All Springer/NP/PCP Air Gun Discussion General > Show Off Your Air Guns With Mods (SHOW and TELL)

45 caliber Big Bird Big Bore Build

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--- Quote from: Rob M on December 29, 2021, 07:14:31 PM ---is that 10.7 ounce hammer ?? sweet

--- End quote ---
The handle will add a little too.

The end cap came out really good somehow they ended up 12 and 6 with the 2 screws tapped for 10-32.  I add some spacers between it and the spring.  I think my plan is to check the force of the 700 spring and probably proceed with a double spring that would incorporate a compression spring guide (plunger) threaded into the end of the cut off 1/4" spring guide.  I'd have to create a fixed 700 spring stop ahead of the compression spring guide.

In other words, the existing spring can be compressed in preload enough to incorporate a pinned spring stop and there would be an attachment on the 1/4" spring guide on the other side of the stop. That compresses another full diameter spring into the end cap.  It already works great in my head.

Cocking handle
I still have a few SHCS left over from the Winchester Restore heydays.  They liquidated the rest probably due to covid.  I don't know how you can send these to be melted for cash as they do serve a purpose.  This is not their intended purpose but they are the right size. 

The more threads the better however I have a great set of 5/16"-24 (bottom, plug, die pictured in next pic) from my fine friends at

Solenberger's True Value Hardware

These were being clearanced out for like $3 a piece.  These guys keep all the GR 8 or 12 SHCS in stock so you can run your hands through them and come home with that unique industrial smell when you wipe them all over your clean pants.  Sorry for the plug (I get no special discount).

This will probably get recontoured at some point.

So here I pushed the hammer all the way up to the valve face and drilled.  This way I found the best place for the end of the slot.

The taps.

Since I estimated the threading on the handle I just drilled, tapped then drilled again.  Not the best estimation or technique but I was centered perfectly here to be able to do it correctly on the second drill.

This was the first drilling before the re-drilling.  All the thread goes in now, hopefully making it a little more secure.

Oh I can go on for days on ‘heat treating’.

Kasenit is a surface hardening treatment that works excellent for a lot of applications. I’ve used it a lot.  Potassium ferrocyanide works equally as well. No it won’t kill ya.

Drill rod and drill bits are different materials. Ashes work better than sand for annealing although still may be too fast for small thickness material. Depends if it’s an oil, air or water quencher.

Have to add, dry powder cement works too. Not as well as ashes though.

Still, excellent stuff you are doing here. You are learning so much by doing here and thanks again for sharing.


Video below shows laser honing the breech to the tube that I did earlier.  I put a laser bore sighting device (attached to a battery pack for longer use) on the barrel and then used several different sized round tubes and sand papers to sand down a grove in the breech.  I looked straight down the tube for the laser to keep it in the center or 12 o'clock.

I may have honed it to exactly at the laser which would be really aiming down but centered.  Not sure how this will affect anything but at least it is centered along that plane.

This process should help any wandering drill bit holes as the screws will pull it down to the grove and still provide lateral stability.

BTW, you cannot do this with computers... only the force.

Brilliant idea with the laser there-will have to remember that!
Lots of ways to reconstruct it to do other things... Hmmm...
Can't wait to see this beast finished-very good work  :D

Made a shallow groove to file against.  Hopefully this will lend to a straight perpendicular line.

Tried the groove like this and the sear cleared fine but didnt look asthetically pleasing to the eye.

Used end mill then a couple grinding stones.

It didn't need this much relief for the sear..

Angles seem about right.  Sear slot isn't as deep as I imagined but you can't add it back.

Seems to line up.

So I attached the trigger and "shot" it without a valve or anything to take the force. The spring had the max preload. It peened the wall with the handle.  I didn't notice until later.  I was testing the sear and hammer engagement and it looks like the sear mark seems about right.  I do need to polish the surfaces at some point.

This video was before I added the preload.  With the preload the trigger pull is pretty heavy unless you pull toward the end of the brass.  However I think it should work.


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