i_wish Posted October 23, 2010 Share Posted October 23, 2010 Would it be possible to create a shim that would raise the hieght of the Benelli M4 rear GRS to it's rail height? Could it match the countour of the receiver and original demensions of the current LPA sight? I would like to get "some" type of co-witness on my red dot sights. I have replaced the original rail with one of yours and I love it. I guess that an "extended" type rail that would screw into the existing GRS holes and then using a LPA picatinny rear sight would work but I would like to retain the existing GRS on the shotgun. What are your thoughts? What is the m4 community thoughts? I'll be the guinea pig. Quote Link to comment Share on other sites More sharing options...
Guest cleefurd Posted October 23, 2010 Share Posted October 23, 2010 Is there an "average" dot height to align with? Sandwiching a shim with longer screws into the sight base would work, but a consensus would be in order along with accepting that what co-witnesses on a trial gun, may not on another due to variables with choke, ammo, hold, Dot-maker revisions etc. At least the irons would be in the field of view though... providing the front were raised similarly. Quote Link to comment Share on other sites More sharing options...
StrangerDanger Posted October 24, 2010 Share Posted October 24, 2010 Kip, What about making a rail that made use of the five mounting holes on the rear sight as well as the 5 holes in the top of the receiver? The rear sight sits on a portion of the receiver that is significantly thicker than the portion that the rail assembly is attached to. It also benefits due to the fact that two of the screws are threaded into the rear sight housing rather than just into the aluminum receiver. Profile the rail in the rear to accept the factory rear sight. Supply new screws that are slightly longer to make up the difference in the rail portion. Supply a replacement front sight and front sight hood that make up the difference for the raised height of the rear sight. Generally, this would only be raised approximately .2" or so. The factory front sight doesn't have enough thread on it to adapt to a .2" rise. You had mentioned in another post that you were thinking about making a replacement set of combat sights anyway. Tritium is nice, but the Meprolight offering is lacking during daylight hours due to the lack of a white ring around the lamps. Quote Link to comment Share on other sites More sharing options...
i_wish Posted October 24, 2010 Author Share Posted October 24, 2010 (edited) Is there an "average" dot height to align with? Sandwiching a shim with longer screws into the sight base would work, but a consensus would be in order along with accepting that what co-witnesses on a trial gun, may not on another due to variables with choke, ammo, hold, Dot-maker revisions etc. At least the irons would be in the field of view though... providing the front were raised similarly. You are correct. What works with one trial gun might not work with what everybody else has. I guess absolute co-witness is ideal but I would settle with a lower 1/3 or upper 1/3 if I had to or heck just being able to see the sights through the glass if the red dot failed. I'd be using an aimpoint comp m2 but hope to use it with my other red dots. Just being able to see the BUIS through the optic would be a plus. IDK more people will hopfully weigh in. Stranger Danger also has a good suggestion. Edited October 24, 2010 by i_wish Quote Link to comment Share on other sites More sharing options...
xamoel Posted October 24, 2010 Share Posted October 24, 2010 i'd be in for a set of combat sights as well, but Tooltech gunsight can actually machine your existing set to fit trijicon night sights (tritium with a white outline) already, though $250 is rather hefty. Quote Link to comment Share on other sites More sharing options...
AggiePhil Posted October 26, 2010 Share Posted October 26, 2010 This is all a bit over my head but I do prefer co-witnessing. So...tagged! ETA: Until something better comes along, I simply have my Aimpoint Micro on a LaRue mount which, though it doesn't allow co-witnessing, can be yanked off and out of the way very quickly should the optic go **** up. Quote Link to comment Share on other sites More sharing options...
AggiePhil Posted October 26, 2010 Share Posted October 26, 2010 (edited) Would it not work to simply construct a taller replacement rear ghost ring and front sight post that would sit up higher in the sight plane? These little parts could just screw right into where the sights currently are. Edited October 26, 2010 by AggiePhil Quote Link to comment Share on other sites More sharing options...
TacticalKoala Posted October 26, 2010 Share Posted October 26, 2010 Save your money, you have a 1.3 trillion dollar tax hike coming in January. Quote Link to comment Share on other sites More sharing options...
BigHat Posted October 26, 2010 Share Posted October 26, 2010 Can someone (with experience) please explain to me why an optic / irons co-witness on a tactical shotgun is even remotely important or desirable? I'm truly at a loss to understand. Comments that if it makes sense for carbines it must therefore make sense for a tactical shotgun have yet to convince me. Quote Link to comment Share on other sites More sharing options...
BigHat Posted October 26, 2010 Share Posted October 26, 2010 (edited) Sorry for the double post. System was slow earlier, either on my end or the site's. Didn't even think one of the posts took. Edited October 26, 2010 by BigHat Quote Link to comment Share on other sites More sharing options...
tucker301 Posted October 26, 2010 Share Posted October 26, 2010 Can someone (with experience) please explain to me why an optic / irons co-witness on a tactical shotgun is even remotely important or desirable? I'm truly at a loss to understand. Comments that if it makes sense for carbines it must therefore make sense for a tactical shotgun have yet to convince me. Sorry, but logic has no place in this discussion. You'll have to leave. Quote Link to comment Share on other sites More sharing options...
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