GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: PyroMonkey on October 01, 2011, 05:46:24 PM
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So today I was outside enjoying the fall-like weather and tried to get some shot groups out of my Benjamin Discovery. It was pretty windy but I figured it would be good practice to estimate wind drift and go for bulls-eyes instead of tight groups. Well the gun is sighted in at 35 yards with jsb 18.1 gr. and usually drives tacks at that distance however today I was shooting at only 25 yards, 1 mil hold under. I guestimated a 5 mile per hour wind and shot... perfectly centered but about 2 inches high??? I continued shooting and noticed the wind severely effected both windage and elevation... I'm starting to get worried if my new TKO has hurt accuracy or if it's just wind. Anyone an expert on shooting in wind? if so is it normal to see a poi change in elevation? or have I ruined the accuracy by installing a second barrel band+TKO?
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If you put a different barrel on the gun, then you have a different gun.
Not all barrels like the same pellets.
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In addition, if you didn't re-sight the gun after installing the barrel band you POI is likely different than before.... The difference in POI at 25 yards for a gun that is sighted in at 35 yards should be only about 1/4", not 1 MilDot....
Bob
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I did re-zero the gun at 35 yards the day before and shot groups seemed to be decent but today using the same pellets I my groups have opened up dramatically. All I did was put the second barrel band on and the poi changed by about 1/2 inch at 35 yards so I adjusted for it, then I went back inside and put the TKO on and then the POI changed by 6 inches! I also cleaned the barrel thoroughly before installing the second band. After all the changes I re zeroed, shot some decent groups with the jsb heavys and went to sleep. I woke up today and there was some wind,nothing else had changed, my question is will wind effect the elevation of the pellet? If not what could explain the inaccuracy? example: barrel band placement? but that wouldn't explain why you got decent groups the day before after you installed it...
Bob, I know for a fact that the difference is one mil. I have tested it on paper and chairgun backs me up. I should probably have clarified some things: .22 caliber, leapers 3-12x40 AO scope (mil dots are true at 10X), completely stock power wise so I'm guessing based on other people's #s 710-730 fps. 1 mill at 25 yds is ~1 inch I think. Don't know if this helps but at 55 yards I hold 2 mils over, the only things I have done modification wise are 5" TKO muzzlebrake, and barrel band. Thats it.
When I first got my disco I was shocked and impressed with how much of a tack driver it was but now it seems like it just can't make up its mind. Sometimes it stacks pellets at 35 yds and at other times it wont put a pellet within an inch of another at 25 yards (today) Every morning I have to re-zero... Everyone says they drive tacs at 50 yard with their discovery and I can't do that reliably at 35 yards with mine. I'm getting really frustrated, either the people driving tacs at 50 yards need a new tape measure or there's something fishy with my gun. I don't think its the shooter... I mean it could be but, I started out with springers so PCPs are pretty easy... I'll shoot some more tomorrow and let you guys know, any Opinions are greatly appreciated!
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JSB 18 gr. at 720 fps, zero at 35 yards is only 0.53" high at 25 yards.... That is 0.59 MilDots.... Sighted at 35 yards the trajectory never gets above 0.7 MilDots.... At 55 yards you would be 3.6" low which is 1.8 MilDots....
If you got a 6" POI shift with the TKO my guess is that it's clipping the pellets.... Try rotating it a quater turn at a time and shoot a group each time....
Bob
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JSB 18 gr. at 720 fps, zero at 35 yards is only 0.53" high at 25 yards.... That is 0.59 MilDots.... Sighted at 35 yards the trajectory never gets above 0.7 MilDots.... At 55 yards you would be 3.6" low which is 1.8 MilDots....
If you got a 6" POI shift with the TKO my guess is that it's clipping the pellets.... Try rotating it a quater turn at a time and shoot a group each time....
Bob
Ok thanks I'll try that tomorrow. It will group perfect sometimes but others... no accuracy at all, even when there's no wind. I can't explain the different hold over calculations, I shoot at about a -5* decline and my scope height is 1.5 inches, this might account for the slight differences but I doubt it, also I re measured the distance to the branch I hang my targets from and its 37 yards. Anyway thanks for the tip on the muzzlebrake, I'll take it off ,inspect it, and rotate it tomorrow and see if there's any change.
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OK so it's fixed, I shot a very small ragged hole at 30 yards yesterday and did it several times in a row. It turned out to be the screws on the muzzlebrake where loose. I was about to rotate it like bob suggested and found one screw to be on the verge of falling out and the other also pretty loose. I don't know if the pellets where clipping or if being loose causes a harmonics issue but either way its fixed now. I still don't get decent groups at 50 yards though, I'm thinking those people just need new tape measures... :) thanks for the help.
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At 50 yards my disco will do dime size groups in a gun vice.
When i take over i get 1.5 to 2 inch groups so the disco is better than me.
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At 50 yards my disco will do dime size groups in a gun vice.
When i take over i get 1.5 to 2 inch groups so the disco is better than me.
I have a bipod and shoot from prone with a rest under the butt of the gun, It's extremely stable and I'm struggling to stay on paper. I have yet to try the big Eunjin 28 gr pellets at this distance yet, maybe the extra weight will help, they actually don't group to bad in the disco at 30 yds, 1/2 inch group! but that's terrible compared to the jsb's.. oh man those things are spot on at 30! I just wish they'd do a little better a little longer.
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Have you ran your disco over a chrony ?
Could shed some light on the it.
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I'm no expert, but I find that winds of 5-10 mph usually don't have an appreciable effect on my accuracy at 75 feet, however 15 mph and up does. We are having occasional wind gusts today around 20mph, and my shooting was varying a little within around a 1/2 inch radius.