GunLab

FN-FAL in 7.92×33

In my list of want to do build projects building an original FAL is on the top. The very first FAL ever built was in 7.92×33 and was slightly different then the current FAL that we know today.

This rifle is missing and all that is left of it are the pictures you see here.

These picture are from the FAL book published by Collector Grade Publications. If you are into the FN FAL rifle this set of books is a must have.

This is Pete’s , a friend of Gun Lab, version of a 7.92×33 rifle. His solution was to put in a new ejector block of his design with a spring loaded ejector. Then remove 0.900″ from the magazine to fit the 7.92×33 round.

A side view of Pete’s rifle. Notice the larger then normal ejector block.

The magazine actually looks like the original.

You can see in this picture the fit on the magazine to the receiver.

You can see here how the cartridges set in the magazine.

This his new follower

A top view of the spring loaded ejector

This photo gives you a good view of the magazine well.

A nice side view of the larger ejector block.

He converted the rifle to take a smaller hand guard .

A visit from AR-180s

Rick from http://ar180s.com/ dropped by yesterday and spent a few hours at Gun Lab. It was a nice visit. We both got to show off projects that we have been working on. I was able to get an up close look at his shorty project and his machined out of tubing AR-180 upper. Nice work. The shorty projects looks like a fun build. Now to go back to the salt mine of my shop for today. Looking forward to your next visit.

AR-180B trunnion design

An interesting question was brought up by Rick at http://ar180s.com/ a while back about making new AR-180B upper receivers. The actual receiver is not much of a problem however the trunnion is. The expense of making a new trunnion would be cost prohibitive so a different solution had to be found. In this case the thought would be to do what was done, or thought to be done by Armalite and that is using an AR-15 barrel extension pressed into a new trunnion block. So looking at a AR-180B we can see what the trunnion looks like in a receiver.

Looking at the above pictures you can see the difference between a AR-180B and the AR-180 below.

The above picture shows a flush front end with the threads. While of the 180B it is recessed.

There are a number of differences. The original is forged and then machined. You can see how the boss sticks out in front of the bolt locking area. While the 180B the rear of the trunnion is flush.

The reasons for these differences is because a AR-180b does use a AR-15 barrel extension pressed in. However there are changes to the barrel extension.

In this hidden view you can see that a AR-15 barrel extension would be to large for a trunnion as originally designed for an AR-180

This is a solid view of the same model. The barrel extension would get in the way of the recoil rods.

Even reducing the diameter of the barrel extension would not be enough to correct the problem. The extension has a diameter much larger then the inside diameter of the trunnion.

This can only work if the trunnion is also re-design. This is what Armalite did for the AR-180B.

Instead of a rounded bottom they squared it off to allow more material to support the turned down barrel extension.

As you can see in this cut away the reduced size of the outer ring of the barrel extension.

In this picture you can see the hole for the guide pin on an AR-15 barrel extension.

OP 7 completed on the MP-44 trunnions

Op 7 has been completed. This is a major mill stone on making the MP-44 trunnions. The rest of the machining will be done on the manual mill. It will be easier on the manual mill then making the number of fixtures and tooling that would be required on the cnc machining center.

This is op 7. You can see the original next to one of ours. The manual phase will add the chamfer to the groves.

You can see that the trunnions are dimensional correct

A close up of the trunnions.

A picture of all 6 trunnions completed and de-burred.

More on the MP-44 trunnion

Operation 6 has been completed on the MP-44 trunnions. A couple of problems were noted. The first is the difference in length on the front of the trunnions and the second was the fit up of the locking shoulder.

This photo shows the difference in the lengths

You can see the corrected locking shoulder fit up

This photo shows where the end mill breaks during op 6 not cutting the slot for the locking shoulder.

Close up of the un-machined area

As with every part made there is always a problem lurking in the back ground. We thought that we had complete op 6 on all the trunnions only to find that on the last part the end mill had broke. This caused a cascading failure problem. The next end mill, which was a custom slot cutting tool, also broke. The program was rewritten again to correct the problem and all six parts were finished through op 6.

Parts cleaning

This last weekend was a busy one, like most weekends here. On the list of projects that had to be completed was get the parts ready for heat treating. This meant bead blasting all the parts going to heat treat. Not a weekend of fun and frolic. Thousands of parts needed to be cleaned and prepped. The though of cleaning them one at a time did not make for a project that I wanted to do. I have been looking at rotating parts bins for my bead blaster but have not had much luck. I knew a simple solution had to be out there, This is a video I saw on the net that I felt would be a long term solution, but for now something quick and simple.

So I made a manually operated rotating tumbler for the bead blaster. Here is a quick video of it and using it.

The first attempt was a 3lb plastic coffee can and just rolling it around.

I needed something that was a little easier to use and could hold a few more parts. So I made one out of a 1 gallon bucket and some old castors.

This is what the rusty bolts looked like starting.

And at the end after a couple of minutes.

Not a perfect solution, but a workable one. When I have some spare time I will make a motorized one with a spray nozzle that does not have to be held.

MP-44 trunnions finish op 6

We have finished operation 6 on the MP-44 trunnions. The reason that we started with 6 samples was to insure that we would have correct samples when we finished. Two of the trunnions ended up out of spec after we finished this operation. The drawings and cam programing were changed to correct and problems. These are the pictures of the remaining 4 on there was to op. 7.

There is still deburing that needs to be done then to the last op on the machining center.

Continuing the MP-44 trunnion

We have just completed the first operation 6 on the trunnion. It has also pointed out a few minor differences. When we started this project all we had was an original trunnion in very bad condition and a collection of out of spec drawings with incorrect dimensions.

Later a trunnion in very good condition showed up from a friend to help move this project along.

So as we have gone through each step of the process of reverse engineering a MP-44 trunnion and making a series of them we correct our solid model and it’s dimensions have rewritten and the machining program changed as well. This is the trunnion as completed on the first sample of op.6. There is a great deal that is correct with this sample, however there are more changes to be made.

The top radius for the gas tube needs to be looked at.

All the machined dimensions are correct.

The angle and radius for the magazine to fit in is spot on

Just check out the finish. These will be perfect when they go out.

The finish on the upper radius is perfect.

So now on to the changes that have to be made. The first is that we have to machine down the side a little more.

A greater radius needs to be added.

We took of a little to much.

We mark each trunnion this allows us to keep track of each change as we make it from trunnion to trunnion. This is the first trunnion that we made.

This is the second trunnion. The magic marker notes the size of the chamfer.

One more sample to finish to correct the last of the small items.

Another update to the cnc router

Here are a couple of pictures of the router setting on the new table. There are corner supports on every corner top and bottom. The next phase is re-wiring the controllers.

Close up of the support blocks. There are six of then to support the router off of the frame and wood cover. The holes on the end of the block is to allow us to bolt the router to it.

Another view of the support block set up.

All the wiring will be changer and run in cable supports.

MP-44 Trunnions up date

We have now finished the first six test pieces up to the 5th operation. This next week we will complete op’s 6 and 7 and send them for verification for proper fit.

With the first 5 operations completed we will be starting on op6 soon. This is a master cam simulation of the process.

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