Now we need the pics showing the gas rings only have .071 end clearance when in the carrier. The huge gaps we are used to seeing don’t exist when the bolt rings are compressed in place.
It helps debunk the gas ring gap “danger” that doesn’t exist - and why other knowledgeable shooters have insisted the AR will work just fine with one ring only.
K.L. Davis’s link is very informative and dovetails well with the slides from TACOM. He acknowledges that rotation of the bolt may be lifting the extractor, so the test by TACOM to spin the bolt with added weight is significant in that it couldn’t achieve lift.
Two forces act on the bolt - pressure from the case, and the DI directly on the back of the bolt. It’s been said DI will actually help compensate for bolt loading by it’s opposing force, allowing the bolt to turn more easily. If rotation isn’t lifting the extractor, what is?
Since headspacing means there is some slight movement of the bolt, could the sudden sequential opposing pressures be causing the extractor to rock on the pivot pin, creating lift? The pivot’s attached to the bolt, and the bolt does move a few thousandths.
Mount a bolt where two opposing pistons can jar it with 10k to 35k pounds and rattle it, I speculate high speed photography will show it rocking.
A brass cartridge expands from the pressure of the burning gunpowder and sticks to the walls. This helps reduce backthrust against the bolt face. When the pressure drops, the brass contracts. (Steel does not expand or contract as well as brass. This is why I do not use steel cased ammo in any of my wepaons.)
Most bolts lock up with no play. Are ARs different?
Head space means there is some play.
Now Im confused and have a question. What happens on a piston gun like the 416 or ADC to the gases that go through the gas key and push forward on the bolt when there is no gas key or gases going into the bolt carrier? Dont piston guns use bolts with gas rings?
There is no gas transfer into the BCG, therefore significantly more force is exerted on the locking lugs and lugs in the barrel extension than with the gas system the gun is designed to work with.
ARs with shoe-horned piston systems do not require the bolt to have gas-rings, though some do to properly align the bolt within the BCG.
Deleted. See below. Site is acting strange.
Well, I obviously transposed the numbers. .017, right. Even better.
And a further question (I never thought to ask) is whether gas opens the port cover, or bolt movement:
http://www.ar15.com/forums/topic.html?b=3&f=118&t=503005
I would have thought bolt carrier movement opened the port cover, but, well, read up for yourself.
LOL……I saw that thread.
I’m going to venture to say that the ejection port cover opening is based solely off mechanical action verses gas pressure.
I do not have hard data to back this up, but I’m guessing that after the energy is expended from the gas impulse of firing the rifle, that little energy is left in the form of pressure exiting the gas vents in an amount large enough to “blow open” the ejection port door.
If this was truly the case, that gas pressure alone acted to open the ejection port door, would we not eventually see gas erosion pitting on the inner surface of the door?
The gas pressure enters the carrier key where it is dumped into a piston chamber. The opening into the carrier (piston chamber) acts as a venturi. And we know that with a venturi, an increase in velocity, equals a decrease in pressure. The pressure remaining from the gas impulse has its energy robbed in the form of work expelled to move the piston (bolt). Therefore, little pressure is remaining in the form of exhaust gasses ported overboard.
This is my take on it. If I’m wrong, I stand corrected.
Well, only the “first” shot expels pressure on the port door. After that, we leave it open for the duration of that shooting iteration. I have seen residue, especially when shooting blanks, but that’s the same as suppressed, the gas trap retains more.
What’s isn’t known is what peak pressures do exist in the bcg. It’s been suggested it’s as low as 1500 psi rifle, 2500 psi carbine. Where the figures are sourced is usually never given.
Yes Sir, only that first shot would be with the cover closed, and that’s if one decided to have it closed to begin with.
I personally dismiss the hole theory though, about carrier exhaust port gas pressure opening the cover before mechanical action does. I would have to see some real hard evidence proving otherwise. And again, if I’m wrong, I stand corrected.
That definitely would be interesting to find out now wouldn’t it.
I completely agree, what would these guys suggests performs the same function in an op-rod AR?