This is why I love this forum. You guys have saved me another thousand bucks by talking me out of a piston AR.
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This is why I love this forum. You guys have saved me another thousand bucks by talking me out of a piston AR.
I agree doc, I was going to order a kit from centerfire systems that was a cheap retrofit set up. save my money and buy cleaning supplies![]()
Whoever said the pen is mightier then the sword
obviously never encountered automatic weapons.-MacArthur
Yeah, seriously... I do think about this a lot. I'm a mechanical engineer, so thinking about this kind of stuff isn't alien to me. Wear is a problem ONLY if you can trace it to a specific issue. Machines wear. If you change the design of the machine it will wear DIFFERENTLY. A difference in wear isn't necessarily better or worse. It's different. You need more data to determine if wear is a problem.
And again, on the bolt lugs.... can you describe the actual stresses an strains on the lugs? How do they compare with the stresses placed on the lugs in a DI gun? I don't know, and I doubt anyone really does.
But I don't think there's an avalanche of data showing a problem in the piston guns. In fact, I'd say lower quality DI guns are a way worse problem for AR users.
But the tube is open to the receiver and BCG and as soon as the bullet passes the gas port, there's gas and carbon in the receiver. The bolt doesn't unlock until after the bullet has left the barrel and the pressure has started to decrease. Once the bolt unlock and extraction begins, the residual pressure in the barrel will blow junk back into the receiver (whether Di or Piston), but at a lower pressure than what came in through the gas tube. Without doing more calculations than I care to, I can't tell you whether more junk in the receiver comes from the gas tube or the chamber, but my limited experience of cans on both piston and DI AR's tells me the DI puts more junk in the receiver than the piston AR.
However, both get pretty darned dirty with a can.
Last edited by Sttrongbow; 03-01-11 at 11:48.
my gen I PWS has an issue with the piston tube weld - but that was a proto and the design was changed to address that. no issues on the gen 2 (built by addax). the 'gen 3' is my addax-built PWS long-stroke 16" piston upper which i've been shooting since aug '09 and it's the upper i shoot the most (i also have about 10 other DI uppers to pick from). the two main reasons are that it's the easiest to clean out of all of them (both DI and piston), and it's also been very reliable through 5 or 6k rounds. i normally do a 15-20 min clean after each range session when shooting DI guns, but the addax reduces it to 5 mins with a bore snake and wipe down. less parts to clean than a DI gun (i don't really clean anything other than the bore - everything gets a wipe down vs a more thorough clean when i shoot DI guns - that's just me).
with the FRS anti-tilt buffer, there's no carrier-tilt wear in the buffer tube, and no more wear on the carrier bearing surfaces than a DI carrier. it has the spring-loaded bolt that puts a bit of pressure on it to keep it in the forward position and i believe that it helps with premature wear seen in some piston guns without it at the cam pin cutout in the upper receiver. it's a midlength, and shoots as soft as any other DI gun - even softer than some carbine gas systems.
for a recreational shooter like me not using cans or an SBR, it may offer no practical advantage over a DI upper, but i still reach for it more often than my other uppers.
my only concern is replacement parts if something breaks, since the system is non standard. other than that, it's been trouble-free for me.
The buffer tube was not designed to be a wear part.
If you look at every ground up piston design they have some form of rails that guide the carrier and stops carrier tilt. This is missing in the AR-15 design because it is unnecessary because there is no carrier tilt present in the DI system all forces are in line with the bore.
I hear ya, but I add: What failure mode are you introducing? I haven't seen any significant evidence of one. The AR-15 was also not designed to operate with a carbine-length gas system, and we KNOW it causes greater wear on the bolt, right? But the design has adapted over the years. Likewise, we've see the appearance of "pads" on the read of the BCG, and "anti-tilt" buffers, not terribly unlike the addition of the H buffers, extra power extractor springs, inserts, O-rings, etc.
Still, I have yet to see any convincing evidence that it's a problem in any significant scale.
Like any design change, you'll eliminate some problems, and introduce others. Determining whether it's a net gain or net loss in reliability requires data however.
Last edited by Sttrongbow; 03-01-11 at 12:50.
I'm no pro or anti piston. I've owned an LWRC and LMT piston which is now DI.
My LWRC suppressed much nicer than my DI guns and was immune to even the crappiest ammo. The main reason I sold it was LWRC making so many upgrades to their system
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