AR bolt lugs stay locked if no gas system present, correct?

[arakboss]

Here's FLT and company building and shooting some modified 300blk and 500 beowulf AR repeating pistols. They stay locked up just fine and are operated manually with no buffer spring.

That was a great video. That is one type of project I want to build. I was slightly concerned that by firing the bcg and barrel combo only (minus the upper receiver) that the bcg could work itself out of the locked position.

Edit: I also need to make sure I am not creating an AOW in the process.

 

[Capn Jack]

Sorry I gotta get back to work.

The only dumb question is the one you don't ask before hurting yourself ,or others.

 

[Alexr4920]

Not Sure, LOL , 5 shots before I gave up and had someone else go over it.

 

[arakboss]

..

Looking at this from a logical standpoint. If the firing of a cartridge unlocks the bolt in an AR even without the gas system in place, what would be the purpose of having a gas tube and a vent hole in the barrel going back into the chamber to push on the carrier?

Hence why, no, it doesn't make any sense that people are claiming the BCG would unlock itself if the gas system was disengaged. They are wrong.

You could function test this without a cartridge, just take the bolt out of the BCG, push it into the barrel as if it was going into battery, rotate it into position as if it was put into battery so the lugs are engaged against eachother, then try pulling the bolt out without rotating it. The lugs will be pushing against eachother and it won't be going anywhere until you rotate the bolt again to clear the lugs.

The bolt carrier rotates the bolt throughout it's movement after getting pushed backward via the gas pressure through the gas tube. No gas tube, no gas vented to carrier, no carrier push, no rotation of bolt, no unlocking of lugs, no bolt getting pulled backward.

People who are saying otherwise don't seem to fully understand how the AR works from a mechanical/gas pressure standpoint.

If you clamp an upper down without a gas system engaged and hit the firing pin, it will fire, the bolt will stay locked against the lugs of the barrel, only after you pull on the carrier, forcing the bolt to rotate and clear the locking lugs, will the bolt be able to move rearward.

Good grief…

Would an AR15 fire and reload if the buffer retaining pin were removed? It seems like the main purpose of the buffer retaining pin is to keep the buffer and buffer spring back far enough so that the upper can be broke open for disassembly, etc. If the buffer retaining pin wasn't there it would probably rest on the back end of the upper receiver, correct?


Edit: After thinking on it for another minute, I think once the buffer head left the ext tube it would not go back in correctly and would probably hang up on the lower receiver. So ignore my question

 

[American123]

..

Would an AR15 fire and reload if the buffer retaining pin were removed? It seems like the main purpose of the buffer retaining pin is to keep the buffer and buffer spring back far enough so that the upper can be broke open for disassembly, etc. If the buffer retaining pin wasn't there it would probably rest on the back end of the upper receiver, correct?


Edit: After thinking on it for another minute, I think once the buffer head left the ext tube it would not go back in correctly and would probably hang up on the lower receiver. So ignore my question

The buffer and spring can't go any father forward than they already do throughout the firing process,

The real question is, how would you get the upper and lower mates together without the bugger retaining post holding those back from springing out without the BCG in the way.

The bigger question is, why would you take out the buffer retaining post.

 

[arakboss]

The buffer and spring can't go any father forward than they already do throughout the firing process,

The real question is, how would you get the upper and lower mates together without the bugger retaining post holding those back from springing out without the BCG in the way.

The bigger question is, why would you take out the buffer retaining post.

I was thinking about different ways to attach a stock to an upper receiver only firearm project (no lower receiver). One solution could be to attach the extension tube directly to rear of upper receiver. There would be no place for a buffer retaining pin but the buffer should stop when it hits the backside of the upper receiver.

I am thinking this type of jig could be utilized as a method to mount a trigger to the upper receiver.

LaRue Tactical TAC (Trigger Action Chassis) - LaRue Tactical

 

[American123]

I was thinking about different ways to attach a stock to an upper receiver only firearm project (no lower receiver). One solution could be to attach the extension tube directly to rear of upper receiver. There would be no place for a buffer retaining pin but the buffer should stop when it hits the backside of the upper receiver.

I am thinking this type of jig could be utilized as a method to mount a trigger to the upper receiver.

LaRue Tactical TAC (Trigger Action Chassis) - LaRue Tactical

I have those and would be happy to get rid of them if you want them. They came with triggers.

 

[arakboss]

I have those and would be happy to get rid of them if you want them. They came with triggers.

Thanks, I let you know if I decide to go that route.

 

[American123]

Thanks, I let you know if I decide to go that route.

I still haven't figured out what the purpose is behind the desire though to have an upper fire without a lower. Seems entirely less than desirable compared to having a lower attached.

 

[arakboss]

I still haven't figured out what the purpose is behind the desire though to have an upper fire without a lower. Seems entirely less than desirable compared to having a lower attached.

I am wanting to see if I can build a operational firearm with AR15 parts that don't require an FFL (no 80% either since they are likely to require an FFL soon). There isn't a strong purpose for the project.

 

[American123]

I am wanting to see if I can build a operational firearm with AR15 parts that don't require an FFL (no 80% either since they are likely to require an FFL soon). There isn't a strong purpose for the project.

You could probably literally take the upper as is, attach a rubber band of high strength to the back of the firing pin, have it attached further up on the rail so as to create potential energy when it is pulled back, pull on the rubber band back, let it go. I haven't tested this, nor will I, but the premise is there since the only thing the trigger hammer does anyway is whack the firing pin hard enough to hit the primer with sufficient strength, in theory a rubber band could do the same thing. This would be a single loaded round into the chamber by hand.

Edit: A bungee or surgical tubing might work better than a rubber band, but the idea remains the same.

 

[arakboss]

You could probably literally take the upper as is, attach a rubber band of high strength to the back of the firing pin, have it attached further up on the rail so as to create potential energy when it is pulled back, pull on the rubber band back, let it go. I haven't tested this, nor will I, but the premise is there since the only thing the trigger hammer does anyway is whack the firing pin hard enough to hit the primer with sufficient strength, in theory a rubber band could do the same thing. This would be a single loaded round into the chamber by hand.

I am sure that would work and I was going to try something simliar. I decided to raise the bar and see if I can make one with a trigger and stock so I can increase the accuracy and avoid creating an AOW.

I was originally inspired by various youtubers who make homemade firearms including the slamfire shotguns. While many of them had success they usually didn't have much accuracy and occasionly the firearms blew apart. That is partly why I want to use off the shelf parts.

If the ATF has their way with the recent frame/receiver definition change proposal, my project idea may become mute anyways.

 

[American123]

I am sure that would work and I was going to try something simliar. I decided to raise the bar and see if I can make one with a trigger and stock so I can increase the accuracy and avoid creating an AOW.

I was originally inspired by various youtubers who make homemade firearms including the slamfire shotguns. While many of them had success they usually didn't have much accuracy and occasionly the firearms blew apart. That is partly why I want to use off the shelf parts.

If the ATF has their way with the recent frame/receiver definition change proposal, my project idea may become mute anyways.

At home tinkering will generally never get you in trouble as long as you don't publicize your results and render them "not a potential problem" after testing. You could test all of this with an empty case and a primer in your house.

If you took a completed upper, the accuracy would be a non-issue, you'd still be dealing with a rifled barrel, which is inherency accurate. The only accuracy issue would be you're own influence on the upper when holding it. The reason those home made slam fires are inaccurate first of all is multi part, but one definitely is the smoothbore, additionally the manner in which they are fired is movement, so trying to be accurate with something you literally are shifting/moving in your hand to fire isn't that great to begin with.

When I was a kid I made a rudimentary crossbow using a 1/2" x 2" x 3' length of wood. Taped a straw to the top, attached a good rubberbang to the front and a clothing spring clip to the opposite end. Wooden shiskabob (spelling?) stick was pushed into the straw, sharp end forward, butt end sat at the rubber band, "trigger" was pressing on the spring clip which released the runner band.

This same concept could just be amended to be a wooden plank with an upper clamped to it and a sufficient bungee system and clamp to control the firing process. The plank would also serve as something to hold onto.

I'd rather have verboten property than deal with all that though lol

 

[arakboss]

This is an oldy but goody:

 

[BrentN]

I am still trying to understand....that direct pressure on the bolt face will not cause the bolt to rotate and unlock, but pressure against the gas key (from gas, or the force of pulling the CH) will do so. I am thinking the magic is in the cam pin, but again, this has not been well explained so far. My understanding is that the rearward motion of the carrier pulls on the cam pin, rotating it, and thus rotating the bolt and unlocking it. Correct statement?

 

[edzz]

I walked over to my front door and pulled hard on the door knob, and the door stayed shut.
However when I pulled on the knob and twisted it the door opened.

The gas forces the bolt carrier to the rear causing the carrier to rotate the bolt there by allowing the bolt to unlock. Without the gas there is nothing to move the bolt carrier thus no rotation of the bolt. No rotate bolt no unlock.
The bolt carrier must move for unlocking to occur.

 

[arakboss]

I am still trying to understand....that direct pressure on the bolt face will not cause the bolt to rotate and unlock, but pressure against the gas key (from gas, or the force of pulling the CH) will do so. I am thinking the magic is in the cam pin, but again, this has not been well explained so far. My understanding is that the rearward motion of the carrier pulls on the cam pin, rotating it, and thus rotating the bolt and unlocking it. Correct statement?

One way to test the fact that the bolt will stay closed unless the carrier is pushed/pulled rearward is to take a bcg and barrel. Install bcg in barrel and run a wood dowel rod down the muzzle end of the barrel. Hammer on the end of the rod. The bolt should stay put. But if you gently tug on the carrier, the entire bcg will come right out of the barrel.

 

[American123]

One way to test the fact that the bolt will stay closed unless the carrier is pushed/pulled rearward is to take a bcg and barrel. Install bcg in barrel and run a wood dowel rod down the muzzle end of the barrel. Hammer on the end of the rod. The bolt should stay put. But if you gently tug on the carrier, the entire bcg will come right out of the barrel.

Stoner knew what he was doing.

 

[arakboss]

Stoner knew what he was doing.

I have developed a deep appreciation for this platform over the years after seeing the almost infinite ways it can be configured, assembled, etc.

 

[American123]

I have developed a deep appreciation for this platform over the years after seeing the almost infinite ways it can be configured, assembled, etc.

What's interesting is:
#1 It was originally developed for .308
#2 The idiots in government willfully used the wrong powder to try and make the performance appear less than desirable.
#3 The idiots in government thought that cleaning kits weren't needed.