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

Yet another parts airgun build.


While doing some maintenance and repairs on my pumper airguns, I realized I had quite a few spare parts, enough to build an almost complete air rifle.

I found I had a pretty good Crosman 766 straw barrel, it has 19'' of rifling starting at the front TP edge. I polished the lead-in and re-crowned it. I made a 1/2'' mild steel shroud for it, along with a front barrel support bushing. I also made a steel pump arm pivot block, that also supports the shroud. I shortened a spare receiver 8-32 screw to hold the shroud. That makes a clean, ''factory'' look 8) . Front and rear sights from a Crosman 760 5th variant (late 70s) are used, and fits like a glove. I found a clean 6-32 screw in my parts bin, just had to turn down the head OD a bit. I still have to cold-blue the parts.

The Cr 760 also gave the metal receiver in very nice condition, trigger group (steel trigger blade  :D ), breech/barrel support and bolt. The bolt will eventually be modified with an Oring and free-flow tip.

A defunct M4-177 rifle provided the pump tube, hammer/spring/guide, de-tuned valve and plastic cup piston and pump arm assy. The rear bottom edge of the aluminum valve was crushed by the boss in the receiver tube, as is often the case. There was at least 0.025'' of compressed material, so pumping efficiency would suffer if I left it like that. I repaired it by making a hardened steel ring 0.100'' thick, shaved 0.100'' off the back of the valve, and pressed the ring onto the back of the valve, creating a new rock-solid ''seat'' for the boss.

I'll be using a hardened steel pivot pin instead of the OEM roll pin, and am thinking about nickel/silver soldering a steel pivot bushing into the pump arm.

I also have made wood blanks for the butt stock and forearm. I don't have an original stock to go with the receiver, and no stock forearm fits with a 760 receiver/ M4-177 tube, so I need to make my own. I'll be using maple from scavenged pallet wood. The wood actually has a pretty nice figuring in it, but is straight enough to have good strength. I'd like this airgun to have a ''slim look'' to it, so the forearm won't be a fatty. Instead I'd like something kinda like the 766/2100/AM77 forearm, sleek and nicely sculpted. Just can't wait to get into that :) .

This is where I'm at into the project, hope you like the view 8) :D.

Very nice ... Done parts & pieces builds a few times myself.

Thanks Scott! Yeah I guess you know that road pretty well :D.

Today I finished making and cold bluing the steel parts. I made a hardened steel pivot pin for the pump arm, it uses an E-clip to stay in place, will be better than the stock roll pin. The action is now ready to be put back together. Next is the wood stock.

I just did the very first chrony test of this de-tuned-for-Canada rifle. It's shooting better than I expected, I guess I did my re-seal job well. I was expecting velocities in the 425-430s, but was pleasantly surprised. Also results are a bit odd, the lighter 7 grains RWS Hobby pellets are flying slower than the Crosman Premier Match 7.9 grains wadcutters, but they do fit tighter in the barrel bore. Also they're much more consistent in shot-to-shot velocity, very curious to see what this will give when I'll shoot some targets.

Here are the shot strings:

Crosman Premier Match wadcutter 7.9 grains pellets, @ ten pumps:
1- 445 fps
2- 452
3- 470
4- 452
5- 472
6- 463
7- 470
8- 468
9- 464
10- 477
Avg: 463.3 fps

RWS Hobby 7 grains wadcutter pellets, @ ten pumps:
1- 448 fps
2- 445
3- 444
4- 445
5- 453
6- 454
7- 454
8- 454
9- 448
10- 452
Avg: 449.7 fps

Will need to test more pellets and check accuracy, but so far I'm pleased with the results 8).  Now getting into the longest phase of the job: wood work. I must tame my impatience LOL!


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