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SSBiggun
September 20, 2008, 11:08
Ok so here's what I have. Armscorp M-21 marked rifle . I just switched from the Armscorp mount which is made of Aluminum to a Smith steel mount. I had to shim the old mount to get proper bore alignment with the Armscorp mount and was hoping the new Smith mount would be a little better in this regaurd but as the case is its actually worse. Unshimmed my POI is 36" right @ 100M which is way more than the windage of the Redfield LE-12 can compensate for . I'm thinking the receiver side is out of spec. as far as the mating surface.

Option 1 shim it again.

Option 2 have the mount surface ground to change alignment.

Option 3 have the receiver surface groung to change alignment.

Shimming is easiest and probably best option. Option 3 is least desirable. Any input would help me resolve the issue.

TerryN
September 24, 2008, 05:26
I have heard that Smith will modify their mount to fit your receiver; it might be worth looking into.

MACV
September 24, 2008, 10:18
Have you tried a Springfield Gen 3 mount. Mine mounted perfectly.

gunshack
September 24, 2008, 10:22
Calculate your potential expenses carefully. Shimming is obviously the least expensive, and the least desirable. It might be time to ditch the Armscorp receiver and upgrade to an LRB.

wolfsburgbob
September 24, 2008, 14:01
Or "downgrade" to a correct dimension Chinese Polytech receiver and use a ARMS #18 for a perfect fit right out of the box.

gunshack
September 24, 2008, 15:04
A chinese receiver would be an upgrade, provided that it's correctly machined to accept a USGI bolt, and then properly heat treaded and refinished afterwords. If done right, that's a great option. And it'll cost about what an LRB would.

wolfsburgbob
September 24, 2008, 15:31
Originally posted by gunshack
A chinese receiver would be an upgrade, provided that it's correctly machined to accept a USGI bolt, and then properly heat treaded and refinished afterwords. If done right, that's a great option. And it'll cost about what an LRB would.

Yes I agree, and I was being facetious.

I have owned many different semi-automatic domestic versions of the M14 and quite a few Norinco and Polytech M14S. I have never had a SERIOUS problem with any one of them. One Norinco had headspace at the maximum and two Springfields had loose bolt roller issues. They all shot fine.

I have only had seven Polys and Norincos, but I have never seen a bad chinese bolt. I think the bolt issue is more hype than issue.

Moral of the story,..."Buy Chinese and laugh all the way from the range to the bank".

:wink:

shortround
September 24, 2008, 16:03
What you might want to do is sell the Smith mount and purchase a Sadlak, which I've found to be every bit as good as the Smith and is based on the same design (BPT). Sadlak has a custom fitting service where you measure your receiver with their kit ($5) and they will machine their mount to fit.

http://www.sadlak.com/Images/Titanium_Scope_Mount2.jpg

http://www.sadlak.com/si_custom_sm_fitting.html

CUSTOM SCOPE MOUNT FITTING
A New Service for the precision-minded M14/M1A rifle owner

We are the first M14/M1A scope mount manufacturer to offer a custom fitting service so you won’t have to compromise on your scope mount fit when your M1A receiver is out-of-spec.
Now, with our new custom fitting service, every M1A owner can have the same perfect fitting scope mount as the military has on their USGI government inspected “original” forged M14 receivers. It won’t matter if your M1A receiver was made to USGI specifications we’ll do the modification to the mount and make it fit perfectly.

We’ve taken the trial and error out of the mounting process by developing an Inspection Kit that includes a detailed colored instruction sheets with diagrams plus two sizes of precision ground inspection pins. The simple, at home, self-inspection procedure allows the M1A owner to verify if their M1A receiver’s left side groove is made to USGI specifications. If it is not, you can easily provide us with your receivers exact left-side groove dimensions without having to ship us your rifle. We will then custom fit your Sadlak Industries LLC scope mount for a service fee of $45.00 and guarantee the fit.

WHY OFFER THIS CUSTOM SERVICE?
Our scope mounts are precision made to fit on M14 USGI receivers. However, not all M1A receivers are made to these same tight specifications.

Because the left side groove depth and width vary greatly between manufacturers, date of manufacture and because of the demands from our military, we cannot realistically make our mounts with a “one-size-fits-all” specification. If we reduce the dimensions on our mounts to fit the worst-case M1A receiver, they will be too loose for the military and will not repeat zero. We do not want to compromise the fit, reliability, rigidity and accuracy that prolonged use demand (ex. military). Instead we make all of our mounts to fit precisely onto receivers that have been built to the original USGI blueprint specifications as most older M1A receivers were. This way when our military requires the use of our scope mounts, we have available the quality product they demand.

Until now, the M1A rifle owner was the one who had to compromise. In too many cases, we have seen the horizontal groove on M1A receivers not machined deep enough and the left side threaded hole not located correctly. The result is a compromised fit between your receiver and the scope mount.

In the past, the solution from other scope mount manufacturers was “Our mounts are made to fit on military M14 receivers. We’re sorry they don’t fit your civilian M1A receiver. There is nothing we can do but you can return the mount for a refund if you like.”

The Inspection kit is supplied free with any purchase of a Sadlak Industries LLC scope mount or, upon request, with any order over $50.00. It is the simplest trouble-shooting tool available if you have misalignment problems when attempting to install a mount on an out-of-spec receiver. These problems have occurred more often on newly manufactured M1A receivers. Older M1A receivers have a better track record. If you’re not yet ready to purchase one of our scope mounts but want to determine your receiver’s groove specifications, the Instruction Kit is available for $5.00 plus shipping. We will credit you the kit’s cost toward any future purchase of a Sadlak Industries LLC scope mount - so you can’t lose.

When you buy a scope mount from Sadlak Industries you not only get a precision product but the service to back it up. Our military doesn’t compromise, neither should you!

Custom Fitting Service $45
Inspection Kit $ 5 (free with scope mount purchase or orders over $50.00)

Links to Inspection images:

Inspection Sheet 1 - M14/M1A Receiver Left Side Groove Inspection
Inspection Sheet 2 - Proper Engagement of Inspection Pin with Left Receiver Groove
Inspection Sheet 3 - USGI Left Side Groove Spec.

gunshack
September 25, 2008, 09:57
Sadlack's fitting guidelines are designed to address groove issues with Springfield Armory's M1A rifles. I don't think it has any bearing on the OP's issue.

Wolfy, the only chinese M14 I've ever owned came to me with the headspace at 1.638. I did a hardness test on my bolt to see if it was close to USGI speck, and it was no where near! Some chinese bolts (most of the ones imported into the US) are too soft to see service, and often the headspace is unsafe for commercial ammo. It is my opinion they should be swapped out for USGI bolts as soon as one can afford the work.

shortround
September 25, 2008, 10:10
Originally posted by gunshack
[B]Sadlack's fitting guidelines are designed to address groove issues with Springfield Armory's M1A rifles. I don't think it has any bearing on the OP's issue.

Should be much the same issue. For $5 it would be a fast check.

Cava3r4
September 27, 2008, 00:57
over the years I've spent a lot of money trying to mount a scope to an M1A rifle.
I bought a generation ONE mount from springfield which was a joke.
7 rounds and the scope mount was loose.
I bought a genration 3 springfield mount which I still have and had a surplus stock customized with an adjustable cheek piece or "comb" and the mount would still shoot loose even with locktite.
My advise is if you want a "sniper" or "varmint" rifle that is scoped for long distance work, buy a commerical bolt gun and the appropriate scope and mount.
HTH
Bob

superjc
September 27, 2008, 21:55
The Scott Duff book says it's difficult to do, so keep it simple and buy the Brooksfield Precision Mount. I understand the Sadlak is an upgrade of that, so I'm planning on getting one of those for the ACOG I plan to buy.