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Gas Piston


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Okay, so I shoot my R-1 a lot. After using this rifle all over Alaska it started to jam on me. When I say Jam I should say that the bolt would not go all the way forward and the trigger would pull and I would hear a click and it would not fire. I would have to recycle the bolt and fire again. I clean this gun like a fanatic, so I clean it again and still it continues to jam. After a while it gets so bad I can't count on it. I hunt bears in Alaska and I bet my life on my rifle and I need to know it will fire when I pull the trigger. I was in a fix, leaving for a hunt in a few days and my primary weapons is jamming. So I tear it down again, I notice that the gas piston feels tight. I remember the piston assembly moving freely with the bolt locked to the rear. Mine was binding badly. I removed the lock ring from the piston assembly and found it to be severely corroded between the rings and the piston itself. I could not find anywhere in the manual that said to clean the piston assembly this way. The corrosion was building up under the rings causing the piston to bind in the barrel. I cleaned the corrosion off and oiled the parts and reassembled the rifle and I and happy to say that she is back in the game. I have now added disassembling and cleaning the piston assembly to my cleaning plan. Hope this might help some others that have had trouble. I ordered a new piston assembly from Brownell's

This is the piston assembly


corrosion under the rings


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I had a problem with shells not ejecting and while taking mine apart to see if I could find the problem I got on the forum and saw Steve's comments and pictures which were a big help. My problem was that the gas piston was stuck in the gas collection cylinder. It was stuck so tight that it wouldn't even wiggle. I put some lubricant on it and after some time I could start to wiggle it but not get it apart. I called customer service and had them look at Steve's comments and pictures told them what my problem was and asked if there were any special ways to deal with the problem. They said that I was on the right track and that it should come loose. They also said that I might take a hair dryer and try and heat it up a little. By tapping on it with a plastic hammer very lightly I end up getting the gas piston to come out but the rings stayed in the cylinder. I had to tap them out threw the top. My gas piston was in good shape but I think that enough crap was under the rings or in the cylinder that it caused the problem. Everything cleaned up fine and it's now back together. The piston moves freely and works like it should so all should be fine. I'll try it out in the next day or two and make sure then off to elk hunting on the Oregon coast. My guess is that this is an area that needs to be looked at and cleaned on a regular basis.

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This whole piston thing is some fabulous information and I thank you for it...but that being said, it does not make me happy. While I absolutely love Benelli shotguns and find them to be flawless in extreme hunting conditions, I just don't think anyone should have to worry about this type of stuff if they are shooting a Benelli. Afterall, isn't that why you own a Benelli? I own an R1 in .308 with some gorgeous wood. I have used it in the field, but not to the extent as it sounds some of you have; and therefore, I have yet to experience any of these issues.....thank god. But when/if I do, I'd better get a little more advice/customer support than a gun smithing lesson on how to better clean my gun. Sorry, just how I feel when I own a spend hard earned money on a Cadillac and not on a Le Car.

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Hey guys, I'm from the shotgun side. The pistons on the M4 shotgun look way different from the posted pictures. The M4 has twin pistons that are about 5"-6" long. They have multiple ribs with slots and move very freely in the piston sleeves. The M4 manual is very specific about NOT lubricating the piston. I suspect any oil residue would speed up the gunkification process.


I just saw the pictures of the MR1 Carbine and that may tempt me into my first rifle purchase. The body looks very similar to my M4. I'm curious as to what the gas pistons look like.

Edited by OhioM4
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300 WSM failed to cycle while in the field, while hunting. Tore it down, and found my piston corroded somewhat like Steves, and the end of it, at the snap ring, looks like it is flaking off. It does not look right. The inside of the tube has a pit in it as well. At most I have put a 100 rds through it!


Is this right? Is it covered under warranty? Is there a recall on this part?

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I bought my R1 in .300wsm 2 years ago. It failed on me at the worse possible time. (in the middle of a herd of elk) I contacted the factory and sent it in after the season. They said they couldn't see what was causing it and replaced the barrel. I got the rifle back and re-mounted the scope and went to site it in this season. It worked fine for the 8 shots I needed to site it in. I went out yesterday to fine tune it (hunting season starts in 4 days) It jammed after 2 rounds. The shell would eject, but the bolt would hang up when the new round was trying to chamber. I came home and stripped it and found the piston all carboned up. My question is-what is the best way to clean this crap off the piston and bore? I see pits in the bore as many of you have stated. How many rounds can you actually shoot before you need to worry about this? I have to tell you , i am very dissapointed in this gun, it shoots nice (when it works) and looks good but if I have to wonder if it will work when I need it then it really isn't much good to me. I have shot a total of 40 rounds through this gun so far. Does the type of ammo matter, is some of it better then others for an auto loader> I am shooting Winchester Accubond ammo. I have heard nothing but good things about Benelli guns over the past 30 years so decided to buy 1, not sure I made a good choice here. Could have bought 2 brownings for the price.:(

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Yes, the piston fouling so quickly and so severely bothered me. That and the fact that the gun didn't have good return to zero after being disassembled.


It simply made no sense to have a rifle that needed to be cleaned so frequently, but also needed to checked for zero whenever it was taken apart and re-assembled.


I sold the R1 and opted for the BAR ShortTrac Stalker.

I am very happy with the Browning.



Edited by tucker301
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OK. All of this talk of pistons got the best of me. So I grabbed my Browning BAR and took it apart.


This rifle has about 200 rounds through it, and I don't think I have ever had the piston out of it completely until today.

It's a bit of a pain to get out, due to some advanced disassembly work, but it's not too technical.

Just follow the guide in the manual and pay attention to what you're doing, and you'll be fine.


The piston is about as simple of a design as it gets.

Gasses from the barrel are imparted to the top of the piston.

The piston then pushes an inertia block rearward, which drives the dual action bars.

A very simple and efficient design. (note: inertia block has been removed in the photo)


The piston below was removed and wiped off with a lightly oiled rag, then wiped dry.

There was just a light powdery sooty coating on it, and it required no solvent to get clean.


Browning states in the manual to never oil the piston, but to merely wipe it down with a lightly oiled cloth.


There are no o-rings in the assembly.



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