New project 5$ Faux 664 pumpmaster

[K.O.]

Yesterday I picked up a July 07 760 for 5 bucks at a yard sale it shot great but was missing the stock. I could not resist, heck just the valve is

that much.

I just finished my 1322 build using the pump assembly from the 664 I picked up so guess what...

I will use the 760 pump to make a short stroke 664 all the parts will interchange...

The 664 straw barrel was rifled but I was having trouble getting it accurate it might have been other factors though. One thing about the straw barrel is that it should be easy to choke, I know I choked the barrel on my 2100 by accident...

only one way to find out...

[K.O.]

modded the valve a touch and of course fit to cup and shimmed and made another probe for the bolt.

no groups yet I think it is shooting low left (windy today) and  no fps testing yet.

Had to drill for one relocated screw, the whole job  did not take long at all.

so here it is the 5$ 764

Could have done it with the 760 receiver(they are exactly the same) they just say 760 or 66 on the outside.

but hey it has a rifled barrel so 66 receiver it is...

[K.O.]

Well it is a shotgun with the scope and its not the barrel.  It is in the design of the 664 in my opinion. It is in the way that the barrel shroud can move around because of the way it connects to the receiver. I will try open sights later they will move with the barrel (on the 760 also).

Fps test

pumps    7.4g    7.9g    10.3g

5            480     460     436
10          613     590     525
15          660     644     565
18          703     667     586
20          715     672     592

so in  my opinion if you turn down a disco barrel or even a 2289 barrel and can get and glue a barrel support on it ,it just might be decently accurate but as it is it flexes and shifts point of aim to much.

I do think the open sights will be better.

[stonykill]

 just get an M4-177 barrel. It is a drop in. M4 Barrel# 417-005 ...Support# 760E-125. Around $11 for both before shipping.

   GTA link is here:
   http://www.gatewaytoairguns.org/GTA/index.php?topic=54178.0

[K.O.]

I looked and the m4 barrel is 17.25" so I would not lose to much fps but this was just a hey I can get it going again type thing.

I think I just might keep my eye out for some salvage 7/16 od tubing and bed the straw barrel in it to stick with a found type vibe plus the

straw barrel is 20.5" and has a bit of an fps edge.

It would also make it easy to do a built in  ldc.

for about a half a second I was tempted to use  the 10.5" 1377 or 1322 barrels that I took off and make a stock a bit like the ones in this thread

http://rabidiga.deviantart.com/art/Attila-760-186949293


But I much prefer more like these and if it had been and older  metal 760 I just might be tempted use some of my Tiger/quilted maple or walnut.

http://www.network54.com/Forum/275684/thread/1263743263/Pics+of+custom+760's


Since it is a newer plastic 760 it will be on the back burner and may get a plain maple or  khaya  stock and pump handles.

these clamshell design guns are ok but I do prefer the 13xx and will be putting my resources mainly to gathering parts for  .177 and .22

2100 pump assembly powered 13xxs.

[K.O.]

I will stuff the piston within a few days hopefully it adds 25-50 fps...

[K.O.]

I put a shim in between the barrel shroud(by the way it has 2 nylon barrel stabilizers in it) and the pump right next to the receiver. It is now a

one holer indoors at 5 yards and I think it will be in good shape at 20 and 30 when the wind calms down and I can test.



I stuffed the piston but I got exactly the same velocities as before.


But

I had not added the wiper (Daisy 853 wiper thinned and doubled)  amazingly that bit of foam ring did the trick and its support of the cup is important!!

pumps    7.4g   7.9g     10.3g
5            500   
10          644    612       550
15          706    662       590
18          725    690       608
20          748   

[K.O.]

I could not get it to calm down quite enough with the scope with low effort methods it would for about 3-5 shots and then wander...

but no wind this morn and it took  five shots to adjust the sights and then I shot the top five shot group. I still hate the front sight but it is useable. 

[K.O.]

just did the finishing touch, rust-oleum bumper and trim paint, you really have to look for the very slight mismatch between the 664 stock and 760 pump arm.


update for fun , now has an MK 177 rifled barrel( exact cross with 760) was able to reuse the barrel support/ breech of the 760 barrel.

so now it is an MK 760/66 I will check accuracy and fps. but the barrel just may be leaving for a 13xx.

If it does I think I will check it out as a dart gun with the 760 barrel...

Point is I think the 66 will do better as Stony suggest with a solid 7/16 barrel

[K.O.]

I think the 66 can work with a straw barrel, I would make a shroud that extended into the receiver (like the 2100)

 and give it barrel stabilizers (like I did the 2100).

[stonykill]

 I forgot about this thread. Over the summer I paid $10 for a 66 and $1 for a 760. Still trying to decide what to do with them.

[K.O.]

If it is the new plastic 66  honestly put a plastic breech and 13xx grip frame on it  If you use a 13xx nose for the valve you can use the front grip frame screw...
the pump tube makes a good 4.2 inch stroke 13xx.(~1.27 ci swept volume)(stock 13xx is 1.05 ci)





If you can get a valve extension made there is room for a .6" longer valve

with a  ~.36 i.d.  you can gain  ~.06 c.i. to add to the about .13 c.i.

I think you could really get the .177 pellets zinging

So you have .19ci for a valve volume to keep at max power or tailor down for less pumping.

pump/valve should build 95 psi per stroke at above swept and valve size.

so just like a  the 13xx efficiency @ 10 pumps is about 95%  ~950 psi,  @ 15 pumps 80-85% and 1150-1200 psi.

take valve size down to .177 ci then you are getting 1230-1300psi at 15 strokes ( 800-825 fps with 7.9g?)   


or forget all that and just cut off .6" of the tube,  drill a few holes grind a bit

and walla it is a 13xx, and you know me I f I can I turn it into a 13xx...

[TheBullsEye]

Can u mix and match 13xx and 760 parts? I have a 13xx in rough shape needing new parts and a fully functional 760 ?

[stonykill]

If it is the new plastic 66  honestly put a plastic breech and 13xx grip frame on it  If you use a 13xx nose for the valve you can use the front grip frame screw...
the pump tube makes a good 4.2 inch stroke 13xx.(~1.27 ci swept volume)(stock 13xx is 1.05 ci)





If you can get a valve extension made there is room for a .6" longer valve

with a  ~.36 i.d.  you can gain  ~.06 c.i. to add to the about .13 c.i.

I think you could really get the .177 pellets zinging

So you have .19ci for a valve volume to keep at max power or tailor down for less pumping.

pump/valve should build 95 psi per stroke at above swept and valve size.

so just like a  the 13xx efficiency @ 10 pumps is about 95%  ~950 psi,  @ 15 pumps 80-85% and 1150-1200 psi.

take valve size down to .177 ci then you are getting 1230-1300psi at 15 strokes ( 800-825 fps with 7.9g?)   


or forget all that and just cut off .6" of the tube,  drill a few holes grind a bit

and walla it is a 13xx, and you know me I f I can I turn it into a 13xx...

  yeah the 66 is a new plastic. The $1 760 is metal. But I have had a plastic 760 since 2000

   Most likely I would do the later, not the former. Parts on hand and such. I do have 13xx plastic breeches in both calibers, but..... oh, yeah, I do have a grip frame. From a 2289. Which is a terrible rusty mess and needs something done with . HHHMMMMMM

[K.O.]

Can u mix and match 13xx and 760 parts? I have a 13xx in rough shape needing new parts and a fully functional 760 ?

I have not put a 760 pump into 13xx yet but I have put a 760 pump no mods straight into the 66... and the above mods to put the 66 into a 13xx.

[rangerfredbob]

The 760 is the same as a 1377 action wise, same valve (minus the front grip screw hole in the valve front), same piston, same pump linkage. If Kirby can switch the parts around from a 66 to a 13XX then a 760 is the same deal...

[K.O.]

http://www.gatewaytoairguns.org/GTA/index.php?topic=64968.0

[TheBullsEye]

Sweet