B391 Posted January 4, 2016 Report Share Posted January 4, 2016 (edited) POA & POI Laser Test I have 3 guns. A Remy 1100 with a skeet barrel [have a full choke barrel but not tested], a MK60 and a Beretta 391. When shooting them the POI seemed different especially with the 391 which I thought shot low so I changed the shim from 60DX to 55DX after which it seemed to shoot much more like the MK60. I cannot find a pattern plate anywhere near me so I thought I would do a test with a laser bore sight. For now I did a 10meter test in the house. The results surprised me. For stability I rested the guns on the back of a chair and aimed at a 2cm black dot on paper and made about 3 simulated aims to get the right marks on the paper. The 391 mark was approx. 1.5cm above the dot centre. The MK60 over barrel 2cm above The MK60 under barrel 5cm above The 1100 9cm above. I also had the same tests made by my son, experienced shooter, and his results were consistently similar to mine but in each case about 2cm higher, but when we shoot he still hits good scores. Interesting that they all shoot high and I dont understand why the MK60 over barrel shoots higher than the under barrel? Probably a very good reason, anyone? Cant wait to see what the results are over 15 and 30 meters, should be interesting. This proves to me where I thought the shot was going for the Beretta and the MK60, I did not realise that the 1100 shot so high but this is an occasional gun mainly used by my wife as I have a short stock on it. Edited January 4, 2016 by B391 Quote Link to comment Share on other sites More sharing options...
Westward Posted January 5, 2016 Report Share Posted January 5, 2016 The geometry of a shotgun means there's less muzzle flip with the bottom barrel because it's closer to being in line with the shoulder, therefore your figures of 2cm high for the top barrel (more muzzle flip) and 5cm high for the bottom (less muzzle flip) make sense. Quote Link to comment Share on other sites More sharing options...
BrowningB525 Posted January 5, 2016 Report Share Posted January 5, 2016 The geometry of a shotgun means there's less muzzle flip with the bottom barrel because it's closer to being in line with the shoulder, therefore your figures of 2cm high for the top barrel (more muzzle flip) and 5cm high for the bottom (less muzzle flip) make sense. He's using a laser, not a cartridge. There won't be any muzzle flip. Quote Link to comment Share on other sites More sharing options...
EMT Posted January 5, 2016 Report Share Posted January 5, 2016 I use an arrow laser shot so I can check I am mounting the gun correctly but I find it needs to be at least 15m for it to be accurate. Quote Link to comment Share on other sites More sharing options...
Westward Posted January 5, 2016 Report Share Posted January 5, 2016 (edited) He's using a laser, not a cartridge. There won't be any muzzle flip. Yes I realise that. Let put more simply: The barrels on and over/under are not parallel. The bore centres are closer at the muzzles than the breech, therefore with a laser they should not point to the same place except at one distance a few feet in front. The reason for this is that when the gun is actually fired, the muzzle flip is greater on the top barrel. Edited January 5, 2016 by Westward Quote Link to comment Share on other sites More sharing options...
wigeon jim Posted January 5, 2016 Report Share Posted January 5, 2016 What!!! So a side by side would shoot left and right as the barrels are on the side? Jim. Quote Link to comment Share on other sites More sharing options...
B391 Posted January 5, 2016 Author Report Share Posted January 5, 2016 What!!! So a side by side would shoot left and right as the barrels are on the side? Jim. now now....don't confuse me. Mind you it could help with some sims! This exercise has been useful for me to help me understand relative POI which I now see is not as straight forward as it might seem. I will try the same tests over about 30m over the weekend. Quote Link to comment Share on other sites More sharing options...
Westward Posted January 5, 2016 Report Share Posted January 5, 2016 What!!! So a side by side would shoot left and right as the barrels are on the side? Jim. A sxs will tend to do exactly that, which is why the barrels are also angled slightly towards each other to compensate so that (hopefully) both barrels shoot to the same place at a given range. Obviously that convergence distance will vary somewhat with different shells. It's only 'O' level physics - or at least it was when I was at school! Quote Link to comment Share on other sites More sharing options...
wigeon jim Posted January 5, 2016 Report Share Posted January 5, 2016 I now have an excuse for missing! Jim. Quote Link to comment Share on other sites More sharing options...
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