Thompson 1928A1 rear sight question


cottage cheese
December 10, 2012, 08:30 AM
Hello all, the local police handed me a Thompson to restore for their museum. I assumed it was an Auto Ordnance M1928A1 because it had all the characteristics of one. The only thing out of place within the limits of my knowledge is the rear sight, which in this case, is a simple fixed inverted 'L' aperture much like that on the Thompson M1A1(?) with no protective ears. I always assumed the 1928's would have that elaborate flip up ladder sight. Was there such a version or would this have been a war time mod? If it helps, this is in India, and as such, the Thompson would've been formerly British. I can post some pictures tomorrow if needed.
Thanks in advance!

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December 10, 2012, 11:59 AM
the kiss principle with the sights.way cheaper in wartime production to stamp that sight than the expensive ladder sights.just set it for 50 and 100 yards.that's what my savage thompson has.the ladder sight i beleive was used more on the commercial thompsons

Jim K
December 10, 2012, 02:59 PM
That "L" (not flip) sight was just one attempt to make the TSMG less expensive and speed production before adoption of the M1 and M1A1 (and later, the M3). The elimination of the Cutts Comp was another.


December 10, 2012, 07:13 PM
If you post a picture of all the parts, it may be possible to narrow it down as to when this particular one was produced, as they made different changes at different times.

December 10, 2012, 07:38 PM
You're looking at a 1928 Thompson that was made at the point where they were just switching over to the M1 version. You will find later 1928s with that simplified type stamped rear sight, and versions with the smooth M1 type barrel without the Cutts Compensator too.
At the point where they were spooling up M1 Thompson production there were a number of these "mixmaster" type Thompsons made. They were making 'em "fast and furious" (sorry..... ;) ) as they were needed for the war so they didn't really care about specific parts for the "right" gun as long as it worked.

December 10, 2012, 09:19 PM
The M1928A1 Thompson with the simple "L" shaped rear sight and a finned barrel is known to collectors as the "2nd variation" and was first produced by Savage under the January 1942 contract. The 3rd and final variation had an "L" rear sight and a smooth (unfinned) barrel. All of the M1928A1's had Cutts compensators. After September 1942, production shifted to the M1 model.

Carl N. Brown
December 11, 2012, 09:42 AM
As I have gathered from reading, the "L" sight fits the same rivet holes in the upper receiver as the elaborate Lyman "ladder" sight on the 1921 and 1928 receivers and could be used as a replacement part on any of the military issue Thompsons. Also, it was a factory part on many early WWII mass production 1928s and the first M1s. I have seen no photos of 1928s with the triangle winged version of the "L" sight. Most "L" sights have the central aperature set for 100 yards and a notch cut in the top for 200 yards adjusted for windage, so the notch usually appears off-center slightly.

cottage cheese
December 11, 2012, 10:06 AM
Gentlemen, thank you for the prompt and helpful information. Collating the information thus given, this appears to be one of the 'transition' 1928A1...2nd Variation apparently. It has a finned barrel with the cutts compensator and markings are Auto Ordnance, NY. The fore grip looks to be a poorly local made and abused Navy type. It is missing its fire-mode selector and the main sear and the magazine latch appears to have received unwelcome attention from a less than careful armorer. I was out of town today so I couldn't take pictures. Perhaps I will tomorrow again. Thanks all again.

December 11, 2012, 10:17 AM
I have also heard my dad talk about them taking the rear sights off & just using the slot in the charging handle, because it got hung on everything.............

December 11, 2012, 11:17 AM
my 28a1 savage was a dewat(500 bucks pre 86)L rear sight and straight plugged now has a nice finned bbl with compensator.gunshow scrounging

December 11, 2012, 11:45 AM
markings are Auto Ordnance, NY

This is interesting. M1928A1's marked "AUTO-ORDNANCE CORPORATION NEW YORK, N.Y. U.S.A." were early production guns made prior to the company's move to Bridgeport, Conn. in 1941. These were all actually made under contract by Savage. All Thompsons are marked "AUTO-ORDNANCE" regardless of who actually made them. Savage-made guns have serial numbers starting with "S" while the ones actually made by Auto Ordnance (in Bridgeport) have serial numbers starting with "A.O."

My point is that there is a discrepancy between the NY address (which ended in 1941) and the "L" sight, which didn't start until 1942. It's possible that the "L" sight was retrofitted during an overhaul. All the sights were interchangable because the rivet spacing is the same.

Carl N. Brown
December 11, 2012, 08:36 PM
I have also heard my dad talk about them taking the rear sights off ... because it got hung on everything.

According to Frank Iannamico, American Thunder: The Military Thompson Submachine Gun 1928, 1928A1, M1, M1A1, Moose Lake Publishing, 2000, field complaints about the plain "L" catching on stuff led to the next version having triangular wings or ears protecting the sight.

December 12, 2012, 09:48 AM
Cost saving measure to make the Thompson cheaper/easier and quicker to manufacture.Many other features were deleted to save money and ease production like no cooling finns on the barrel,no checkered safety/selector levers(later switched to simple stick levers),no cutts compensator.
Even with these measures,the 1928A1 version was still too costly in time and money to produce.This led to the M1 and M1A1 variants.The Thompson in any shape and form was a First generation type SMG and they took too long to make and cost too much,steel stamped guns like the Sten,M3 and MP38/40 were the future.

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