AR Pistol Project

arakboss

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I finally got my workbench cleared off enough that I could begin a build project. I decided to start with putting together a manual loading AR pistol. This pistol will utilize my quick change barrel idea on a left side charging upper receiver and buffer tubeless lower. I bought the assembled left side charging upper receiver from Bear Creek Arsenal and it has a 10.5 inch 350 Legend heavy barrel on it.

The handguard on this upper is one of the older styles that requires timing and uses six allen head screws to secure the HG to the barrel nut. All of the handguard screws were very tight. 5 screws came out without issue but the last one was extremely stubborn. I ended up breaking the head of my Husky brand hex key tool off in the screw and ultimately had to grind off the head of the screw with a dremel bit. Of course I marked up the handguard in a couple of spots while grinding:(

I removed the gas block (five screws) and gas tube assy. That came off easy. Then it was time to remove the barrel. I have a plastic vice block made for standard upper receivers but it would not fit correctly on the billet BCA upper receiver. I made an attempt to use it anyways and the barrel nut was very, very tight. I was using an adjustable wrench to remove the nut and finally got it to break free. The upper slipped a little inside the vice block at one point while I was putting half my body weight on the adjustable wrench but it doesn't appear to have damaged the metal of the upper receiver. It did mar the finish a little. A high quality crow foot wrench and breaker bar would have made the barrel nut removal job easier.

Now that the upper parts are taken down I need to bring them to work and clean out all the grinding dust left from my grinding the screw off, it got everywhere. After that I will be reassembling the barrel with an Aero Bar nut (hand tight only) and installing a gas block backwards or upside down to block off barrel gas port. I expect to have it ready for test firing next weekend and I will check the barrel nut for loosening after each shot. I will bring my tapco ar wrench with me in case the nut needs a little more than hand tightening but I do not want to have to use a vice to tighten the barrel nut or that will defeat the idea behind a quick change barrel set up. I am going to run the pistol with out a handguard. When setting the pistol on a rest for shooting, it will be similiar to setting a long barreled revolver on a rest.

I will stick with shooting this off a rest to sight it in and once I am confident that the accuracy is there, I will try some free hand shots. Next step will be to load up my pistol length 5.56 and 300BO barrels with the same BAR Nut set up so I can change barrels at the range or out in the field.

Running the lower without a buffer tube will require a fix for the detent/spring that is held behind the endplate. Any ideas?
 

arrowshooter

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I have read of others who tapped the hole for the detent/spring and used a set screw.
I have a number of lowers tapped for 4-40 and really like the idea.

Look forward to your continued reporting, especially since you went with the 350L.
 

arakboss

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I have a number of lowers tapped for 4-40 and really like the idea.

Look forward to your continued reporting, especially since you went with the 350L.
I took the easy way out and bought a SS cotterless hitch pin. It fits nice and tight. Not the most attractive method but does the job for $4.29.


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arakboss

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These pistol builds were part of the inspiration for my build. Rather than cut the bcg like they did I am leaving the buffer tube hole open. This allows the full length carrier to extend out the buffer tube hole when racking the BCG.

 

arakboss

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Any creative (but cheap) ideas on how to keep a 9mm bolt in an AR from moving on it's own after a cartridge is fired? One idea I read about was to use a rod of some sort installed through the forward assist port and positioned into the bolt. Another suggestion was to drill a hole through the upper and bolt, than run a pin through it. I want to be able to run a 9mm barrel on my lower with no buffer tube.
 

arakboss

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Any creative (but cheap) ideas on how to keep a 9mm bolt in an AR from moving on it's own after a cartridge is fired? One idea I read about was to use a rod of some sort installed through the forward assist port and positioned into the bolt. Another suggestion was to drill a hole through the upper and bolt, than run a pin through it. I want to be able to run a 9mm barrel on my lower with no buffer tube.
I am thinking about drilling a hole in the top of the lower receiver area where the extension tube threads are and dropping a pin through that hole and into the hole where the buffer retaining pin and spring normally reside. I do not have these parts installed in my lower so that hole is free to use. When I fire a round the bolt will be lodged against this pin not extract the case. I will pull the pin and charge the bolt (side charger), reinstall pin and fire next round.

I might have to install a short buffer tube in case I forget to reinstall pin, that would be bad news if bolt came at me.

Did somebody call out Bubba, I'm coming.
 

arakboss

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Any creative (but cheap) ideas on how to keep a 9mm bolt in an AR from moving on it's own after a cartridge is fired? One idea I read about was to use a rod of some sort installed through the forward assist port and positioned into the bolt. Another suggestion was to drill a hole through the upper and bolt, than run a pin through it. I want to be able to run a 9mm barrel on my lower with no buffer tube.
I found what might be a solution to keeping the 9mm bolt from moving. I am going to pick up one of these aluminum caps from ebay and install a silicone cork on the inside of it before threading it into the lower receiver buffer tube threads. I will size the length of the silicone cork so that I can engage at least two full threads of the aluminum cap into the receiver threads and barely snug the cap/cork combo up against the back of the 9mm bolt. This set up will require unscrewing the cap each time to reload a new round in the chamber. To convert back to semi auto function the user can swap the cap/cork combo for a regular pistol buffer tube assy.

 

arakboss

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I found what might be a solution to keeping the 9mm bolt from moving. I am going to pick up one of these aluminum caps from ebay and install a silicone cork on the inside of it before threading it into the lower receiver buffer tube threads. I will size the length of the silicone cork so that I can engage at least two full threads of the aluminum cap into the receiver threads and barely snug the cap/cork combo up against the back of the 9mm bolt. This set up will require unscrewing the cap each time to reload a new round in the chamber. To convert back to semi auto function the user can swap the cap/cork combo for a regular pistol buffer tube assy.

If a person wanted to get fancy they could weld up a couple of end plates together with solid plate sandwiched in between end plates to make solid piece. Then thread the receiver so that end plate assy could be bolted to the lower receiver and swiveled out of the way to charge the bolt and load the next round. After a new round was loaded you would swivel the end plate assy back to "closed" position. This would make the loading more similiar to the Lone Eagle handgun.
 

arakboss

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I found what might be a solution to keeping the 9mm bolt from moving. I am going to pick up one of these aluminum caps from ebay and install a silicone cork on the inside of it before threading it into the lower receiver buffer tube threads. I will size the length of the silicone cork so that I can engage at least two full threads of the aluminum cap into the receiver threads and barely snug the cap/cork combo up against the back of the 9mm bolt. This set up will require unscrewing the cap each time to reload a new round in the chamber. To convert back to semi auto function the user can swap the cap/cork combo for a regular pistol buffer tube assy.

I rigged up a pistol buffer tube with silcone corks. The final cork is sticking out of the tube about a 1/2 inch. I will use a dummy round and see how it mates up with bolt in the upper later this morning. The silcone corks have a little bit of compressibilty to them. When I screw in the buffer tube I will snug it up tight to the bolt and hopefully remove most of the compressibilty. I would really like that bolt to stay fully closed even under +p+ rounds.

The reloading of rounds in the upper will be a pain in the arse. Starting from fired round in rear charging upper, here are the steps.

1. Unscrew buffer tube.

2. Pull back charging handle to eject spent case and reset trigger.

3. Push bolt and CH back into battery by hand from rear of upper. Edit: If I really end up liking this combo. I may drill into one of my 9mm bolts and install a BCA side charger handle so I can run it in a BCA side charging upper. For testing I am just going to use a rear charging upper.

4. Screw buffer tube back into lower.

5. Rinse and repeat.

This will be a slower process than an Altor 9mm single shot pistol. Some of the advantages are that it would make for quieter suppressed firing.

You can load rounds as hot or cool as you like and not have to worry about buffer and spring combos.

Upper and lower should run cleaner as less to no gas will be returning from chamber.

Ammo will last much longer at range trips:)

You can run the same lower with any blow back barrel/bolt combo 40/45/10mm.

It will be unique.

I don't expect this set up will be any more than a range toy.


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arakboss

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I suspect this $1800 single shot 9mm AR is really just a fixed one round mag (probably bobsled type follower). Blow back action is still present so you may still have to deal with buffer weight issues if shooting hot rounds.



 

arakboss

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I rigged up a pistol buffer tube with silcone corks. The final cork is sticking out of the tube about a 1/2 inch. I will use a dummy round and see how it mates up with bolt in the upper later this morning. The silcone corks have a little bit of compressibilty to them. When I screw in the buffer tube I will snug it up tight to the bolt and hopefully remove most of the compressibilty. I would really like that bolt to stay fully closed even under +p+ rounds.

The reloading of rounds in the upper will be a pain in the arse. Starting from fired round in rear charging upper, here are the steps.

1. Unscrew buffer tube.

2. Pull back charging handle to eject spent case and reset trigger.

3. Push bolt and CH back into battery by hand from rear of upper. Edit: If I really end up liking this combo. I may drill into one of my 9mm bolts and install a BCA side charger handle so I can run it in a BCA side charging upper. For testing I am just going to use a rear charging upper.

4. Screw buffer tube back into lower.

5. Rinse and repeat.

This will be a slower process than an Altor 9mm single shot pistol. Some of the advantages are that it would make for quieter suppressed firing.

You can load rounds as hot or cool as you like and not have to worry about buffer and spring combos.

Upper and lower should run cleaner as less to no gas will be returning from chamber.

Ammo will last much longer at range trips:)

You can run the same lower with any blow back barrel/bolt combo 40/45/10mm.

It will be unique.

I don't expect this set up will be any more than a range toy.


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I think this will work but it's going involve a lot of wear and tear on the threads. I am going to give it a go on next range trip.
 

Will_White

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I think this will work but it's going involve a lot of wear and tear on the threads. I am going to give it a go on next range trip.
A 5.45 bolt and replacing the barrel extension with a standard one will let you keep the 9mm locked up.
 

Will_White

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Can you explain this in a bit more detail? Is this how the 9mm DI AR guns are made?
Yeah basically converting it to DI without drilling a gas port. It would allow you to keep the same operation between calibers. I looked into it when I was building my blaster, ultimately I decided to just go with 6.5 grendel and a cut down carrier.
 

arakboss

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Yeah basically converting it to DI without drilling a gas port. It would allow you to keep the same operation between calibers. I looked into it when I was building my blaster, ultimately I decided to just go with 6.5 grendel and a cut down carrier.
I think I will stick to the standard DI cartridges myself. I am going to do a right handed side charging upper to go along with my left side charging upper. I suspect there are going to be an abundance of cheap short AR barrels once the pistol brace rules come to roost.
 

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