Crosman "Big Bore" 760 BYOB Gun (Bring your own bottle)

[Tack Driver 10]

The trigger has a lot of creep and quite frankly, It was.....creeping me out....LOL
Previously I cut the bar on the trigger back to .100" so the gun can be decocked.

To reduce the creep made a 5/32" bushing that fits over the bar and pulls the sear off the hammer.
Should cut the creep down to an acceptable level while still being safe.

[Tack Driver 10]

Didn't get a chance to shoot the 760 BYOB gun today.

So to keep myself entertained converted my 760 Plastic Fantastic to HPA.
I've had this gun since the mid 80s and it was OK at the time.

The bolt would fly back when pumped for high power.
Used a bolt body from a V5 760 and notched the receiver, problem solved.
Also swapped the plastic breech for the cast metal type, drilled and tapped it for 6-32 screws.
The valve is similar to the BYOB gun with an external spring on a Delrin stem.
Pumped it to 1600 psi, should get a chance to chrony test it this weekend.
Weighs in at a feathery 3.5 pounds.
Here it is along with the BYOB gun for comparison.
This bad boy is too cool for school....LOL

[Tack Driver 10]

Time to road test the 760 Plastic Fantastic PCP.
Charged the 90 gram spent CO2 bottle to 2000 psi.
With a stock 30 gram hammer, 2100 spring, 18" smooth bore barrel:

7.9 CPHPs
1003 FPS 17.64 FPE

10.65 Barracuda Match
933 FPS 20.58 FPE

The 30 gram hammer and 2100 spring was too much so......
Installed a 12 gram hammer with a lighter 2400 spring.

7.9 CPHPs
853 FPS 12.76 FPE
846 FPS
852 FPS
844 FPS
840 FPS 12.38 FPE
850 FPS

10.65 Barracuda Match
742 FPS
745 FPS 13.12 FPE

Looks like a great config for this gun.
Using about 20 psi per shot and making good power.
Gun has iron sights and a smooth bore barrel.
Took a few shots at a can at 20 yards, seems pretty accurate.
More testing to follow.

[Tack Driver 10]

When I assembled the 760 Plastic Fantastic PCP I cut a few corners.
I used a metal breech but left it stock in order to "get er done".
I modified the breech by drilling it 1/4" and used a Delrin TP at .157" vs the stock .140".
Also made a new probe since the one I was using wasn't sealing good.
Velocity increased 60 FPS about the same as a hot 2100 pumped 15 times.

Bottle pressure 1900 psi

07.9 CPHPs
918 FPS 14.78 FPE
911 FPS

10.65 Barracuda Match
795 FPS 14.94 FPE

[JuryRigger]

Some cool stuff here; following along. 
Jesse

[Tack Driver 10]

Continuing on with the 760 Plastic Fantastic:
Put a scope on the gun to test accuracy.

The original barrel was a smooth bore, not going there.
The barrel I put on the gun is a 760 rifled barrel from another gun.
It has the 3 sight screws drilled into and through the rifling.
The rifling was almost non existing probably had a lot of BBs through it....LOL
Wasn't accurate (no surprise) so prepped a 1760 barrel and installed it.

Shots taken benched at 13 yards.
The upper LH orange target is sight in.
The upper RH orange target is 5 shots with 7.9 CPHPs.
The center orange target is 10 shots with H&N FTT, 4.52 head
The lower LH orange target is H&N Barracuda Match, 4.50 head

Looks like the H&N pellets did best.
Need to stretch out the distance but very pleased with the accuracy at this point.
An LW barrel on this gun would really improve the accuracy.