Armory Sponsor
Posted: 9/9/2002 8:40:13 AM EDT
| I recently bought a B-square mount (I know, I know...it was real cheap) for an M1a to see if I would like a scope on one of these things. My problem is that I am having trouble getting the mount level (longitudinally) with the barrel. This mount has a thumbscrew and two screws that are levelers. Is there any special/easy way to do this? Also after mounting this I do believe I like the setup--who makes the lowest sitting (closest to centerline of rifle) mount for an M1a. Thanks |
|
I would suggest seeing if you like the scope on it first and not worry about leveling the thing to any degree of precision. M1's with scopes are great but I can say that a good mount will cost a pretty penny. I went through two fiarly cheap ($120 and $80) mounts before stepping up to a SMITH arms mount. Most mounts that just attach to the side mount will shift you want a steel mount with hex head bolts with multiple attachment points. The other option is a mount that relaces the rear sight and also bolts to the side. This is not for everyone due to the loss of the rear sight but its solid and low. Brownells has the smith mount I thinh the other is still available from SA's custom shop DC1 |
|
I'm not 100% sure what you mean from your phraseology "longitudinally" - do you mean making the axis of the scope run parallel to the barrel? If so, read on. I'll cover scope levelling (i.e, horizontal axis) afterwards just to cover everything. I am assuming you know how to zero your scope using std. windage and elevation settings and are asking about control of mounting... Scopes work best, in general when their windage & elev. settings are corrections from their physical zero. Mounting a scope and then having to crank a lot of turns of windage and elevation just to get zeroed means your mount is off. You ideally should only need a few clicks adjustment either way. Sooo... get that scope back to "0" (centered) windage & elevation position. (This doesn't mean, and in fact probably assures, that your rifle is NOT zeroed - that is POA is not point of impact at zero range (25 or 100yds, whatever). You HOPE that your rear mount needs to be RAISED (that is, a scope set at Wind=0, Elev=0 shoots low) so that you can shim up the base (else you have to take off metal from base or rifle to lower impact). Gunsmiths have shim material (sheet metal - brass?) pre-punched with holes for this for under a buck for a few pieces. Find out at range how far off you are in elevation at, say, 100yds (or 100m). Figure out length of scope base in inches. (We'll assume 3.25" for example here.) Let's say you're 8" low. We now have a geometric similarity proportion problem. 3600" 8" error ------- = ----------- 3.25" X shim We solve this: X = 8x3.25/3600 = 0.0072" In a perfect world you use a .007" shim. The standard thickness values (dunno what they are, guessing) and their movement of impact for this scope base: .001" shim ==> 1.1" elevation increase .002" shim ==> 2.2" elevation increase .0025"shim ==> 2.75" elev increase .005" shim ==> 5.5" elevation increase .0075 shim ==> 8.25" elev increase .010" shim ==> 11" elevation increase Other info I've heard is that, on average, about .01" shim gives you 7" to 8" elevation increase; I've made a few assumptions about what forms the triangle, and what the typ scope baase is, etc. But it's close enough for ballpark, and gets you in good enough, when shimmed properly, to only be a few clicks off on elevation. Unless you have special scope rings (Burris has some, maybe Leupold has some too) DON'T SHIM INSIDE SCOPE RING as it ruins concentricity. Instead shim under the base. If you have Leupold (& perhaps others) base, the rear mount of the scope can be drifted left or right. Take rifle to range and get it zereod (centered L<->R) as closely as possible after shimming and then your windage is zeroed as well. You should be able to get close enough to require only a few clicks' worth of scope adjustment for windage. Great. But you really meant to ask "How do I level the horizontal reticle of my scope?" Put scope in gun vise on level, flat surface. (I used my breakfast bar.) Tighten up. Sight in on something level & horizontal a ways away (my Venetian blinds, after having checked blades for being level, with a level.) Unloosen scope and rotate til scope horizontal crosshair parallels your horizontal edge under consideration (my Venetian blind blade.) Retighten scope in mount and verify zero (or rezero.) I think I tried to answer what you asked.. Bill Wiese San Jose, CA |
|
I've tried several mounts over the years. Don't wast your time and money. Buy the A.R.M.S. #18 mount. It's not the cheapest, but it is THE BEST. Add the #22 quick release (throw lever) rings and you can pull your scope off of the weapon in less than 5 seconds (without tools) and use your iron sights. These rings are the only rings QR I've tried that will return with LESS than 1/4 MOA when re-mounted on the weapon. You will not have alignment problems associated with other M14/M1A mounts. Oh, the A.R.M.S. #18 offers the lowest possible mounting available. |
Armory Sponsor