Lothar Walther twist rate for slugs @ 1100 FPS

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Azycray

Azycray

Member
Oct 19, 2016
238
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Virginia, United States
I'm looking for advice from the balistically gifted on this one. My first question is if I'm shooting or planning on shooting slugs at around 1100 fps do I want LW's air rifle barrel with a 17.3:1 twist rate, which if I'm not mistaken was designed for pellets, not slugs? The other option would be a straight, no contour target barrel in .25 with a 10:1 twist rate as long as the half of the barrel that fits into an Impact can be turned down to .550" But for now lets assume that is an option. Which would be the best choice?
 
10" twist sounds pretty fast. What kind of slugs are you planning to shoot? Length of the projectile is important when calculating proper twist rate for given bullet. Longer the bullet, faster the twist rate should be. If you're looking LW's 25acp barrel with 10" twist, as far as I know, it doesn't work very well with slugs and lands/grooves are way too tight for .250 slug.
 
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If you have an Impact why wouldn’t you get the X barrel and slug liner?

I have a .25 LW poly barrel on my Impact and its my favourite barrel and most accurate shooting the King Heavy mk2’s. There is quite a bit of work turning down the stock 16mm barrel to fit the Impact. 

Its a choked barrel and I have tried the Nielsen slugs through it and it didn’t shoot them that well. For the cost involved in fitting the LW you could definitely buy the X-barrel and probably a couple of liners as well. 

I don’t know that any other barrel manufacturers would have done as much research to get the slugs to work in there barrels as fx. 

Michael
 
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Well I can always have a slug made to .248 or .249 if the barrel is too tight but the length is not that long. A .25 slug in the 50 grain size range give or take is not going to be very long. And the choices are either 10:1 or 17.3:1, not ideal but I think I'm leaning towards the 17.3:1. I'll wait and see what LW says when I talk to them next week. I've also sent an e-mail to Nielsen Specialty Ammo since I heard he has done a lot of testing with different barrel twist rates. So once I hear from these two I'll report what decision I have made and why. I suppose there might be other barrel makers out there that make a .25 with a twist rate of maybe 14:1. If anyone has a link to other possible sources I will contact them. But most likely it will turn out to be something of a unicorn barrel, if in fact a 14:1 would be better than a 17.3:1. Just seems to me that since it will be a slug of the general size and shape of a .22LR, just slightly larger, and going close to a .22LR velocity, that a similar twist rate to a .22 would be better than a twist rate designed for diablo pellets. Stay tuned.......
 
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The Lothar Walther is also available un-choked, which is what I would get. I realize the new Smooth Twist X has a slug liner but they are designed for slugs of 39 grains and under if memory serves and I wanted to shoot something a tad heavier. I may still try out the STX slug barrel at some point but the LW should shoot better with a heavier slug.
 
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I did look up the twist rate of the .22LR which is 16:1 so that also makes me feel better. That is pretty close to the Lothar barrel twist of 17.3:1 Then I found this twist rate calculator which also agrees. In fact as the length of the pellets get shorter in the 39 grain and below range, the twist rate calculator goes up higher than 17:1 So this could help in choosing which slugs to try based on their length. The calculator does not take weight into account, only bullet type or material. Very nice tool to have!
 
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I'm wondering what airgun platform you are going to use to achieve your goal of 1,100 fps .

Here is my modified Wolverine 303 it is now a 22 cal with a Daystate 24" barrel in 22 cal

this gun now shoots a 24 grain slug at 1090-1100 fps and does good , it also shoots a 40 grain

very good and can easily shoot 1" groups at 100 yards .



Here is the gun I was testing the DB on this day got 67db with the 40 grain slug at 935 fps

1530990504_13950582165b410fa8cfca99.46895582_1F7zO80.jpg


Here are the 40 grain slugs in 22 cal

1530990670_17004830215b41104ea9a649.86661805_IMG_1955.jpg


Here are the 24 grain slugs that shoot 1,100 fps from a 1:18 choked Daystate 24" barrel . 

1530990783_15580763455b4110bf303ab6.94341970_IMG_1634.jpg





 
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I'm wondering what airgun platform you are going to use to achieve your goal of 1,100 fps .

Here is my modified Wolverine 303 it is now a 22 cal with a Daystate 24" barrel in 22 cal

this gun now shoots a 24 grain slug at 1090-1100 fps and does good , it also shoots a 40 grain

very good and can easily shoot 1" groups at 100 yards .



Here is the gun I was testing the DB on this day got 67db with the 40 grain slug at 935 fps



Here are the 40 grain slugs in 22 cal



Here are the 24 grain slugs that shoot 1,100 fps from a 1:18 choked Daystate 24" barrel . 



Where do you get those slugs from?



Click to expand...
 
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I also recommend to get get the thickest OD barrel you can 

the ones from TJ are available in a 9/16 OD and then run a

carbon fiber tube over that . If you going to make big power 

I'd look into a product called " Limbsaver " this product can 

take a gun that does not shoot well and by adjusting the harmonics

with the Limbsaver you can get your rifle to shoot much better just

by moving the rubber isolator to change the harmonics of the barrel .


 
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I got another response from Nick Nielsen: "I have guys shooting 65 grain on the LW barrels in condors. Fx guns are typically lower powered and 39 grain is the heaviest I sent them. 18 twist is very good for the weight range you are looking at. Even .257 barrels shooting 90 grain slugs are 14 twist."

I guess I didn't mention the rifle for the new barrel is the Impact .25. I got it in Nov. of 2016 so it's a gen1 and have been filling it with helium since it was new, that is how I get up into the 1100fps range which is where I want to stay. When I get it up to about 1118-20fps you get the crack from sound barrier, so I want to shoot as heavy a slug as I can to be right around 1100fps. I might have to mod my magazine to fit the slightly larger slugs. There is room to route the clear front mag. cover to gain internal room. I'm still leaning towards getting the LW if possible, I'll see if I can custom order in 30". If not, then the X slug barrel might have the advantage. Stay tuned....
 
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