You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
Serbu RN-50 explodes
- Thread starter ghbucky
- Start date
I agree. Terrible design.Serbu has posted a new youtube video yesterday. He is now saying that to blow that breach cap off is 161k+ psi.
https://www.youtube.com/watch?v=na1Qo7FxDeM
He's going with the "there is nothing wrong with my design" approach.
He is saying that it was a 'counterfeit' slap round. He apparently still does not have the rifle or ammo.
He does not at all address the plain fact that the shooter received all the energy when the system failed, regardless of the cause.
Lucky
Or blessed. Whichever it is he is happy to be seeing the green side of the grass.
The builder? Best hope his Atty. approved the video he posted.
My 64,000 dollar question? Two actually.
How can the builder state the PSI for this to have happened?
What was the percentage of thread engagement of the blown up rifle assembly?
Those questions are related, no? The rifle in question is older and well used per the shooter. What was the thread engagement of that rifle?
No horse in this race, fascinating overall. I think that regardless of what the builder chooses to do, he's screwed.
Or blessed. Whichever it is he is happy to be seeing the green side of the grass.
The builder? Best hope his Atty. approved the video he posted.
My 64,000 dollar question? Two actually.
How can the builder state the PSI for this to have happened?
What was the percentage of thread engagement of the blown up rifle assembly?
Those questions are related, no? The rifle in question is older and well used per the shooter. What was the thread engagement of that rifle?
No horse in this race, fascinating overall. I think that regardless of what the builder chooses to do, he's screwed.
stagpanther
New member
I remember when Mark was developing these things and was offering pre-production discounts. I was really interested and a local GS owner was also--he got one and I took a look at it, but the screw-on breech was the show-stopper for me. Even though I know squat about engineering I figured no way that was going to be the equivalent of locking lugs--and I'm not saying this just because of this one failure. It's true anything can fail--I have personally blown up 2 AR's, but they had a "graceful suicide" and luckily I escaped any injury (except maybe to my pride, what little I have).
I see this thread has not been updated in a little while. Mark Serbu himself has posted three videos about the incident. The first is his initial reaction the the incident:
https://youtu.be/5AY6iEVhJE8
His second video he explains the strength of the threads used in the design:
https://youtu.be/na1Qo7FxDeM
His third video are his initial thoughts upon receiving the RN50 in question:
https://youtu.be/4ny_V_VfT3Q
https://youtu.be/5AY6iEVhJE8
His second video he explains the strength of the threads used in the design:
https://youtu.be/na1Qo7FxDeM
His third video are his initial thoughts upon receiving the RN50 in question:
https://youtu.be/4ny_V_VfT3Q
Last edited:
Mike Irwin
Staff
"How can the builder state the PSI for this to have happened?"
Materials modeling.
Materials modeling.
RN-50 Thread Failure
RN-50 Thread Failure
As stated in this video ‘RN50 Accident Preliminary Analysis, on markserbu YouTube Channel” it was reported the force in pounds to fail the threads on the RN-50 was calculated to be 19,965 pounds of rearward force. Everything in the report is correctly stated for any fired round without case head separation. In Scott’s case, there was total case head separation. When total case head happens the ignited gas will also pressurize the rifle chamber. In most rifles and pistols the rear of the chamber is the exterior diameter of the cartridge case. The RN-50 has a screw-on cap with 1.5 in x 12 threads. So the rear of the RN-50 chamber has an area of 1.76 in². The calculated rearward force on the RN-50 cap when total case head separation occurs at normal pressures of 55,000 psi is 55,000 psi times 1.76 in² which equals 96,800 pounds of rearward force. The force that occurred during a case head separation is 1.65 times the force to fail the threads. Case head separation does occur has you mention and is more common with rounds used in automatic weapons with more headspace. I and lots of my friends which are across the course shooters carry case removal tools. However, most if not all rifles and pistols have some sort of ventilation system to redirect combustion gases away from the shooter when case head separation occurs. The RN-50? The only way I would fire one is using a long string.
RN-50 Thread Failure
As stated in this video ‘RN50 Accident Preliminary Analysis, on markserbu YouTube Channel” it was reported the force in pounds to fail the threads on the RN-50 was calculated to be 19,965 pounds of rearward force. Everything in the report is correctly stated for any fired round without case head separation. In Scott’s case, there was total case head separation. When total case head happens the ignited gas will also pressurize the rifle chamber. In most rifles and pistols the rear of the chamber is the exterior diameter of the cartridge case. The RN-50 has a screw-on cap with 1.5 in x 12 threads. So the rear of the RN-50 chamber has an area of 1.76 in². The calculated rearward force on the RN-50 cap when total case head separation occurs at normal pressures of 55,000 psi is 55,000 psi times 1.76 in² which equals 96,800 pounds of rearward force. The force that occurred during a case head separation is 1.65 times the force to fail the threads. Case head separation does occur has you mention and is more common with rounds used in automatic weapons with more headspace. I and lots of my friends which are across the course shooters carry case removal tools. However, most if not all rifles and pistols have some sort of ventilation system to redirect combustion gases away from the shooter when case head separation occurs. The RN-50? The only way I would fire one is using a long string.