jjhuep Posted August 2, 2004 Share Posted August 2, 2004 Hello, I have a .270 Win that I am having an odd problem with. Ok at 100 yards I shoot a good grouping that is 3 inches above the bullseye. The problem is that at 200 yards I still shoot a good group but all the bullets land 5-7 inches high. At 300 yards they all land 7-9 inches high. How is that possible? Anyways, I am using this gun for deer hunting and I cannot figure it out. I want this gun sighted 2.5 inches high at 100 yards and was assuming that would be close to dead on out to 300 yards. Anyways, my findings seem to tell me an odd story. Please help. Link to comment Share on other sites More sharing options...
EricW Posted August 2, 2004 Share Posted August 2, 2004 Your scope is probably not parallel to your bore axis. Link to comment Share on other sites More sharing options...
rhino Posted August 3, 2004 Share Posted August 3, 2004 How high is the centerline of the scope above your boreline? Where your zeroes are depends greatly on that distance, as well as the exterior ballistics of the projectile. Link to comment Share on other sites More sharing options...
Chriss Grube Posted August 3, 2004 Share Posted August 3, 2004 What rings and Bases do you have? The only time I've seen this type a problem was when someone managed to take a 20 MOA canted base and put it on backwards. The scope being canted or not in alignment with the bore won't do this, it will throw your shots off on an angle but not rasie the POI like that. Please tell me you don't have see thru mounts in it. Link to comment Share on other sites More sharing options...
jjhuep Posted August 3, 2004 Author Share Posted August 3, 2004 Hello, I do not have see through sights. My scope is 1.5 inches above the barrel. Here is my theory: When I draw it on paper the only way this can happen is if my gun is actually sighted in for like 300+ yards. If you draw a straight line on paper (the scope) and then draw the bullet curve through the straight line, it will intersect twice. I believe that the first intersection is just before the 100 yard target, while the second intersection is somewhere out at 300+ yards. If this is actually true, that would cause the bullet to actually hit higher at around 200 yards then it would at 100 yards. Do you guys think this is possible? Link to comment Share on other sites More sharing options...
Dead Buff Posted August 3, 2004 Share Posted August 3, 2004 We all know that bullets fly in an arch. The bullet normaly has two crossings with line of sight; first at ±20-30m for all guns and the second at your desired zero setting (100/200m/or what ever). Your gun/scop combo is zeroed with the 20-30m crossing out at ±80-90m (my guess since 3in high at 100m). IMO your scope is too parallel with the bore. The rear base has to lift/front has to drop. Are your scope settings close to centre settings? Turn knob all the way one way until stops. Now turn it the other way until stop counting all clicks. Divide by 2 and turn that back. Do the same for the other adjustment. Ensure that your scope, when set centre for up/dwn and l/r, is mounted in such a way that you will be able to hit a 0.5x0.5 m target out at 100m and be close to centre at 25m. Then you know the mounts are correct. Now do final adjustments. This, btw, is where the old "zero at 25m" comes from. If you zero at 25m you are zeroed for somewhere between 100 and 200m (depending on calibre, etc....). Link to comment Share on other sites More sharing options...
Dead Buff Posted August 3, 2004 Share Posted August 3, 2004 Agreed - you figured out what I explained above (posted 'boit same time). If you have enough scope adjustment play, adjust it down until you get to ±25m zero. This might cause some paralax probs with some scopes. Best is to have the bases adjusted so when the scope is centre adjusted your zero is close..... Link to comment Share on other sites More sharing options...
para45 Posted August 3, 2004 Share Posted August 3, 2004 What kind of bullets are you using??? Are they hand loads. I just looked at the ballistics on the Winchester sight and even zeroed at 200 it should be over 6 inches low at 300 with a 130 grain bullet. I shoot the bullets below...Winchester Ballistics Link to comment Share on other sites More sharing options...
Yardbird Posted August 3, 2004 Share Posted August 3, 2004 I'm confused. +3" @ 100yds, +6" @ 200yds, +9" @ 300yds. Isn't that a straight line? How can there be no arc till out past 300 yds? .270 sighted at 2" high @ 100yds is zeroed @ 200yds and is 8.5" low @ 300yds according to my tables. Link to comment Share on other sites More sharing options...
jjhuep Posted August 3, 2004 Author Share Posted August 3, 2004 Maybe I am just a really crappy shot. I am shooting the Winchester 150 grain Nosler Partition. My plan for this weekend to try and get the scope sighted perfectly for an exact hit at 100 yards. After that, I will shoot a few shots at 200 yards. It should be lower not higher then the bullseye. After that, I am going to go back and resight the gun for 2 inches high at 100 yards and hopefully it will be dead on or close at 200 yards. Again, maybe I am a horrible shot. Also, before I try to zero the gun at 100 yards, would you guys try to sight it in at 25 yards again? Link to comment Share on other sites More sharing options...
D.carden Posted August 3, 2004 Share Posted August 3, 2004 You need to choose a distance to "0" your load ( preferably 100 yds). If you are 3" high at 100 yds, your bullet has raised anywhere from 5"/6" from leaving the barrel( 2" barrel/scope + 3'' above crosshair @ 100 yds) . You shooting " up-hill". Sight for "0" @ 100 yds, with POI to be just below crosshairs ( 1" will do). Your 200/300 yd hits should be lower. Check your reloading manuals-long range tables for rate-of-drop. Hope this helps! Dan Link to comment Share on other sites More sharing options...
para45 Posted August 3, 2004 Share Posted August 3, 2004 Here is the chart for the 150 Winchester (Partition Gold). I hope this helps. Make sure your scope mounts are tight.. both the base and the rings. Next may be check your scope to make sure your crosshairs aren't moving. Good luck..... Win Partition Gold 150s Link to comment Share on other sites More sharing options...
Chriss Grube Posted August 4, 2004 Share Posted August 4, 2004 Ok you have something really F'ed up or you should just sell the rifle and learn to knit. What brand of bases and rings do you have? Is it a one piece base or two. Who mounted the scope? I'm betting somebody put the bases on reversed. When you look at the profile of the rifle the scope should cant down toward the barrel, if it goes the other way you're screwed and need some parts switched around. You are holding the same POA at all distance right? Not using Kentucky Windage? Link to comment Share on other sites More sharing options...
Dead Buff Posted August 4, 2004 Share Posted August 4, 2004 Just like my previous post stated. Your scope appears to be too parallel to the barrel, hence the reletivly straight line (3@100, 6@200, 9@300). Either your scope bases are fitted incorrectly (mmost likely) or your elevation adjustment is adjusted too high. ALL rifles cross line of sight between 20 and 30m (from a 505 Gibbs to a 7mm STW) with a normal zero of between 100 and 200m. So yes, get your rifle to hit an A4 page at 25m and then do final adjustments for you selected zero distance. To do this your scope must be mounted correctly with the windage and elevation adjustments centred as described before. Link to comment Share on other sites More sharing options...
Zak Smith Posted August 4, 2004 Share Posted August 4, 2004 I just ran some quick ballistics for .270, assuming a 0.40 BC bullet launched at 3200fps. If zerod at 100 yards: _BC_ _MV_ 0 100 200 300 400 500 | YARDS 0.400 3200 > -1.46 -0.00 -2.50 -9.79 -22.57 -41.97 | > .270Win 130gr If about 3" high at 100 yards: _BC_ _MV_ 0 100 200 300 400 500 | YARDS 0.400 3200 > -1.43 3.26 3.98 -0.05 -9.61 -26.01 | > .270Win 130gr -z Link to comment Share on other sites More sharing options...
Marine shooter Posted May 3, 2005 Share Posted May 3, 2005 I just ran some quick ballistics for .270, assuming a 0.40 BC bullet launched at 3200fps.If zerod at 100 yards: _BC_ _MV_ 0 100 200 300 400 500 | YARDS 0.400 3200 > -1.46 -0.00 -2.50 -9.79 -22.57 -41.97 | > .270Win 130gr If about 3" high at 100 yards: _BC_ _MV_ 0 100 200 300 400 500 | YARDS 0.400 3200 > -1.43 3.26 3.98 -0.05 -9.61 -26.01 | > .270Win 130gr -z <{POST_SNAPBACK}> They make a cool little laser place it in the barrel aim it at 1 inch above 100 and put the dot in the cross hair you'll be right onafter that for 200 yards. Link to comment Share on other sites More sharing options...
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