939Parting to length. I placed the old metal cup in the picture to show that the new part isn’t that much longer. DSCF2943
Getting it to run true.  DSCF2947Drilling. I didn’t want to break through into the cup chamber. DSCF2949
Tapping 1/4”-28 tpi. DSCF2951Definitely enough threads. DSCF2954Done.  DSCF2958 Came out well in my opinion. Next comes cleaning all the mechanical bits and reassembling, which is straightforward (I hope). Then some quick stock refinishing.

Thursday, July 17, 2014

Early Sheridan Model C, Part 3

On I go…DSCF2876One pin for the trigger assembly. DSCF2877This shows two springs, a heavier one for the trigger and a lighter one for the safety. Good to note so they don’t get swapped. DSCF2878The safety spring slips into a recess in the top. DSCF2880 Trigger parts.DSCF2881The safety pin is staked in and there is no reason to remove the safety. DSCF2884I would love to see the fixture that holds the end cap and stakes the pin in place. DSCF2887Three screws, the bottom one is a flat head. DSCF2889Hammer, spring guide pin, hammer spring, end cap. DSCF2896Removed the valve bits with a standard valve tool and puller. Notice the conical exhaust valve spring.  DSCF2897Interestingly the current replacement valve is the same length, while both are shorter than those used on interim models that have a pressed in pin to lengthen the valve stem. DSCF2900But the boss on the end is larger on the replacement… DSCF2901And will not fit in the end of the exhaust valve spring. DSCF2904So I decided to take a bit off, hoping that there was enough material. DSCF2905And it appears there was. DSCF2907I dug out the other lead seal – on later models a rubber seal is used for the forward seal.  DSCF2909The trigger guard needs removing. DSCF2911An offset screwdriver does the trick. DSCF2914Will have to clean it up a bit. DSCF2915Interesting dings in the pump rod linkage. DSCF2918Lots of adjustment left, so I should be fine making a pump cup adapter. DSCF2921Preliminary sketches and measurements.
So now I need to make the cup adapter, clean all the parts and refinish the stock. Should take a while.

Early Sheridan Model C, Part 2

On I go…DSCF2829Two roll pins removed.  DSCF2832 Nice square rubber bumper in the forearm slot.DSCF2834 Odd dings on the pump lever. Note the flat spring down in the slot.DSCF2835Formed bushing. DSCF2836It’s always risky when pushing the roll pins out of the forearm, especially when they have complex grain as this one did. countersinking the hole edge can help, but it’s no guarantee. In this case it popped a small chip out. Not a disaster, it will be barely noticeable when glued back in and refinished.  DSCF2838 A small piece of rubber behind the square bumper…DSCF2840 DSCF2841 I just find it interesting. An afterthought at the factory or did a previous owner jam a scrap of rubber into the forearm?DSCF2843 The linkage is color case hardened.DSCF2845 Cam plate and screws. One screw has started to strip.DSCF2847 The bolt, notice the lack of an o-ring groove. It uses a metal-to-metal conical seal, like the old Crosmans.DSCF2851 Pump rod & cup.DSCF2852 It was oiled by the previous owner, but did not respond, being hard as a rock.DSCF2853 An adjustable rod at both ends, unlike the current pump rod.DSCF2856 Digging out the old pump cup.DSCF2866 A pile of rubber. I believe the old cups were molded in the part, not separate.DSCF2868 A new pump cup does not fit the old part. Will have to make an adapter.DSCF2871 The end cap is held by screws.DSCF2873 Three screws, one under the sear/trigger.DSCF2874 Detail of the safety.DSCF2875Somewhat interesting.

More to come…