Veteran Long Re-barrel (X2)

I've started a few posts about this gun in the last 6-8 weeks. 

Full version in these links:

https://www.airgunnation.com/topic/barrel-pellet-mismatch/

https://www.airgunnation.com/topic/opening-up-a-tight-choke/

https://www.airgunnation.com/topic/veteran-long-22-plenum-install-and-outcome/

https://www.airgunnation.com/topic/bc-measuring-and-optimal-speed-and-pellet-for-long-range-shooting-theorizing/

Short version: I bought the gun to be a long range shooter, with either JSB 25.4 MRDs or an NSA slug, and it hated everything but JSB 18.13s, which limited the power (and left me with an inherently low BC pellet), which negated the whole purpose of buying this gun. Shot really well with the 18.13s, but couldnt make them go any faster than about 940 without accuracy degrading, with a measured BC of 0.034 (18.13gr @ 940 @ the muzzle and 789@ 48 yards) 

I considered the 700mm barrel being offered as a drop-in for the Veteran, but decided against that 27.56 incher for various reasons (mostly the length, but also that there haven't been many reports on them yet and I was concerned that it would be over-choked like the OEM barrel that already wasn't cooperating with my plans).

And that's how I arrived here-have a buddy machine me a .22 Lothar Walthar unchoked barrel. Working hypothesis being: that really nasty tight choke on the barrel that came on the gun is throwing a wrench in the system, lets go 180 degrees the other direction and try an unchoked barrel. Perhaps the new unchoked barrel will like a better BC projectile and, worst case scenario, can always go back to the OEM barrel and just try to live with 35fpe and not the greatest wind deflection resistance. Nothing ventured, nothing gained. 

Would have really preferred a polygonal rifled barrel, but OD on these Vet barrels is 15mm, and polys are only listed as 16mm OD on the LW USA website. I even emailed John McBrayer at LW Precision Tool, Inc in Georgia and he confirmed that they did not have any 15mm polys. Interesting to note here that Daystate has 15mm LW poly barrels in some of their guns. I don't know if that extra 1mm is getting machined off at some point for the Daystate barrels, or if LW is making them that way, but this only further confirms what I've stated elsewhere about Daystate LW barrels, THEY ARE SPECIAL and very different than the barrel blanks that are available to the public. So, I ordered what they had, 15mm unchoked traditionally rifled blanks. 

Today I picked up the barrel and did a little prelim accuracy testing. 

Here is what the gun looked like after the plenum install (with the OEM length barrel), just a bit of an underbite with the shroud being longer than the barrel. 

underbite.1605072844.jpg


And what it looks like after the install of the newly machined blank.....(REALLY helped with the odd visual effect of the underbite)

new barrel on gun.1605073195.jpg


Comparison of the barrel lengths...(the difference, after the machining-the new barrel is 1.875 inches longer than the OEM length)

barrel length comparison.1605073239.jpg


And a little bit of a hiccup when installing.....(turns out the OD of the "15mm" blanks were 0.006inches bigger than the OD of the "15mm" OEM barrel). Installed just fine, except the shroud fits so tight on the OEM barrel that it wouldn't slide over the new barrel. Machinist friend was kind enough to take just a bit off. First pic is what it looks like on the OEM barrel after being machined just a bit bigger. Might have to put a VERY thin shim on it if I ever decide to go back to the OEM barrel. 

shroud.1605073407.jpg
shroud1.1605073407.jpg


And now, the big question.......how does it shoot? 

Well, the first couple shots were on paper at 50 yards, shoot, adjust turret, shoot, adjust turret. By the third or fourth shot I decided to just hold in the center of a circle on the target and see how it'd group. Next 5 or so holes were all touching, with the JSB 25.4 MRDs. Not too bad. 

Friend had his Labradar set up and I was curious about a few things. I shot some 18.13s to see what kind of gain I was getting from the extra barrel length, and fps was only 904. I thought that I had last had the gun doing 940fps with the 18.13s with this same hammer tension and the OEM barrel, so initial assumption was that I had LOST some fps. Only when I got home did I find in my notes that I last had the gun doing 870fps with the 18.13s for the BC comparison I covered in one of the above links. That means the extra 1.875 inches of barrel, with the same hammer tension and 18.13grainers, increased the fps from 870 to 904, 34fps faster.

After that I cranked up the power and the range. With the new barrel, and the plenum and the hammer at nearly it's max, the 25.4gr MRDs were doing 872, for about 43fpe. This is just a couple less fpe than it was doing when new, which could be variance in my chrono and the Labradar, or the fact that every regulated PCP I have shot in the past couple years loses 2 or 3 fpe once it is broken in. After that, I came down just a bit more, to get them going 850-855fps for around 41fpe, and left the hammer tension there for the rest of the accuracy testing. At this hammer tension it was very easy to cock and didn't sound or feel like the gun was wasting air or working hard for its power output. I know guys are putting really heavy hammer springs in their Vets or bumping up the reg pressure for max power but I just don't think I want to got that route. Machinist friend also pointed out that the traditional rifling might do better in this realm of 850-870fps (vs the 960-970 guys are pushing these pellets in the poly barrels). We also measured the BC of the 25.4s at 850fps and found them to be 0.049, I can live with that-MUCH better than the BC of the 18.13s. 

I compared the accuracy of the 25.4 gr Monster RDs to the NSA 23 flat base (0.217), the NSA 17.5 dish base (0.2165), and the NSA 20.2 dish base (0.216) all at 100 yards. Friend had some EBR type paper targets out at 100 yards and I shot multiple 5 or 6 shot groups with each of the projectiles. With the same hammer tension (850fps with 25.4gr) the 17.5gr NSAs were doing 960fps and the 20.2s were doing 860fps. Sorry, didn't think to get any BC collection of the slugs. 

Wind was variable and tricky, but not so bad that I couldn't compare general accuracy. The 23gr slugs were the least accurate. The 17.5s and 20.2s both did pretty well, definitely hunting accurate. But when all was said and done and I looked back through the various 100 yard groups, the JSB 25.4gr Monster RDs were the two best groups. I didn't walk out to see them up close, but groups were probably 1.25 inches with the 25.4s. I was able to ding a bell at 125 yards 5 or 6 times in a row with the 17.5gr NSAs (I think about a 2 inch killzone). And I was able to group the 17.5s, 20.2, and MRDs on a steel plate at 150 yards (once I figured out holdover). I could see some of those in flight at the longer ranges and they're flying straight and true, none of the wobble and curveballs I was seeing with the good BC projectiles from the OEM barrel.

All said and done, prelim results from today seem to suggest a massive success. Needs a lot more shooting to gain familiarity, but I think that I've got a long range shooter now. I feel it can be much more competitive in the Extreme Field Target matches that a friend is putting on monthly here in AZ. AND this new long ranger Vet will be hell on the pdogs next summer when it warms up enough for them to come out of hibernation.

(Much thanks to Bobby for his superb machining and barrel prep skills and general willingness to humor me. )


 
Yup .. n that's the reason I sold both of my taipan veteran long..I didn't buy such a long n heavy .22 bullpub to shoot 18g .. mine were the first gen when they used to cost 1,200 as soon the price go up to 1,450 they were gone..but now there are plenums n huma HP regulators..Tony at TT has tune them to sling 25g rd in the 940fps the gun is very robustly made so it will handle well tuning .. I wish I haven't sold mine those laminated stocks look great..
 
Did some shooting with this gun again today, mostly continued testing for accuracy, but also a little bit of data collection of impact points at various distances. Same conclusion as the initial testing, likes the JSB 25.4gr Monster Redesigns better than any of the slugs I have on hand. Although, at 63 yards I was getting 5 shot groups with all holes touching with three different projectiles: 25.4gr MRDs, and NSA 17.5 and 20.2. 

I was most impressed with the following: After setting up the chrono to compare how my personal chrono compares to my buddies Labradar in its readings, I kinda forgot I was shooting over it. The gun seems to be getting about 45-50 shots and somewhere into the third fill I realized the chrono was still catching all the shots. I thumbed through the screen views to find that I had taken 124 shots at that point....... High of 861.9, Low of 853.1, ES of 8.8 and SD of 2.0!!!! Let me say that again.....124 shots with an ES of 8.8. Pretty dang consistent! I'm attributing that to the plenum as others have stated they can help in this regard. Oh, and my chrono seems to be in line with the Labradar. 

I had a blast with the gun, the first time shooting at the property of the house we're having remodeled. It was pretty fun to set up in what will eventually be the family room and shoot from the opened sliding glass door. The wind was brutal, so bad that I was watching an old tire swing moving with the gusts, that's some serious wind to be pushing a tire around. 

Looked up today's history on the NWS and looks like I was shooting in 9-22mph winds. The gusts were the worst, that much variance in the wind speed makes long range shooting a hope and a prayer. 

The best I could muster was a 212 with Centercut's EBR practice target at 109 yards (yeah odd distance but there was a hump of dirt right there to get my target up high enough above the weeds to see). The new barrel seems to show some promise, on one of the targets I had three tens in a row (2xs) and then the wind got me on the last two to completely ruin the group. Very excited to see how it shoots in less wind, or at least more consistent wind. Also would have probably helped to have some wind flags thrown out there. For some reason that tire swing didn't seem to show the subtle changes in the wind speeds-not the greatest wind flag. 

Current plan is to shoot this one at the November Extreme Field Target comp down in Phoenix. Likely going to be using the 25.4gr MRD at the 855fps average I'm seeing with hammer tension in it's current position. 
 
As a sort of conclusion/the rest of the story, this whole project appears to have been a success. 

https://www.airgunnation.com/topic/extreme-american-field-target-11-28-20-results-phx-az/#post-865226

The goal was an extremely accurate long range .22 that could/would shoot a projectile with a relatively decent BC and it appears that we're there. 

I went 26/40 at the recent monthly Extreme FT match, creating a tie for the highest pellet score. As reported, the tie was broken by longest string of misses, and Bobby had one more in a row than I did. 

That 65% knockdown doesn't sound too impressive, but we're talking about shooting pretty difficult targets out to 100 yards, without wind flags, and not from a bench.

For the number crunchers amongst us, I shot the entire match without refilling. Started at 250bar and ended at 175. Reg pressure in this gun appears to be 140 bar so I likely could have taken another 10-15 shots. That is primarily due to the temps coming up during the day and gaining some pressure from that. It's good for about 45 shots in a steady temperature situation. Not too bad from a non-bottle gun, I'm plenty happy with 45 shots (all above regulator pressure) of about 41fpe each from a 292cc air tube (some debate there as to how much of that is taken up by the in-tube regulator, and this gun also has a plenum addition so not sure on air volume, guessing around 300 ccs as the plenum and the regulator volumes are probably about a wash).

The prelim testing with slugs also shows promise, and while I plan to revisit the slugs, overall I'm very happy with the gun in it's current configuration. 

Great little Extreme Field Target competition gun, and the pdogs are gonna wish I didn't own it when they come out of hibernation next summer. 
 
I had a chance to do some chrono work and a bit of shooting today. Just kept the testing to the same projectiles as before (NSA 17.5, NSA 20.2, and JSB 25.39). 

NSA 17.5s are going 972fps these days, very consistently. 

NSA 20.2s are going 905fps, also very consistently. 

The purpose of this was to see if one of these light weight slugs could become the primary projectile for this gun, beating out the Monster RDs that have proven to be a very accurate combo from this gun. 

Testing at 103 yards, using Centercut's EBR practice target (5 shots at 5 different bulls for a possible total of 250). I had a pretty decent left to right wind, coming from mostly 7 or 8 o clock with occasional shifts from 4-5 oclock. 

I started with the 17.5s and just couldn't put anything together worth scoring. They were doing okay but too many of them were not hitting where they should, taking into account wind and operator error. 

Moved on to the 20.2s and I could control these much better, no "what the heck happened to that one" here. I shot a couple cards and they were all in the low 200s, so nothing too impressive. That was just the kind of wind I had today. It was taking most of a mil worth of hold-off, call it 0.8 mils for most of the shots. 

Finally decided to see how the 25.39s would do in the same wind. I had a tin with only four pellets left in my gun case so shot those first, giving it the same most of a mil hold off. All four went into a group less than an inch and the group was left of where I wanted the pellets to go, by about 0.5 mils (too much hold off). Pondered this and thought,
"dang, the JSBs are requiring less hold off." Then had the idea that maybe the impact point is just different for pellet vs slug so grabbed another tin of 25.4s from the truck and shot at my 45 yard target and they were hitting dead-on (just a little bit of difference in vertical between the NSA and the slug, but left to right was perfect). 

I ended up shooting a couple of cards with the MRDs and couldn't do much better than I could with the NSA 20.2s, low 200s. But, it was CONSISTENTLY requiring half the hold-off with the MRDs that the 20.2gr NSAs were requiring. I even confirmed that the wind hadn't died off by going back to the 20.2s and they needed double the hold off again.

Really quite interesting, as the 20.2s are listed as having a BC of 0.07 and I've measured the MRDs as having a BC around 0.05. The 20.2gr NSAs SHOULD do better in the wind, but the real-life shooting results didn't play out that way. 

One other thought I've had is that I might want to revisit different sized NSAs to see if some improvements could be had there. Most of my on-hand slug selection is on the smaller side (0.216 or 0.2165) as I bought them when trying to make choked barrels agree with slugs. Since the barrel on this Vet is unchoked, I'm curious to see if a larger diameter slug would shoot better. More testing for another day I suppose. 

Nothing today convinced me to change over to slugs from the MRDs though. At least not at this relatively low power level (35-40fpe). 


 
I thumbed through the screen views to find that I had taken 124 shots at that point....... High of 861.9, Low of 853.1, ES of 8.8 and SD of 2.0!!!! Let me say that again.....124 shots with an ES of 8.8. Pretty dang consistent! I'm attributing that to the plenum as others have stated they can help in this regard. Oh, and my chrono seems to be in line with the Labradar.

The 124 shot count and ES are amazing and I don't think it gets any better. Slinging 25.4gr .22cal from a non-choked barrel is something I assumed, with all of the slug threads I've read, was an unreasonable expectation. Went through my Taipan VL .25 regulator recently, belville polishng, and got great results in ES and shot count with reg set at about 100 bar.

I am shooting the 25.4 JSB/FX .25 cal 52 shots ES 10 avg 907fps (high=912, low=902). It seems odd that my reg is at 100bar and yours at 140ish. I will understand it better someday. Looking at your results it makes me seriously ask why am I shooting .25. We have a velocity difference but I am not sure it matters that much. I 'tuned' for accuracy only but ended up doing OK in ES and shot count.

I enjoyed your write-up, VERY COOL and Thank You.




 
@JohnnyPDX, I'm only assuming 140 bar as that's what other Czech Veteran Long Owners have reported (this one came from Utah Airguns but Tony At Talon Tunes told me these are coming with reg set at 140 bar). 

I've never adjusted it from oem settings though. 

I read and enjoyed your optimization of the reg in your Vet a few weeks ago. I've considered doing the same, just don't want to mess up an already good thing with my gun. In my case, if it ain't broke.....

Yes it was a pleasant surprise that the unchoked blank likes the Monster RDs. Machinist was concerned that it would like anything since he said he could tell where the bore opened up just a bit at the muzzle from machining the threads. 

As for the .22 vs the .25, oh the debate, and it continues to rage. JSB put out a chart of BCs they collected in their test facility not too long ago. Their 34gr .25 pellet was the highest overall BC, with the 25.4gr .22 pretty close behind it. The 25.4gr .25 (that you're shooting) was lower still. The majority of the competitors in Extreme FT here in AZ either are, or have started shooting the 25.4gr Monster RD in .22. This Vet Long I've been doing write-ups on has gotten me two different second place finishes in the last couple months. On average we have about 15 shooters, the bulk of which are shooting really high end guns (FX, Daystate, RTI, etc). Most guys are shooting the 25.4gr .22s much faster than my 850fps though. But, most of them have poly barrels, which seems to like the speed higher. Look at the Field Target results section for some match reports if interested in long range accuracy. 
 
Thank you for the prompt response. Tony at TT indicated 140bar as well on mine. " just don't want to mess up an already good thing with my gun." and I see why you wouldn't!!!

I had, lost the data, probably a 20+fps ES and that was worth messing with AND I got away with it. The 22/25 Debate goes on to the pinnacle of tedium. I do love the SMACKDOWN of mine in .25 but my BSA R10 SE/TH .22 is every bit as accurate as the Taipan even out to 60+yards or more. .22 is great and I have both.

I am curious about re-barreling, in .22, my Taipan just for the fun of it. The gun is soooooooo easy to work on especially compared to the Daisy M853 I took apart yesterday for trigger polishing!

Very cool that you have a machinist capable for that kind of work, it could go seriously DooDoo wrong in a hurry in the wrong hands. Looking forward to next writeup.


 
Decided I'd like to play around with getting a bit more juice out of the long ranger, with hopes of getting those 75+ yard shots to go where I want them to, more often. So, Late at night and out in the garage spending time in front of the chrono.

I suspect the final answer is going to be to up the reg pressure, but seeing what I can do without going there.

Been shooting it at the above described 850fps with 25.4gr Monster RDs for about the last year, what little shooting I've been able to find time for anyway. Just a bit under 41fpe

First attempt was to remind myself where it maxes out, and that # is 893fps, for just about 45fpe (5 shot average). 

Next attempt was to see what some more hammer spring preload would do....

This configuration....

preload.1631429699.jpg


preload1.1631429706.jpg


provided about 0.170 inches of preload....

0.170.1631429726.jpg


and it gained me 15fps, to get up to 907fps, for 46.2fpe (5 shot average). 

The preload experiment was not intended to be a long-term solution, but more to see if hitting the valve harder would get any more energy,

I suppose I'll do some long range accuracy testing with it just under max hammer tension, no preload, no adjustment to the regulator. Should be good for about 890-895 (versus the 850 that Ive shot it at mostly) before I dive into the regulator. Which makes me curious about shot count now......back to the adjustments and then the chrono

Wont' cock here...

wont cock.1631432006.jpg


will cock here...

will cockc.1631432017.jpg


(face of brass hammer adjuster is just about flush with the black anodized surface of the action)

fill to 250bar.....

started at 899

and here is how it went from there...

Shot #30-895-150bar

shot #37-891-135bar

shot #41-901-120bar

shot #46-882-110bar

shot #50-856-90bar

Data for shots #1-50

lo-856.2

hi-908.3

ave-894.6

es-52

sd-11.31

lowest in first 40 shots was 894.1 and highest was #27 @ 908.3

So, obviously shot down a bit too far, was kinda curious where it'd drop off the cliff. Looks like it's good for 40 shots, from 250-120bar for a extreme spread of 14.2fps and an average fps of 897- 900 (kinda guessing on the average for the first 40, there were quite a few in the 905 realm from 200-160bar (4 or 5 in a row read 905.something). The last 6 or 8? of those 40 are likely off the reg, but still within reason for fps spreads (in my opinion). 

After all that, I'm not so sure my estimate of 135-140 on the reg pressure is accurate now. Also, the increasing the preload on the hammer spring experiment didn't seem to have increase it as much as I initially thought, when shooting an entire string.....too late at night for these deep ponderings.

As previously stated, going to do some long range accuracy testing at some point with it right here, 895-900fps for 45.5ish fpe. Will be interesting to see if the roughly 50fps increase helps with the wind and whether or not it has an effect on the measured BC. Pretty happy that it's still getting a fairly consistent 40shots with the increase in energy output (40/4 = a nice even 4 mags). 

and.....bed time!
 
In case it can help someone.....

OEM hammer spring dimensions (at least the one that came in mine)

OAL = 1.175in

OD = 0.455in

ID = 0.320in

wire = 0.067in

9 coils (7 if you subtract the two closed and ground ends) (see the pic of the spring in the above close-up as I'm no expert in coil counting)

The "peg" on the brass hammer tension adjustment area's OD is 0.315in (this peg slide INTO the spring when assembled).

The way the hammer tension adjuster slides into the spring, coupled with the step on the long thin "hammer" that also slides into the spring (but at the other end) makes the window of acceptable springs seem like it's pretty narrow. All the particulars (OAL, ID, OD) can't deviate much from the OEM spring and have the gun still cock and function properly. 

Would also be curious to see if the hammer springs issued in other's Vet's are similar to this one. 
 
Mine was one of yhe first longs aviable from tonny, CZ barrel ant it liked air arms 18g at 950fps n light flat base slugs up to 22g .. nothing heavier than that except for 28g bt but with a lot of hold over .. but they fly really stable.. I didn't purchased that rifle to tinkering I purchased them for heavy pellets...but both the .22 n .25 were so under powered .. I sold them both right away .. i wait a bit n then purchased uragans..they came tuned to my liking so no custom gun for me .. a standard uragan. 22 tuned for 25g knockouts at 960fps pure fun.. I use pellets only on my cricket compact..light small gun..NOW the new vulcan 3 looks even better on the power department.. I could say that with the launch of the vulcan 3 ..speaking of power for heavy pellets n slugs.. older generation cricket ..and the taipan platform are outdated guns good only for pellets n light slugs...taipan must do something quick about power in the next year..
 
.177 slugger?? Looks like fun! Great platform to do it from also.

Not necessarily .177 slugger at this point, just experimentation with heavy .177s.

I'm told the NSA 20.5s (longest one in recently posted photo above) have to be leaned on real hard so the Vet won't likely have the oomph there. I'll try them to see though. I'd guess 750-850fps. 

I've got more hope for the JSB 16.2s, 13.34s or maybe even the NSA 15s. I've got it on good authority that the heavy .177 projectiles can be scary good for long range, if pushed fast enough. So some long range paper shooting and BC collections are coming. 

Should be entertaining and maybe we'll even learn something from the experiment.

I'll share as it progresses. 
 
I've been having fun with the .177 project and want to share where it's at so far. 

It's a 24inch .177 poly barrel with a slight choke, it is just a bit more than the choke on the poly .177 in my USFT but nowhere near anything I'd call 
"tight" when compared to many airgun barrels. Otherwise, bout the best you can hope for a pellet to feel as it is pushed through: slight bit of pressure to get started, and then nice, easy consistent resistance the whole way to the muzzle, with just a touch more resistance to pop through the choke prior to exit. (no loosy goosy alternating with grabby/tight spots like some barrels possess). 

10mm OD, which presented a bit of a problem for the Vet, as it requires an OD of 15mm. Machinist friend's clever solution was to attach two brass fittings on each end and machine them appropriately, as well as source some carbon fiber tube with a OD pretty close to 15mm (more on that in a sec). 

The ID of the carbon fiber was just a bit too small for the 10mm barrel to fit so a flapper wheel of sorts (another clever solution from machinist friend) was used to slowly and carefully bring the ID of the carbon fiber up to a point that the barrel would fit inside, quite snuggly too. 

bare barrel.1643439342.jpg


The cf tubing is 19 and 5/8 inches long, leaving about 2.375inches of bare barrel right in front of the breech. It could probably just be left bare but I got in my head that I wanted to cover it up so I first tried shrink tubing, in various flavors.

shrink tubing.1643439438.jpg


The result of the shrink tubing was a lumpy, multi-shaded mess. Removed it. Got to thinking about options and thought, "maybe orings?" Now, some will see this wasteful, but these were from a failed attempt at getting a cheap ebay fill station to seal, so really just surplus, and don't fit anything specific. 

orgins 1.1643439545.jpg
orings.1643439545.jpg


At that point, I proclaimed the barrel assembly complete and examined the pellet seating situation. Going from a .22 to a .177, I had some slight concerns about using the .22 probe in the .177. The .22 to .20 Vet conversion worked just fine with the .22 bolt, but would it work for the .177 too? Seems like there should be a ledge in there for the pellet to have to go over. So, screwed the barrel assembly in to the breech and seated a pellet to see. 

pellet seating.1643440588.jpg


Pellet seating seems just fine to me. 

Next I decided to torque down all the scope tower bolts. I found another problem during moderator/shroud fitment though, the barrel was spinning....."oh no!" Initially though the barrel was spinning inside the brass threaded end pieces but I figured out that was not the case, but rather the barrel was unthreading from the breech. That's not supposed to happen with the scope tower all tightened up. hmmm......Determined that the CF tubing actually has an OD just a bit smaller than 15mm, more like 14.9mm or so (ish cuz calipers on a round object). So the scope tower bolts bottom out before they fully contact the CF...okay, SHIMS.

shim stock.1643439980.jpg


But first a bit of math rather than just trial and error. OD of 14.9mm (diam) = circumference of 46.8mm, or roughly 1.84 inches. Towers are each about 1 inch wide so, shims 1 inch by 1.84 inches should be about right. Cut them at more like 1.837 inches though, as I'd rather have a small gap than have the shim overlap. 

shims.1643440431.jpg
shims1.1643440432.jpg


Tightened everything down again and success, barrel will no longer spin. 

Chrono testing in the garage.....

There's surely some academic items to note here, and probably curiosity to satisfy as "how much power loss/gain happens with a caliber change, all else equal" comes up on occasion. Like most things though, there are some facts to kinda muddy the water as I went from a 23.5 inch .22 barrel with standard rifling and no choke to a 24 inch .177 poly barrel with a slight choke. I did not change the hammer tension or the regulator pressure, same "settings." So, it's not cut a dry caliber change since the rifling is different as is the choke, and then there's that pesky (for data comparison) 1/2 inch difference in barrel length. 

As this is primarily a HP/ long range endeavor, stuck with mostly heavy stuff.

Remember, the same settings with this gun and the .22 barrel produce about 43fpe (875fps with JSB 25.4gr Monster RDs). 

13.43s, five shots: 1019, 1023, 1022, 1017, 1022 for about 31fpe

16.2s, five shots: 957, 961, 966, 963, 962 for about 33fpe.

NSA 12.5s, five shots, 1012, 1012, 1012, 1009, 1005 for about 28fpe (three repeat fps! might be the first time I've had 3 consecutive shots with same fps). 

NSA 15s five shots: 893, 892, 900, 899, 881 for about 26fpe

NSA 20.5s, zero shots. The gun could not overcome the resistance of all that bearing surface to fire the pellet, had to resort to pushing it out with a one-piece cleaning rod. 

I'm measuring the 20.5s at about 0.353 inches long, with roughly 0.23inches of bearing surface. just too much for this gun. Some maybe interesting photos of the 20.5 and imparted rifling. Remember, poly so not a whole lot of marks left on the pellet. I added some lines to help point out those marks. 

2022-01-28_23h55_03.1643441502.jpg
rifling.1643441502.jpg
rifling1.1643441502.jpg
rifling2.1643441502.jpg


Accuracy testing to come. 




 
I read through all your veteran threads and love what your doing. They are such fun guns to work on and tinker. I just started experimenting with a .22 700mm impact barrel on my taipan. Lucky enough to snag one from Utah while they were in stock for a brief time.

My reg is 140-145bar and is slinging fx 25.4gr at 960fps. Now if I could only source a plenum extension.

Looking forward to your accuracy results. The thought of a .177 slugger always intrigued me.