Does anyone have experience of converting the 1077 into a .22 or even .25 calibre (I guess we are talking barrel mods, magazine mods & possibly valve mods) ?

I know that in spring guns, if you take a .177 gun & fit the equivalent .22 barrel to it the power tends to increase (here in the UK this is one trick the teenagers, fruit loops, etc use to push an air rifle over the legal limit.

I ask about a larger calibre, as I think the 1077 would make a great ratting rifle, but It would need a wee bit more than 7 ft lbs of energy to ensure humane kills.

The larger slug & more efficient operation would go a good way into turning this lovely little rifle into a real specialist pest control tool.

Does anyone know if Crosman's .22 rotary magazines would fit the into 1077 ?

Cheers,

Matt W

Howdy Matt , im new to the 1077 so cant help with Mods , i cant think how fitting a .22 barrel to a .177 is going to increase power ? Its going to decrease power id have thought.
Putting a .177 barrel on a .22 would increase power to my thinking , id be interested to know more as it defies my understanding of physics...which admittingly isnt great.

Matt,

To get more CO2 flowing through, there's a couple of things you can do.

Cut a couple of coils off the hammer spring to get it to strike the valve a little harder...theory is that the valve will stay open a tiny bit longer, allowing for more CO2 to flow through. This will make the trigger pull a little harder since the action is actually a double action.

Add a piece of lead weight (fishing weights will do nicely) to the back of the valve. The idea is again to get the hammer to strike the valve harder.

Remove the magazine clip and look at the nose of the valve, opposite the barrel. Is it grey or black. The black ones are the full power valve. The grey ones are the de-tuned valves sent to countries where they have power restriction on airguns. Let me know if you have a grey one, I can write up how to mod it to get it back to full power....alternatively, I have a post here somewhere listing what to do to those grey valve detents.

As for the barrel, I think a barrel for the Crosman 2200 will fit. I don't have one on hand to measure barrel OD. what's missing from that barrel is the groove for the barrel latch (black plastic wings on the barrel...you move it when you need to clear jams). If you have a lathe, no problem, otherwise, a machine shop or maybe a gunsmith should be able to make that groove for you.

The one thing I haven't been able to come up with a solution for is the round magazine. I don't know of any .22 cal magazine in that size that can be substituted. Compound that with the problem that you have to re-index the clip for the new calibre, and we have a show stopper. I don't have an answer for this one.

Good luck. Post if you find a solution for the clip issue.

Matt, the other thing you could do to get more CO2 to propell a larger pellet is to lighten the valve spring. I'm not a valve modder so I can't say how light you'd need. If I had to guess, 1, maybe 2 coils off the valve spring. But I wouldn't try it without a replacement spring within easy reach.

Keep in mind that all the mods is a balance between how much CO2 you want flowing thru the valve, and how much CO2 efficiently expands in the barrel. Too much CO2 and too short of a barrel and the CO2 is just wasted...would make a nice loud bang though.

Hi Four Eyes,

Thanks for the info. The good news is the valve on the gun is black, so that I believe is the unrestricted one (I am in the UK).

I will try the hammer mods before even thinking about touching the valve.

Do you know how much power a well mod'd 1077 will produce ? Our legal limit is 12 ft lbs of energy (Velocity = approx 800 FPS *). I don't need this much (I have a .22 Theoben for when I need more power).

I think a stock 1077 at 20 celsius temperature gives about 7 ft lbs of energy (Velocity = approx 625 FPS*).

I am looking for approx 9-10 ft lbs energy which equates to approx 700-750 FPS*.

* based upon an 8 grain pellet.

Would the hammer mods + 35 Celsius C02 capsules get me close to this mark. Someone told me a good trick when out shooting a 1077 is to take a small Thermos Food Flask & fill it with a few C02 capsules, then add 35 Celsius water to the flask. The capsules will stay warm for 6+ hrs.

Because of its weight, size & 12 shot capacity I would like to take it Rat Hunting around barns, but would want the confidence that the power was high enough to ensure clean kills at approx 15 yards.

What are your thoughts on this ?

Have a great weekend,

Mattw975

Hi Matt,

I'm not a valve modder either. It's the last thing I like to open up in any of my guns, if I ever do. I had a heck of a time trying to fix a leaky valve from a Crosman 357, I gave up and just orered a new one.

Anyways, back to the 1077. After opening up the hole in my grey valve detent to be the same as the black ones, my chrony shows that my 1077 is doing around 610's fps with the 7.4 grain pellets. Everything else on my gun is bone stock.

I haven't tried adding the hammer weight yet, so I can't say how much more power it will add. Adding weight to the hammer, and shortening the hammer spring, I'm thinking 650 fps at best (and that's being optomistic). Dumping more CO2 past that (lighter valve spring??) with the stock barrel and you'll start to see droplets of liquid CO2 coming out of the muzzle.

To bring it up to 700-750 mark (with 8 grain pellets), I think you'll need a longer barrel. The Crosman 2100 is the only other gun I know of that uses the same soda straw barrel as the 1077 (same circa), but IIRC they're about the same length.

At 15 yards, 600-650 fps, using pointed pellets, you should be able to take out rats with head shots.

Good hunting.

A word of caution to anyone wanting to cut the hammer spring. It will add additional strain on the little plastic nub on the receiver (where the spring is anchored to) so be careful. Too much strain and that nub could break off. Also, cutting the hammer spring will add to the trigger pull.

possibly increasing the hammer by preloading it would work, I'd be careful with this, but I'm not really too familiar with the strength of the 1077 compared to the 13xx and 22xx guns.

But the real point here is the goal- rats at 15meters. For that I might suggest testing out kodiaks in the 10.6 gram range. I don't think you'll have enough power to push eunjin 16.1 gram ammo all that well.

Of course, I could be completely wrong and at the power range mentioned gamo armor PBA might blow rat guts out the other side!

I have 3 squirrel at ~10m with a springer that gets 590 using gamo master points. So it doesn't look impossible.