I ordered this from Krale. It was packed superbly with very good speed of delivery. It has a 1 in 17 inch twist and has a label from FX on the liner identifying as such. I have done nothing with it yet, but I will measure it for bore diameter and choke, if any and get back to you on this thread.
Just received my STX Superior smooth twist heavy 600mm .25 cal liner
- Thread starter steve-l
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Now the fun begins! I've had mine in .22 for my 600mm for about a month and I'm having great results with NSA Slugs, the 31.2 gr especially-
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Followup, the bore diameter measured with precision pin gauges is .243" go and .244" no-go on both ends. (no choke). The JSB Knock-Out slug is .2505" for about 50% of its length. The JSB King Heavy pellet has a dome diameter of .247" and a skirt diameter of .256".
It should be clear the liner swage for the pellet is .007" and the heavy pellet will experience a light swage at the dome and a heavy swage at the skirt, but because of skirt taper, the swage length is relatively short. So, liner /projectile resistance will be quite a bit higher for the slug than the pellet of almost identical weight. My takeaway from this is that the slug will benefit from a wax lube and probably have a slower muzzle velocity than the heavy pellet. I predict excellent accuracy of the heavy pellet and not quite as good accuracy with the slug. Of course the slug advantage is a much better BC of .092 (advertised). Only testing will tell.
It should be clear the liner swage for the pellet is .007" and the heavy pellet will experience a light swage at the dome and a heavy swage at the skirt, but because of skirt taper, the swage length is relatively short. So, liner /projectile resistance will be quite a bit higher for the slug than the pellet of almost identical weight. My takeaway from this is that the slug will benefit from a wax lube and probably have a slower muzzle velocity than the heavy pellet. I predict excellent accuracy of the heavy pellet and not quite as good accuracy with the slug. Of course the slug advantage is a much better BC of .092 (advertised). Only testing will tell.
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Follow-up:
I installed the liner and compared the bore size with the standard pellet barrel and the bore size was .002 smaller than on the new superior heavy barrel .241" go .242" no-go. In testing the new liner was shooting in the same place with the JSB exact heavy 33.9 gr as the old liner. No POI shift, but very consistent. Same hole at 25 yards. So I loaded the new JSB slugs. They too shot in exactly the same place at 25 meters, they were slightly lower at 120 yds. I'm very happy/ The Crown is certainly more accurate than I am. I have not checked speed today, but I will and get back to the thread.
I installed the liner and compared the bore size with the standard pellet barrel and the bore size was .002 smaller than on the new superior heavy barrel .241" go .242" no-go. In testing the new liner was shooting in the same place with the JSB exact heavy 33.9 gr as the old liner. No POI shift, but very consistent. Same hole at 25 yards. So I loaded the new JSB slugs. They too shot in exactly the same place at 25 meters, they were slightly lower at 120 yds. I'm very happy/ The Crown is certainly more accurate than I am. I have not checked speed today, but I will and get back to the thread.
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The new JSB Knock Outs in .25. They are same weight as the Exact heavy pellets. As far as the FPS, I have not measured yet, but with the standard barrel, it was 880 FPS. Since the POI did not change, I suspect the speed is similar. My reg is set at 135 bar.
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