Rear Sight Collar misalignment?

Greetings... I recently picked up a SA 1903 from an acquaintance of mine. apparently he bought it back in 2002 and never really disassembled or possibly even fired it during the past 8 years. It (supposedly) originated from CMP.

The big issue I found is the rear sight collar, which appears to be outside of its index...

the sight base is not level with the receiver raceways (used scope levels) and it's visually apparent when you've leveled the gun itself and put the leaf sight up. probably the most obvious indicator is that the leaf assy. doesn't align completely with the sight cut in the upper handguard

doesn't really seem like it should happen... I've never torn apart a 1903 before but it's my understanding there should be a pin to keep that collar indexed properly... but nonetheless it's noticeably rotated clockwise

the left-right drift pin in the front of the collar is missing, and there are signs of slight impact damage on the lower lip of the collar, so I'm thinking it was re-installed by someone at some point who might not have done it properly

I've searched through google and this forum but haven't found a similar problem... I'm thinking my only option is to remove the rear sight collar and see wtf is going on in there...

in my google searching I found a couple threads here relating to that daunting task so I made myself an account to get some expert opinions on my specific problem and hopefully help in solving it.

Cheers :cheers:

could be a couple issues.
one, and what you suspect, someone installed a rear sight base the hard way, with premitive tools.{and the most likely choice.}
second.
someone installed a barrel, and didnt index it far enough.
to see of this is the case.
remove the rifle from the stock, carefully remove the fromnt sight{not the base}
then set the receiver in a soft jawed vice, and level with the machined flats accross the tang.
when you get a level, but the same level accross the front sight base, it should be level as well,
if it maches the rear base, then you have an index issue.
if not you have a sight base issue..
missing the pin isnt a real big issue, as most rear sight bases are tight enough to be driving on..
however, if they messed with the contour of the barrel, you may have some other issues.

The receiver and front sight base are level with one another, the rear sight collar is the only thing that appears to be out of whack... it's currently soaking in Kroil oil for if/when it needs to get removed.

oil shouldnt be needed.
careful how you drive it off, or you may be buying a new one.

Got it off ok... Barrel indexed to receiver OK according to index lines. When the collar is indexed properly with levels it also indexes along the receiver and barrel lines.

it appears the collar spline and/or the barrel spline for the index pin is off as they do not appear to line up when everything else is. :crying:

is the indexing pin absolutely necessary to keep the collar from rotating through use or can I reinstall the collar without it and live out the rest of my days in happiness?

I actually ordered a replacement collar several days ago from Numrich along with the assorted other parts that were unservicable/worn... so I'll wait and see if that one aligns differently... if not it's going to be "What if" time. :runaway:

well,
youll be sending the POS reproduction sight base back for sure, they are cheesy, and dont fit. as are the rest of the crap they sell.
be patiant, and get REAL GI parts..Bill Ricca, myself, and Fleabay are good places to find real parts.
only luck plays into having the hole match the notch from a base to another barrel, as they drilled and pinned each one after the base was installed.
some things to look for first, other then the early sight base with a cutout on the bottom.
they made 4 sight bases..and heres what i have seen.
first and the most common, is the standard SA with cuts on each side, the square pin{thats the one at the back of the base, that keeps the base center} is at 1:00,
second is the same type later production likely Remington, with the pin at 11:00
3rd is a smooth replacement with a pin at 1:00
4th is a smooth replacement likely HS made at 11:00 and 1:00
however, unless you remove the barrel, that pin is real tough to set, so i just leave it out.
if you have the barrel off, then its easy.
if the base fits tight,,,and by tight, needs driven on with a tool..{i make one}
that pushes the rear sight base on snug without ruining the outer edge, and if you have a few buggers, it will straighten them out as well.
if you can push the base all the way on by hand, its too loose.
if you have to drive it on, it should be ok, as long as you can live with not having a pin in the hole.
anther way, is to set it up after the base is on and square, and chase the hole with a carbide drill bit, be careful and go slow..

That's good info, thanks.

the one that came with it has a the hole cut at 11:00 and had a round indexing pin with a short taper at the front. It has an "F" stamp toward the front and toward the rear of it on the bottom (opposite the sight base) if that helps ID it at all. The barrel is an SA made in March 1938 (same year as receiver)

what bothered me is the barrel spline isn't a 90 degree cut... it drifts off (slightly) to the right as you look down at it... so when you lead the collar up to it, the collar hole is markedly off when level so it would have to twist slightly on the way in to match-up in the back when fully seated... however it still seems like the back of the spine and the back of the hole in the collar won't index it well enough... which is probably what happened

If the Numrich replacement doesn't work out for whatever reason(s) I'll drop you a PM,

thanks again for the assistance/advice.

try removing the pin, and slide it on,,id bet the base has stretched a bit from forcing the pin over the barrel.