I'm Inspired By Wombat To Share My Break Open AR15 Idea.

[RX-79G]

Have you considered what happens if you have a case head failure or other overpressure event?

 

[arakboss]

Have you considered what happens if you have a case head failure or other overpressure event?

I would imagine the same thing that would happen if those events happened in any break action rifle.

 

[RX-79G]

I would imagine the same thing that would happen if those events happened in any break action rifle.

The difference in where they hinge probably matters.

 

[arakboss]

The difference in where they hinge probably matters.

It might matter but I doubt that is going to be a big concern. I don't believe there is going to any more risk in my design versus a CVA Hunter for example. I don't have any plans to purposely test the firearm in the situation of a case rupture so it's unlikely I will ever know how the firearm will handle it.
Homemade firearms will carry some additional risk over proven commercial designs and I'll accept that additional risk.

 

[RX-79G]

It might matter but I doubt it that is going to be a big concern. I don't believe there is going to any more risk in my design versus a CVA Hunter for example. I don't have any plans to purposely test the firearm in the situation of a case rupture so it's unlikely I will ever know how the firearm will handle it.
Homemade firearms will carry some additional risk over proven commercial designs and I'll accept that additional risk.

Your upper stability problem and the safety concern could probably both be addressed if the two halves of the upper had overlapping side "ears" rather than a straight vertical cut.

 

[Yarome]

It might matter but I doubt it that is going to be a big concern.

I highly doubt it. Pressures are contained within the barrel and the brunt on the locked lugs and boltface. The upper itself provides pretty much NILL in terms of pressure containment. If the bolt and barrel fail, the aluminum frame doesn't stand much of a chance in "whole" or "in part".

It might help the barrel blow OUT more easily... vs... the upper fragging you... if anything(?)

 

[arakboss]

Your upper stability problem and the safety concern could probably both be addressed if the two halves of the upper had overlapping side "ears" rather than a straight vertical cut.

I had thought about adding overlapping side plates to one half or the other until I came with the tension pin fix. I will keep it up for consideration if the tension pin doesn't work out well.

 

[RX-79G]

I highly doubt it. Pressures are contained within the barrel and the brunt on the locked lugs and boltface. The upper itself provides pretty much NILL in terms of pressure containment. If the bolt and barrel fail, the aluminum frame doesn't stand much of a chance in "whole" or "in part".

It might help the barrel blow OUT more easily... vs... the upper fragging you... if anything(?)

Correct, but I'm talking about the bolt opening too early rather than a straight double load situation. Receivers have a secondary function of containing gas and brass fragments to keep the shooter from being hurt in the event of something like a bolt head failure.

It was enough to bulge this aluminum upper and destroy the polymer lower.




Just be careful with that thing.

 

[arakboss]

I highly doubt it. Pressures are contained within the barrel and the brunt on the locked lugs and boltface. The upper itself provides pretty much NILL in terms of pressure containment. If the bolt and barrel fail, the aluminum frame doesn't stand much of a chance in "whole" or "in part".

It might help the barrel blow OUT more easily... vs... the upper fragging you... if anything(?)

In a normal uncut upper, if a case ruptures occurs, most of the gas will be funneled through the upper and exit out the ejection port and the charging handle slot hole at the rear of the upper. In my design some of that gas would escape out the area where the upper has been cut and out the ejection port.

 

[arakboss]

Correct, but I'm talking about the bolt opening too early rather than a straight double load situation. Receivers have a secondary function of containing gas and brass fragments to keep the shooter from being hurt in the event of something like a bolt head failure.

It was enough to bulge this aluminum upper and destroy the polymer lower.

View attachment 1249813


Just be careful with that thing.

Since my upper is going to be shot in manual load only mode, my lugs would have to fail, they won't be opening early. That photo demonstrates that all firearms carry risk. I did not take mine out yet as I am going to keep looking at it for a few days to make sure I haven't overlooked any obvious shortcomings. I appreciate your input.

 

[Geardo]

Here are a few photos of assembly mock up.


View attachment 1249157


View attachment 1249156



View attachment 1249155

I've been under a rock. WtF why?

 

[Geardo]

I've been under a rock. WtF why?

Never mind, answered. Thought this was a weird legal thing and I was ripping my hair out.

 

[Yarome]

I haven't overlooked any obvious shortcomings.

The only thing I see is likely accuracy. Ie., keeping the barrel poa with your sights/red dot. If the alignment pin is secure enough... maybe not a big deal, but I would imagine there is going to be alignment inconsistency between shots. I dunno what you mighta done to reduce pivot pin "play" though.

That said, I hightly doubt pinpoint accuracy was a predominate concern with a concept build like that.

More... "Will it make smoke?"... right?

 

[arakboss]

The only thing I see is likely accuracy. Ie., keeping the barrel poa with your sights/red dot. If the alignment pin is secure enough... maybe not a big deal, but I would imagine there is going to be alignment inconsistency between shots. I dunno what you mighta done to reduce pivot pin "play" though.

That said, I hightly doubt pinpoint accuracy was a predominate concern with a concept build like that.

More... "Will it make smoke?"... right?

I agree accuracy will not be a strong point for this configuration. It's just a fun project to see if it can be done without blowing any body parts off. If I want to increase accuracy a bit, I can bridge the two upper halves together with a picatinny riser and install the optic on top of the riser.

 

[Yarome]

I agree accuracy will not be a strong point for this configuration. It's just a fun project to see if it can be done without blowing any body parts off. If I want to increase accuracy a bit, I can bridge the two upper halves together with a picatinny riser and install the optic on top of the riser.

Short of having to lock/unlock/relock between shots with a picatinny, using some type of silicon washer to tighten up the pivot pin tolerances might be an easy cheap compromise with marginal improvment.

I fuly get it's just a concept build, though. I certainly don't see any red flags.

Your next one. Do a top hinged breaker for a compact folder. Or double barrel it! Challenge ON!

 

[arakboss]

Short of having to lock/unlock/relock between shots with a picatinny, using some type of silicon washer to tighten up the pivot pin tolerances might be an easy cheap compromise with marginal improvment.

I fuly get it's just a concept build, though. I certainly don't see any red flags.

Your next one. Do a tip hinged breaker for a compact folder. Or double barrel it! Challenge ON!

I like the revolver washer idea @RX-79G proposed. That might work for the rear since it is slightly loose fitting in that area. The front pivot pin is tight in the front upper section, so no room for washers there. I thought about powder coating just the upper lugs. That would build up the sides of the lugs as well as the lug holes that the take down pins slide into. That would temporarly tighten the fit, at least until the powder coat wore off. I am going to run it as is for now. If I can hit a man size target at 100yds I will call it a success. I have a slam fire shot gun build that my attention needs to be turned back to, among hundreds of other projects. Distractions easily find me.

 

[spookshack]

@Yarome Please don't feed the squirrel! The world may not be able to handle what he's going to cook up next!

 

[Yarome]

Distractions easily find me.

I'm intimately familiar with the, "OK. What's next on my list? Oh.. look... a puppy!" syndrome.

I have the 7.62 upper and dangling gongs to prove it!

 

[arakboss]

I'm intimately familiar with the, "OK. What's next on my list? Oh.. look... a puppy!" syndrome.

I have the 7.62 upper and dangling gongs to prove it!

I already neutered my 7.62x39 Optics Planet upper but I haven't shot it since the vasectomy was performed. That is just one more project on the list. Gong action is probably going to have to wait until fire season ends for me. Muzzleloader ideas will also have to wait. I have a shooting shack that needs to get started on my next trip to property. Shooting will be taking a back seat to construction for the next few trips.

 

[Yarome]

I have a shooting shack that needs to get started on my next trip to property. Shooting will be taking a back seat to construction for the next few trips.

Wait. You STILL haven't finished your shack??

OK. You win!!