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Posted: 12/25/2002 8:42:04 AM EDT
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So, some of you may remember I had some issues with my 16" Hbar that came on my NIB Bushie about 2 months ago... BM took care of it, without any delay, and replaced the barrel with a new one, and sent me back my Upper. I reassembled, and all was well. Well, I was shooting it yesterday, then cleaning it off, and noticed that the front sight post (the whole thing, not just the pin itself) is canted to one side, about 5 degrees to the right (ejection port side) It only became clearly apparent because I was mounting my SIR on the rifle after the cleaning, and the post does not sit centered between the weaver rail when viewed from above. I checked my armorers manual, and they indicate that when installing the barrel to the upper with the barrel nut, that things should be lined up, etc etc etc. But they don't mention how exact, and that misalignement will just cause 'excess' windage. Now, here's the thing; I don't have a 'ton' of windage, it's about 10 clicks to the right. BUT, knowing that the point of aim is not exactly centered over the flight trajectory, I can visualize that only if I cant the rifle slightly, so that the front post sight IS vertically over the barrel, will the downrange (200M +) POI will be on. Otherwise, it'd be skewed off slightly to the right (the POI). Here's my question; how important is this, and how 'off' do you all think the POI would be if the rifle is held vertical, and the POA is 'offset' like such? Lastly, can this be corrected just by removing the driven pins from the base of the front sight post, realigning it, and then driving them back in? Or will that cause a misalignement of the Gas Tube to Gas port on the Barrel? E. |
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Now, here's the thing; I don't have a 'ton' of windage, it's about 10 clicks to the right. BUT, knowing that the point of aim is not exactly centered over the flight trajectory, I can visualize that only if I cant the rifle slightly, so that the front post sight IS vertically over the barrel, will the downrange (200M +) POI will be on. Otherwise, it'd be skewed off slightly to the right (the POI). Here's my question; how important is this, and how 'off' do you all think the POI would be if the rifle is held vertical, and the POA is 'offset' like such? |
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Thanks for replying; I guess I'm not very good at describing this, but: I zeroed at 25M. The Rear ghost ring required 10 clicks to the right to come onto 'zero' This is with the rifle as vertical(properly held without any cant) as I can possibly tell. With that said, if you look from the top down, the FSP will seem like it's 2-3mm offset to the right side of the bore line, such that front rear ring to front pin, to where it intersects with POI, will be an 'X' (albeit a very long long skinny one) After the zero point (25M) the line from the Ring to the Pin will continue off to the 'left', as the bore line will continue forward, towards a different POI other than where the POA is looking. I did not get a chance to actually shoot at 200M, due to time constraints, so this is all an imagined hypothetical POI that will not be inline with my POA if the rifle is held properly without any cant. But the logic of what's being discussed here obviously makes sense, I've run it by a few people and they all thought the same as me... Does that make sense? But, from what you said, it sounds like 10 clicks to come onto zero was too much... Is it really safe for me to go whacking the FSP with a hammer, even with gentle force? Will I damage the alignment pin, or the FSP while doing this to try to correct the cant? or should I just buy the armor's wrench (DPMS), a barrel vise block, and remove and reinstall the barrel? E. |
| NEPAshooter, Now I understand what you were saying. I wouldn't recommend trying the hammer. It sounds like the same old problem Bushy had a while back with the barrels being over torqued. As far as the 10 clicks of windage, that's not really too much considering that 1/2MOA rear sights have about 35 clicks from mechanical zero(the center line) in either direction before you hit the end. Mine has 14 clicks. If you are unhappy with your upper call the service dept again and tell them about the front sight assembly being canted and see if they will exchange it. Good luck with the rifle. |
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Thanks for the advice and answers oneshot; I thought about the 10 clicks, and rationalized that 2-3mm of offset on the rear sight, results in about 1-2" off at 200 yards supposedly... (based on a 25yard zero) way more precise than I or the ammo or a turned chrome lined barrel will ever shoot, so the theory really eclipsed the reality of the situation... I think at this point, I'm going to splurge, and buy a action block with insert, and a DPMS wrench, chuck it up in a vise, and pull it apart to see if the indexing pin is bent. If the hole for the pin doesn't line up with the FSP, then I'm going to assume that the FSP is not mounted to the barrel properly, and since I'm going to have Kurt from KKF turning down under the H/G's and Fluting my barrel forward of the FSP up to the muzzle shortly anyhow, I'll have him correct the FSP problem for a few bucks, and make sure it's aligned to the index pin. If the Indexing pin is bent or the indexing pin hole lines up good with the FSP, I'll assume that it was overtorqueing that caused the cant. Then, I'll just throw a new pin in, reassemble barrel to upper carefully, and see if the cant goes away. I'm sure I made more of an issue out of this than it really is, but hey, when you drop almost a grand on a new rifle, then have to have them replace the barrel for one factory defect, the last thing you want is ANOTHER problem... [:\] E. |
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