FX Streamline - The rest of the story

In my first post on the Streamline, I omitted some of the gory details of my quest for accuracy using the JSB pellets. I see that some people are having what sound like similar problems with their FX rifles, and thought this post might be of interest.

​Because the Streamline is my first .22 caliber airgun, the first shots were over a chronograph at 3 and 50 yards to develop BC numbers for the pellets I hoped to be using. I started with the JSB 15.9 pellets, and encountered no real surprises. Group size for 10 shots at 50 yards was a little less than an inch, and the spread on the chronograph readings at that same distance was 16 fps. I did omit the reading from the first shot, because at that time the first shot readings at both distances tended to be a little lower.

​The experience with the 18.1 pellets was an entirely different story. My first attempt at chronograph readings at 50 yards produced a 4" group with several low shots that just missed my chrony! I The spread on the chronograph readings was 118 fps. I decided to try again, and here are the results:
Date Spread (fps) Group (in)
6/16/17 94 2.43"
6/17/17 50 2.30"
6/17/17 34 1.33"
6/17/17 26 0.84" (omitting one flier)

​Note that each subsequent set of 10 shots produced a reduction in both velocity spread and group size. The large velocity spread at the beginning of the series was caused by one or more unstable pellets in each group. These lower velocity pellets would often produce keyholes in the target.

​Even though I had decided to standardize on the 15.9 grain JSBs due to their apparently greater inherent stability out of my gun, I thought I would give the 18.1 grain pellets another try since I have continued to see a steady reduction in group size with the 15.9 pellets since those early June trials. Here are today's results for four 5 shot groups at 50 yards using lubed 18.1 JSBs:
Group Size(in)
​#1 0.42"
#2 0.38"
#3 0.56"
#4 0.42"

​I had hoped to see some improvement since June, but these are really good groups, almost on a par with what I am getting from the 15.9 JSBs. As I mentioned in my first post, after running into accuracy issues with the 18.1 grain pellets in June, I stopped cleaning the Smooth Twist barrel in my rifle, and began seeing improvements in accuracy. In the case of the 18.1 grain pellets, the improvement is dramatic, having gone from the initial 4 inch group to the under 1/2" groups shown above.

​My take on all of this is that the FX rifles, probably due to the design of the Smooth Twist barrels, may need to be shot for a while before developing top accuracy. My rifle now has almost 1000 pellets through it, and I don't envision it improving much more. I don't know why accuracy/stability improves over time. I have not been cleaning my bore. Is the resulting coating of lead on the barrel ID somehow responsible? Is the barrel being polished after all those shots? If I cleaned the bore would accuracy go away, and I would have to start all over with seasoning of the bore? I don't know, and don't plan to try to find out as long as the rifle keeps shooting well.

​So if you encounter some initial accuracy problems with your FX rifle, it may be that you just need to season the bore by putting some more pellets through it. In my case, I would guess it took at least a couple hundred pellets to develop consistent accuracy.

Chuck
 
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FunGun, the scope is a Bushnell Elite 4200 4-16X. This is a very rugged scope with a very crisp image even at 16X. The turrets are of the low finger adjustable type and have the ability to reset zero. I prefer this type of turret for hunting. To prevent flare, the supplied hood must be attached when any amount of backlighting is present.

Chuck
 
Many reviewers state especially with barrels like the Walthar Lothar that they have to be seasoned by shooting at least a tin of pellets through them. Even after cleanig. you may find that the first 5-20 will be off before the rifle settles in. I just watched the video of Steve a AEAC on cleaning barrels and I believe he had the same experience with a Streamline. 
 
Gwelo, I probably should redo my velocity tests now that the gun seems to have settled down. The best I can do at the moment is to pass along the information I collected in June.

JSB 15.9 Velocity Averages (fps)
​Muzzle 3 yds 50 yds
​902 890 717

JSB 18.1 Velocity Averages (fps)
​Muzzle 3 yds 50 yds
​840 832 713

​When calculating the averages, the first reading was ignored as it was usually lower than any of the following readings. The muzzle velocity was not measured directly, but calculated using ballistics software and the 3 and 50 yard values. If you run these numbers through your favorite ballistics software, you will find the BC for the JSB 15.9 to be about 0.03, and about 0.04 for the JSB 18.9. The difference seems a little large to me, but that is what I measured.

Chuck

 
My .25 streamline is literally shooting hole in hole at 30yds. I have not cleaned the barrel at all. I shoot .301 inch 9 rings and limit 3 shots per hole due to penetration of my back stop. I have so many targets that have 3 shots thru the same hole with the 9 ring still visible all the way around. I love this streamline!!! I hope never to have to clean the barrel. Hope this trend continues!
 
"Michigander"Gwelo, I probably should redo my velocity tests now that the gun seems to have settled down. The best I can do at the moment is to pass along the information I collected in June.

JSB 15.9 Velocity Averages (fps)
​Muzzle 3 yds 50 yds
​902 890 717

JSB 18.1 Velocity Averages (fps)
​Muzzle 3 yds 50 yds
​840 832 713

​When calculating the averages, the first reading was ignored as it was usually lower than any of the following readings. The muzzle velocity was not measured directly, but calculated using ballistics software and the 3 and 50 yard values. If you run these numbers through your favorite ballistics software, you will find the BC for the JSB 15.9 to be about 0.03, and about 0.04 for the JSB 18.9. The difference seems a little large to me, but that is what I measured.

Chuck

Thanks for the reply! I get .027 and .038 using your numbers here: http://www.pyramydair.com/airgun-resources/widgets/convert.php?Units&u=14
Pretty much the same if you round off. A full .01 better using the 18.1's, that's seems significant. Yes, it would be interesting to see what the numbers are now!