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T21 Rear Sight

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carbinekid View Drop Down
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    Posted: Apr 12 2020 at 3:27pm
Has anyone seen one of the modified T21 sights made by Mossberg for standard M1 receivers? I found the thread from 2017 showing the original T21 sight as devised by Inland for its own unique receiver. I think I found one...


















Edited by New2brass - Apr 12 2020 at 6:39pm
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Dan Pinto, Photo Editor

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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 6:23pm
thanks for reporting. 
Which board was that on?

We have seen at least one on the special receiver

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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 6:28pm
the sight is mine. The thread I reference is the one you posted the link to that is on this board.
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Dan Pinto, Photo Editor

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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 6:32pm
Well tell us where you found this great piece of carbine history!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 7:00pm
no great story unfortunately. I stumbled on it while scouring eBay. The seller had another mixed lot of small screws and other sight bits. In that lot was the missing windage plate and another aperture. Sadly, there must have been something in the pile that was valuable to someone else because what I thought was a totally safe high bid was overtaken in the final seconds. Pretty heart breaking. I asked the seller to pass my info on to the buyer of the lot, crossing my fingers that the person will contact me. I can’t imagine anyone else but me is looking for that bit. If I can’t get it then I’ll just make one. I don’t know if the screw was in the pile or if anything was supposed to go in the whole on the left side or if it supposed to be open. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 7:28pm

Hmm, something looks different


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Post Options Post Options   Thanks (0) Thanks(0)   Quote GotSnlB28 Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 7:59pm
The base isn't tapped for the set screw like the one on X61 in the newsletter is.
Definitely an interesting sight though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Apr 12 2020 at 8:28pm
I was pointing out the base difference, but looking at the article again that  I linked above

The carbine production expansion program was rapidly accelerating at that time, 
and a redesign of the receiver would have caused unnecessary delays. 
The O.F. Mossberg Company was consulted and the T21 rear sight was redesigned to fit the standard carbine receiver. 
The M1A2 receiver design was then made obsolete on 25 November 1943. A photo of the T21 adjustable rear sight can be found in War Baby! page 96. (The Mossberg-modified T21 rear sight is the common adjustable rear sight that was first assembled onto carbines in March-April 1944.)


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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Apr 17 2020 at 11:05pm
Today I received the sight in the mail and was able to give it a good looking over. Of note, on each side of the sight there some hand added markings. On the right side is a large “7” and on the other side is “.025”. This leads me to believe that perhaps this is sight number seven out of an unknown number. The other marking must indicate an amount of material added or removed, maybe off of the base as the edges of the dovetail show hand fitting. The edge of the dovetail also shows a chisel type stake mark as was common at the time with the stand flip sights.

Looking through the pictures I saved of the parts lot auction I missed out on, I found there was another sight aperture that clearly was a little bit different spec. The sight hole has a larger dish on the front side than the aperture currently installed in the sight. As for the aperture on the sight, perhaps the .025” is in reference to a taller aperture as it looks different and mine also shows to be two pieces with the sight loop brazed on to the base.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Apr 17 2020 at 11:32pm
I forgot to add that the on the left side at the end of the windage pinion there is no retaining screw or missing piece. The indented/stepped down appearance is due to how piece is staked in place.

Overall this is a very nicely made sight right on par with the eventual standard type 2 rear sight.

Now I need to get to the task of recreating the missing windage plate. Anyone happen to have a spare screw from a the rear of a type 2 rear sight? No idea what the thread pitch is on this sight, but it seems like the first place to start is with what is on the type 2.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: Apr 21 2020 at 3:17pm
Might I suggest doing nothing that would alter the sight. It detracts from its history.
Any luck with the seller contacting the buyer of the loose parts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Apr 28 2020 at 1:24pm
Still no luck getting the missing piece to the sight. I did get an appropriate screw from a local old time gun shop. I have a buddy working on fabbing the plate up. Not original, but it will complete the look. Nothing on the sight will be permanently modified of course.

I’ve got a Winchester carbine on the way that was victim of some light sporterization. The rear sight is fubar, so I’m going to give this one a go and see how it actually works out...at least for one range trip. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: May 04 2020 at 10:14pm
I spent some time fabbing up the missing rear sight windage plate and modifying the retaining screw. 

As it turns out, a flip sight leaf spring is the perfect material and thickness. I had several that are likely repros given what I paid for them, I still see them listed on eBay all the time. So, I sacrificed a couple for the cause and I’m very pleased with the end result.

http://www.uscarbinecal30.com/forum/uploads/2217/E09BA84C-C37A-489D-A60F-74DBBBC39C98.jpg
http://www.uscarbinecal30.com/forum/uploads/2217/D5679A67-BA1B-4A8F-B8F4-2D78DA86FC01.jpg


Edited by New2brass - Nov 23 2022 at 11:22am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: May 04 2020 at 10:44pm
That looks pretty good, nice job.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: May 17 2020 at 3:06pm
Anyone have a copy of CCNL #168? Looking through the index I see that there is some discussion of a prototype adjustable rear sight.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote New2brass Quote  Post ReplyReply Direct Link To This Post Posted: May 17 2020 at 4:28pm
CCNL 168 Discussed the original prototype adjustable rear sight. If you read an early FM-7 1942 it states "models of the carbine initially will will be equipped with an L-type rear sight, consisting of two arms at right angles, each pierced with an aperture .... Later models of the carbine will be equipped
with an adjustable sight generally similar to that shown in other figures in this
manual."
page 11 shows the rear sight and it appears to have two knobs. One for elevation and one for windage.

There is another thread somewhere. Maybe someone remembers it and can link it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: May 17 2020 at 5:00pm
The double knob sight sounds like the oddball prototype that Ruth discusses in War Baby. 
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Post Options Post Options   Thanks (1) Thanks(1)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Jun 01 2020 at 12:44pm
So I got in touch with the folks that handle some of the historical records of Mossberg to see if they could shed any light on their participation in sight development for the carbine. Unfortunately they couldn’t provide much. What they did provide was enlightening though. Below is what they told me. Also I managed to find the patent file showing the sight. Very different from mine and the other version of the T21 from the M1A2.

“Most of what we have is anecdotal, with a small blurb related to the patent 2,407,437 which was received by Harold Mossberg

The number S105 was assigned to a receiver sight listed as "designed for the War Department, June 1943 for use with the M-1 .30 caliber carbine", yet no record of an approved contract or production numbers can be found.

Mossberg would have made pre-production prototypes and samples of course - yours could be one of those.“

http://www.uscarbinecal30.com/forum/uploads/2217/B55E12CB-5816-47E9-AE00-A98B68EB67A2.jpg




Edited by New2brass - Nov 23 2022 at 11:23am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Marty Black Quote  Post ReplyReply Direct Link To This Post Posted: Jun 01 2020 at 2:01pm
Nice job, Carbine Kid !   

MB
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carbinekid Quote  Post ReplyReply Direct Link To This Post Posted: Jun 01 2020 at 3:51pm
I just got another update from the Mossberg folks. This was in response to me saying that my sight and the drawing show significant differences...

 “One of the things that Alan Mossberg told us when we interviewed him for the book back in 1993 was that patent drawings versus production samples are designed to be approved "substantially as rendered" rather than "exactly as rendered."  Having never seen one in hand, I don't know if they would have been stamped S105, as the peep sights were stamped S100, No 4, S130 etc.”
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