Modifications for ARMS 18 optic mount ?

Murray 3-D

Murray 3-D

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Stumbled across info like this before on CGN but cant seem to find the threads again. So what the heck ill just ask.

Wanting to install an ARMS 18 mount onto my 2009 Norc receiver. So far its looking like it will fit trouble free :rockOn: except that it may slightly angle off to the left. Fairly certain my 30mm scope will be able to adjust for it.

Ive heard however that these mounts tend to cause stove pipes and that the remedy for that is to shorten the length of some springs in the bolt.

My question is:

What springs need this treatment and by how much ?

Also is there any other mods that should be made regarding this setup ?

And dont worry, ill be sure to verify that the mount installs correctly and the optic can be zeroed before making any of these mods. ;)

Thanks M1a gurus
 
Ya the ARMS 18, some were good batches and some weren’t. The latest model seems ok.

My Norinco went good but my buddies Springfield M1a Loaded, we never could zero his Leupold scope after all but this was his receiver that was a bit off not the mount as we tried a Smith Enterprises and it did the same.

I loved their low profile approach and a bit lightweight compared to others about 10-15 years ago. It was the best if I remember correctly.

Since it’s the front part of the receiver that seems to have issues, I’d give the M14.CA CASM series a try since they do not attach to the front.

Good luck and the ARMS is stil fave.
 
Had a full length rail that gave me intermitten stove pipes, chased down the problem after eliminated other suspects and switched to the pro mag split rail version and never had a problem since. I know Norincos have a different spring power/angle when it come to ejection and the split rail gives just enough clearance to eliminate the chance of casing contact. My recievers geometry is slightly off and find the casting of the rails were slightly different aswell making alligment pain.
 
a lot of the times that angle to the left can be solved during the mounting process.
first, if the mount is installed with the horseshoe washer it comes with.... ditch that washer.
next, take a stone or diamond file and use it to clean up the forward portion of the mounts horizontal key
Then there is adjusting the rear tension pad correctly so the mount doesn't want to pull out of true.... very important.
More often than not the arms 18 needs a bit of care for a proper install.
It remains my favorite of all the mounts for these rifles.

trimming 2 coils off the extractor spring and 3 coils off the ejector spring for Chinese springs is a common mod. I don't modify usgi springs.
 
^ source a set of USGI springs (I think Wolff makes them) and it should help.
I still ran into stovepipes even with the swap though (full length rail).
the arms mounts really low, much lower than the M14.ca mount, so it's kinda worth it, but the older split rail is preferred if you ask me.
 
45ACPKING said:
a lot of the times that angle to the left can be solved during the mounting process.
first, if the mount is installed with the horseshoe washer it comes with.... ditch that washer.
next, take a stone or diamond file and use it to clean up the forward portion of the mounts horizontal key
Then there is adjusting the rear tension pad correctly so the mount doesn't want to pull out of true.... very important.
More often than not the arms 18 needs a bit of care for a proper install.
It remains my favorite of all the mounts for these rifles.

trimming 2 coils off the extractor spring and 3 coils off the ejector spring for Chinese springs is a common mod. I don't modify usgi springs.
Click to expand...

Yah i noticed comparing my Norincos bolt springs to the GI springs "Tonyben3" had in his dissembly video, the Norinco ones appeared to be atleast a 1/8th of a inch longer... making reassembly of my bolt an absolute b!tch of a task!
 
I was honestly tempted to get the newer gen Springfield split rail mount. It appears to be getting positive reviews. But judging by pics i saw on google i figured i would run into mounting issues with my 50mm obj scope caused by the rails excessive length. CASM mount was also considered but i ultimately dislike the look of it.
 
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