A Stainless Steel Century Piston? And is it Better than a Carbon Steel One?

[cchiang1]

Greetings:
Some time ago, I read one or more threads here about the poor quality, bending, etc. of pistons in the newer generations of Century VZ 2008 rifles (something about avoiding the "bronze" colored ones, I believe?  I can no longer find those threads using the search feature).  Anyway, today I examined the piston in my 1st Gen. VZ 2008, and compared it to a spare piston that Century had sent me around 2013 or so.  Both were shiny (not tinted), the original had a smooth shaft, while the spare one had small parallel ridges along the shaft from not being as well machined.  Both weighed 3 ounces & appeared to be the same dimensions, however I noticed that the original piston attracted a magnet, while the spare one did not! 

Questions: Since both pistons weigh the same and one attracts a magnet, I assume that the other is not made of aluminum, but must be made of Stainless steel, right?  I have not read anything on this or other VZ 58 forums about stainless Century pistons; would the stainless one be more, or less durable & likely to bend than the carbon steel one?  I'm not too concerned about corrosion or ease of cleaning, just long-term durability.  I realize that there are different grades / types of stainless and carbon steel, and no one knows exactly what mine are made of, but your opinions are welcome!  Thanks in advance!

Cary

P.S. FWIW, I decided to compare both of my Century pistons to the one in my recently acquired, 2009 vintage D-Technik VZ 58.  The color / finish on the D-Tech piston looked the same (if it was chrome-plated like I think the military pistons are supposed to be, I couldn't see the difference), but the shaft seemed to be slightly thinner, and it only weighed 2.5 ounces (1/2 oz. less). 

[TJNewton]

While I have seen a couple pics of Century-made pistons bending, I think that most reports are merely due to the piston hole in VZ2008 rear sight blocks being especially small and needing minor opening up.  It may be because of the final coating Century used.  I have a surplus rear sight block and its hole is relatively huge compared to those of my VZ2008's.  Gas pistons, both US-made and surplus, seem to vary significantly in width, which is why most reports of bent pistons are probably just the rear sight block hole being too small.  If the piston isn't visibly bent, and any imperfections need to be detected by use of a caliper, then the piston probably isn't bent.  I have several surplus Czech gas pistons and they all have slightly different diameters, and none of them are machined to be completely plumb.  They all have imperfections noticeable to the eye.  Those imperfections are irrelevant as the none have malfunctioned and none bind at all after the sight blocks have been opened up to dimensions even smaller than that of my surplus sight block.

Bottom line, your Century pistons are likely fine.  If they bind at any point of rotation, but are not visibly bent, then your rear sight block piston hole likely needs to be opened up with a round file -- slowly and carefully.  I have all three of the Century pistons -- gold, reddish, and stainless steel -- and all have worked fine.  Even so, I replaced them with NOS surplus ones as they are chromed and slightly easier to clean.  If you do replace the US-made piston with a surplus one, remember that you may now be non-compliant with 922r, for whatever that's worth.  To compensate, I replaced my pistol grips with US-made brands.

[gwvt]

I had a century piston that started binding after several hundred rounds use. I did open the hole up a bit and it seemed to alleviate the problem for awhile but the same piston began to bind again after awhile, leading me to believe that it was due to slight bending of the piston getting worse over time. I replaced it with a milsurp piston and haven't had a problem since.

http://www.czfirearms.us/index.php?topic=82456.15

[TJNewton]

I had a century piston that started binding after several hundred rounds use. I did open the hole up a bit and it seemed to alleviate the problem for awhile but the same piston began to bind again after awhile, leading me to believe that it was due to slight bending of the piston getting worse over time. I replaced it with a milsurp piston and haven't had a problem since.

http://www.czfirearms.us/index.php?topic=82456.15

Good point and good link to a thread with more info.

[briang2ad]

NO commercially made piston should be thought to be equal to or better than an original 'made for military use' piston.  Especially Century. 

[MeatAxe]

The gas piston from CNC Warrior has been out of stock for some time. I contacted them and heard back that they don't know when (or if) they'll resume production. Obviously not enough demand at this point.

So, I would contact CNC Warrior and give them an incentive to produce more. It's an easy 922r compliant part. No doubt that CNC Warrior would produce a better part than the drunken monkeys at Century.

[gwvt]

I'll just note that if you look at that discussion I linked to, at least one person has found that the CNC Warrior piston would not fit into the VZ2008 sight block opening.

[TJNewton]

I'll just note that if you look at that discussion I linked to, at least one person has found that the CNC Warrior piston would not fit into the VZ2008 sight block opening.

That's why it needs to be opened up with a round file.  The openings on VZ2008's are very narrow, likely due to coating they used.  There's no worry in doing that -- the hole in my surplus sight block is huge and even the thickest surplus piston I have (they vary considerably) will rattle around in it.

[gwvt]

I did do a little filing on one of mine but my take on it is that if the milsurp pistons will function without modifying the rifle, I prefer that as a solution.

[TJNewton]

I did do a little filing on one of mine but my take on it is that if the milsurp pistons will function without modifying the rifle, I prefer that as a solution.

I agree with the concept of altering the part instead of the firearm, but Century VZ2008's are probably an exception in this particular case, or at least in my cases.  I would also be skeptical if didn't have the surplus part for reference.  The opening on my surplus sight block is 7.81mm; the opening on my accessible VZ2008 -- after using the round file -- is 7.40mm.  I can't quite remember but I believe that almost all of my four surplus and three Century pistons binded at some rotation in two of my VZ2008's, both of which required substantial opening.  The third VZ2008 accepted most of the pistons with much less binding and required very little opening.  Unfortunately, I didn't have calipers back when I did the modifications so can't say how much narrower the measurements were. 

No VZ58 pistons, not Century nor Czechoslovakian, are machined to be perfectly circular (and they don't need to be).  What convinced me to widen the opening was having the surplus sight block in hand and noticing how much both the Century and surplus pistons rattled in there with no spring present, and how both articulated perfectly with the spring installed, no matter the rotation.

But, yes, I completely agree that if the piston articulates with no binding, than no need to do any filing, especially of the firearm instead of the part.

I wish that CNC Warrior would make some more pistons as that's a great quality part to go towards 922r requirement.

[RSR]

IIRC, the stainless were the first versions that had more pronounced bending issues.  The brown/carbon ones were Gen 2 and seem to have less issues with malfunctions overall...

CNCW is best, and I can't believe they haven't started back again on parts w/ the downturn.  Perhaps their non-firearm business is keeping the mills busy?

[Franz Maurer]

Perhaps someone can convince kns precision to make the adjustable variant for the VZ

[czgunner]

Perhaps someone can convince kns precision to make the adjustable variant for the VZ

That would be great