The 177 barrel, mag, probe and removal tool was delivered today. I swapped out the 25 barrel to the 177 and started checking for groups.. (FX 10.3gr) at first they wouldn't group worth a crap.. I knew from past post daitboy had it shooting good on his RTI compact.. I cranked the reg down to 80 bar...backed the hammer spring screw flush and tried again. Groups improved but still not real good...I had to check it through the chrony at this point.. the FX 10.3 was a smoking 985fps... and wouldn't go any slower without the hammer spring set screw 4 threads sticking out!! I can't have that... I ended up taking the hammer weight out.. giving it one turn in and shooting it across the chronograph... 700's... now we're talking.. I bumped the reg up (according to the factory gauge 95-100 bar) tweaking on the hammer spring and 890fps it is.. shooting freaking great!! After I had it set I couldn't help but to set it up for the 13.43 gr jsb and tweak on it a bit... I had those hitting 913fps and also shooting great.. after I shoot all the tins of 10.3gr I'm going with the 13.43gr monsters.. I believe I'm gonna enjoy plinking with a 177...
RTI compact 177 barrel...thanks Dairyboy
- Thread starter Jasonmc
- Start date
Hi Jasonmc, I actually bought a 2nd hammer spring for my Prophet Performance - with the thought of making it shorter so that I could use it with .177 and be able to tune velocity below 900fps.
It sounds like removing the hammer weight is another option - was it difficult to remove?
It sounds like removing the hammer weight is another option - was it difficult to remove?
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No not hard at all. I took the 4 screws off the but of the rifle. Spring and hammer weight fell right in my hand. Its very adjustable without the weight in 177.
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One other thing to consider. There is a brass grub screw under the barrel at the transfer port with ~1-3mm holes in them best guess. I believe these are sized/optimized by caliber so when switching between 25 and 177 I suspect there’d be a difference that would effect velocity.
Transfer port size is damn near rocket science to me but Ive been making more of an effort to understand it. Either way for folks switching all calibers on one platform like the RTI I’m curious of the effect.
So instead of optimizing the hole size in the grub screw for example are velocity issues being adjusted out with regulators and hammer weight?
Transfer port size is damn near rocket science to me but Ive been making more of an effort to understand it. Either way for folks switching all calibers on one platform like the RTI I’m curious of the effect.
So instead of optimizing the hole size in the grub screw for example are velocity issues being adjusted out with regulators and hammer weight?
In my case yes..going from 25 to a 177...I removed the hammer weight and cranked the reg down to 80 bar.. turning hammer spring while shooting groups watching the chrony.. and listening (without a moderator on) when I found what speed the 10.3gr liked best (which was about max for 80 bar reg pressure) I upped the reg to 100 bar...backing out the hammer spring back to the velocity the pellets told me it liked... without the mod on its pretty quiet... when I installed the moderator it is very quiet.. so far I have shot it several times keeping track of my shot count and I'm very happy with the tune... 220cc tank filled to 300bar 10.3gr....890fps....112 shots (8 mags) I've been popping the crap out of starlings in my pasture out to 70 yards ( very little wind) without any issues.. when squirrel season comes in (August in my state) I will install the 25 barrel... check my notes on the way I had it tuned in 25... takes about 15 minutes to set up...tweak in....I love how quickly a RTI can be tuned to one caliber to the other..
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I had a almost "empty" 300 bar tank ( 12 L ) so as it was too low for the first REG on my maverick, i just brought my vulcan 3 which one regulator are set lower ( 100 BAR )
So yesterday i took my 12 L bottle from 140 BAR to 100, shooting tethered, and a good old time was had as i shot a little slugs first, then as evening approached and wind died off a bit i changed to MRD pellets, shooting them first at 90 M and then at the spinner put up around 75 - 80 M.
Okay not that much challenge hitting the 1 - 2 " paddle on the spinner, still tore right thru 400 pellets. with a big smile on my face.
Most of the shooting was done with no speed info as even though i have 4 sets of batteries for my chrono, well i somehow forgot to charge them all, so tonight / soon i will have two 6 bay chargers going and so charge all 12 batteries in one swift ( 500 mah ) go.
So it was just change weight / ammo, dial a little on the hammer spring until things start to group up,,,,, and the MRD did not do that at first shooting them very HOT as i had been shooting a few 16 grain slugs before, so in the scope it looked as if my Vulcan 3 expelled a metallic looking smoke ring, the pellets spiralled that bad.
But just going down a bit more in hammer spring / speed and the MRD pellets was right on the mark, so much so that while i am slug shooter, the 4 tins i have left of the MRD pellets are clearly not going to be enough.
I would like to give a RTI a spin, but dont know anyone here having one.
So yesterday i took my 12 L bottle from 140 BAR to 100, shooting tethered, and a good old time was had as i shot a little slugs first, then as evening approached and wind died off a bit i changed to MRD pellets, shooting them first at 90 M and then at the spinner put up around 75 - 80 M.
Okay not that much challenge hitting the 1 - 2 " paddle on the spinner, still tore right thru 400 pellets. with a big smile on my face.
Most of the shooting was done with no speed info as even though i have 4 sets of batteries for my chrono, well i somehow forgot to charge them all, so tonight / soon i will have two 6 bay chargers going and so charge all 12 batteries in one swift ( 500 mah ) go.
So it was just change weight / ammo, dial a little on the hammer spring until things start to group up,,,,, and the MRD did not do that at first shooting them very HOT as i had been shooting a few 16 grain slugs before, so in the scope it looked as if my Vulcan 3 expelled a metallic looking smoke ring, the pellets spiralled that bad.
But just going down a bit more in hammer spring / speed and the MRD pellets was right on the mark, so much so that while i am slug shooter, the 4 tins i have left of the MRD pellets are clearly not going to be enough.
I would like to give a RTI a spin, but dont know anyone here having one.
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What do you guys think is the best brass grub screw port for an RTI 177 slugger 3mm or even 4mm can be good ? a port too big can bad ?
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