AR-180 part 2

In part 2 of making the AR-180 we will be looking at the upper receiver and the steps necessary to make one. There are a number of rifles that use the same basic design concept. So this build concept would work for any of them.

This is the AR-18/180.

DSCN2975scAnd a close up of the upper receiver.

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A number of other weapons have the same basic upper receiver design. This includes the AR-180B

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DSC_2737scThe early Bushmaster rifle

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DSC_2739scThe Leader rifle

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DSC_2741scAnd the Vulcan V15DSC_2743s

DSC_2744csSome of these have strengthening ribs while other do not.

 

 

This is what the flat would look like after the initial pressing. The holes would be alignment holes for set up and the groves would be pressed in.

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This pressing shows the unnecessary sheet metal cut away and the remainder of the holes in the receiver.

 

 

 

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The other side of the same pressing

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At this point there were probably 2 or three ops performed between this pressing and the last one.  The hole has been cut into the receiver for the ejection port and for the bolt operating handle. In addition the first and second bend has been completed.

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The other side of the same pressing.

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You can now see the upper receiver completely bent and welded.

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These 4 holes on both sides of the receiver are to tig weld the barrel extension to the upper receiver.

DSC_2538sThe vertical run of holes is to tig weld the “u” channel that the bolt runs along into the receiver.

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Close up of the welding performed to close the upper receiver together.

DSC_2545sOur next post on this type of rifles will be the smaller parts and how they were made.

EM-2 30-06 rifle

During the time period that the EM-2 was design it was made in a variety of calibers. These calibers ranged from the original caliber of .280 to the NATO standard of 7.62×51 through 30/06. This post is dealing with the 30/06 rifle. Basically what they did was to cut and weld a 7.62×51 rifle to convert it to 30/06 as a trials weapon. This is the only one that I know of and it makes for an interesting study in cartridge conversion.

 

This is a full view of the rifle showing the total amount of work required to do this conversion.

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A close up of the welding required to complete the conversion to the receiver and magazine.

 

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The other side.

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This picture is from the book EM-2 concept and design published by Collector Grade Publications, a must have book in any gun library. It shows the different lengths of bolts in the three calibers.

30-06 boltcsA great deal of work, but an interesting project.

Weekend update 11-10

It was a productive weekend as weekends go. The holes were drill into the side or the forging press I-beam to support the fluting machine. Here are a few pictures and a quick video of the process.

Moving the back plate over was no big deal, once in the fab shop it was loaded on the die cart with an extra steel plate to allow us to move it closer to the press.

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DSC_2703sThe backing plate was clamped and then marked.

DSC_2705sA bushing was made to allow for proper alignment.

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DSC_2708sThen the best money spent on this part of the project.

DSC_2713sA magnetic drill was rented. It made the job so much easier. I really want one of these.

A quick video of the process

 

We went through the wood shop to get it back in order to allow me to finish the stocks for the VG1-5 rifle project. I have to tell you this took some doing. It has been the junk holding room for a while. This is how it looked last night. I finished the electrical Sunday morning.

DSC_2725sOne problem was found though. Termites.

DSC_0106sOne more thing to fix.

I moved the big dust collector outside and started a new room for it and the air compressor. This is the dust collector.

DSC_2732sAnd the new room.

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DSC_2729sIt is not large, but it will hold the equipment just fine. I also started on the table saw back bench.

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The fab shop ceiling was completed.

DSC_2728sAnd caulked

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Sunday answer 11-9

The picture from the post on 11-8 is from the bolt of a Beretta model 1957 carbine in .30 M1.IMG_0045s

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Here is the write up on it from the book ” The World’s Assault Rifles”. This is another book you should have in your library.

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beretta 2cs

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What is it Saturday 11-8

Another interesting part.

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EM-2

A rifle that I have been interested in for quite some time is the EM-2. It is one of those rare rifles that you read about but generally don’t have a chance to see, examine or shoot. I have had the opportunity to do all three.

To start all of the rifles came with a fitted wooden box holding the rifle and it’s accessories.

david's collection 009_sYou will notice that it comes with 6 magazines,bayonet,sling,grenade launcher, cleaning kit and winter trigger,which is missing from this box. It just looks like the center piece for a gun collection.

So lets chat about this set up.

First thing is that the rifle is a bull pup design and was initially made in .280 and later made in what was to become the NATO standard, 7.62×51.Here is a picture of the two of them together.

visser 059 - Copy_sThis rifle that was are looking at is the NATO standard version.

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david's collection 064csOne of the first things you notice is the wood veneer on the rifle receiver where you rest you cheek. With the machining and wood veneer it looks more like a custom built sporting rifle then a military contract rifle.

david's collection 069swThe next item that really sticks out is the low power scope that comes attached to the rifle.

david's collection 062swAnother component that sticks out is the beautifully made hand guard.

david's collection 033s Now to leave the art portion of this weapon to the more practical. The grenade launching sights are built in and the front sight automatically cuts of the gas system.

david's collection 034sAnd the rear sight is built is as well.

david's collection 036swThe safety is in a well design location, in front of the trigger guard.

david's collection 063swThe cartridge deflector is machined into the receiver.

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The machining on this rifle is something to admire.

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Here is a video for papa Joe of me shooting the EM-2. Enjoy papa Joe you could have come with me.

 

Stay tune for the next part of the EM-2 saga.

 

HEAT TREATING

 

During our recent trip through the mid-west I had an opportunity to stop in and chat with John D.,a metallurgist, and Joe P.,a heat treating professional. I ended up taking a number of pictures and John was nice enough to do a write up for me concerning what we looked at, what it does and how it works.

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Nikon inverted stage ‘Optiphot’ optical metallurgical microscope with a CCD camera and flat screen display for group viewing..  This type of reflected light microscope is usually referred to as a ‘metallograph’.  Metallographs provide useful magnifications from 10x to 1,000x plus and are distinguished from most scientific microscopes by their use of reflected light, rather than transmitted light.  The illumination light is introduced into the image axis via a half silvered mirror and broadcast upon the sample surface by the objective lens, the same objective lens which generates the reflected image..

Image on the flat screen is a polished and etched, through hardened, medium carbon, manganese-chromium alloy steel transverse section (cut perpendicular to steel rolling direction).  Area being viewed is deep in the sample, away from its quenched surface. This steel sample image reveals decided chemical segregation remaining from its original solidification at the steel mill.  The light yellowish blotches are alloy rich ‘strands’ in the steel which fully hardened to martensite at this depth from the quenched surface.  The darker greenish envelopment is the much softer, alloy depleted matrix which did not fully transform to martensite (the strong, hard constituent of hardened steel) at this depth.

This type of alloy segregation is termed ‘banding’ by metallurgists and can severely degrade mechanical properties in the directions perpendicular to steel rolling.  Banding in alloy steels can be diminished by greater reductions in steel mill hot rolling (requiring a larger initial size cast form), or adding alloying elements like nickel which promote more chemically uniform solidification.  Banding is a major issue in the AISI/SAE 4140 series (chromium-molybdenum) steels popular in American firearms construction.  It is also a major issue in the manganese and manganese-chromium steels popular for firearms construction in Europe.

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Fully automated Newage ‘MT-90′ microhardness test system used to measure the hardnesses of very small volumes in metals.  Microhardness is usually measured on the Vickers or Knoop scales using single indentation loads ranging from 100 grams to 2.5 kilograms.  Microhardnesses are determined by measuring the width of impressions made by known dimension diamond penetrators.  Microhardness testing – due to its inherent sensitivity – can only produce accurate hardness measurements on highly prepared (polished) surfaces.

The more commonly used Rockwell scale differential-depth (dual load to eliminate instrument lash) hardness values are determined by directly measuring the depth of penetration, using indentation loads ranging from 60 kg to 150 kg.  Microhardness measurements can be converted to the more commonly understood Rockwell values by using conversion tables, but the microhardness measurements only read the hardness to a depth of about 0.1mm, while Rockwell measurements routinely read the hardness to a depth of 1mm.  This is an important distinction when evaluating metals with hardness gradients.  Side note: the indispensable Rockwell hardness test is 100 years old this year, having been invented in 1914.

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At the top of the lower right quadrant in this screenshot from the Newage MT-90 automated microhardness tester, you can see what metallurgists call a ‘microhardness traverse’.  This shows the gradient in hardnesses from near the surface, towards the interior, in a carburized steel section.  The surface of the steel sample is directly under the center cross of the quadrants.  The material imaged to the left of this point is a phenol formaldehyde plastic mounting compound (‘bakelite’) used to preserve flatness of the metallurgical specimen during polishing.  The material imaged to the right of this point is the actual steel metallographic specimen.

The light area at the surface is extremely hard, high carbon martensite which has fully transformed.  As the steel darkens away from its surface, its carbon content is lower and hardness is declining due to reduced hardenability and less transformation to martensite. [Hardenability is a direct function of carbon content in this case].  The individual HV(1kg) impressions are increasing in size further from the carburized surface, reflecting declining hardness.  This particular traverse has been performed to determine ‘effective case depth’, the depth below a carburized surface where hardness falls below 50 Rockwell ‘C’ scale equivalent [the term equivalent is used to indicate that the original measurements were not performed using the Rockwell ‘C’ scale].  Effective case depth is the most important property of precision carburized steel parts.  Core hardness and percentage of retained austenite (a soft constituent) in the case are the other two commonly specified properties which influence part performance.

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Metallographic image of an etched section through fully hardened and then tempered medium carbon steel specimen without a carbon gradient.  Bakelite on the left, steel on the right hand side.  A good metallographic structure not evincing much evidence of banding, such as might be obtained from AISI/SAE 8645 or 4340 nickel containing steels.  The faint striations visible are polishing artifacts which do not reflect upon the actual sample structure.

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Another view of the Nikon ‘Optiphot’ inverted stage metallurgical microscope.  The sample being viewed is in the exact center of the square stage, in front of the binocular eyepieces, on the round white metal stage insert.  The sample is fully encapsulated in bakelite, which is also seen on the left side of the flat screen screenshot.

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Two Struers ‘Tegramin’ automatic metallographic polishing machines.  Six bakelite mounted steel specimens are locked in the holder at the bottom of the vertical drive column and then spun on abrasives affixed to the spinning platen below.  Steel metallographic specimens are first leveled and polished on 120 grit to 600 grit silicon carbide abrasive papers in progression, then 6 micron diamond particles in oil on cloth, and finally 0.05 micron alumina particles suspended in water on cloth.  Specimens are ultrasonically cleaned and the platens changed at every progressive polishing step. The resulting mirror finished surface is then etched in weak acid solutions to reveal the steel microstructure.  Some steel microconstituents like hard martensite are highly corrosion resistant, others like iron carbide easily corrode in weak acids.  This corrosion differential provides the structural images seen in a metallograph.

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John Dingell, III, Charles Kramer, and Joseph Pieprzak, Jr. discuss the metallurgy of several firearms parts and assemblies.  Note the VG.1-5 rear assembly to the left of the reading glasses; can anyone recognize the shiny bolt to the right of the reading glasses?  Hint: it is from a firearm that could be politely described as Chuck’s obsession!

A few other pictures testing the shiny bolt thing.

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DSC_1729sThis is a real close up of the part being tested.

DSC_1728sThis is the rest of the shiny part being tested.

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Thanks to John for adding the technical aspect for this write up.

You will get extra brownie points for guessing the shiny thing.

Ar-180

I am always interested in how weapons are made, a major reason for this site.  So when I had the opportunity to stop at a friends house on this last trip to look at components of the AR-180 in in various stages of manufacture I jumped on it. For those of you that do not know what a AR-180 is here are a couple of pictures.

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DSC_2634cClose up of the receiver.

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The Ar-180 is a gas operated multi-lug  sheet metal stamped  rifle. Eugene Stoner is one of the designer of it and it was design to be produced in countries that did not have a strong manufacturing sector. To me it is interesting to see the steps necessary to make this weapon. I don’t have all  pictures of the different stampings however there are enough to see how it is made.

So lets start with the lower receiver. This first set of pictures is the completed cut out flat prior to any press shaping.

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DSC_2274sBoth sides are  shown and you will notice that the slots are not cut for the fire control and magazine catch.

This next series of photos show the initial pressings that are put in for the magazine housing.

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DSC_2280sStill no fire control or magazine release cut outs. There is a set or two missing between these photos and the next ones. This next set shows the body bent now.

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DSC_2283sYou can see that flat had been pressed out for the fire control group of the AR-18. The hole for the selector and magazine release has not been put in yet and none of the holes for the fire control group have been punched or drilled. The holes on the bottom of the receiver have been punched though. No engraving has been performed and the front strengthening stamping has not been spot welded on.

this next series shows what is now looking close to a complete lower receiver. This is where it gets a little confusing. There are samples showing different states of completion. This leads me to think that the holes for the fire control group were drilled in and done on a fixture. These  next series of photos will show three different lowers some with holes and some without.

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DSC_2296sYou can clearly see that the front strengthening stamping is installed but that the holes are not drilled yet.

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DSC_2291sThese photos shows all the holes for the fire control group in the receiver and the front strengthening stamping located but not spot welded on yet.

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DSC_2307sThis series of photos shows the magazine guide welded into place and the trigger guard installed but the fire control holes not drilled yet. There is also no front strengthening support welded on yet.

Now there are a variety of answers for these differences. The first is that the AR-180 went through a number of changes as to design and manufacturing methods. The second is that samples were pulled from the line as example board production steps. The third is that they were manufacturing examples for the floor personnel. This concludes this portion. In the next installment I will show the upper receiver being made.

 

 

 

Weekend update 11-3

A number of items were worked on this weekend. Another section of the fab shop ceiling was completed as well as the out side cover for my forge exhaust.

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DSC_2609sThen it back at the fluting machine back plate.

The last item worked on was the stocks for the VG1-5. The have been roughed out and ready for the final machining.

That is it for this weekend. I have also written a few other up coming posts and now time to relax.

Sunday answer 11-2

For those of you that correctly knew the answer give your self a gold star. It is the winter trigger for a EM-2. Here are a couple of references from Thomas B. Dugelby’s book EM-2 concept and Design. This book is published by Collector Grade Publications and should be in your reference library.

winter trigger 1csThe first is a line diagram of the pistol grip assembly with the winter trigger.

winter trigger 3csThis picture is of it attached to the pistol grip.

winter trigger 2csAnd this is showing it as it sets on the rifle.