M1A/M-14 Rifle Rear Sights

G

Gregory Gauvin

New member
I have an accurized Armscorp M14/M1A build that I have spent years in my free time building. Its got the works - Gene Barnett barrel, trigger job, unitized gas cylinder, padded handgaurds, extremely tight fitting rare (camo) Springfield stock (not bedded...yet), titanium gas piston, NM front sight, trigger job...etc. Other than the tight chamber on the barrel (I believe most Gene Barnett barrels were reamed to .308win minimum headspace tolerances) it fires beautifully, providing it is fed properly trimmed brass. 7.62 Nato rounds will chamber but not going to chance blowing a case apart from a out of battery condition. I had one Nato round mixed up in my 308 brass that didn't lock, and later found it to measure longer than spec.

I plan to outfit this rifle with a Leupold MK IV on a ARMS #18 mount, but wanted to dial in my irons before doing so.

My windage is spot on. I witnessed marked my sights (along with gas plug, etc). With my elevation dial cranked all the way down, rifle hits exactly POA/POI at 50 yards. Should be close to a 100y zero on a SR1 Target. I set my elevation dial to the corresponding mark.

My question is, my elevation dial bottoms out and stops. But when raising elevation (turning counterclockwise), the peep sight will eventually stop moving upwards, but the elevation drum will continue to click. Is this normal? Should MAX elevation have a stop as well on the elevation knob?
 
The sight aperture has a sector gear attached to it, and the elevation knob is connected to a pinion gear. If you raise it too far, the gear teeth run out, and it will not raise farther. If I'm not mistaken, when you go that far, the sight, (aperture), should not move, nor the knob, as the pinion is still meshed with the gear, and the gear does not have teeth to the end. If it keeps turning, it could have ran out of teeth, and the aperture could come out. Someone may have made the aperture with full teeth, but most are not fully toothed at the bottom, so they will stop.

NM_rear_sight.JPG


Go here, and look for the post "Rear Sight Apertures":

http://m14forum.com/reference/73813-m14-iron-sight-guide.html
 
If I keep raising the aperture, it does stop, will not come out, but elevation knob will continue to click. Odd. I'm having a master gunsmith take a look at the rifle later this week. Having it bedded and mounting a Leupold Mk IV, and giving the trigger a cleaner break. I'll let you know what he discovers. Thanks.
 
Some folks used to grind down the untoothed portion of the rear sight rack so the sight could be removed without full disassembly. Undesirable on a battle rifle, but desirable if you switch match sight aperture sizes depending on light conditions. If yours won't come out, it most likely is not modified.

The cause of your problem is most likely the screw on the elevation knob is too loose and the internal knob zeroing or calibration teeth are slipping under it or are worn out. When all is working properly, you are supposed to find how many clicks past your 100 yard zero your sight bottoms out (10 or 11 is typical for a six-o'clock hold, and 7-8 for Navy hold), loosen that screw and position the knob so the registration mark on the rear sight base lines up with it just far enough behind the 100 yard (100 M on some knobs made for Europe) so that when you tighten the screw again it will be calibrated so that turn the knob to the 100 yard mark occurs at the right number of clicks off the bottom position of the rear sight rack.

If you can't correct this tightening the screw, you probably need to replace the pinion, as it is slipping due to wear and will only get worse with time.

Oh, do check that the leaf spring/dust cover is holding the rack against the pinion firmly enough. If the sigh jumps up and down a little with each click, the dimple on the leaf spring may be worn out and need replacement.
 
From fully down, bring your rear aperture up nine clicks. That should get you on paper a 100 yards.

Jim
 
Using a standard SR1 Target? I do assume POA/POI at 50 yards hitting a 1 inch square will hit low at 100 with a SR1 military target. I assume 50y to 100y perhaps a 1/2" bullet drop...Since the SR1 target is 6" round, 8 or 9 clicks sounds correct.

Thanks. But I'm going to be using a new optic. I am mounting my Leupold Mk IV this weekend.
 
Which bullet? Which sight? The point blank range (the range at which the bullet crosses the line of site on the rise) depends on the height of the sight above the bore line. For the iron sights it's about 1.1", and about 40 yards PBR with 100 yard zero for M118 and M852. Closer to 45 yards for M80 ball. I have no idea what it will be for your scope because I don't know the scope center height above the bore line.

I've attached the PDF file of 100 yard sighting targets. They are for the Garand, originally, but cross M2 with M80 and M72 with M118 and you'll be very close.
 

Attachments

POA/POI was on with iron sights. I have not zeroed my optic yet. I will be using a Leupold Mk IV scope mounted on a ARMS #18 low base mount. As far as rings...going to mount scope close to bore as possible don't know exactly how high above the bore it will be yet.

I will zero the scope at 100 yards. As far as the ammo I will zero it for...I'm not quite sure. I have not worked up hand loads yet for this rifle. Until I find what groups best, I will know. The Match barrel, although receiver is marked 7.62 NATO, is chambered in 308 with tight tolerances. Because my local range is only 100 yards, I probably will just use 150 grain bullets, 308 winchester brass trimmed to spec, with a charge of H-4895. I was thinking of trying the 168gr sierras, but, unless I can find a range and do some serious 600 yard shooting, the cheap 150 grainers should suffice. I shot single hole groups with the iron sights with mixed brass run of the mill 150 grain handloads I had laying about.
 
Lots of guys just run the Hornady 150 grain FMJ's at 100 and 200 yards for Garand as-issued matches. I bought a bulk pack to keep cost per bullet down. If you don't expect to shoot that many, see if friends will share in the buy. Blemished seconds are also often perfectly good if the maker is good.

If you get a bullet too cheaply made or buy government ball ammo pull-downs, you can find they scatter on you pretty badly. But the Hornady's are available in bulk for a lower price than the MatchKings, and some report getting 1 moa out of them gas guns. I think my best groups have come from the 168's, even at that range, so you may want to get a box to run some comparisons. Whether the cost is worth it or not will likely depend on the accuracy you get.

There are also some guys running even lighter bullets at 100. The 135 grain MatchKing is one I've been meaning to try.
 
You must log in or register to reply here.
Back
Top