Hey FX R&D Team
- Thread starter brillerino
- Start date
I'm caliber restricted here in IL, so .177 slug guns interest me greatly. Currently working on a Hatsan Flash to see if I can get a 12.5 NSA to 950+ and good accuracy.
I eventually want to get a Taipan Veteran Long and turn it into a .177 slug monster.
I eventually want to get a Taipan Veteran Long and turn it into a .177 slug monster.
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I would be happy to purchase a .177 set up for my Impact if I could get accuracy from the heavy NSA slugs. I’m starting to see a couple members here exploring long range slugs with their .177 rifles.
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100% agree, a superior with 1:16 and heavy with 1:12 or 1:13 would be awesome. I do have descent luck with 12.5 NSA currently with 1:18 to my surprise.
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The NSA both work just fine with the new 600mm SUPERIOR FX liner, there is also a 700mm .177 on it's way in the next few months and the carbon sleeves for these to suit the IMPACT set up can be pre-ordered now.
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1:12, 1:13 are too fast of a twist for any slugs that will fit the FX magazines. I've been playing with the .177 slugs for a while now. I have an Alfa Precision 1:14.6 twist, and it is fast enough that it only likes 20-24 grain slugs in my testing. I also have a AP 1:16.5 twist, and it does very well up to about 22 grain. The 24 grain flat base .177 slugs are pretty much the limit on what will fit my Maverick magazines, fwiw. I built a Flashpup just for shooting the .177 slugs a while back. I used an unchoked LW polygon barrel in it, and it was crazy accurate with the older 15 grain NSAs at 1000 fps. I did well with the 18 grain NSAs at 1060 fps. It didn't have a fast enough twist for the heavier stuff, unless they were shot at really fast speeds.
I would love for FX to come out with a 700mm .177 slug liner though! The extra length would be very useful for slinging those heavier 20+ grain slugs at 1000 fps, without having to push the gun too hard. I think a 1:15-1:16 would probably be about perfect for that. I machined the AP 16.5" twist barrel to fit my Maverick, and it works great with Griffin 22 grain, and the newer NSA 20.5 grain slugs. I haven't had the heart to sacrifice my faster twist barrel, and machine it to fit the Maverick though. An FX slug version would solve that problem, and probably allow for some serious power tunes in the 50+ fpe range
I would love for FX to come out with a 700mm .177 slug liner though! The extra length would be very useful for slinging those heavier 20+ grain slugs at 1000 fps, without having to push the gun too hard. I think a 1:15-1:16 would probably be about perfect for that. I machined the AP 16.5" twist barrel to fit my Maverick, and it works great with Griffin 22 grain, and the newer NSA 20.5 grain slugs. I haven't had the heart to sacrifice my faster twist barrel, and machine it to fit the Maverick though. An FX slug version would solve that problem, and probably allow for some serious power tunes in the 50+ fpe range
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1:12, 1:13 are too fast of a twist for any slugs that will fit the FX magazines. I've been playing with the .177 slugs for a while now. I have an Alfa Precision 1:14.6 twist, and it is fast enough that it only likes 20-24 grain slugs in my testing. I also have a AP 1:16.5 twist, and it does very well up to about 22 grain. The 24 grain flat base .177 slugs are pretty much the limit on what will fit my Maverick magazines, fwiw. I built a Flashpup just for shooting the .177 slugs a while back. I used an unchoked LW polygon barrel in it, and it was crazy accurate with the older 15 grain NSAs at 1000 fps. I did well with the 18 grain NSAs at 1060 fps. It didn't have a fast enough twist for the heavier stuff, unless they were shot at really fast speeds.
I would love for FX to come out with a 700mm .177 slug liner though! The extra length would be very useful for slinging those heavier 20+ grain slugs at 1000 fps, without having to push the gun too hard. I think a 1:15-1:16 would probably be about perfect for that. I machined the AP 16.5" twist barrel to fit my Maverick, and it works great with Griffin 22 grain, and the newer NSA 20.5 grain slugs. I haven't had the heart to sacrifice my faster twist barrel, and machine it to fit the Maverick though. An FX slug version would solve that problem, and probably allow for some serious power tunes in the 50+ fpe range
Nice input, ive just used the twist rate calc mcthingy and it calculated that 1:12/13 was best. Sometimes reality beats matrix
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@rallyshark, why do you say 1:12 is too fast? If you take nsa 20 grain slugs and plug it into bullet stability calculator shooting them at 900 FPS the stability and factor is 1.75 which is optimum or just above 1.5. With 1:13 the stability factor drops to 1.45 which is very good but still considered marginally stable. I’ve ran these numbers many times and 1:12-13 would be ideal for slugs. For pellets it’s way too fast but I usually shoot pellets very slow so it would work great for me also with my use case.
these mathematical calculation have proven to be accurate beyond doubt. Hell G1 calculation started well over 100 years ago when rifles artillery started, math and physics are absolute.
edit: for a billet/slug to achieve optimal/advertised BC it needs to have a minimum stability factor of 1.5. If a billet is shot through a barrel that generates a stability factor below 1.5 then ballistic calculation based on factory BC numbers will like be off, it very well may group very well still but not optimal. Another reason 1:12 is a good target twist rate for slugs up to 20 grain, If the slugs are heavier/longer the we will likely need 1:11. SF of 1.75 barely cleared the 1.5 target.
these mathematical calculation have proven to be accurate beyond doubt. Hell G1 calculation started well over 100 years ago when rifles artillery started, math and physics are absolute.
edit: for a billet/slug to achieve optimal/advertised BC it needs to have a minimum stability factor of 1.5. If a billet is shot through a barrel that generates a stability factor below 1.5 then ballistic calculation based on factory BC numbers will like be off, it very well may group very well still but not optimal. Another reason 1:12 is a good target twist rate for slugs up to 20 grain, If the slugs are heavier/longer the we will likely need 1:11. SF of 1.75 barely cleared the 1.5 target.
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math and physics are absolute, these calculators have been proven accurate every possible way. Only time reality beats ballistic calculator is when the data input into the ballistic calculator is wrong.
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I mean no disrespect, and I can only go by the thousands of .177 slugs I've wasted trying to find the best .177 slug solution. I've machined no less than 6 or 7 different barrels in the process of testing. I've tested every weight from 10.5 grain up to 24 grain, and done a lot of testing at velocities from 800 to 1100 fps. I've done a lot of testing for some of the slug makers. I know very well what the calculators say, I went through them, until I was blue in the face. Math and physics are absolute, no disagreement there. The problem is, there are variables those calculators can't quantify. I'm not smart enough to tell you what all those variables are either. I can only say what I've seen with my testing. I thought for sure that my 14.6" twist barrel was going to be THE barrel for shooting 15 grain slugs, but it flat out won't shoot anything well lighter than 20 grains. I It works very well with 23 and 24 grain slugs though. It turned out that the 16.5" twist barrel is the winner for lighter slugs, and it even does better with the 20.5 grain than the 14.6" twist barrel. There's also the sizing side of things to consider, and barrel type, etc. etc. Try this: pull up the ballistics calculator, put in 15.5 grain slugs with a 1:17.7 twist barrel, and see how well it says that will work. I say that, because one of my most accurate .177 slug combos was with an unchoked LW polygon shooting those slugs at 1000 fps. I made my longest ever hit on a target with that combo, which was a 1 liter pepsi at 400 yards. Or take that same barrel, and put 18 grain slugs in the calculator. The calculator can only give us a idea of what should work, but it isn't gospel. That is especially so, when we're talking air guns and slugs.
When you or anyone else can point me to a 12-13" twist .177 barrel that works, I will happily take note and order one myself! I'm not necessarily saying you're wrong, so much as I'm saying I haven't seen results produced. Granted, fast twist .177 barrels aren't something that really exists to test, so the twist calculator is the best thing most people can go by. I totally understand that. That's why I went to all the trouble I did to get the fastest twist .177 barrels I could from Alfa Precision. Those barrels proved to me that faster twist isn't always the solution we think it is for .177. I've seen the same thing happen in .22 slugs too. I've seen where a 1:20 barrel shoots like a laser, when ta 1:16 barrel with the same sizing wouldn't shoot the same slugs for anything(and I'm talking 38 grain slugs). That flat out shouldn't work by the twist calculators, but it does? Sure, there are guys shooting great with faster twist .172 barrels, but that's a different ball game there.
Honestly, I'm not really sweating the twist rates as far as FX R&D may be concerned. I know they'll do their own testing to determine what will work, should they produce a .177 slug barrel. If it turns out to be a 12" twist, that's cool by me
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@Rallyshark
Not saying your testing is wrong and my FX 1:18 barrel has been pretty accurate with NSA 12.5 grain slugs even. But physics is physics and the calculators for ballistic and twist rates are 100% accurate in all calibers airgun and center fires, there simply is no doubt on that. I'm not saying the slow twist rate can't be accurate but still not optimally stabilized even though they can group very well at certain distances but the BC certainly will not match to manufacture published numbers. All slug and bullet makers uses these stability calculator and they will pick the best possible BC which is always achieve above stability factor of 1.5 and usually much higher. I know to some airgunners these calculators may seem a bit foreign but these formulas has been proved to be 100% accurate for many many decades.
To your point there aren't any available 177 barrels made for airgun slugs to begin with let along one with fast twist rate but just look at 17HMR barrels, even at over 2500 FPS they are still running 1:9 twist rate for 15.5, 17 and 20 grain bullets/slugs and they are only slightly longer than the 177 slugs. Based on the calculator I suspect FX will be targeting slugs 15 grains and higher and for that they will need 1:12 twist rate or maybe even 1:11 twist rate once if they will target above 20 grain. No one in the industry that does not use the calculators to design a product because trial and error is ridiculous waste of time, we have the technology decades ago.
There are definitely many other variables like choke and bullet design but some airgun barrel makers are trying to shoot both slugs and pellets or make pellet barrels to shoot slugs and it just won't work. They are better off just modify some 17 and 22 rimfire barrels. This stuff has been done for so long in center fire and rim fire world it baffles me that air gun industry is so behind, they just need to copy stuff from rim and center fire stuff that has been around forever. For crying out loud anyone can spend less than $1000 dollars and get a gun with scope to shoot 1000 yards all day and we can't even figure out how to shoot 100 yards with slugs from 2000 dollar airguns? It's not like centerfire worlds don't have sub sonic ammo in many calibers which behaves JUST LIKE an airgun!
My centerfire Tikka T3x creedmoor project should shoot out of box to 1000 yards all day and with right factory ammo out to 1 mile! And it cost only half of the price of my Impact. it's kinda sad if you really think about it. LOL
Not saying your testing is wrong and my FX 1:18 barrel has been pretty accurate with NSA 12.5 grain slugs even. But physics is physics and the calculators for ballistic and twist rates are 100% accurate in all calibers airgun and center fires, there simply is no doubt on that. I'm not saying the slow twist rate can't be accurate but still not optimally stabilized even though they can group very well at certain distances but the BC certainly will not match to manufacture published numbers. All slug and bullet makers uses these stability calculator and they will pick the best possible BC which is always achieve above stability factor of 1.5 and usually much higher. I know to some airgunners these calculators may seem a bit foreign but these formulas has been proved to be 100% accurate for many many decades.
To your point there aren't any available 177 barrels made for airgun slugs to begin with let along one with fast twist rate but just look at 17HMR barrels, even at over 2500 FPS they are still running 1:9 twist rate for 15.5, 17 and 20 grain bullets/slugs and they are only slightly longer than the 177 slugs. Based on the calculator I suspect FX will be targeting slugs 15 grains and higher and for that they will need 1:12 twist rate or maybe even 1:11 twist rate once if they will target above 20 grain. No one in the industry that does not use the calculators to design a product because trial and error is ridiculous waste of time, we have the technology decades ago.
There are definitely many other variables like choke and bullet design but some airgun barrel makers are trying to shoot both slugs and pellets or make pellet barrels to shoot slugs and it just won't work. They are better off just modify some 17 and 22 rimfire barrels. This stuff has been done for so long in center fire and rim fire world it baffles me that air gun industry is so behind, they just need to copy stuff from rim and center fire stuff that has been around forever. For crying out loud anyone can spend less than $1000 dollars and get a gun with scope to shoot 1000 yards all day and we can't even figure out how to shoot 100 yards with slugs from 2000 dollar airguns? It's not like centerfire worlds don't have sub sonic ammo in many calibers which behaves JUST LIKE an airgun!
My centerfire Tikka T3x creedmoor project should shoot out of box to 1000 yards all day and with right factory ammo out to 1 mile! And it cost only half of the price of my Impact. it's kinda sad if you really think about it. LOL
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As I said, I will happily purchase any twist barrel that comes out and works for .177 slugs. If that barrel happens to be a 10" or 12" twist, that's just fine by me. I don't want to sound repetitive, but all my testing with every weight slug I could get my hands on, points to a little slower twist than what you're suggesting. Of course there are sizing variables and bullet shape and rifling type etc. etc. that must also be considered. We also can't compare .172 ammo/barrels to .177. That is physics, and those physics are quite different between the two. The diameter of the .172 is smaller, the bullet is longer, and the speed is faster. The guys shooting .172 in air guns are usually using a 9" twist I believe, with 29 grain bullets in most cases and sometimes 32 grain. That is a whole different projectile, that most air guns(short of an Airforce) have a hard time dealing with. Yes, there are exceptions, but generally speaking there aren't. My replies are directed at the FX platforms and magazines. I don't foresee anything much heavier than 24 grain fitting the FX magazines.
The calculators are usually on point, assuming the right info is entered. As mentioned, there are variables the calculators can't account for. Some of the problem happens when we try to do it for .177 slugs, in which there is no standardized sizing, or bullet shape/design. One maker sells .178, another .177, and another still .1775. We can make good guesses, but it isn't 100%, because we aren't. That's why I said, I've looked at the calculators, a lot. They all told me the same thing you're suggesting, give or take. However, I haven't been able to duplicate that in my testing. The results from my testing are different, and I can't change that. It is what it is. The slugs that I have had good results with are not "good at certain distances" either. If I say it is good, I mean it stabilizes and stays that way from 30-400 yards. I can't get the 16.5" twist barrel to shoot well with anything under 15 grain, but it is good from 15-22 grain. I can't get the 14.6" twist barrel to shoot well with anything under 20 grains, but it does well from 20-24 grains. I tried every speed from 800 to supersonic, and I tried sizing from .177, 1775, and .178. I tried changing the leade in, seating depth, porting type, still the same results. I could only get the LW 17.7" twist barrels to do well with the lighter 12.5 grain slugs. I tried polygon and grooved, choked and unchoked. Heck, the same LW polygon that shot like a laser with the 15.5 grain .177 slugs, wouldn't shoot the .178 15 grain slugs to save it's life. That's a sizing issue though, obviously.
I'm definitely not saying the calculators are wrong a lot or anything like that. I am saying that there is more to it than just that calculator. Ask any of the air gun slug gurus on here or any other air gun forum. They will also tell you the calculator is not gospel. It's a great place to start, but it isn't always perfect, because we and our data aren't always perfect. The calculator is the best place to start most of the time. I'm also not willing to say my data or testing is gospel. Even with all of my testing, there are things I surely missed. I do trust what I've seen with my own eyes more than a calculator. At least, until I see those calculations reproduced on target.. I'm more than willing to admit I could be wrong, and I know those calculators have been proven on more bullets and platforms than I can even imagine. I'm just not willing to bet the bank on the calculators is all
I completely agree with one thing. We can make 1000 yard powder burners all day long without much effort, so why on earth can't we do the same with a .177 slug at 100 yards, LOL! There are a couple of guys that have figured that out, and shooting sub MOA with .177 slugs well past 100 yards, but you might be disappointed to find out the twist of their barrels, haha. I have done it, but not documented it like they have. Flintsack has been doing amazing things with his Red Wolf and .177 slugs to name one. He's got some pretty amazing groups and photos on here too. Honestly, I'm happy to be wrong, especially if that means we get a laser of an FX .177 slug liner as a result! I welcome whatever they come up with. If it happens to be a 12" twist, awesome. I'm betting it will closer to the 15" range though. Either way, I want the same thing the other folks in this thread want, and I don't mind one bit if I have to be wrong for it come to fruition
The calculators are usually on point, assuming the right info is entered. As mentioned, there are variables the calculators can't account for. Some of the problem happens when we try to do it for .177 slugs, in which there is no standardized sizing, or bullet shape/design. One maker sells .178, another .177, and another still .1775. We can make good guesses, but it isn't 100%, because we aren't. That's why I said, I've looked at the calculators, a lot. They all told me the same thing you're suggesting, give or take. However, I haven't been able to duplicate that in my testing. The results from my testing are different, and I can't change that. It is what it is. The slugs that I have had good results with are not "good at certain distances" either. If I say it is good, I mean it stabilizes and stays that way from 30-400 yards. I can't get the 16.5" twist barrel to shoot well with anything under 15 grain, but it is good from 15-22 grain. I can't get the 14.6" twist barrel to shoot well with anything under 20 grains, but it does well from 20-24 grains. I tried every speed from 800 to supersonic, and I tried sizing from .177, 1775, and .178. I tried changing the leade in, seating depth, porting type, still the same results. I could only get the LW 17.7" twist barrels to do well with the lighter 12.5 grain slugs. I tried polygon and grooved, choked and unchoked. Heck, the same LW polygon that shot like a laser with the 15.5 grain .177 slugs, wouldn't shoot the .178 15 grain slugs to save it's life. That's a sizing issue though, obviously.
I'm definitely not saying the calculators are wrong a lot or anything like that. I am saying that there is more to it than just that calculator. Ask any of the air gun slug gurus on here or any other air gun forum. They will also tell you the calculator is not gospel. It's a great place to start, but it isn't always perfect, because we and our data aren't always perfect. The calculator is the best place to start most of the time. I'm also not willing to say my data or testing is gospel. Even with all of my testing, there are things I surely missed. I do trust what I've seen with my own eyes more than a calculator. At least, until I see those calculations reproduced on target.. I'm more than willing to admit I could be wrong, and I know those calculators have been proven on more bullets and platforms than I can even imagine. I'm just not willing to bet the bank on the calculators is all
I completely agree with one thing. We can make 1000 yard powder burners all day long without much effort, so why on earth can't we do the same with a .177 slug at 100 yards, LOL! There are a couple of guys that have figured that out, and shooting sub MOA with .177 slugs well past 100 yards, but you might be disappointed to find out the twist of their barrels, haha. I have done it, but not documented it like they have. Flintsack has been doing amazing things with his Red Wolf and .177 slugs to name one. He's got some pretty amazing groups and photos on here too. Honestly, I'm happy to be wrong, especially if that means we get a laser of an FX .177 slug liner as a result! I welcome whatever they come up with. If it happens to be a 12" twist, awesome. I'm betting it will closer to the 15" range though. Either way, I want the same thing the other folks in this thread want, and I don't mind one bit if I have to be wrong for it come to fruition
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Thanks for sharing great testing information Rallyshark! Unfortunately I have not done enough testing in 177 caliber to put forth better evidence/results but I've shot thousands of slugs in .22 and .25 FX barrels. What's I've learned is the best accuracy and BC comes in around stability factor of around 2.
Here is what I do for testing which is a bit more than just shooting groups as that is only the base of accuracy. As soon as I find a tune and ammo/barrel combo that can group sub MOA at 100 meter I would then plug all the info into ballistic calculator especially the published BC and pick random distance targets and range then shoot. With the right combo I can dial and shoot just like Matt Dubber on youtube and the accuracy/precision is astonishing. Even when I do miss it's barely which can be attributed to me. What I realized is that when the slugs are stabilized above 2 then accuracy is very easy to achieve, since it's FX STX barrels the actual twist rate might be a little bit slower but with the math SF at 2.x the actually would still be well above 1.5. I've had slugs show below SF of 1.5 and the BC seems to be a bit off and so is the wind drift calculation from ballistic software, this is when I know the slugs aren't optimally stabilized but they will group well past 100 yards still. I then just bump the speed up as much as I can to get SF close to 1.5 then the BC/POI seems to match with ballistic software better. Forgot which slug/barrel combo that was though. Of course I can adjust BC in the ballistic software a little lower to match the actual BC and everything would line up if it's not lower than SF of 1.0, definitely NOT a deal breaker but if I use published BC and SF calculation as the starting point and if the slugs would group sub MOA then the deviation of BC usually is pretty small and easily adjusted to. I really hope one day the airgun slug makers will publish BC numbers for ever 100FPS increments from 600-1100FPS similar to what centerfire bullet makers do for their bullets. This would eliminate a ton of guess work!!!
I'm not saying stability factor has to be above 1.5 for it to group at all, in my experience with other calibers it certainly seem to be the common denominator to achieve amazing accuracy. Having that starting point cuts down enormous amount of time and slugs for testing and enables me to focus on other variable such as tunes because with the SF in the right range chance of it working is almost certain unless I got a bad barrel. So another way to put it is I would pick barrel and slug combo with the calculator and then work on tunes and other variables and so far has been a very successful approach, like you said there are a ton of variables and I like to make sure the fundamentals are solid or it's a wild goose chase. With that said the superior heavy barrels in other calibers do have relatively aggressive twist rate, I got SF of 2.5 with lighter .25 slugs. FX published that it's not for pellets which is very smart to do! I'm hoping to they will make the barrel in 1:12 but it's completely possible they lean towards 1:15 range which should still has a SF of 1.15 for the 20.5 grain NSA slugs @900 FPS. That is a bit too low from my experience with other caliber slugs I've tested so I'm hoping they will go 1:12 because the SF is only 1.75 with the NSA 20.5 grain slugs so it's well below "over stabilized" territory.
There is a bit of wildcard in the calculation is at what point in the stability factor score the slugs would be "over stabilized" so the slugs won't track the trajectory? I personally have not found it to be an issue even with SF of 2.5 at 150 meters which should have enough arc to have that problem surface but that's something I haven't been able to find the answer to but given my testing we shouldn't have that problem at SF of 2.5 and below.
Then, I don't like to shoot slugs at 1000 FPS, I'm punching paper so no need for crazy power. Also it much easier to tune for accuracy at 800 FPS range, at least in FX guns because it's just not pushing the gun really hard so harmonics is a lot less of a problem. Because of my preference for slightly lower speed I like to see a little more aggressive twist rate so lower speed isn't an issue. Who know what FX will end up at with the twist rate but I'm hoping it's more aggressive like what they have done with other superior heavy barrels, they have the luxury to do that because they have pellet barrels and caliber/barrel change is so easy.
EDIT: I’ve done pretty much all my testing with FX barrels because they are easy to change and get hold of new barrels(relatively). I did try a TJ pellet barrel which shot .22 slugs ok but doesn't seem want to group pass 80 yards, but I didn't really spend a lot of time on it as it didn't seem very promising and the barrel/choke is extremely tight.
BTW I do appreciate the nerd talk, I'm a nerd and love this kind of nerd talk. LOL
Here is what I do for testing which is a bit more than just shooting groups as that is only the base of accuracy. As soon as I find a tune and ammo/barrel combo that can group sub MOA at 100 meter I would then plug all the info into ballistic calculator especially the published BC and pick random distance targets and range then shoot. With the right combo I can dial and shoot just like Matt Dubber on youtube and the accuracy/precision is astonishing. Even when I do miss it's barely which can be attributed to me. What I realized is that when the slugs are stabilized above 2 then accuracy is very easy to achieve, since it's FX STX barrels the actual twist rate might be a little bit slower but with the math SF at 2.x the actually would still be well above 1.5. I've had slugs show below SF of 1.5 and the BC seems to be a bit off and so is the wind drift calculation from ballistic software, this is when I know the slugs aren't optimally stabilized but they will group well past 100 yards still. I then just bump the speed up as much as I can to get SF close to 1.5 then the BC/POI seems to match with ballistic software better. Forgot which slug/barrel combo that was though. Of course I can adjust BC in the ballistic software a little lower to match the actual BC and everything would line up if it's not lower than SF of 1.0, definitely NOT a deal breaker but if I use published BC and SF calculation as the starting point and if the slugs would group sub MOA then the deviation of BC usually is pretty small and easily adjusted to. I really hope one day the airgun slug makers will publish BC numbers for ever 100FPS increments from 600-1100FPS similar to what centerfire bullet makers do for their bullets. This would eliminate a ton of guess work!!!
I'm not saying stability factor has to be above 1.5 for it to group at all, in my experience with other calibers it certainly seem to be the common denominator to achieve amazing accuracy. Having that starting point cuts down enormous amount of time and slugs for testing and enables me to focus on other variable such as tunes because with the SF in the right range chance of it working is almost certain unless I got a bad barrel. So another way to put it is I would pick barrel and slug combo with the calculator and then work on tunes and other variables and so far has been a very successful approach, like you said there are a ton of variables and I like to make sure the fundamentals are solid or it's a wild goose chase. With that said the superior heavy barrels in other calibers do have relatively aggressive twist rate, I got SF of 2.5 with lighter .25 slugs. FX published that it's not for pellets which is very smart to do! I'm hoping to they will make the barrel in 1:12 but it's completely possible they lean towards 1:15 range which should still has a SF of 1.15 for the 20.5 grain NSA slugs @900 FPS. That is a bit too low from my experience with other caliber slugs I've tested so I'm hoping they will go 1:12 because the SF is only 1.75 with the NSA 20.5 grain slugs so it's well below "over stabilized" territory.
There is a bit of wildcard in the calculation is at what point in the stability factor score the slugs would be "over stabilized" so the slugs won't track the trajectory? I personally have not found it to be an issue even with SF of 2.5 at 150 meters which should have enough arc to have that problem surface but that's something I haven't been able to find the answer to but given my testing we shouldn't have that problem at SF of 2.5 and below.
Then, I don't like to shoot slugs at 1000 FPS, I'm punching paper so no need for crazy power. Also it much easier to tune for accuracy at 800 FPS range, at least in FX guns because it's just not pushing the gun really hard so harmonics is a lot less of a problem. Because of my preference for slightly lower speed I like to see a little more aggressive twist rate so lower speed isn't an issue. Who know what FX will end up at with the twist rate but I'm hoping it's more aggressive like what they have done with other superior heavy barrels, they have the luxury to do that because they have pellet barrels and caliber/barrel change is so easy.
EDIT: I’ve done pretty much all my testing with FX barrels because they are easy to change and get hold of new barrels(relatively). I did try a TJ pellet barrel which shot .22 slugs ok but doesn't seem want to group pass 80 yards, but I didn't really spend a lot of time on it as it didn't seem very promising and the barrel/choke is extremely tight.
BTW I do appreciate the nerd talk, I'm a nerd and love this kind of nerd talk. LOL
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It was probably my test that rally is speaking of. I used Redman lainers from Brownells Gun Smithiing supply and they are heavily wrapped with thick walled twill CF Tubing. I first ordered the LR version at .223 groove dia. and it shot somewhat ok. I then tried the .223 LR Short barrel at 1 in 20 twist. It is a laser with my 39 gr slugs. No comparison!
Yes, the calculators say this is dead wrong, however the targets tell a different story.
I design and test slugs for both my own use and for a few different manufactures of slugs. Here is a pic of the .223 at 80 yards Results. 11 shots. One to settle the reg, and 10 oin target.
KnifeMaker.
Yes, the calculators say this is dead wrong, however the targets tell a different story.
I design and test slugs for both my own use and for a few different manufactures of slugs. Here is a pic of the .223 at 80 yards Results. 11 shots. One to settle the reg, and 10 oin target.
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Last night, pic taken a few minutes ago. 6 yards, breeze (Mild) from dead behind. .25 Uragan, fully lapped and
polished CZ bbl. Slugs sized to .2516" CTC .159mm or .0062 Inch. 98 fpe
KnifeMaker
KnifeMaker
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Last night, pic taken a few minutes ago. 6 yards, breeze (Mild) from dead behind. .25 Uragan, fully lapped and
polished CZ bbl. Slugs sized to .2516" CTC .159mm or .0062 Inch. 98 fpe
KnifeMaker
That CZ barrel choked or no?
One of the biggest hurdles that I see with factory guns is that so many barrels (especially high end like CZ and LW) are choked from the factory. That's great for pellets, but generally bad for the larger bearing surface of slugs. FX has minimized this by using slugs that are very thin walled and able to be choked more easily.
I have a goal of turning a .177 Taipan Veteran Long into a .177 slug monster, since the porting is massive for the caliber, but it's going to take a rebarrel to get the accuracy I want.
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@knifemaker: thanks for sharing your data! I’ve also long believed powder burner .223 barrel would work well as long as the slugs are sized correctly and it’s just subsonic 223, again been done many times before. The 1:20 twist isn’t that slug given the slug length, what’s the slug length?
my testing was superior .22 barrel that has 1:24 twist shot the 23 grain the best. It also has the best GS factor of 1.1 in .22 caliber light slugs beside the 17 grain because it’s short thanks to the flat base. Very low GS factor so in Theory the BC should be off a bit but in my testing it does match with calculator very closely, it’s lower by 1-2 clicks or 0.1-0.2 Mil at 100 yards and groups very well. This proves to me the formula is correct and a good starting point for finding ammo/barrel combo. Also keep in mind that since the slugs are so short the pitch and yawn affect in BC is fairly small compared to a very long creedmore bullet with BC .65.
In effect I think short airgun slugs can work at low GS factor just above 1.0 but that does not prove the formula is wrong, it’s just proves the margin of error is much larger than the much longer PB bullets. Or the short airgun slugs are more tolerant of slower twist rates, doesn’t proof GS factor is 1.5 and higher won’t work. Personally I would still try to find slug and barrel combo with GS factor of 2.0.
my testing was superior .22 barrel that has 1:24 twist shot the 23 grain the best. It also has the best GS factor of 1.1 in .22 caliber light slugs beside the 17 grain because it’s short thanks to the flat base. Very low GS factor so in Theory the BC should be off a bit but in my testing it does match with calculator very closely, it’s lower by 1-2 clicks or 0.1-0.2 Mil at 100 yards and groups very well. This proves to me the formula is correct and a good starting point for finding ammo/barrel combo. Also keep in mind that since the slugs are so short the pitch and yawn affect in BC is fairly small compared to a very long creedmore bullet with BC .65.
In effect I think short airgun slugs can work at low GS factor just above 1.0 but that does not prove the formula is wrong, it’s just proves the margin of error is much larger than the much longer PB bullets. Or the short airgun slugs are more tolerant of slower twist rates, doesn’t proof GS factor is 1.5 and higher won’t work. Personally I would still try to find slug and barrel combo with GS factor of 2.0.
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I'll get a measurement for you. they are out in the shop and I've been up all night. Way past time to go to bed. LOL! but they are long! I'll look up the spec's on NOE Molds right now. .
.457 with HP, .489 without.
Knife
.457 with HP, .489 without.
Knife
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For what it's worth with regard to barrel twist rate...I have a Cooper 17 Rem Fireball that shoots 20gr V-Max bullets at 4000fps. The twist rate is 1:10. A 30-06 shooting a 220gr bullet at 2500fps also has a twist rate of 1:10. I would expect the 30-06 to have a much faster twist rate, but it doesn't. I'm guessing the calculators are right though.
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Very good info qball! Especially the BC stuff. I do the same thing when I get a tune I want. I'll test the numbers in Strelock Pro, until it dials spot on, regardless of distance. It works really well with the .22 and .30 slugs. I haven't tested it much in .177, since I machined the barrel for the Maverick, but the same thing does apply for sure. It sure is cool to be able to dial in a distance and hand your gun over to someone else and watch them pop a long range target on the first try
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