New Member 1st Post

[Ron]

Hello, thanks to all for some informative posts.

I have read many threads here in the past several weeks before I decided to join .

I see there is quite a lot of devoted members here.

I dont know if this will post or not but thought I would give it a try , I dont know the rules although I have looked for them so maybe I have to be here for a time before I can talk or ask questions?

If this posts , I have a lot of questions that so far I have not found answers for so my question may be "common Knowledge" for everyone but me.

I do not currently own a Thompson although I do collect firearms and have thought about trading for a semi auto version , have not done so yet.

Price and not being within a 150 miles of a class III dealer prevents me from getting a FA one.

So I will se if this thread posts and will return.

Again thank you for the forum.

Ron

 

[reconbob]

Welcome to the board. Our fearless leader (Dave Albert) has done a wonderful

job with this forum. You can start asking questions right away, but be prepared

that simple, new-guy questions rub some here the wrong way, so you may get

a little flak in addition to answers. If the answers to your questions have not

shown up in searches or in your monitoring of the board, then you have good

reason to ask them, and I am sure you will enjoy getting to know the usual

suspects...

 

Bob

[Ron]

Hello Bob,

Hopefully I will stick my foot in my mouth for all to see.

I will try and get that out of the way first thing.

Like I said I dont own a Thompson nor have I ever, I have tinkered with a few to get them operating again but it has been a while.

Amateur gunsmith mostly on my own collection.

I mostly understand their history and different makers .

I see most of the forum is dedicated to Full auto types, my question will be framed mostly to the semi auto versions.

I own no books containing any pictures, diagrams or information on the workings of the Thompsons and their variants.

So I am pretty stupid to start with..

My first question is with their history.

Was there anytime pre war or soon there after any Semi autos manufactured and if there were , were they

the same types that we see today manufactured?

This will lead me to some of my more juvenile questions.

Ron

 

[reconbob]

For a detailed (hopefully not too detailed) history of the Thompson

go here http://www.auto-ordnancecorporation.com/

 

In general no semi-auto Thompsons were made until 1974 when the

then-new West Hurley Auto-Ordnance started making them. Every effort

was made back then, and continues to be made today by the Worcester

Massachusetts Auto-Ordnance (known here as Kahr - they bought the

WH semi Thompson line in 1999) to make people think

that these semi-autos are "original" Thompsons - their entire sales pitch is

built around this.

 

And yes, I know, somebody will point out that some original M1921

Thompsons were reworked into semi-automatic carbines in 1927 and while

that is interesting trivia I do not think that will help the cause here.

 

The semi-autos are a lot of fun. For many people this is the

alternative due to living in a non-MG state or due to not having an extra

$20,000-$30,000 to buy a true original gun.

 

Some semis have a lot of problems - well documented here -

but they can be tuned and improved and accessorized and can give

long service.

 

Bob

[Ron]

,Thank you Bob ,

I had read somewhere that the early 1927a1 were all semi, so that is a reason for my asking.

I could understand that some were reworked FAs to make semi for whatever reason but not in production until 1974.

Also that is why I had tinkered with some years ago to make them run and not jam up.

Brings up another question , one of my important ones.

The cocking knob on the top of the receiver, I see these labeled as 1921s 1927s 1928s , then sometimes I see the 1928s as side cocking knobs.?

Are these 27s 28s or variants of both?

Are the internal workings of the side cocking knob the same as the top cocking ( because of the brass block found in the bolt of the 1927) looks like there is not room for the slot in the receiver if it were on the side?

That is what leads me to believe the side cocking model not only has different bolt but entire locking system ?

Ron

[TD.]

Hi Ron,

As you can tell, there is a lot to learn about the Thompson. The good news is the information is available. May I suggest you visit the below website and purchase American Thunder II by Frank Iannamico. It is $29.95 plus shipping and will answer most of your questions about the history of the Thompson. Frank will be glad to autograph a copy if you ask him. A few days reading this book will make you a much more knowledgeable Thompson enthusiast. Then comes the decision - buying more expensive books with much more detail. But American Thunder II is a great start and at a bargain price.

 

Thanks for joining the Board

 

http://www.machinegunbooks.com/

[Ron]

Hello,

I did read about the book a few weeks ago and went to lengths to read reviews where it was sold.

Seems it deals with Full Auto,

So it doesnt seem like that will tell me what I am looking for?

Ron

[gijive]

The cocking knob on the top of the receiver, I see these labeled as 1921s 1927s 1928s , then sometimes I see the 1928s as side cocking knobs.?

Are these 27s 28s or variants of both?

Are the internal workings of the side cocking knob the same as the top cocking ( because of the brass block found in the bolt of the 1927) looks like there is not room for the slot in the receiver if it were on the side?

That is what leads me to believe the side cocking model not only has different bolt but entire locking system ?

Ron

 

1928 Models are not "side cocking" models. Your reference to the 1927 Model having a bronze lock is incorrect also. Reconbob pointed out that there were early prewar full autos that were made from 1921 Models that were marketed as semi-auto carbines. For your general purposes in understanding the models, that is a bit too much to start with. Generally, 1927 Models were made as semi-auto models in the 1970's as Reconbob mentioned. The "side-cocking" full-auto models were the M1/M1A1 series made between 1942 and 1944 and were only produced during that period of the war. They have no bronze lock system. A later full-auto variant was made by Auto-Ordnance, West Hurley, NY sometime in the 1980's or 1990's but you are apparently only interested in the semi-auto version. Take TD's advice and get American Thunder II, it will answer many, if not all, of your questions.

 

[newtommygunner]

Welcome to the boards Ron, you'll get all ur q's answered here plus some. The book american thunder 11 does deal with full autos but it will give u a great deal of info on how the diferent model thompsons work. I personally found it to be an excellent source of info. I am also new to the thompson world and this book has helped me immencely. Don't be afraid to ask, you'll be surprised how many opinions there are on almost any one subject. But it's always fun. Just ask away. Welcome to the world of Thompsons! mike

[dalbert]

Hello,

I did read about the book a few weeks ago and went to lengths to read reviews where it was sold.

Seems it deals with Full Auto,

So it doesnt seem like that will tell me what I am looking for?

Ron

 

Ron,

 

Welcome to the board! I hope you find what you're looking for here. I'm interested in your perspective, as the folks who visit this board have experience levels ranging from novice to expert, and I probably need to add some more information in the FAQ, or other section that covers more of the front end questions. The board mostly focuses on full auto Thompsons, however semi-auto Thompson questions are a welcomed part of the whole perspective. That being said, TDs recommendation about purchasing Frank Iannamico's "American Thunder II" is still well advised for anyone learning about Thompsons.

 

To answer one of your questions, it is the M1 series of Thompsons that have the cocking lever on the side. The original, full auto version of the M1 was introduced in 1942 as a way to simplify production, and it significantly reduced manufacturing costs. The original M1's had normal firing pins, and a fixed firing pin setup was soon after introduced to further simplify the design, and the changeover resulted in an "M1A1" designation for the weapon. The M1 series of Thompsons use box magazines, and are not designed to accept drum magazines. Semi-automatic versions of the M1 Thompson were (are) built under West Hurley (Numrich) and Kahr ownership of Auto-Ordnance.

 

The Thompsons having cocking knobs (actuators) on the top of the receiver are variants of the original Thompson Submachine Guns, including early prototypes, Model of 1919's, and the most famous version, the Model of 1921, of which 15,000 were produced by Colt from 1921-22. These are the ones that capture everyone's imagination, and were used on both sides of the law, although they were not commercially successful for the first 18 years. These early Thompsons were modified internally and externally to become Model of 1927's (Semi-Auto, but still NFA), and Model of 1928's, and also the military M1928A1's used extensively during WWII.

 

Today's semi-auto Thompsons feature a different internal design to conform with ATF regulations. The West Hurley and Kahr Thompsons with the top cocking knob are based on a semi-auto design known as the "Model 1927." Numrich Arms of West Hurley, NY submitted a semi-auto Thompson design to ATF in 1966 that was rejected, and was similar to the original Colt era Model of 1927, and they subsequently arrived at the current design approval in 1974, which came to the market in 1975, and has been available since through the West Hurley and Kahr Thompson operations. (Keep in mind that the original, semi-auto Model of 1927 was not regulated at the time of its manufacture, and the later design had to conform to the NFA of 1934.)

 

I hope this all helps, and I have to say that there is a huge amount of Thompson information that one can literally immerse themselves into, if they wish. Once that happens, there is no cure.

 

Good Luck!

 

David Albert

dalbert@sturmgewehr.com

[Ron]

Thank you Mike and Dave, very much good information.

Yes I understand the book is a must and will definitely get one soon.

I will commit the information to memory , and to make sure I have it right .

Some of the 1921s were changed internally and externally prior to the war to make semi auto version that were called 1927s ? Correct?

These were done either by the factory or by gunsmiths?

When AO decided to make semi versions in 1966 they submitted a prototype (of the 1927) that failed to pass.

But retooling it they succeeded in 1974 then went into production of the semi version designated as the 1927 ?

What designates the 1927A1 model from this 1927 model?

 

On the military part a full auto was needed but as military contracts go they wanted to change the full auto version to their specs.

Were the Full Auto versions up to that time called 1921s or?

When they were changed was the military number 1928M1? and later with mods became 1928M1A1?

Also I understand this 1928 model is with-out the bronze block that locks the bolt?

So this would mean a cut back in machining costs and time, ie. no extra receiver slot cuts or bolt cut slots and with the introduction of the A1 the bolt would receive even less machining , firing pin hole etc. and possible less

parts in the lower receiver in the trigger groups parts?

So what made the bolt lock up ? just stronger recoil springs?

Thank you for your detailed answers and patience.

Ron

 

[gijive]

On the military part a full auto was needed but as military contracts go they wanted to change the full auto version to their specs.

Were the Full Auto versions up to that time called 1921s or?

When they were changed was the military number 1928M1? and later with mods became 1928M1A1?

Also I understand this 1928 model is with-out the bronze block that locks the bolt?

So this would mean a cut back in machining costs and time, ie. no extra receiver slot cuts or bolt cut slots and with the introduction of the A1 the bolt would receive even less machining , firing pin hole etc. and possible less

parts in the lower receiver in the trigger groups parts?

So what made the bolt lock up ? just stronger recoil springs?

Thank you for your detailed answers and patience.

Ron

 

All 1921 Model Colt guns were full auto guns with bronze locks. In 1928 the U.S. Navy wished to purchase an order but specified a lower rate of fire. No new guns were produced; the original 1921 Models were refitted with a heavier actuator and smaller recoil spring, fitted with a new buffer and pilot system and dubbed the U.S. Navy Model 1928. The bronze lock, bolt, etc were the same as the 1921 Model, the modified parts were the actuator, spring and buffer/pilot. The U.S. Army purchased some for testing and eventually christened the standard 1928 Model as the 1928A1. The 1928A1 was standard with the slowed rate of fire (described previously as the U.S. Navy Model 1928) a horizontal foregrip, Cutts compensator and sling swivels. No changes were made to the bolt, bronze lock, firing pin, etc. to warrant the A1 designation. A Model of 1928 is the same internally as a 1928A1, except that the Army designated their guns 1928A1. This was the model that was mass produced by Savage and Auto-Ordnance at the entry of the U.S. Military into WWII. The 1928/1928A1 model was manufactured from 1940 to 1942. The M1/M1A1 series was the modified bolt with no bronze lock and was manufactured from 1942 to 1944.

 

There was never a military 1928M1 Model. That designation arrived much later with the resurrection of Auto-Ordnance in the form of the West Hurley and Kahr guns.

Edited April 12, 2009 by gijive

[bug]

Thank you Mike and Dave, very much good information.

Yes I understand the book is a must and will definitely get one soon.

I will commit the information to memory , and to make sure I have it right .

Some of the 1921s were changed internally and externally prior to the war to make semi auto version that were called 1927s ? Correct?

These were done either by the factory or by gunsmiths?

When AO decided to make semi versions in 1966 they submitted a prototype (of the 1927) that failed to pass.

But retooling it they succeeded in 1974 then went into production of the semi version designated as the 1927 ?

What designates the 1927A1 model from this 1927 model?

 

On the military part a full auto was needed but as military contracts go they wanted to change the full auto version to their specs.

Were the Full Auto versions up to that time called 1921s or?

When they were changed was the military number 1928M1? and later with mods became 1928M1A1?

Also I understand this 1928 model is with-out the bronze block that locks the bolt?

So this would mean a cut back in machining costs and time, ie. no extra receiver slot cuts or bolt cut slots and with the introduction of the A1 the bolt would receive even less machining , firing pin hole etc. and possible less

parts in the lower receiver in the trigger groups parts?

So what made the bolt lock up ? just stronger recoil springs?

Thank you for your detailed answers and patience.

Ron

 

Ron,

 

Your enthusiasm is commendable but I think you need to take the board members advice and get the book. Your first post had 1 question but your last had 10. Of course that's the way it is with Thompsons. The more you learn, the more you find you don't know. The books will give you a good linear history of the gun and put all of the models in perspective. Many of your questions will be answered along the way and you'll be left with a sound knowledge of the gun. Trying to pick up the knowledge in bits and pieces can lead to misunderstanding and confusion. Please don't take this suggestion the wrong way. You sound genuinely interested in the gun but I can sense the frustration building as you try to absorb the information being presented. Good luck.

 

Bob D

 

[Ron]

Thank you, Have a good one,

Ron

[dalbert]

Thank you Mike and Dave, very much good information.

 

What designates the 1927A1 model from this 1927 model?

 

Ron

 

Ron,

 

I just realized I left off the "A1" on the Numrich/Kahr "Model 1927" in my earlier post. It should be the "Model 1927A1." My apologies for the confusion. The "Model of 1927" was a Colt manufactured and later modified "Model of 1921" TSMG that had internal parts changed out, had the "Model of 1921," "Thompson Submachine Gun," and "Full Auto" markings milled off, and became a Model of 1927 Thompson Semi-Automatic Carbine. They are still considered machine guns under the NFA, and most have had full-auto components reinstalled.

 

David Albert

dalbert@sturmgewehr.com

 

[PhilOhio]

Ron,

 

You are getting a lot of really good, detailed advice from all of the people who have posted above. The best advice is to study those reference books, a lot. It has taken all of us years to absorb just some of it. And there's alway more. But it won't take as long to understand enough to make a fairly good purchasing decision.

 

The only advice I would add is to back track a little, and reconsider whether you would really prefer to own a semi or a full auto Thompson. In quality, there is no comparison. Most full autos are totally superior to any semi ever made. You would never be unhappy with a full auto Thompson, and your investment is more secure, but it doesn't often work the other way around.

 

Cost is high, but it is possible to get a full auto WH Thompson (made post-war in West Hurley, N.Y.) in the $12,000 range, I believe, especially in these softening market times. And the price may go lower.

 

If you have the ability to sell some other guns to fatten your Thompson budget, it is worth seriously considering. Looking back, you will never be sorry.

 

The critical factor is whether you live in a state where all this is possible. If you do, you should not let distance of the nearest Class III dealer license holder slow you down in any way. All of this is small stuff.

 

If you really get into the appreciation of Thompsons, you may wish you had bitten the bullet at the outset, as you come to realize that the cost of buying a semi would be a significant part of the cost of a full auto gun.

 

But if you are pretty sure that a semi will make you happy, and simply don't want to have a lot of money tied up in a full auto gun, then go for the semi, and make the additional investments necessary to get it to run right and be a treasured possession. Some members here have created real show pieces, with the help of specialists referenced in the FAQs section.

[dalbert]

Thank you Mike and Dave, very much good information.

Yes I understand the book is a must and will definitely get one soon.

I will commit the information to memory , and to make sure I have it right .

Some of the 1921s were changed internally and externally prior to the war to make semi auto version that were called 1927s ? Correct?

These were done either by the factory or by gunsmiths?

When AO decided to make semi versions in 1966 they submitted a prototype (of the 1927) that failed to pass.

But retooling it they succeeded in 1974 then went into production of the semi version designated as the 1927 ?

What designates the 1927A1 model from this 1927 model?

 

On the military part a full auto was needed but as military contracts go they wanted to change the full auto version to their specs.

Were the Full Auto versions up to that time called 1921s or?

When they were changed was the military number 1928M1? and later with mods became 1928M1A1?

Also I understand this 1928 model is with-out the bronze block that locks the bolt?

So this would mean a cut back in machining costs and time, ie. no extra receiver slot cuts or bolt cut slots and with the introduction of the A1 the bolt would receive even less machining , firing pin hole etc. and possible less

parts in the lower receiver in the trigger groups parts?

So what made the bolt lock up ? just stronger recoil springs?

Thank you for your detailed answers and patience.

Ron

 

Ron,

 

I'm going to answer some more of your questions, as I think the information may be useful to yourself and others, and potentially lead to additional FAQ material.

 

Some of the 1921s were changed internally and externally prior to the war to make semi auto version that were called 1927s ? Correct? Yes, they were modified into Model of 1927 Thompson Semi-Automatic Carbines.

 

These were done either by the factory or by gunsmiths? Factory (Colt)

 

When AO decided to make semi versions in 1966 they submitted a prototype (of the 1927) that failed to pass. But retooling it they succeeded in 1974 then went into production of the semi version designated as the 1927A1? Yes, they redsigned the semi-automatic prototype, and it was approved by ATF for sale in 1974.

 

On the military part a full auto was needed but as military contracts go they wanted to change the full auto version to their specs. Were the Full Auto versions up to that time called 1921s or? Yes, up until the time of the changes that resulted in the "Model of 1928," the Colt produced models were known as Model of 1921's. There is also one other variant known as the "Military Model," or "Model of 1923," which were modified Model of 1921's made to fire a more powerful .45 cartridge known as the .45 Remington-Thompson cartridge. There were probably only about 6 produced.

 

When they were changed was the military number 1928M1? No. M1928A1 was the military designation beginning in 1936.

 

..and later with mods became 1928M1A1? No.

 

Also I understand this 1928 model is with-out the bronze block that locks the bolt? No. You're probably thinking about the M1 Thompson that does not have a Blish Lock (bronze block).

 

So this would mean a cut back in machining costs and time, ie. no extra receiver slot cuts or bolt cut slots and with the introduction of the A1 the bolt would receive even less machining , firing pin hole etc. and possible less parts in the lower receiver in the trigger groups parts? You're thinking of the M1.

 

So what made the bolt lock up? Just stronger recoil springs? It was found that the Blish Lock was not necessary for the new model (M1) Thompson to operate effectively, and it was designed for ease of manufacture without the lock.

 

David Albert

dalbert@sturmgewehr.com

 

 

 

[PhilOhio]

David,

 

When you mentioned the ".45 Remington-Thompson cartridge", were you referring to a ball round with almost the same name as the shot cartridge? If so, guess I've forgotten that one.

 

Ron,

 

When David mentioned that it was discovered that the Blish bronze lock was not necessary, it was because of emerging appreciation for the fact that several other factors did a "good enough" job of keeping the action from opening too soon after firing. First, the weight of a heavy forward moving bolt generates enough inertia to delay ejection slightly. Second, during the high pressure phase of the ignition cycle, the walls of the cartridge case expand to seal the chamber and also adhere with great force. We're talking about thousands of pounds per square inch. This is more than enough to seal the breech and prevent ejection until long after the bullet has left the muzzle. Pressure then rapidly drops almost to zero, but just before that, residual low pressure helps to eject and drive the bolt rearward, along with rearward energy now equal to the kinetic energy of the moving bullet. Pretty interesting physics.

[dalbert]

David,

 

When you mentioned the ".45 Remington-Thompson cartridge", were you referring to a ball round with almost the same name as the shot cartridge? If so, guess I've forgotten that one.

 

PhilOhio,

 

The .45 Remington-Thompson cartridge was a ball round, and the case was a bit longer than a normal .45 Auto, producing higher velocities due to the added powder volume. It was designed specifically for the longer barreled, bipoded Model of 1923 Thompson, and the designers apparently had grand visions of the Model of 1923 competing with the BAR in an infantry support role. I had 2 of the cartridges that I sold for Helmer, and each had a different shape to the bullet. One had a rounded bullet, appearing to be a 230-Grain FMJ, and the other was also FMJ, but more elongated in shape. Somewhere, I think I have a picture of both of them. A member here purchased one of them. The .45 Remington-Thompson cartridge was a failed experiment at the time.

 

David Albert

dalbert@sturmgewehr.com

 

[35divmp]

...the longer barreled, bipoded Model of 1923 Thompson, and the designers apparently had grand visions of the Model of 1923 competing with the BAR in an infantry support role.

 

David:

 

Which brings up a question...

 

Are there any survivors of this weapon in existance? Museums or private collections?

 

How rare are the cartridges?

 

Thanks!

Jay

 

[Ron]

You guys have been super,

questions were highly detailed and information was what I was seeking.

I would like to address a few of them , and then go out on a limb and risk asking a couple questions.

First I will get the book ,that is a must along with a couple more I have picked out.

Second, more than you know I would like to have a full auto to be able to take care of and listen to it run but

you all know the main reason and I dont think it is going to ease up , ever.

And I dont think my stash of collectable guns would ever add up to the greed of a dealer wanting to sell me one.

So semi is what I will have to live with.

Third , I realize that unless I do some clever machine work I would not be able to just buy one with all of the "options" I would like to have on it.

That said I would like to ask a couple of questions.

Knowing that AO , West Hurley and now Kahr in Mass. has produced the only Thompsons in Semi mode,

do all of their models , 1927s and 1928m1 differ with the internal workings ?i.e., no "bish block" you called it and just rely on the system that Phil explained in detail?

Or are they different as were their predecessors?

I do understand that the FAs fired on and open bolt and the semis are closed as what we are accustom to.

So there are differences in the trigger groups as there should be , but I am not asking about that, mainly just how the semis of today function as compared to the FAs.

Keep in mind I do know that upper receivers and bolts are built to different dimensions so parts cannot be interchanged between semis and FAs.

So I am curious of how the bolt obtains battery in the semis. Thru bish block or just recoil springs like a

auto pistol?

Thank you again for your detailed answers.

Ron

[PhilOhio]

Ron,

 

All the post-war semis work about the same, because it was so much trouble coming up with a design which would satisfy ATF that nobody wanted to go through that again, until recently. Tim Polston has a newly approved design which will be more like the "real" Thompsons, uses more of their modified parts, and will be rather expensive, I suspect. Sounds like it would be The one to have. You might want to research those threads on this site and take a look at http://www.thompsonsmg.com/SEMI_AUTO_INFORMATION.htm

 

All of the semis marketed so far fire from a closed bolt and use a spring-loaded striker firing pin. You can also fit an original full auto lower assembly to them, which will still not let them fire full auto.

 

There is no Blish lock in any of these. They are all unlocked, depending upon the weight of the bolt and high pressure metal adhesion to keep the breech closed until it can safely open. The spring which drives the bolt and helps hold it forward during firing is also MUCH stronger than the spring on a full auto Thompson. This whole system works just fine and is quite safe.

 

This is a long and complicated subject, but in a nutshell, that's it. The Polston design is very different and I am not familiar with all its details.

 

You still need to get the nomenclature untangled a little bit more. It takes awhile to remember all this trivia. The full auto versions, in historical order, were 1921A, 1921AC, 1928A1 and 1928AC, M1, and M1A1. There are a couple semantical variations within those, such as the "Navy" and the 1927 semi. There was no 1928M1. All the postwar guns were semis, except for a few full autos which George Numrich put together during the '60s from surplus parts and a few which he made.

 

All of them up through the 1928 series were much the same. The M1 was a major wartime redesign, as was the M1A1 which followed closely. That was the last of the classic full auto Thompsons. All the semis which followed may look like Thompsons, but they are very different internally and the dimensions were required, by ATF, to be quite different. Sadly, what differed most of all was the often poor quality of the semis. Those from Kahr Arms, most will agree, have so far been the very worst. Just when we think it is improving, our optimism usually turns out to be premature. So when buying one, especially a new one, you have a more daunting task than if you were buying a full auto gun which passed through a rigid military acceptance screening procedure decades ago.

 

David,

 

Another question which occurs to me...by any chance, do you know if the .45 Remington-Thompson ball cartridge would fit the special magazine made for the shot cartridge? That might be where the shot mag originated, and it could have dictated the overall length of the shot round, as a matter of convenience.

 

As I recall, the 1923 Thompson was very different from the series which started with the 1921, and existed as what were basically prototypes. Doesn't Allan Cors or Tracie have one of those? I know I've seen one someplace.

 

[Ron]

Thanks you Phil,

This is getting very close to most of what I am asking about.

a few things to clarify,

 

first

"There was no 1928M1. All the postwar guns were semis, except for a few full autos which George Numrich put together during the '60s from surplus parts and a few which he made."

 

So there was not a 1928m1 but only a 1928M1A1 ? was there a 192? M1 ?

2nd,

they were all Semis after the war except a few Full autos? They waited until 1974 to make semis?

 

3rd , you answered two of my future questions ,

One was the quality of the semis, the other was the use of a Full auto lower on the semis.

This is an idea I have been thinking about, of using a M1a1 lower on a good quality semi upper to be able to have the 2 side slides, one for safety and fire and one to select to hold the bolt open to change the drum which I want to incorporate on to a M1 semi upper ( which I understand there is not slots for , but could be perhaps milled into?) The lower bolt catch would take some thought and machine work .

This is why all of the questions about operation of the bish blocks and bolt lock up.

 

I see that the spring in the M1 was and is very critical in its design and strength.

 

The lower and the drum are 2 of the options I want in a side cocking type semi, others are more easily obtained as for sights , barrels , grips and buttstocks.

 

Thank you for your expert answers.

Ron