GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Motorhead on November 05, 2021, 03:27:24 AM
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Just picked up a 700mm STX Superior Heavy Slug liner in .30 caliber ( 1-22 twist )
My War Flex had been running with the OEM 17" TJ's set up for high power, yet not leaned on so hard to be an air hog. Shooting a JSB 44.75 gr at a 2400 psi set point there at @ 880 fps for @ 78 fpe give or take.
* Doing nothing but a barrel change to the 700 mm ( 27 inch ) the output has skyrocketed !!! Now the JSB 44.75 smokes out at @ 1005 fps for 100.3 fpe :o :o
Loading up a 61.9 grain slug it's going to @ 870 fps for 104 fpe ;) Crazy the power is so close with a dramatic weight change and pellet to slug ???
Oddly the gun appears no louder, actually quieter in residual report, but the snap is crisper.
Spend a good part of the day machining the needed parts and pieces to adapt it. Took an @ 3/4" piece of a cut off 16mm barrel that has 1/2-20 threading and bored it out for a light press fit over the liner which is @ .395" diameter.
Then with Aluminum machined up a 3 1/2" sleeve at 1/2" O.D and I.D for the liner to fit the WAR receiver. Put in a snap ring groove & Drilled a 1/4" transfer hole & deburred. Light press fit the parts with Loc-Tite 640 sleeve retaining compound we have a complete barrel and Thin Noodle really bendy one at that !!
Next needed to fabricate the shroud, using a JSAR air stripper / end cap and DOM 1" tube was able to square up everything, get a thin nylon compression collar for tube to butt against at receiver. Tightening down the end cap placed the barrel in STRETCH or as we say ... TENSIONED. Now Long and Stiff ???
Not shot for accuracy yet .... had customer jobs to do as well and will for a few weeks yet. It is at least assembled now for another days testing.
Scott S
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At least a picture or two
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At least a picture or two
Yeah ... Really Scott - No pics ??? :P
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I recall seeing some threads at The Other Place RE: FX barrels and carbon sleeves being used to good effect on other brands, so this just adds to the excitement.
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no pics.. didnt happen :)
so you gearing up for EBR or RAMC next year?
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Wow.... That's quite a jump, with just a barrel change...
Any theories as to the why's? Smoother ID, looser ID? Slower twist using less energy to give rotational velocity?
Jesse
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Yep I'm going to go along with the other post and say a picture or 2 would be great .
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Wow.... That's quite a jump, with just a barrel change...
Any theories as to the why's? Smoother ID, looser ID? Slower twist using less energy to give rotational velocity?
Jesse
Probably the 10 inches of extra barrel mostly.
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Following along. Can't wait to see the flex and some target work. I always enjoy your threads Scott.
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Wow.... That's quite a jump, with just a barrel change...
Any theories as to the why's? Smoother ID, looser ID? Slower twist using less energy to give rotational velocity?
Jesse
Probably the 10 inches of extra barrel mostly.
+1 ;)
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I will say that the FX Slug liner creates a lot less drag when pushing a slug end to end .. a Lot less than the TJ barrel.
While i do agree LENGTH has a lot to do with it ... less in-bore drag from 4 narrow lands certainly is helping too.
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"less in-bore drag from 4 narrow lands certainly is helping too."
you said slugs... and then I dont get it.... so the slug is NOT "riding" on the entirety of the bore diameter, just the lands? SO only 4 points of contact with the bore....so less friction. But how does it seal ? or am I missing something (always a possibilty...)
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Appears NOT .... Pushing a few .300 slugs, NSA & others, there is no groove contact, only land. Sighting down bore with slug down a few inches there is just a very vague trace of light around it. So very very close but no contact.
Land lines on a pushed threw slug are well defined so there is good bite on keeping the spin going by the looks of it.
As to the seal or a slight lacking off is doubtful to creating much loss or air being the total area on .30 is so great. Big blast of HP air and slugs gone !!!
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Did someone mention ... we need pics :D?
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Ok folks ... went back into it increasing the throat depth so slugs would just be seating into rifling as well pellets. SO took some pictures for Ya !!
Chrony shot is with a NSA 49 grain dish base ... 957 fps = 99.63 fpe Yea that's healthy enough ;D
Being we could NOT machine in o-ring grooves either side of transfer port due to the liner ... opted to machine the slip fit sizzle tight. Then placing a 1mm o-ring against breech face, then washer & clip. When drawn into tension the o-ring crushes into the small bevel on receiver/ barrel hole & crushes in enough to flush up & make a seal.
Last pic was my idea to stabilize liner within the shroud. What is ? It's a core of a printing paper roll … LOL Made a split sleeve to snap over the liner having the paper roll core press over it. Then slightly built up the O.D. with @ 2 wraps of gorilla duct tape for a firm press fit into shroud tube. No internal shakes or vibrations now !! This Roll Core allows air to pass threw it between webs allowing the entire shroud length to be effective !
Only played a bit this morning for accuracy … 80 yards able to hit walnut size rocks shot after shot easily !!!!! Paper is going to be another day.
Scott S
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Also make note on the 4th picture the COLLAR up against the receiver on the shroud mounting shoulder. It is NYLON and gives tad bit of yield when tensioning the barrel and helps stabilize the shroud assembly letting it find it's natural square to base position.
Also on picture 6, is a Donny FL TATSU Moderator that is threaded on a dummy 1/2-20 stud on forward side of Butt plate. Muzzle has a thread protector cap in place and if you need to hush it down simply swap em out. Interesting tho is the fact the rifles not that loud for making 100 fpe and this has a lot to do with the JSAR inspired hybrid balanced valve, SSG hammer spring and light hammer. Air delivery is switch on / switch off fast having a fairly short dwell cycle … Just a quick SNAP firing cycle.
Scott S
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Ive got ONE question. How much do you want for it!!!!
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Always interesting !
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Big blast of HP air and slugs gone !!!
ok, gotcha. And didnt remember it was 30 cal.....
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Just a follow up on a few fronts ;D
Cold Shot with a NSA 47.2 grain .... 1000 fps for 104+ Ft lbs.
Seems the hammer sticksion is 100% gone. This due to using a Glass filled acetal poppet and X ring within my custom balanced valve configuration.
So we now have total confidence in picking this beast up and sending a shot on target not worried about the PITA sticky valve / cold shot issues of the past. STOKED !!!!
Scott S
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Scott ,
I see there are more than a few choices with the actetal to glass ratio. From 20 to 40% , what are you using? I have a gun on the bench in pieces that is in desperate need of a new poppet and I’m out of PEEK. Thanks
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Scott ,
I see there are more than a few choices with the actetal to glass ratio. From 20 to 40% , what are you using? I have a gun on the bench in pieces that is in desperate need of a new poppet and I’m out of PEEK. Thanks
If your just making a conventional poppet, straight up acetal or delrin works fine. The balanced chamber / inverted custom poppets I designed are of the lower % glass fill to avoid porosity while maintaining high self lubricity traits.
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Ok thanks Scott. I won’t be needing it then. I’ll place an order for some more PEEK. By the sounds of it it might be a great material for a cobra valve.
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Accuracy update and Efficiency numbers.
4000 psi fill on a 350 cc bottle. Plenum volume @ 45cc
21 shots at @ 977 fps being Average 104.9 fpe
Shot NSA 49.5 dish base slugs.
Numbers crunch at .96 FPE/CI using 74 psi per shot.
At 70 yards ( Zero ) all 21 landed in an @ USA Nickel diameter while being shot on a bipod and tri stool seat. Stable but not BR stable :P So it's ACCURATE !!!
Muzzle report w/o an LDC a crisp yet muted SNAP !! not really blasting and making a loud air discharge report.
Think we're done here ... Powerful, Accurate & fairly quiet for the output.
Scott
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WOW thats awesome!!! Well done man!
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Think we're done here ...
I don't care who you are, that's funny right there . . . . ;) I think I remember reading those exact words earlier on this very gun!
But that is some seriously nice work!!
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Great build, Scott.... The numbers are not too surprising for 2400 psi and a 27.5" barrel.... I was getting 95-100 FPE at 2200 psi with a 25" TJ's barrel in my "Bobcat" .30 cal (modified FD-PCP).... The efficiency was originally running 1.15 FPE/CI at 95 FPE with 44.8 gr. pellets, dropping to 0.87 when turned up to 100 FPE with 70 gr. slugs.... After I fitted an SSG and a different hammer spring I got 1.43 FPE/CI at 93 FPE with 50 gr. pellets.... When I turned it up for hunting to nearly 100 FPE, the efficiency dropped to 1.2 FPE/CI.... I don't shoot slugs in that gun, the 44.8 pellets are plenty for the Marmots I use it on.... ;)
I am somewhat underwhelmed by the commercially available .30 cal PCPs on the market, even the expensive ones.... I think they are leaving a lot on the table.... In any case, nice job.... 8)
Bob
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Very similar t the build I did for the Raptor with installing an FX Supior Heavy Scott. Iwas very impressed with the results. It is a fine slug shooter.
I also used the nylon spacers as you show here, only mine are a light brown in color. the pass the air blast thru the shroud well. I have three on the bbl for stiffness along with a high modus CF tubing locked in with Loc-tite green.
Sadly, not having a mill, my fitting does not loos as nice as yours ;<)
Knife