Easy/inexpensive way to boost fps/fpe on a Discovery

[wabi]

Had about given up on my old Discovery when my air pump failed for the second time. I bought this rifle when the Disco was first introduced, and have had a lot of fun with it, but the supplied air pump has been the source of discontent. When it was new it took a lot of sweat to top off the gun at 2000 psi. The pump got worse as it got older and finally got to the point where it was taking forever to get the gun filled. I bought a re-build kit, installed it, and the pump was more efficient than when it was new. That lasted a couple years before it failed again. I was not in the mood to re-build it again, and was seriously considering just going back to my springers and letting the Disco set in it's box unused, or selling it for anything I could get for it.
Found out yesterday I could get a pump re-build for a very reasonable price (from Sun Optics) and it's on it way to them now. 

Now I'm thinking about trying to get a little more performance from the Discovery.
New to this forum, and I've read a lot of good advice here, so I thought I'd ask - What would be some easy ways to boost the Disco's performance in regard to increasing fps/fpe?

The only experience I have with mods is that I have modded a couple 2240/2250 CO2 guns I have (aftermarket valves & trigger/sear ploishing), but have never even taken the Discovery apart.
What would be simple mods for the Discovery?

[dmeguy]

Change out to 3200 psi valve screws and start playing with different hammer springs to find a hotter tune. These are a drop in replacement, I highly recommend! I would also consider changing out the gauge block for a Prod block to increase airflow to the valve.

[Ribbonstone]

EAsy/Inexpensive?...not sure he was looking for a gut-n-rebuild job, although that would bring up the power to what other small 3K guns can do for a few shots (at least it would once put together, adjusted, tested).

Guess the two questions are:
1. How much power is it getting now/how many good shots?
2. How much power do you want it to get/how many good shots?

[Rob M]

installing a lighter valve spring and drilling out the Transfer port will yield the biggest gains for almost no money since the springs are dirt cheap ( most of us have spare springs laying around)
matter of fact don't even do the TP yet, just the valve spring will be a big gain.. ( if you do the Tp you will also want to do the barrel

[dmeguy]

EAsy/Inexpensive?...not sure he was looking for a gut-n-rebuild job, although that would bring up the power to what other small 3K guns can do for a few shots (at least it would once put together, adjusted, tested).

I guess easy and inexpensive are a little subjective. 


If you really want easy and inexpensive and don't mind a significant drop in shot count, you could just swap for a heavier hammer spring (just a couple $) or better yet a power adjuster ($10 and up).

[Lostcoast]

Easiest and most inexpensive thing would be to get three products from Magnum Airpower: the Compact Power Adjuster, the Magnum hammer spring and the replacement valve screws (so you can fill safely to pressures above 2000 psi). For increasing power while also keeping a good shot count you won't have to go above 2400-2500 psi. Do some playing with these simple parts and see if that takes you where you want to go.

[sawtoothscream]

Personally i didnt see any great results going to 2400 psi on stock discos with just the heavy valve screw mod and heavy hammer springs,  on both discos i worked on.          switched the one back to the stock spring with a RVA filled to 2300   and mine has a heavier hammer spring and no rva also filled to 2300.       

will have to look into the lighter valve spring.       

OP if you plan on going with a m rod trigger on your gun in the future keep in mind the heavier hammer springs can blow the sear apart on them.      My brothers gun with the mag air heavy hammer spring  blew its sear in under 50 shots.       

[wabi]

installing a lighter valve spring and drilling out the Transfer port will yield the biggest gains for almost no money since the springs are dirt cheap ( most of us have spare springs laying around)
matter of fact don't even do the TP yet, just the valve spring will be a big gain.. ( if you do the Tp you will also want to do the barrel

This sounds like something I might try. I don't really want to get into too much as far as mods, just something to give it a little boost in power.
Where could I get a suitable spring?

[dmeguy]

You can probably find one locally. If not, here is one.

[Lostcoast]

If you do a forum search for power mods on the Discovery you will see a number of threads including one I created a few months ago that chronicles a series of simple mods that I did and provides chrony numbers showing their results. It has been a fun and satisfying journey.

[KnifeMaker]

I have litteraly thousands of shots thru mine (maximus) with a valve spring adjuster, Spring from Discos-r-us, valve screws from Magnum air, drilled valve port, tp made from Ice maker line, oblong barrel port, M-Rod trigger and spacer, Huma reg with .25 plenum, and added Challenger hammer to prevent sear breakage.

I don't know how high you want to go, as I am only shooting mine at 880's with Crosman Domes, but can hit over 900 with JSB 18's, (940). ?Well over a grand with the Crosmans if wanted. But would kill accuracy at anything like longer ranges.

Just added an SSG, which gives the Max. more shots at 880 than it got stock at 740's. Woo-Hoo!!!

Yes, adding a Huma reduced the volume of the air tube, but the 2300 psi fill afforded by the Magnum Air screws, along with the SSG, and the gun shoots hotter, and for more shots. A Win-Win In my book!

No where near done. Reg could give a flatter string. Grrrrr!!!

BNM Breech due to arrive Saturday. Double Woo-Hoo!!!


KnifeMaker 

[dmeguy]

BNM Breech due to arrive Saturday. Double Woo-Hoo!!!

Be prepared to take a hit on your speed with the BNM. I love mine but was shocked by how much it affected the speed. If I remember right it dropped about 10%.

[Techie]

Found out yesterday I could get a pump re-build for a very reasonable price (from Sun Optics) and it's on it way to them now.

You can get a better pump than the Benjamin on ebay for around 50 bucks including shipping: http://www.ebay.com/itm/222430868088

[KnifeMaker]

BNM Breech due to arrive Saturday. Double Woo-Hoo!!!

Be prepared to take a hit on your speed with the BNM. I love mine but was shocked by how much it affected the speed. If I remember right it dropped about 10%.

Not to worry! I've got the adjuster backed all the way out, SSG backed a bit, med. Spring from Discos-R-Us, and it is still border line too hot. And the Challenger hammer is still giving a short stroke. Time to take it to the mill, and set the striker pad deep or at least flush. It is at least 3/32" if not more proud of the hammer body right now.

It can afford to lose a little. In fact, thinking of shortening the bbl. a bit. Hate long guns. LOL

Phils speed went up. Odd as the tp is longer, making for more volume to be moved before it sees the pellet. However, my Ice Maker TP is putting out a good puff of air, so it has more in it on L-_O-_W power setting as it is. I can get more fps if needed. 

Knife

[mann]

The biggest gain I found was to remove the disco valve stem get a marauder valve stem go to hobby store for brass tubes find the brass tube that fits over the mrod valve stem cut the tube to length it slides right into the disco valve to busy it for the mrod valve stem . Epoxy in the new bushing and install the mrod valve stem into the disco valve with a lighter valve spring . You can then use the stock hammer spring for the disco with a power adjuster to make alot of power a medium weight spring can get you into the 50 ft lbs are using heavier pellets . Or use the 18 gr. And get over a 1000 fps but that is to fast for 18 gr. Easy mod and cheap to do.

[Lostcoast]

Another thing is to replace the stock gauge port with a large bore gauge port, which allows more air to reach the pellet more efficiently. Made a big difference in my results.

[KnifeMaker]

Thats one thing Crosman did right. They use the MRod type poppet in the Maximus.  Just one thing that doesn't have to be done.

I milled my own gauge block, but once I installed the Huma, had no use for it. 

Knife

[Smokehogan]

Heavier hammer spring and power adjuster.  Beware though, I lost accuracy at farther distances.  I would port my valves but I too have a BNM breech and don't think i can do it.  with the power adjuster cranked full, trigger pull is harder.  Big loud CCCRRRAACCCKKK when it was fully cranked lol.

BNM Breech due to arrive Saturday. Double Woo-Hoo!!!

Be prepared to take a hit on your speed with the BNM. I love mine but was shocked by how much it affected the speed. If I remember right it dropped about 10%.

this happened to me too.

[TF89]

BNM kit for .22 disco, stock disco before conversion, 800 fps chp 14.3, 22 shots @4% using rear spring adjuster.  Now BNM kit, barrel and shroud shortened by 4 inches, ssg, 750fps, using
 same fill 1800 down 1050, get 28-30 shots at 4%.  Disco still stock internals. 

[mann]

I have a bnm breach opened the ports to about .170 used mrod poppet and a lighter spring . Using a medium hammer spring and a power adjuster I'm also regulated to 1800 psi and can get the 18 gr pellets up over 1000 fps using my modded stock valve . Running 850 fps with the 18 gr pellets using stock disco spring and a Challenger hammer