The recoil spring, which has been compressed by the BCG, pushes the bolt carrier forward again, stripping a fresh cartridge from the magazine, chambering it and, through interaction of the cam slot and bolt lug, the bolt is rotated into locked position again. This arrangement allows not only in-axis action , but also moving parts that possess a low mass, keeping shaking to a minimum. Recently a new breed of AR came to rise: piston operated rifles.
A short stroke piston replaces the gas tube, and operates against a bolt carrier appendix much similar to the gas key. Actually, the old mechanism is not a direct gas impingement mechanism.
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Find out what it takes to get the perfect pistol grip …. In a series of interviews and videos they explore the value of working with a shooting coach. In this chapter they meet with gunsmith Andy Coull and explain why a correctly fitting gun is important. In this chapter, they explore the importance of a pattern plate, and why it is vital to understand where your gun shoots. Linda Mellor, 52, has had a lifetime around guns but only started shooting four years ago. Determined to approach shotgun shooting correctly, she contacted Perth based shotgun coach Iain MacGregor.
Iain has been coaching since the early s, and is one of the UK's few highly qualified shotgun coaches, and holds international qualifications at the highest level. Please try again. Key Points About How AR Piston Systems Work Because they are relatively new, many gun owners are still somewhat unfamiliar with how AR pistons work, as well as their potential advantages and disadvantages. Back to Top. Get Exclusive Deals. Email Address:. Register Forgot your password?
At this point the gas is pushed to the rear of the rifle, and the spent case is extracted and ejected. It is then pushed forward by spring-loaded action, and strips an unspent round from the cartridge, loading it directly into the chamber of the barrel. Contrary to the statements of Gas Piston proponents we have put over rounds through rifles without cleaning and without malfunction. Gas piston technology was first used in modern firearms by Mikhail Kalashnikov on the AK While similar at first blush to direct impingement systems, there are a few key differences in operation.
The firing process again begins with propellant gases being bled into the barrel. However, instead of being forced into a tube as it is in a direct impingement system, it is contained in a separate cylinder. This cylinder contains a piston similar in operation to what you may find in an AK I think it was Ben Cartwright before he opened that ranch on Bonanza.
Part of the function of the gas block is to redirect some of the gas back towards the action of the gun.
The gas is moving towards the muzzle, then straight up through the hole in the barrel. The gas block redirects it through a gas tube that leads back to the receiver.
The key fits over the gas tube and redirects the gas into the interior of the bolt carrier where it can move the bolt itself. Here, the bolt and carrier act pretty much like a piston the bolt tail and a cylinder the bolt carrier. The gas enters the bolt carrier and fills a chamber created by the space between the gas rings on the bolt and the internal wall of the bolt carrier where the firing pin body is located. In the locked position, the bolt is pressed all the way into the bolt carrier.
The expanding gas moves it forward and the carrier backward, so the bolt rotates as the cam pin follows the angled path of the cam pin slot. The bolt carrier movement drags the bolt with it, causing ejection of the round. At some point, the resistance of the buffer spring overpowers the declining gas pressure and starts to move the whole assembly forward again, picking up a new round in the process. The bolt carrier and bolt slam into the barrel extension and pressure pushes the bolt back inside of the bolt carrier, rotating due to the cam pin slot.
In the context of direct impingement versus piston operation, it all boils down to this. The bolt itself is a piston. The bolt carrier is a cylinder. Hot and dirty gas flows directly into the bolt assembly causing movement, extraction, hammer re-cocking and chambering of a new round. With piston operation, the interface between hot expanding gas and moving parts happens far away from the bolt itself. When you fire a shot, hot, high-pressure gas moves down the barrel, driving the bullet forward.
Piston guns still have a small gas port in the barrel that allows some of the expanding gas to move into a gas block. Rather than directing the gas all the way back to the receiver, the block directs the gas into a cylinder above the barrel.
Inside of this cylinder is a piston that moves forward from the gas pressure. With most designs, the cylinder impacts some type of operating or connecting rod, which carriers the movement back to the bolt carrier group. On an AR-type rifle, the connecting rod impacts a modified gas carrier key. On the direct impingement gun, the gas key just directs the flow of gas to the bolt.
The net-net of the piston system is that the bolt is moved via impact of a metal rod rather than flow of gas into the bolt carrier. The bolt and carrier do not operate as a piston and cylinder — those equivalent parts are located far forward above the barrel.
That just sounds bad, right? Of course, there is truth to this. Hot and dirty gas DOES, in fact, go straight into the bolt area. The real question is, how much does that matter?
In my view, not much. The system is designed that way and offers plenty of offsetting advantages which we will touch on elsewhere in this section. As mentioned earlier, the carbon build up on the boat tail is largely a self-cleaning scenario. In terms of other cleaning and maintenance, there are fewer moving parts in a direct impingement system, so there are fewer parts to get dirty to the point of malfunction. With piston designs, the gas moves a piston located far from the action.
The net result is that the bolt and carrier area stays pretty darn clean, making your cleaning chores fewer and farther between. On the flip side, you now have parts up front, under the hand guard, that are subject to other types environmental dirt and subsequent jamming. From a reliability related to cleanliness standpoint, I would consider the two designs a wash. The bottom line is that you still need to maintain your gun properly.
In a traditional direct impingement AR-type rifle, the gas that enters the bolt and carrier area are HOT. Predictably, those parts, and the surrounding upper receiver, get hot pretty quickly. Of course, hotter temperatures can break down lubricants faster, so you will need to pay more attention that and use high quality, temperature-resistant gun oils.
On a piston gun, the action stays surprisingly cool. Of course, the chamber will get hot and bleed heat into surrounding areas, it just takes a lot more shots to get the bolt and carrier area to the same temperature level.
There are a lot of theoretical arguments about which platform is better for suppressor use, but my view is far more practical. Many piston systems offer adjustable gas features which let you decrease the amount of gas fed into the system for suppressor use, or increase the amount of gas for adverse conditions.
The extra gas flow makes things work even when dirty, to a degree. I suspect this is for a variety of reasons. The direct impingement system is a very smooth operation. The flow of gas to the bolt and carrier creates no movement of parts until it enters the cylinder bolt carrier. The forward and backward motion of the bolt and carrier is very linear, with no torque or off-center force.
While the bullet is gone by the time all this happens, many folks believe the linear action of the direct impingement system does improve bolt locking and unlocking, which can affect accuracy.
Overall mass might come into play also. The extra piston and operating rod components add weight. And movement of mass during firing cause overall movement. While the bullet is gone by the time things really start to move, this shift mass can force the rifle off target between shorts more than with a direct impingement model. The classic direct impingement AR-type rifles usually have interchangeable parts as they follow the design on the original AR Generally speaking, parts are easy to come by from a variety of manufacturers.
Piston designs are generally proprietary. Everyone has a slightly different design, so parts are usually not interchangeable. Like most things gun-related, much depends on the intended use and your personal preferences. Decide what features you care about for your anticipated type of use. Golly, I have over 25, rounds through my two BCMs with never a tick, most of those rounds were reloads … 55, 62, and 77grain heads.
I pass a patch through the bores every rounds or so. I inspect and wipe down the bcg about as often, but no scraping. What did the sargeants say? It was a good order. If you are building a pistol… AR vs Piston… Short barrel AR direct impingement pistols have a reputation for not operating dependably. If you are going DI, then use a
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