Just re-entering the game

[Boolseye]

Had an air gun as a kid, a Crosman .22 as I recall-that's long gone, but I picked up a nice 760 recently and have been plinking cans feverishly, and a few pellets (also have a Blue Streak .20 cal, but dad's holding onto it). Anyway-kind of surprised at how well made this thing is, and thought I'd throw it out there in case anyone has any suggestions for mods or upgrades that are commonly done.


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[Multigunner]

If that's one of the versions with smooth bore barrel first mod you should consider is switching it out for a rifled barrel. I used a barrel made for the Crosman M4 177 rifle which uses identical power plant.

The barrel costs $9.95 the plastic barrel support which is a necessary item cost $1, shipping was $4. My package got here in three days, much faster than I thought possible.

Yours has very different iron sights than mine, My sights were welded on. If those sights can be removed without damaging them they should fit on the M4 177 barrel. If not mount a cheap 4x15 scope till you find the iron sights you like. I can't see mounting a scope any more bulky than that on the plastic receiver.

The barrel number is Mk177-010, the barrel support number is 760E125. Notice the barrel support still bears the 760 designation.

The M4177 barrel is a bit over 16 inches, about two inches shorter than the 760 barrel. I'd prefer a much longer barrel but this barrel works out just fine at this length.

I cut a fresh crown on mine before doing any serious shooting. The factory crown was ragged looking. Accuracy is great, much better than I'd expected. One hole groups at 25 yards are common.
Others don't seem to be getting that high level of accuracy so I'm pretty sure that the ragged factory crown is a common problem, but one easily addressed.

I just used a small grinding ball tip on my Dremel tool set on its lowest speed. A concave crown has always worked well on my cartridge firearms and works fine for air guns as well.

You might want to make some sort of spacer for the butt stock. I mounted a wooden adult sized butt stock salvaged from another air rifle.

I'd like to find a tutorial on improving the trigger pull which is the only real draw back of these little rifles. The trigger pull was designed to be very long to avoid AD's, product liability issue when marketing a fairly powerful air gun targeted for children rather than adults. Its almost like firing a double action revolver. The 760 trigger pull reminds me of the trigger pull of the Crosman 10/77 which is a DAO action.

[Boolseye]

Great, that's a lot of very helpful info, thanks.
Trigger pull on this not bad, maybe 9-10 lbs, but smooth. Fairly clean break, actually!
I was impressed with the thought that went into the engineering–pretty accurate with pellets, BBs minute of pie plate at 50 feet. I'll check to see whether it's rifled. Stock is short, but very little recoil


Where do you get your parts?

[Multigunner]

"Where do you get your parts? "

I ordered straight from Crosman. They don't sell parts online you have to order by phone.

The toll free number is 1-800-724-7486 .

They usually only charge the minimum for shipping , $4.

The plastic barrel support must be carefully pressed or tapped on with a mallet. Once on there's no way to remove it without destroying it.
If you can remove your old front sight the barrel can be drawn backwards through the barrel band without cutting away the old support.
There's a indexing nib on the barrel support that wasn't on the original part in my rifle so I had to trim that off before it would fit. Later models like yours may need that nib intact.

[Boolseye]

OK, thanks much.

[Black Beard]

Modifying is fun but it might be less hassle to just get something better. Like an Hatsan springer (if you get a Hatsan, make sure it is a model with a quatro trigger).If you put on a rifled barrel, don't use steel BBs, they will ruin the barrel.Instant upgrade would be a scope. Something like a 4x32 or 2-7x32 would work well with low mounts. Preferably with a mil dot reticule.

[Boolseye]

The barrel doesn't look smooth bore, but there are what appear to be lands and grooves with no twist. It shoots pellets quite accurately.

[Black Beard]

Mine looks the same as yours and has a smooth barrel. There are marks parallel with the barrel which might be from a reamer. If it shoots well, that is all you need.

[Multigunner]

The smoothbore 760 does often shoot pellets with more accuracy than you'd expect, but no where near the accuracy of the same gun with a rifled bore.
Most air rifle pellets have a shape that gives a measure of aerodynamic stability, something like the Foster slug from a shotgun bore.

The smoothbore barrel I replaced had at first looked to have very faint rifling, but this was an optical illusion.

With the rifled barrel, and properly cut crown, the 760 is now capable of one hole groups at 25 yards. Not quite as accurate as my Daisy 880, but that's mainly because the 880 has other qualities that make it much easier to shoot with precision.

I've killed very large rats with the 760 using only BBs. Fully pumped up it will drive a steel BBs completely through the body of a rat at close range.

[Boolseye]

what's the max pumps on these things? And any idea what fps should be w/ pellets and/or BBs?

[Multigunner]

"what's the max pumps on these things? And any idea what fps should be w/ pellets and/or BBs? "
I never go above twelve pumps with the 760 and only then if I'm using 10.5 gr Gamo pellets.
I'd stick to ten pumps or less for 7.4 pellets. I found that theres little difference in impact of a 7.4 gr pellet at 8 pumps compared to ten. No need to over stress the valve for little return in performance.
If a pump up gun has a weak hammer spring it won't exhaust all the air if the chamber has too much pressure.

Twelve pumps seems suited to the 10.5 gr pellets but the Gamo 10.5 pellet I'm using is not as accurate as the Crosman 7.4.
These Gamo pellets often have out of the round rims.
Visible effects of the Impact of the 10.5 rivals that of the .22 14.3 fired from my other guns at similar velocities. Impact and penetration on steel cans nested one inside the other is far greater that with the 7.4. Best pellet for close range execution of vermin but not very accurate.

I hope to be able to chronograh this and my other air and CO2 guns pretty soon. I don't have a chrono but a friend has promised to bring his over so we can determine the velocities from each of my guns.

I don't intend to use any BBs in the rifled barrel. From the smooth bore six pumps seemed as good as any for plinking. For close range execution of pests ten does very nicely.

[Boolseye]

Great info, thanks m.g.

OK, just chronoed. I can't quite break 500 fps-BB at 10 pumps was 485. 7.5 gr. pellet at 12 pumps was 490.


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[Multigunner]

If your rifle has a weak hammer spring pumping more than ten times can actually lower your velocity. If the pressure in the chamber is too high in relation to strength of the striker then not all the air will escape, at least before the pellet leaves the muzzle.
You might try a stronger spring.

I'm pretty sure I'm getting better than 500 FPS with the 7.4 even at ten strokes.

BTW
Tried out some of a dwindling cache of Beeman coated wadcutters today while fine tuning my scope. Each of 3 three shot groups was a one holer.
The Beeman coated wadcutter has been extremely accurate in every .177 gun I've tried them in.
local stores don't seem to carry them anymore, so I'm going to order as many tins as I can.

PS
If your pump piston is a bit dry try a few drops of ATF transmission fluid. The brand I used has stop leak in it. Its greatly improved compression in all my older guns while at the same time making them easier to pump up. Plenty of resistance but not from friction. It reconditions the O-rings and the quad seal of the transfer tube as well.

Also if the gun was fired much before you got it clean the bore with a swab soaked with lighter fluid and a 177 bore brush. A pull through can be made from a sturdy but slender cord, or as some prefer a length of weed eater string.
I use the thick waxed thread I use for leatherwork. I also have a .177 one piece cleaning rod I found at Walmart years ago.

Airguns don't produce powder fouling but lead dust and residue from oils can gum up a bore. All my pellet guns shoot much better since I started cleaning the bores more often.

[Boolseye]

Thanks again. I'll keep at it. I'm getting a lot more trigger time since I dusted this think off, which has made a big difference in all my shooting. A teardown and a few upgrades at some point may happen, in the meantime I'm satisfied to just plink away. all of your suggestions are noted and appreciated.