.177 Smooth Twist X - general consensus?

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nervoustrig

nervoustrig

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Jan 21, 2018
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Laurel, MS, United States
Can you guys tell me the general consensus on the .177 Smooth Twist X barrels? Seems like from what I’ve read, they’re kinda ho-hum compared to the .22 and up.

I’m holding one a guy sent me out of frustration. I haven’t done much testing with it yet, just an initial inspection. Bore seems to have a good surface quality, crown looks fine, no unusual loose or tight spots along its length.

The first thing that jumps out at me are the bore dimensions. The breech end accepts a 0.174” gauge pin readily and almost accepts a 0.175” so I’ll split the difference and call it a 0.1745”. That’s a tight bore compared to most .177s I see. And then we have the choke…the muzzle accepts a 0.172” snugly so the choke seems to be a very aggressive 2.5 thousandths or so.

Any comments on this all being normal or not? Or suggestions on things to look at or try?

Just looking for a good pellet shooter that will run the 10.3s at about 20fpe for field target. If it ends up needing a new barrel, so be it.
 
My Dreamline Tact Compact's barrel will squeeze a slug from .178 to .173 inch diameter. That's way too tight. It leads up fast. FX has not put any development into this caliber and it's kinda sad. I'd like to find someone who will machine an LW barrel to fit my rifle. Funny, you hardly ever see FX rifles competing in FT because the others outshoot them big time.
 
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Interesting, while I’m aware the choke is very tight but they seem to shoot just fine for me. At 20-35 yards they can put pellets on pellet if the wind or wind call is spot on. But keep in mind that I usually shoot pellets at 600-650FPS or 6-8 FPE, shoot both crosman and hades and both shoot great. It’s possible the tune is a bit off with too low of reg pressure so there is some dirty air/turbulence at the muzzle, light 177 pellets are far more sensitive to turbulence. One thing some 177 people do is tune the regulator way too low but I’m a fan of high regulator pressure tunes so take my opinions on that with handful of salt. IMHO the tight barrel is there by design so the barrel isn’t pellet fussy like some barrels in 177, since the margin of error is very small with 177 pellets it’s better to error on the tighter side, it really isn’t that much lead to squeeze so I don’t see a tight barrel/choke being an issue and it isnt an issue for me so far from my testing as long as the tune is efficient. I have 2x 300mm, 600mm FX barrels and sold my 500mm barrel which I deeply regret. LOL 


took the 500mm to the range with nsa 12.5 slugs and it’s a laser also. I know this is only 3 shots but it’s 0.57 inch at 100 yards with a bit of adjustment for wind. Haven’t mounted my new 600mm superior 177 to try at the range yet.
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Okay thanks guys, that’s right along the lines of the info I was looking for.

Paul, thanks for the confirmation on the dimensions.

When weather conditions improve, I need to shoot some groups with different batches and see what it will do. I ended up finding a few assembly & fitment issues in the barrel and shroud assemblies that I want to address. Maybe it will turn around. Or if it proves hopeless, I’m thinking about lopping off the choke just to see how it responds.


This all may develop slowly but I’ll update the thread along the way. 
 
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This is an interesting subject. I have been interested in changing my FX Impact to 177 for a little over a year but have read many posts complaining about issues with the FX Smooth Twist X barrel in 177. I am curious if the FX barrel technology has issues with a 177 barrel. Best I can tell the 177 and 22 barrels have the same OD but different IDs. I wonder if this has an effect on the precision of the bore in the 177 barrel pressings.
 
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This is an interesting subject. I have been interested in changing my FX Impact to 177 for a little over a year but have read many posts complaining about issues with the FX Smooth Twist X barrel in 177. I am curious if the FX barrel technology has issues with a 177 barrel. Best I can tell the 177 and 22 barrels have the same OD but different IDs. I wonder if this has an effect on the precision of the bore in the 177 barrel pressings.
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If anything, the thicker wall barrel should improve accuracy because it will be stiffer. I don't think FX has put any money in developing the .177 since the fad today is bigger and faster. Maybe Matt Dubber and Ted Bier could put some pressure on FX. I wanted to promote some long range BR shooting using .177 and challenge some of the locals here. Right now, the .22 seems to be the most popular 100 yard shooter. Now that more and more slugs are available for the .177, it would be nice to see how well they can be made to shoot.
 
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Qball, thanks for the suggestion about the state of tune. I have not yet tinkered with the knobs and dials, just confirmed it’s producing a consistent velocity. I’ll get a baseline at the present tune with the barrel & shroud assembly corrections/tweaks and go from there.

I had failed to say it is a Crown with a 500mm barrel.
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I use both my Dreamline and crown mk2 with 177 barrels and with the right tune they both shoot great. The 100 yard group was with my crown with 500mm barrel. Consistent speed is good but shouldn’t be the baseline IMHO because if there is turbulence you still won’t have consistent small groups especially in the wind even if all 5 shots are at the same exact speed. 10-20 fps will not make any POI change. 


Also if you use heavier ammo then the reg pressure will need to go up just like when you have a heavier car you need more horse power to get the same 0-60mph. In my crown is don’t usually go below 130 bars even shooting 7.4 grain 177 pellets, granted it’s for a different reason but it greatly reduces the muzzle turbulence or dirty air, both light pellets and slugs are very sensitive to muzzle turbulence. 






 
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Qball, thanks for the added detail about your preferred setpoint. The owner currently has it at 100 bar so I’ll definitely try at least a couple of higher levels to see how it responds. A quick pulse of HPA does seem to work nicely in most cases…one of the things I like about PCPs retrofitted to a PEEK poppet and lightweight hammer. 
 
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i have a 700mm .177 i got from huma-air ..my mk1 impact gained 70fps with just a barrel swap. then i installed a CF liner sleeve the dual hole transfer port and a pin probe mow i am shooting the 13.43 JSB KOs at 988fps and this are my groups at 84 meters. plus i managed to get a MOA group at 100 with the NSA 15 but i was getting unexpected fliers so i stopped using them.. the shot on the right i pulled the rifle out of excitement 

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@trumpis: the FX barrel does not have enough twist rate to shoot the 15 grain nsa at sea level with only 1:18 which give stability factory of barely 1.09, probably won’t be acceptable till 3000-5000 feet elevation. The 12.5 slugs in 1:18 FX barrels has stability factor of 1.3 at see level and 1.4 at 1000 feet where I live so barely enough but good enough to be consistent. 


However even with 700mm barrel the reg is a bit low for slugs, I would try at least 120 bars at same speed to see if your flyer problem goes away. 






 
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I'll give my setup a Ho-hum +. Impact with a 500mm + 100mm air stripper, CF sleeve, Huma spring kit and 2nd regulator. Shoots the JSB 13.4 monsters well out to 30' (my limit until it warms up) at 812 fps, just under 20 fpe (setting up for HFT). It does lead up quickly so I clean it every 3 mags or so.

Sitting on a stash of .177 slugs to try if/when a 600 / 700 barrel with the CF tensioning housing hits the market. Not worth bothering with the current setup
 
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So I’m not the only one? I don’t remember the post? But we went through a lot of these same points.

they really are hit or miss! But that being said, I am 4-0 with 500 mm in crowns and one impact shooting 8.4’s and 10.3’s? I am 0-3 in 600 mm? Total mess with those! I even cut the choke off one and that was a bigger mess! So to explain the results with the 500’s all between 880 and 900fps 3/8”-1/2” 10 shots @50 yds no flyers, indoors. 600mm not even minute of starling @ 50

so definitely not as good as 22-30 cal, most of you know you can pretty much go same hole @ 50 indoors with the right set up. I so like the rest of you, here I wait. 
i did however learn a few things through all of this fairly unique to .177 Fx barrel kits? The .177’ liners are the flimsiest of them all, therefore you can really mess things up with the liner nut torque! Easy to test and it will walk all over if you are much past finger tight, very frustrating, the crowns and the super lite systems don’t have this issue, no jam nut to flex that little liner, the cf sleeve does aid this problem, but didn’t totally eliminate it? 

good luck boys! Hope some of this helps? But if anyone will nail it? it will Probably be NS, he knows his stuff!


 
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Following this.

I have been on a quest for a .177 slug shooter for the last year or so. I just acquired an Impact and a .177 barrel kit for it is on its way as well. This will be my .177 slug shooter project.

This last weekend I was shooting slugs out of my .177 DreamTac and although it shoots 13.4 Monsters very well, slugs are only so, so. Best results were with the 13.43 Knockouts.

Hoping to achieve results like what I see here, at 100 yards.

Thanks nervoustrig, for starting this thread :)
 
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@trumpis: the FX barrel does not have enough twist rate to shoot the 15 grain nsa at sea level with only 1:18 which give stability factory of barely 1.09, probably won’t be acceptable till 3000-5000 feet elevation. The 12.5 slugs in 1:18 FX barrels has stability factor of 1.3 at see level and 1.4 at 1000 feet where I live so barely enough but good enough to be consistent. 


However even with 700mm barrel the reg is a bit low for slugs, I would try at least 120 bars at same speed to see if your flyer problem goes away. 





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hello sir.. i live 500 meters above sea level..my reg was at 130 for the NSA 15s i detuned it for the JSB KOs and they like the pressure to be at 95 
 
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Well I’m beginning to think the problems were somewhere in the barrel assembly, not with the liner itself.

Top group at 30 yards shot yesterday, shooting between the wind gusts. Right at MoA.



Bottom group shot today to see if the first was a fluke. Fairly calm conditions. A bit under 0.8 MoA.

That represents about all I can do consistently with an accurate rifle...supported forestock but shouldered (movement from pulse and respiration). Not cherry-picked. And actually those two are somewhat better than I could have even hoped with the beater scope I threw on it, with a thick reticle and only 10x magnification.

I’m not celebrating just yet. Definitely needs more testing and experimentation but this little bit tells me it can be tamed.

For anyone interested, here’s a detailed list of my observations from disassembly and reassembly of the barrel:

1. The O-rings supporting the liner inside the barrel allowed some free movement. Somewhere in the ballpark of 10 thousandths of an inch. So although the ends are well supported, my thinking is it can give rise to violent vibration along its length. In other words, neither supported nor free-floated…a no-man’s land somewhere in between where vibrations are unpredictably additive or subtractive.
-> Applied a strip of electrical tape across the series of O-rings. Takes up the free play and simultaneously keeps them positioned while inserting the [now snug] liner into the barrel.
2. The steel adapter piece (forward of the brass inlet) had an O-ring on the ID that was flopping around in the groove, doing nothing to seal to the liner’s OD.
-> Custom fitted an O-ring (a modified -010 with its thickness and OD abraded down for a snug fit)
3. The outer collar on the barrel was fastened about 40% of the way forward of the receiver.
-> Relocated it to its intended position next to the receiver (where its locator pin indexes to the shroud adapter).
4. The shroud and air stripper were loooooong overdue for a cleaning. Caked heavily with gunk.
-> Neither degreaser nor mineral spirits would cut it. Had to scrub it free with a Scotch-Brite scuff pad. Honestly the most tenacious buildup I’ve ever seen.
5. Applied just enough torque to the barrel nut to snug it up. Do not want any undue forces trying to turn the liner into a banana.
 
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