QB79 tank block improvement

[wll2506]

Thanks Bob,
We'll have to label this as THE Tank Block Fix

Looking at the two tank block pictures above, we can see that this needs to be a pretty precise hole.
And this needs to be drilled with the block in the gun under slight pressure.  So a good fix, but this needs to be a well planned drill job .  Not too far right, left or low - maybe right on center of a whisker high.

This is quite obvious this is not a job for me... if I had ten of these blocks I might be able to get one right.. I would take Bobs advice. drill the hole in the tube first and then work backwards by taking a little of the front end at a time. The 79 tank is in very much need of re-design !

wll

[rsterne]

That advice (drill first, shorten the tube to fit) was for installing a block in a shortened QB78 tube using the original holes.... The spring pin idea is for making a QB79 safer....

Bob

[Buldawg76]

Hey mackeral5,
Where can I find this Alchemy?  For only $6 it could be worth it .

Kirk
The best bet for a rear cap for the crosmans is to call crosman themselves at 1-800-724-7486 and ask for part sales and you can get a disco end cap that already has a threaded hole for the adjuster screw in it with threaded holes to hold the cap in the tube or one for a 2240 that has the threaded holes to hold it in the tube but no hole threaded for the adjuster so you can thread to the screw size of your choice.
The disco end cap is part number 1761-012 and the 2240 cap is 2250-004. If you call then any parts ordered are a flat rate 4 bucks shipping so the end cap with shipping should be less than ten bucks total. The threaded hole in the end cap of the disco cap is not for an RVA it is for a degassing tool which is just a long threaded screw that pushes on the hammer to open the valve in case of overfilling and creating valve lock but can be used to install a screw as a RVA. I don't remember the thread off hand but I believe its 10-40 or a fine thread close to that size but is not an oddball thread so any local hardware will have the right thread screw. Its way cheaper than Alchemy and shipping is less than a week.

Mike

[cclingma]

Took a stab at one using the recessed socket head screw method.  I drilled a third hole through tube and block with a few hundred PSI on system as recommended for alignment.  Tapped hole 10-32 and drilled tube 5/16" to recess screw head.  Hit all three with no need to enlarge holes.  This rig gets a Ninja SHP 13ci tank left at the factory 1100psi.  I went and got hardened socket head cap screws for the block after taking picture.

Now the questions,
This block is one I ran on a converted QB78 for a while so it had a through hole drilled for a pin.  I didn't want to pin this setup and therefore drilled for 10-32 SHCS.  Also, this a Crosman tube which I've learned from Mr Rsterne is slightly thicker wall.  Look okay?

[Buldawg76]

That tank block looks good with the hardened screw being installed but as Bob has stated a spring steel poll pin in the hole you already have in the block would make it far above the 3.5 to 1 safety margin.

The thicker tube will increase the strength as well.

Mike