T21 Rear Sight
Printed From: The Carbine Collector's Club
Category: The Club
Forum Name: General Discussion
Forum Description: Carbine Related
URL: http://www.uscarbinecal30.com/forum/forum_posts.asp?TID=4616
Printed Date: Apr 19 2024 at 7:40am
Software Version: Web Wiz Forums 12.01 - http://www.webwizforums.com
Topic: T21 Rear Sight
Posted By: carbinekid
Subject: T21 Rear Sight
Date 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...       https://i.imgur.com/8NVw708.jpg" rel="nofollow - https://i.imgur.com/8NVw708.jpg https://i.imgur.com/BBWuE85.jpg" rel="nofollow - https://i.imgur.com/BBWuE85.jpg https://i.imgur.com/IG8P4x0.jpg" rel="nofollow - https://i.imgur.com/IG8P4x0.jpg https://i.imgur.com/FeRl2j5.jpg" rel="nofollow - https://i.imgur.com/FeRl2j5.jpg https://i.imgur.com/sOICsGp.jpg" rel="nofollow - https://i.imgur.com/sOICsGp.jpg https://i.imgur.com/ubkabsM.jpg" rel="nofollow - https://i.imgur.com/ubkabsM.jpg https://i.imgur.com/pfCsULC.jpg" rel="nofollow - https://i.imgur.com/pfCsULC.jpg |
Replies:
Posted By: New2brass
Date Posted: Apr 12 2020 at 6:23pm
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thanks for reporting. Which board was that on? We have seen at least one on the special receiver http://www.uscarbinecal30.com/forum/the-m1a2-carbine-was-it-ever-issued_topic2832.html" rel="nofollow - http://www.uscarbinecal30.com/forum/the-m1a2-carbine-was-it-ever-issued_topic2832.html ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: carbinekid
Date 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. |
Posted By: New2brass
Date Posted: Apr 12 2020 at 6:32pm
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Well tell us where you found this great piece of carbine history! ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: carbinekid
Date Posted: Apr 12 2020 at 7:00pm
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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. https://i.imgur.com/wOXXEiw.jpg" rel="nofollow - https://i.imgur.com/wOXXEiw.jpg |
Posted By: New2brass
Date Posted: Apr 12 2020 at 7:28pm
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Hmm, something looks different
  ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: GotSnlB28
Date Posted: Apr 12 2020 at 7:59pm
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The base isn't tapped for the set screw like the one on X61 in the newsletter is. Definitely an interesting sight though. |
Posted By: New2brass
Date Posted: Apr 12 2020 at 8:28pm
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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.) ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: carbinekid
Date Posted: Apr 17 2020 at 11:05pm
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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. https://i.imgur.com/utd3xJZ.jpg" rel="nofollow - https://i.imgur.com/utd3xJZ.jpg
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Posted By: carbinekid
Date Posted: Apr 17 2020 at 11:32pm
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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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Posted By: New2brass
Date Posted: Apr 21 2020 at 3:17pm
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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? ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: carbinekid
Date Posted: Apr 28 2020 at 1:24pm
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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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Posted By: carbinekid
Date Posted: May 04 2020 at 10:14pm
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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.   |
Posted By: W5USMC
Date Posted: May 04 2020 at 10:44pm
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That looks pretty good, nice job. ------------- Wayne USMC Retired NRA Life Member |
Posted By: carbinekid
Date 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. |
Posted By: New2brass
Date Posted: May 17 2020 at 4:28pm
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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. ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: carbinekid
Date Posted: May 17 2020 at 5:00pm
| The double knob sight sounds like the oddball prototype that Ruth discusses in War Baby. |
Posted By: carbinekid
Date Posted: Jun 01 2020 at 12:44pm
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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.“
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Posted By: Marty Black
Date Posted: Jun 01 2020 at 2:01pm
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Nice job, Carbine Kid ! MB ------------- Marty Black |
Posted By: carbinekid
Date Posted: Jun 01 2020 at 3:51pm
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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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Posted By: carbinekid
Date Posted: Jan 27 2021 at 2:22pm
| I just wanted to bump this back up to see if it generates any new discussion. Not often that prototype stuff turns up. Makes we wish we still had a print newsletter. Definitely fit for publication I’d think. |
Posted By: painter777
Date Posted: Jan 27 2021 at 7:20pm
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Great find, your fix looks great. I applaud your research and Appreciate you sharing this with us. We need more of this......... 'Sharing Thing'. Many just want answers it's refreshing seeing a member pull up his sleeves. I'm also in Michigan, East of Lansing. But grew up in the Downriver area town called Flat Rock. Thx Again, Charlie-P777 ------------- Living Free because of those that serve..... |
Posted By: painter777
Date Posted: Jan 27 2021 at 7:36pm
Dan, Is that the FM that shows the Hammer Stop coming from the Magwell wall? Plus the grooves on top of the trigger housings rear lug? And I believe mentions the coming new adj site will provide
for 3 points of left and 3 points of right windage ? I'll look for it when time allows. Thx for the heads up. Charlie-P777 ------------- Living Free because of those that serve..... |
New2brass wrote:Posted By: New2brass
Date Posted: Jan 27 2021 at 8:22pm
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Charlie, yea it was the first FM. I do not remember if it stated points of windage vs just adjustable. ------------- http://www.uscarbinecal30.com/forum/club-assistance-saginaw-receivers_topic4716.html" rel="nofollow - Club Survey Saginaw Receivers |
Posted By: carbinekid
Date Posted: Jan 27 2021 at 9:12pm
My eBay scouring has turned up something interesting that is related to this topic. The sight below seems like it must have been influenced by the oddball double knob rear sight. Looks like it was put into practice post WWII in Europe.    |
Posted By: carbinekid
Date Posted: Nov 23 2022 at 11:12am
I finally got around to doing a comparison between this protype sight and standard production type 2 and 3 sights. I’ll post the measurements I took after the photos.         |