bigbrowndog Posted April 20, 2007 Share Posted April 20, 2007 has anyone had a POIC, when the barrel heats up with an AR??? I've heard of it with regular rifles, but not with floated AR's. impact changes aprox. 8" at 300yds. Any thoughts???? Trapr Link to comment Share on other sites More sharing options...
Merlin Orr Posted April 20, 2007 Share Posted April 20, 2007 Thoughts...? Time for a new barrel. Way to much to be acceptable. Link to comment Share on other sites More sharing options...
outerlimits Posted April 20, 2007 Share Posted April 20, 2007 if yer using optics, look there. what type of scope/mount. Link to comment Share on other sites More sharing options...
GentlemanJim Posted April 20, 2007 Share Posted April 20, 2007 When I have shot AR15s I have seen poi climb as the rifle gets real hot. I have no idea how much is TOO much. Jim Link to comment Share on other sites More sharing options...
Scott R Posted April 20, 2007 Share Posted April 20, 2007 If poi is climbing when barrel gets hot it could be due to round cooking in chamber and giving more fps. Not sure if you could get 8" at 300yd due to this alone. Link to comment Share on other sites More sharing options...
Dan Sierpina Posted April 20, 2007 Share Posted April 20, 2007 Is the change consistant in direction? Are you firing it from a rest? Most people don't believe it, but an AR is very sensitive to pressure, free floated barrel or not. I can open the groups up by leaning a bit on the stock. That's from a Hart rest, rear bag set up. Need more info Trapr. Link to comment Share on other sites More sharing options...
Nick Weidhaas Posted April 20, 2007 Share Posted April 20, 2007 Trapr- With a 50 / 200 yard zero I'm 8" low at 300 yards, so there is a poi change at this distance (20" JP 1:8 w/Georgia Arms 55gr NBT). Not sure if you were taking this into consideration or not. Like Dan said, some more info would be helpful. Best, Nick- Link to comment Share on other sites More sharing options...
Bear1142 Posted April 20, 2007 Share Posted April 20, 2007 Trap, 8" seems pretty excessive. How much did you heat it up? Mag dump, Beta dump? Erik Link to comment Share on other sites More sharing options...
bigbrowndog Posted April 20, 2007 Author Share Posted April 20, 2007 rifle was shot from prone, with little pressure to forend, rifle had 30-40 rds thru it in 5 rd intervals for the previous 30 minutes, barrel is relatively new, a couple of months old. rifle was previously zero'd at 275, when zero was rechecked, it was low 14" at 300, then rezero'd at 300, and 30 minutes later rechecked and was found to be 8" hi at 300. Sights are iron, all mounts were tight, rifle shot 2min. groups, routinely, throughout the day. I am going to the range today, with a scope mounted to verify my suspicions. Trapr Link to comment Share on other sites More sharing options...
Dan Sierpina Posted April 20, 2007 Share Posted April 20, 2007 Trapr, Next question. Now that we know you were shooting iron sights, did the lighting change at all? Did you go from bright sunshine to heavy cloud cover? Highpower shooters adjust their sights for varying light conditions. The phrase is "Light's up, sights up, light's down, sights down" Were there no left/right changes only vertical changes? Putting a scope on the rifle will definately take the iron sight/ lighting variation out. Link to comment Share on other sites More sharing options...
Bronco Posted April 20, 2007 Share Posted April 20, 2007 It' all that Wolf crap you have run through the poor rifle. If it were barrel heat your poi change would be in all directions not just vertical, look for barrel deflection, sight misalignment (I know, this never happens) crap ammo. Keith Link to comment Share on other sites More sharing options...
P.E. Kelley Posted April 20, 2007 Share Posted April 20, 2007 Double whammy. #1 Barrel bore not concentric with outside diameter. Heat causes barrel to "bend" non-uniformly. #2 Front sight attached to "bending barrel". Just a SWAG Patrick Link to comment Share on other sites More sharing options...
bigbrowndog Posted April 20, 2007 Author Share Posted April 20, 2007 (edited) horizontal changes were negligable, 2" at 300, could have been wind, sights. partly cloudy day, mostly sunshine throughout day, it was all done in about 1.5 hours. Shooting took place under a covered firing point, I can't recall if front sight stayed in the shade throughout the day or not, rear was always in the shade? Wild horse, this rifle has minimal Wolf thru it, 100rds at the most by the way have you sorted thru all the "brass" I left for you............. i'm also taking my "old" 20" iron gun with me this afternoon, to see if maybe (heaven forbid)it was me. I don't recall an impact change ever with the 20" gun. Pat, yer just full of good news.........aren't you!!!!! Trapr Edited April 20, 2007 by bigbrowndog Link to comment Share on other sites More sharing options...
benny hill Posted April 20, 2007 Share Posted April 20, 2007 It's the eye's old man. Welcome to my world. Link to comment Share on other sites More sharing options...
bigbrowndog Posted April 20, 2007 Author Share Posted April 20, 2007 Benny, you obviously missed the part about the gun shooting 2 min. grps. all day Don't think I haven't thought about that possibility, though. .....................Maybe you can track me down a Meopta, quick!!!!! The eyes haven't degraded any in visual acquity, but who knows!!!!! If it turns out to be gun related i'll be seein' you sooner than later, if it turns out to be me, i'll be putting my tr21 on the gun, till I can find a Meopta. Trapr Link to comment Share on other sites More sharing options...
benny hill Posted April 20, 2007 Share Posted April 20, 2007 I thought that strap I saw on scout when he came in looked funny. Last time I saw one it was on a seeing eye dog. Link to comment Share on other sites More sharing options...
oddjob Posted April 20, 2007 Share Posted April 20, 2007 My AR with scope changed POI quite a bit until I figured out that it was the glasses I was wearing that was screwing me up. Link to comment Share on other sites More sharing options...
Mike P Posted April 20, 2007 Share Posted April 20, 2007 Were you using the same rear aperture the whole time? Mike Link to comment Share on other sites More sharing options...
EricW Posted April 20, 2007 Share Posted April 20, 2007 Try shooting the same sheet of paper and have a spotter check the pattern as the rifle heats up. It should walk in a line or curve across the paper if it's not human-induced. Link to comment Share on other sites More sharing options...
P.E. Kelley Posted April 20, 2007 Share Posted April 20, 2007 Try shooting the same sheet of paper and have a spotter check the pattern as the rifle heats up. It should walk in a line or curve across the paper if it's not human-induced. Very good idea! Just make sure your spotter is not your competitor! "oh no Trapr your rifle is fine, you are shooting one heck of a good group" "no,no you don't need to look, I got it all memorized." Patrick Link to comment Share on other sites More sharing options...
gunny Posted April 20, 2007 Share Posted April 20, 2007 has anyone had a POIC, when the barrel heats up with an AR??? I've heard of it with regular rifles, but not with floated AR's. impact changes aprox. 8" at 300yds. Yes, when you really heat up an AR it will start shooting high. At the IRONMAN in 05 there was a course that really heated up the guns. To finish the rifle portion you had to engage the tiny poppers on sniper bases at approx. 100 yards. Everyones gun that I recall was shooting about 18" high. Two of these were 20" heavy barrel guns with free float tubes and TA-11's. Link to comment Share on other sites More sharing options...
StealthyBlagga Posted April 20, 2007 Share Posted April 20, 2007 Does the barrel have a heavy weight or light weight/govt profile ? Link to comment Share on other sites More sharing options...
bigbrowndog Posted April 20, 2007 Author Share Posted April 20, 2007 4 hours, 100 rds, and two different targets later, I have figured out my problem. I made a point of going to the range at the same time of the day as the last time, because of what Dan, said about light affecting your aiming. The day was very much like the first, cloudy but mostly sunny. The 18" rifle never shifted POI, once I resighted it with the scope. However, once I started rezeroing the other iron gun, I noticed that the front sight was originally in the shade, but over time it shifted to being in the sun. What I really noticed was that I was having difficulty picking up the front sight on the target, so I put up another target, this one was set up the opposite of the first, in that, the first was a white Bull, on a black background, the second was a black Bull on a white background. It was much easier to notice exactly where the post was on the white background. So, I switched back and forth between targets,...............and Lo and Behold, someone hit me with a sledge hammer, it was hard to determine wether or not the post was on the bottom of the Bull, or beneath it, and at 300 that could easily be 3 or 4 inches, as the light hit the front post, the tip could be lost and be partially in the Bull, again easily being 2 or 3 inches. All this to say that, It was MY problem, and not the gun, simply a poor choice in target/background selection. The "old" iron gun, suprised the heck out of me, allowing me to shoot Metallic Silhouette chickens out to 300, easily. Thanks for the suggestions......................................Trapr Link to comment Share on other sites More sharing options...
Dan Sierpina Posted April 21, 2007 Share Posted April 21, 2007 Trapr, I too have that same problem with determining the "bottom" of the bull. I went to a center hold shooting highpower. Elevation was MUCH more consistant. I also dumped the "match" post and went back to a battle sight, again, better consistancy. Glad you discovered the problem. Lot's of good info gets shared here.....and some not so good Link to comment Share on other sites More sharing options...
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