The gas system of the RIA VRBP100 is not necessarily new, but it is slightly different from other more common designs people are familiar with. I personally am not familiar with too many semi auto shotgun gas system designs, but I know that this shotgun gas system is relatively unique to Turkish shotgun designs. However, it is basically akin to a short stroke gas system you seem piston operated rifles. I have had a little bit of an issue with this shotgun gas system during the break-in period. I am going to go over this issue and discuss how the system works and what might be happening internally to cause these issues. MANUFACTURER Derya Arms is a Turkish company that makes this shotgun, and it is RIA who imports it. Being of Turkish origin, this shotgun has some unique characteristics that are pretty sound. Turkey is known for creating pretty good guns overall, to include some of the nicest shotguns on the market. Though Derya Arms is a pretty new company(founded in 2000), they have been busy exporting their shotguns to over a dozen countries at a very reasonable price. Their website says that they focus on making shotguns that are made to CIP(Permanent International Commission for the Proof of firearms), SAAMI(Sporting Arms and Ammunition Manufacturing institute), and TSE(Turkish Standards Institute). One thing I have learned about Turkey's firearm manufacturers is that they are very prideful and dedicated to perfection. Though perfection is subjective to ones definition, Turkey is home to some of the best firearm manufacturers in terms of quality for the price. GAS SYSTEM DESIGN The gas system of the VRBP100 is not a very unique one, in concept. I have noticed that many shotguns that come out of Turkey have a very similar gas system but with small variations between them. You will notice that the VRBP100 and the VR60(AR15 style 12 gauge shotgun) share the same gas system but with a difference in charging handle location and function. The gas system on the VRBP100 is pretty simple, consisting of merely a gas block, piston, and bolt carrier system which acts as an operation rod. In the picture below you will notice the gas block with the gas piston tucked inside. There are two gas pistons to choose from in this shotgun. You have the "LIGHT" load piston and the "HEAVY" load piston. The light load piston is going to be the most common piston since it is designed to be used with most 2 3/4" shells. ![]() The "HEAVY" piston is designed to help mitigate the pressures of most of the 3" shells, in theory. I still have yet to test any 3" shells, but it is on my list of things to test. I am curious myself whether or not the 3" shells are going to be too much to comfortably control. The difference between the two pistons are quite apparent. The "LIGHT" piston has a metal ring that keeps it secured in the gas block. This makes it relatively easy for the gases of lighter loads to build up pressure in the gas block, sending the piston rearward. The "HEAVY" gas piston has several grooves cut in it that seem to be designed to build up the gases prior to moving rearward. This is why this piston does not stay in the gas block like the "LIGHT" piston does. When you are firing heavy loads with alot of gas pressure, you need to have somewhere for that gas to go that will not cause unnecessary pressure and wear. This "HEAVY" piston makes it to where the extra gas pressure has to fill in the gaps between the piston and the gas block before the piston can drive the bolt carrier rearward with enough inertia to cycle the action. As the picture shows above, the barrel has 2 vent holes that throw the gases into the gas port. I can only assume that they use two vent holes because having one big one is not practical, but they need a generous amount of gas in order to get the pressure needed for reliable cycling of the action. In front of where the gas ports are, there is something called a gas discharge shell that basically functions as a secondary gas chamber when the gas pressure becomes too high in the gas block. If you fire alot of high powered ammo through the shotgun, you will notice the area on the "magazine tube"(the rod/tube that the carrier, piston, and barrel is held on. Not quite an accurate description considering that the "tube" has nothing to do with ammunition) gets very dirty where the gas block discharge shell is. This observation, along with the name "gas block discharge shell" seems to point to this part having the function I described. BREAK-IN REQUIREMENT In the owners manual, it states that you need to shoot 50 shells no smaller than #8 shot before trying to shoot anything lighter. However, they fail to say what kind of velocities you will want to stick to. In my experience, you will have the best luck with loads that have a velocity greater than 1300FPS. I found RIO buckshot to be sufficient. The buckshot loads have a velocity of just over 1400FPS, which seems to hit the spot for this shotgun. Many people dislike the fact that this shotgun requires a break-in period at all. Out of impulse, I also dislike this, but I think I can shed some light on why. If you read my previous chapter, I mentioned that the gas block has a bit of room, along with the gas block discharge shell. In my opinion, the gas system needs firing residue built up in order to create a tight seal that will encourage the gas system to function smoothly. Think of it as being similar to a precision rifle that needs the barrel to be fouled up in order to maximize the accuracy potential of the rifle. But, in this case, the gas system is what needs firing residue in order to tighten the fit that the gas block has around the magazine tube. CONCERNS I HAVE Given that this gas system needs the fouling to fill in the gaps that the manufacturer left, I am a bit concerned about what to do when it comes to cleaning. Should I just let the gas block/piston get all nasty and only clean the magazine tube and bolt carrier? There are no instructions on what to do with this shotgun in terms of cleaning and maintenance, so I am going to have to seek out answers in the future. This is the most frustrating part of having this shotgun, in my opinion. You are left to figure things out for yourself without any useful guidance. CLOSING COMMENTS I am not sure that I am too happy that the gas system on this shotgun is in need of continuous firing residue build up in order to function properly. However, I have seen plenty of people who were okay with light loads right out of the gate with their own VRBP100, which means that I may have a gas system that is just barely within spec. Perhaps the manufacturer has too loose of tolerances for their gas block and gas piston dimensions. In my recent experience, shooting 50 shells did not quite cut it for getting this shotgun to function smoothly. It took me about 100 shells of self defense loads to get the shotgun to start ejecting the target loads. However, after doing a simple cleaning on the gas block and piston, I was back to square one in terms of getting malfunctions. The difference is that this time, I could not get the shotgun to reliably cycle AT ALL after 100 slugs going 1300FPS. I decided to stop cleaning the gas piston and gas block, which seemed to produce good results, but I am unsure about how this will affect the system down the road. How long until I need to wipe down or clean the piston and gas block before things get too gunked up? I guess I will just have to find out by shooting and shooting until something happens in the gas system. What choice do I have?
1 Comment
westly vander meer
9/8/2020 16:32:58
I have fiocchi 2 3/4 1325fps 12guage rounds which gas piston should i use
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