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Discussion Starter #1
My latest M1 Garand has a rear sight apeture that wobbles. I have tried to adjust the "curve" of the sight cover (spring) but it does not solve the issue. I think the rear sight cover is worn out and no longer holds tension on the apeture. So, I will order a new sight cover.

My question, is there anything else I should check, or other parts that may beed to be replaced. To me, all other parts look to be in good shape, but I am no expert.

I just want to make one order, and fix the sight just one time.
 

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If you can try more than one sight cover it'll help. No two of them seem to be exactly alike, no two sight bases are exactly alike, no two commercial receivers are exactly alike at that sight deck. You probably need more front lip. You can take a hard, sharp steel punch and a mallet to the front corners of the sight cover you have (remove it from the rifle, set it on a hard wood bench surface) and see if that helps. A stiff spring is your friend.
 

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Discussion Starter #3
If you can try more than one sight cover it'll help. No two of them seem to be exactly alike, no two sight bases are exactly alike, no two commercial receivers are exactly alike at that sight deck. You probably need more front lip. You can take a hard, sharp steel punch and a mallet to the front corners of the sight cover you have (remove it from the rifle, set it on a hard wood bench surface) and see if that helps. A stiff spring is your friend.
I tried bending it, and as soon as I re-install it, it looses the tension. I can remove the sight cover without the use of tools. I just think there is no "spring" left in the steel.
 

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Are yiu sure the spring cover is seating in the receiver? Typically the bottom in the back of the rear sight base needs to be pushed in the little slot with a small screw driver. If the aperature itself is wobeling in the base you may get away with peaning it a little. All the aperatures I have installed I needed to use lapping compound to get them to fit. New they typically fit to tight. I used 600 grit garnet.
 

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Discussion Starter #5
Are yiu sure the spring cover is seating in the receiver? Typically the bottom in the back of the rear sight base needs to be pushed in the little slot with a small screw driver..
Yes, it is in correctly, I do need to push it in with a screw driver, but than I can pull it off with no tools. The sight cover on my other Garand is far harder to remove, as is the sight cover on my M1A.
 

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Well you still need to determin if the aperature is moving in the sight base or the entire sight base is moving in the receiver. That would be a big help.
 

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Discussion Starter #7
Well you still need to determin if the aperature is moving in the sight base or the entire sight base is moving in the receiver. That would be a big help.
I will check it out tonight when I get home.
 

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Get a new sight cover and peen the rear sight base. Take a flat headed screwdriver or center punch and peen each side of the aperture track on the sight base. Two times....one low and high on each side. The base will need to be in a vice. Apply lapping compound and insert rear aperture, then use elevation pinion to run it up and down until it travels smoothly. You have to give it a decent whack to deform the metal sufficiently. A rounded center punch (1/16") is commonly used. This removes any side to side wobble and tightens up the sight in general. Works like a charm. All my JCG match accurized M1s and NM/SM M1As have the rear sight base peened as was described.

Pretty standard accurization protocol for a match rifle build. Many sights are loose and this adds to inaccuraacy as the aperture is shifted under recoil.

Run the aperture up about 20 clicks, then push forward on the aperture with your thumb - it should move against the spring pressure of the cover, and move right back when you release the thumb pressure. If not, it is a rear sight cover issue. Then push the aperture back and forth sideways - if it has significant movement, the aperture is loose in the sight base. Peen it.
 

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Discussion Starter #9
Okay, after further investigation, the sighaperture and base both wobble. So I will replave the cover/spring and see if that solves the issue. If not, I will peen it.

Thanks for the help!
 

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+1 on what MadMinute said. Lightly peening the sight base track along with grinding down the underside of the front of the aperture is how Hook Boutin mod'd the rack grade rear sights on my sticks. They're nice and smooth, no side-to-side play on the apertures when running them up and down. Hope this helps. TD
 

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Sight base peening

Great stuff, MadMinute, thank you!

My aperture had lateral movement of 6-7 thousands of an inch. A NOS GI sight cover made it harder to displace the sight laterally but the slop was still there.

Peened each side of the groove in the bottom of the sight base in which the toothed rack of the aperture slides, in three places high middle & low with a small round nose punch. Couldn't find my valve lapping compound so I gently filed the peened areas with a fine jeweler's file until the aperture would just fit in the track, then used whitening toothpaste and slid the aperture up & down by hand until it worked smoothly. Cleaned, greased and re-assembled.

No discernible lateral slop in the aperture now.
 
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