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Tuning RTI Prophet Performance Settings

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I guess the better question is at what velocities different projectiles shoot well out of the 22 long range barrel, which is twisted more slowly.

I sighted in with JSB 15.89's, at 120 bar with hammer spring flush to buttstock (apparently stock setting). That yielded 950 fps and put 10 inside a dime at 30 yards. Lowered to 95 bar and backed off the hammer to get 850 fps, and it isn't quite as accurate, fliers make groups quarter-sized. I will play with it some more, as I'd like to get a setting for light and slow, since it's quiet and efficient.

Next up is what the barrel was designed for - the monster redesign 25.39's. Apparently they like 1040 fps in this barrel, but I will see if I can find some lower nodes as well.
 
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No help from me as I have the 25 High power unit, I am watching you as I may get the barrel kit for the 22 down the road, Mine likes to shoot the 34 gr pellets at 940 FPS running 130 on Reg a thread sticking out on the hammer screw, Backed out the hammer screw about 3/4 turn to get 840 860 FPS out of the 34 gr pellets still super accurate at 48 yards, I am running a Donny Tatsu and just needed to reduce the noise a little and its a LOT less noise at 860 FPS, 

The more you shoot this gun the smoother it gets , 

Oh one more thing, I think its strange it seems the 22 caliber is running a lot higher Reg than the 25, When I got mine it was set at 120 Reg, I been reading the 22 Regs are set at around 160 wow, 

Just thinking out loud, And there is a RTI site on Face book

Mike
 
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My .22 Prophet came from AoA set at about 150 bar, HS in about 2.5 turns, shooting 25.39 pellets @ 984 fps. (by their chrono test)

I ran some test curves at 120, 140, 150 bar. Currently shooting JSB redesigned 25.39 @ 150 bar, HS screw in 1.75 turns from flush, 970 fps. (Max speed at 150 bar was about 988 fps). Pic is from a group of 6 shots into a 2 inch target @ 30 yards. (Naturally, I posted the best one, but really pleased with how consistent it is, and I'm an airgun newbie).



20210410_172315.1619188907.jpg



 
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FYI 80 bar and flush HS with 25.39 Re-designs gives me ~833 fps in one hole @ 30 yds. It seems almost all settings "work" - it's just a question of whether they shoot one hole or have a few fliers making it say, 3/8". At this velocity, with the Sarissa, noise is ~2 magazines dropped from waist to wood floor.

Of course, we want velocity for longer ranges due to time of flight / wind, but at 1040 fps there was much more of a crack when firing, I'd say 8 magazines dropped to wood floor.

I tried backing the hammer down further for a very quiet shot, but accuracy suffered - whisper quiet at 580 fps, but maybe 5/8" @ 30 yards.
 
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Kovacs, thank you for this information,

580 fps shooting 25.39 , 19ftlbf, ( 15.89 @ 580fps would be even better😏)

5/8" at 30 yards is MOratshead, and the tune/power up to 1040 with 25.39 is Rabbits at 100m,

This is what I seek, a gun I can dispatch rats/pigeons at close range (in barns ect) and then stretch it out.

You have reaffirmed the Prophet may do the job, pray tell more.

again, thank you.


 
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No worries, these things are commoditized at this point, and it's not rocket science to tune them, so we should all be sharing info. 15.89's did run that slow also FYI, but I didn't check accuracy at that velocity because I want my target load to have some crossover potential for gophers. A video I watched said the regulator is variable down to 80 bar, so I haven't tried to go below, but I will check that out tomorrow. If the regulator can go even lower, there might even be a one hole accuracy node down there too.
 
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Hi Harry,

Sorry but I've not tuned it to shoot sub 20 but I am sure its possible. However, the new Compact version might be better suited to those lower tunes since it has a completely different barrel and faster twist rate for lighter pellets. This Performance barrel is specifically engineered to shoot Monster Re-Designed 25.4's, using a slower 1:32 twist, at much higher power levels and velocities. Therefore, I have only used the 25.4 MRD pellets in mine.

I've been tweaking this rifle for weeks and having a blast shooting it and have learned a lot about its nuances. I didn't include any hammer settings because I am using a 3D printed butt hook plate so my measurements would be quite different and much longer than with the stock butt plate. If you use my bar settings and velocities and tune your HS to get these velocities then you will accomplish a similar tune.

I went through some virtual spin drift calculations using Streloc Pro, made the spreadsheet below and found what the pellet's sweet spot should be. Then I focused on tuning within those speed ranges which are 800-920. Although a person from JSB said the range they found to be the most accurate for MRD's is 880-970 using their barrels. They had no data with a slower twist rate of the LR barrel.





This range in GREEN (800-920) shows the least amount of spin drift (3.6 mils) using a GA drag model and .050BC with a 15 mph 90* cross wind factors. 940-960 was 3.7 and 980-1000 3.8. Above 1000 the pellet's calculated spin drift increased dramatically and linearly up to 4.3 mils of drift. Right now I am shooting at 965 but will continue to work my way down to 900-ish all the while by taking copious notes. The 965 tune is shooting the best this rifle ever has so I am very pleased with it as is but being a former Mechanical Engineer I will continue chasing perfection ;)

I experimented with tunes up to 1050 and I had a lot of fliers and severe leading in my barrel even after just 20 round shot strings. The rifle was not friendly to shoot at these higher velocities and seemed to jump around with each shot. I tried all kinds of different lubes and waxes on the pellets and nothing reduced the leading until I dropped my pellet speed below 980. Then White Lightening Bicycle chain wax did the trick at completely reducing the leading in the bore, fliers were almost non existent and group diameters shrank. 

It wasn't until I started using the HS to harmonically fine tune the reg setting that I started to notice significant accuracy improvements and more efficient air consumption. Before, I was just randomly tweaking the reg then the HS then the reg and then the HS mostly chasing my tale hoping to find a lucky combination that showed up as accuracy on paper. It wasn't until I started to harmonically tune that I saw huge accuracy improvements.

For those of you that don't harmonically tune (like me) try it because it works. Set the reg to any PSI you want, increase the HS 1/4 turn at a time until the velocity peaks or starts dropping. Lets say the max peak velocity is 1000 FPS. The harmonic tune should be somewhere close to 3% under the max velocity of 1000 or 970 FPS. To get there start by backing off the HS 1/4 turn at a time until you reach 970 FPS. That is close to where the reg and HS are in harmony. You guys who have done this for years I am preaching to the choir but for a relatively newer shooter like me this was an enlightening A-HA moment.

Once you get to 970 then start shooting for accuracy and take notes. REMOVE the chrono if its an FX and hanging on the end of your barrel!!!! Just the weight of the FX chrono will affect POI, barrel harmonics and accuracy. Are the pellets going where you expect them to at this velocity (970)? Is the gun friendly to shoot? Is it efficient on air consumption? If the accuracy isn't where you expect it then fine tune the HS either way by 1/8 turn and see if the accuracy improves or suffers. If the accuracy simply isn't there then repeat the process using a lower or higher reg setting keeping in mind the data set you calculated in StreLoc Pro or similar shooting APP. Its not a fast process so be prepared to take accurate notes that you can refer back to and hurl lots of lead down range.

I want to publicly thank loneranger, Cworkman74, Centercut, MikeVV and zx10wall because they were all very helpful in sharing rifle set up, tuning advice and shooting tips which has made a huge improvement in my tuning process as well as my shooting techniques. Thanks guys!
 
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