Sunday, March 26, 2017

An Adjustable QB Recoil Pad Part One

Looking at the modified QB rifle,  I noticed it would be relatively easy to make a new pad spacer that both adds length to the "kinda short-for-me" stock and makes the existing butt pad adjustable at the same time.

Here's the hodgepodge extended gas tube QB77 action in a AR2078A stock.  

The white line spacer and recoil pad aren't especially well fit at the factory.  Suppose that's about par given the cost of the rifle, but it looks pretty bad up close.

A "normal" recoil pad like a Pachmayr, is ground to fit the stock and has hidden mounting screws that are buried in the rubber.  The QB pad has two holes for ready access to the mounting screws and a metal plate molded into the base.  The pad design actually lends itself to this modification.

Pad and white spacer removed.

I splurged and spent $6 in 1/2' thick UHMW black plastic for the new "base plate".

 Cut a piece on the bandsaw about 1-7/8" wide.

Yep.  Almost done. 

Fly cut the edges to clean it up.  Makes it easier to clamp in the vise.

Measured the width.

Marked the center.

Got out the transfer punches.

Centered the recoil pad's holes on the scribed center line,

and spotted the hole locations with the transfer punch.

Drilled clearance holes in the spacer for mounting screws.  These are the holes to secure the plate to the stock.

Milled a 7/32" slot down the center.  This slot is clearance for the shank of the key seat cutter in the next step.

Here's the cutter for that next step.  

Took several passes back and forth to make, size and clean up this slot.  I've no experience machining plastic.  None.  The plastic wants to melt, make strings and gum up the track.  I don't know exactly what I expected, but it didn't go quick and easy.  This track will allow the recoil pad to be adjusted vertically.

Eventually, it was clean enough to fit a 1/2" wide, 1/8' thick piece of steel.  Used a parallel to test the slot clean up.   I'll countersink the clearance holes in the base plate and use flat heads to mount to the rifle stock.  The stock mounting screws will need to be slightly below the bottom of the slot.

Milled a piece of mild steel to size and deburred all the edges. 


 Again, marked the center line and the holes.  

Spotted, drilled, tapped the holes.  The rifle is made in China, everything is metric.  Went with M5x0.8mm threads.

Plate is done and slides in the t-slot track with no slop.


Steel plate is fit to the recoil pad.

Sized the pad mounting bolts.

Next, the base plate will be cut and ground to fit the rifle stock. 

Thanks for reading.  I'll post more in a few days.

Saturday, March 18, 2017

Flag City Toys that Shoot 2017 is Coming

It's almost that time again!

Toys that Shoot Airgun Show in Findlay, Ohio
Saturday, April 8th.   

Check their website for full details 


Wednesday, March 1, 2017

Crosman Model 357 (Phase 1) Disassembly, Part 2

On I go…
The cylinder plate pops off.
Nothing special about the valve tube.
My valve tool may need some refurbishing…IMG_6259IMG_6262
Crosman uses quad seals here. These seem pliable and will be reused.IMG_6264
The #38-128 end seal is deformed and clearly not up to the task anymore. Luckily I had a few spares on hand.
The guts.
The #38-130 o-ring has given up the ghost. I replaced it with a 009 viton o-ring. Urethane would be better.
Not wanting to place an order for parts or spend more time making a seal than the gun is worth, I flipped the #357-041 valve seal over. It was still pliable. It had a scratch in the face that could have made the gun leak.
The gun went back together without a hitch, I suppose it’s possible that the latch support could shift, but it seems to lock up fine without play. It’s held gas for 5 days and shoots as accurately as one would hope. I didn’t chrony it because of general laziness.