How could I tune the Fortitude for more power?
My Benjamin Fortitude in .22 cal. is firing CPHP 14.3 gn. pellets at +or - 750 fps.I'd like it to fire @ 900 fps.but I wouldn't even dream that big.If I could get a 40 fps.,or greater increase,I would be happy with that .I tried to use spacers to increase the preload on the hammer spring.I couldn't get any meaningful increase because the added spring compression did not allow the hammer to come back far enough for -the sear to latch.I guess I have shown "SG"to be correct in his U-TUBE video.
Next idea.Can the non - adjustable regulator be moved forward toward the muzzle to allow for more regulated air capacity for each shot?If so,how far would be recommended? Can a threaded rod be screwed into the muzzle end of regulator to move it?Or would a more complete disassembly be needed?How much should I oversize the transfer port to pass the extra air efficiently?I would appreciate any help answering these questions,and any alternative ideas.
Enlarge gauge port with a #33 drill or anything closer to .151" that you have. Or, just buy Magnum Airpower's bypass magnum valve, heavy hammer & spring, +Grade 8 (2) valve screws, (Discovery has 3 valve body screws, Maximus has 2, I don't like that but even with screws, if 26" stock barrel & all other parts a 2700psi fill is best, not higher.)
My 10+ year old first run .177 Discovery just about is dead. It can be fixed, no problem; but I see no need in building a magnum platform on a 10+ yr old rifle. I wanted a Maximus for their 26' barrel. LW's longest commercial barrel is 23.8" not 24" regular people round up. Precise machinist types that want things to work measure to the thousandths and add in interference fits & such, OO grade accuracy. It transitions to small groups. You eliminate variables, you get small groups.
I'm not going to just buy a Maximus. I need to talk to 2 guys that know them better than I do & see if My bling can be transferred over or just used as extra spare parts for .22 I like single shots. I'm just not sure if I want to do what you're trying on the Maximus, or just with a Maximus barrel. I could go hog wild and buy a 28-32" TJ Liner barrel with micro bore. His barrel liners are custom to any length, rifleing, ID, OD limited as they are firearm liners. They are tougher steel than any airgun steel. On a PCP, if you go longer, you make use of the air. Keeping a long 28" barrel steady would need 2 barrel bands at least. On a spring gun, 10" and the swept volume of any normal tube is exhausted. After 10", friction slows springer pills down. In a PCP, timed valves can make the most out of a longer barrel.
Example. Your Maximus rifle should be capable of slinging 14.3's well over 900fps. It's the valve, TP, hammer weight, spring preload, gauge hole needs to be enlarged so valve can breath. So change nothing except barrel length. (The more common thing is opening up & angling the air passages to the right dimensions) If that valve, hammer, etc were all the same but a 32" barrel were on that Maximus and stability of said barrel was sound, no harmonics, swaying, change of impact. It would raise the 700-750fps to 900fps easily as the air would have time to push it faster. General rule of thumb. If a PCP is loud, it is wasting air. If it hits like a hammer and is medium loud, it's getting were it should be. If, (and this CAN be done without any LDC) your PCP slings a .177 or .22 like a Discovery with a TKO on it set on low power but hits like a hammer against a steel plate, 30ftlbs or more, THEN, it is tuned VERY well. See, all these buyers want short, maneuverable rifles for hunting and not banging on things. Give me a 26-32" barrel for any rifle up to .357 & a rifle that doesn't waste much air can be built. Crosman says this Maximus barrel has better rifleing and they went from 24" to 26" on purpose to get more shots/more power. It's really more powerful shots with the same amount of air. Barrel length does wonders.
You though, need to talk with Bill Baldyga of Magnum Airpower and either buy his recommended aftermarket parts or simply open her up yourself, after degassing and porting your gauge block to no more than .156 (I don't have a chart but I think it's 5/32's). Iy you want to do this yourself, I hate how Crosmans are built but I'll send you my ported gauge block and it, is NOT accurate in reading fill pressure. It WILL allow more air to valve though, and not waste it. Porting these things, metering air correctly so you get the most bang for your buck but not going overboard and wasting air is tricky and involves complicated math. It's complicated to me. I just know some basics. They say you gain 10-15fps per inch of barrel you add on a PCP. That's true up until you hit, 23.8", then for every inch you add you start gaining more. Bill's Discoveries are making over 50ftlbs with a 26" barrel & other aftermarket parts but you can gain up to 100fps by just adding2" to a 24" barrel & porting the gauge block. After 24", you start gaining more like 20fps per inch. This is why big bores have literally 3' barrels or longer like on the .72 & 20mm .82 they must have like 48" (4ft) barrels but they are screaming cast slugs out. They are also using Helium and it's got one molecule, not 3 so it provides 30-40% more power at the same pressure as regular HPA (breathing air compressed to 4500psi) and those rifles are not regulated.
I skipped James' post... (sorry man, too long and wandering), sorry if I'm duplicating anything.
Eric, I know ZERO about the reg crosman is using. But, I've never seen one that can't be adjusted or replaced.
Heavier hammer/spring, correct alterations to the TP, other, might yield some gains. Adding some extra plenum space may too. That's all effecting air flow/volume and sounds like some work and experimentation. Remember, if the reg is working correctly, it's limiting air pressure before the TP/hammer/spring even matter. I'd actually start by finding out what you CAN do to adjust the reg and use all the other stuff to fine tune it afterwards if needed. You probably don't need to up the reg much if your going to combine that with a slightly larger plenum and a little more hammer spring.
Gotta wonder who would pay $299 for a regulated gun, and then remove the regulator and add a $180 valve to it?
BTW - of anyone does decide to consider one of these "SS" valve you may want to research the stiction issue they have. Might be OK for a target gun where you cqn just blow off a shot, but absolutely horrible design for a hunting gun. (50-100FPS slower on the first shot)
The Fortitude simple doesn't have enough plenum volume to develop more power. The way Crosman put in the regulator also severely limits your options. The Hammer spring was made specially for the Fortitude: I have a hard time calling it a regulated gun, because with the rate they have on that hammer spring, they are knocking the crap out of the valve, the Valve dwell is probably long enough to where the regulator valve is contributing to shot power.
There are two ways to go about this:
#1: Modify the valve body to allow for more plenum space, space the Regulator as far away from the valve body as possible including modifying the notch in the regulator and modifying or eliminating the manometer.
#2: Drill/ Ream/ Hone the Airtube Valve retainer holes to 0.3125". Replace the stock Valve with a bored-out Disco Valve/Baker Airguns BOSS Valve using 10-32 LHSHCS, make a long airtight spacer to cover the manometer hole, install the regulator and put in a small vent hole in the air tube for the regulator.
It's actually easier to regulate a Disco, IMHO.
I have two Fortitudes, and everytime I look at what was done to get to "work", I shake my head. They achieved their goal, but they didn't achieve it without sacrifice. I actually want to de-rate my guns to 12 Ft-Lbs, and for that, it won't be too bad to do; Dial the regulator down (it looks adjustable) until the velocity gets in the ballpark and probably play with the hammer spring/ hammer spring tension until it's shooting right.
James Dingle,I'm not sure that I understand what you mean by" guage block".Do you mean the block that holds the manometer?Do you think that the through passage for air in that block is too small?
Your idea of changing the barrel for a longer one would have to be late on my list of things because of the expense.I'd love to have an L.W. barrel ,but as you point out ,their length would not help me with my quest for more power.
MulitmediaMan2k6,Please tell me more about the manometer block.
#1 Is it absolutely symmetrical with the guage hole exactly in the middle ?Or is it shorter from the middle of the gauge hole to one end, so that I could turn it around ,end for end, and allow for moving the regulator away from the valve body?
#2 How far are the O-rings from the ends of the manometer block? Could enough metal be removed ,without compromising the O-ring seat,and yet still allow room to move the regulator away from the valve body?
#3 Would you care to outline a basic procedure to tear the air tube down for modifications.? As an all thumbs backyard mechanic with poor eyesight ,I tend to require extra guidance.