GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: thumbs on August 25, 2015, 01:24:45 PM
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I am probably going about this backwards but just trying to get started. The question is once you find the right pellet for your rifle what range of velocity is normally considered to be within your rifles accuracy range? I know all rifles and pellets are different but just in general. I am shooting a Disco .22. What I am trying to figure out is approximately at what point will my accuracy start to drop off. I have a string of shot that run form 808 up to a max of 844 then back to 807fps. This is from a fill pressure of 1900 down to 1100psi. Haven't shot them for accuracy yet but just wanted to get an idea as to what range is a good one to be looking for?
thanks
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It varies tremendously according to the rifle and pellet.... A wadcutter may start to drop off in accuracy at 700 fps, while a good round-nose pellet may still provide stellar accuracy at 1000 fps or beyond.... sometimes even supersonic.... As a general rule of thumb, many rifles and pellets show a decrease in accuracy above 900-950 fps.... and many shoot the best in the high 800s.... As you push beyond about 850 fps, the Ballistics Coefficient tends to drop off rapidly, and that leads to increased wind drift.... so if you are shooting at longer ranges and in windy conditions, you may have better luck under 900 fps than over.... FT and Benchrest shooters tend to stay around 880ish a lot of the time, for these reasons....
Bob
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Or, do the trial and error thing to find out where your accuracy limits are. Different pellets will vary drastically in this.
Richard
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I decide what power I want/need based on what I plan on using the airgun for. I then grab some pellets and tune for that power range. Once I get the power adjusted I try different pellets to find the most accurate two. After thats done I play with the velocity to see if either pellet performs better slightly faster or slower.
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Depends on a lot of things. I've found for all of my guns I can shoot pellets as fast as I want at up to 50 yards.
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Hey thanks guys. I think I asked the wrong question. I agree with all you guys about matching pellet rifle and the rest. What I was trying to ask is just as dependent on variables but just a rule of thumb.
After I chronyed the rifle with a couple of pellets, still working on that, I am trying to decide what a reasonable spread in fps is acceptable for accuracy. I know I have to test the pellets for what shoots best, that's why I am probably going about this backwards, but can't shoot much further than 20 yards here.
In other words where is it reasonable to say accuracy is going to start to drop with a spread of 20, 30 or 40fps. Just a rule of thumb. I will test it when I get a chance to shoot at longer ranges but just a general rule. If I know this I can kinda tune the rifle to stay within this range with an acceptable energy at target.
Right now my spread is about 30fps to get the power I want on average. From high to low with 30fps effect accuracy much?
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Totally different question.... you are asking about the Extreme Spread (ES) in velocity, highest to lowest.... That really depends on the range you want to shoot at.... For 50 yards, you need to keep the ES to 4% or less.... at 75 yards, 3%, and at 100 yards 2% or less, of the peak velocity.... If the ES is larger than that, you may start to notice vertical stringing on the target.... If you are shooting at 900 fps, 4% is 36 fps, so you wouldn't want any shots slower than 864 fps at 0 yards.... At 100 yards, you would want to stay within 2% = 18 fps, so no shots under 882 fps....
Bob
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Yep I was asking the wrong question. Thanks. That is what I was looking for.
So in my particular case right now my ES is 771. So if I take 3% of that would be about 23fps. So according to that I should be able to go as low as 748fps and be safe. I will probably keep my shots to 50 yards so that should be a safe number, right?
thanks