I've had some issues with my MK1 and it won't fire if I don't rack it with all it's might.  If I don't, I get super light primer strikes and a FTF.  It's kind of odd as if I hit the foreword assist it still happens.  So today I troubleshot the thing with different lowers and ammo, measured firing pins, cleaned lubed, and came up with nothing as I can tell when it won't fire.   Best I can figure is that the bolt spring is pushing back ever so slightly and causing the light strike.  So I took it out as It's not really needed and once removed it fires 100%.  I still think something must be off by a thousandth or two as I'm guessing most peoples work just fine.  Perhaps a few mags down the pipe might loosen things up as well.  Just checking to see if others have observed this, and if they've had PWS get involved.

For those not familiar, PWS and AA put a spring in the BCG for no apparent reason, other than your bolt is always extended.

marko16...have you spoken to PWS Customer Service? BTW, 208-780-6122 is the number. Did you buy this rifle new or secondhand? I have a Mk114 Mod1 and have no issues whatsoever. It seems odd that removing the Bolt Spring miraculously fixed your issue.

Old_Navy

Have a mk116 with about 9000 rounds through, never had single problem.

If you're just saying you don't think a bolt spring accurately replicates DI gas, well then disregard this.

If you're saying the spring is irrelevant, I'm sure you know but it's supposed to replicate the forward force DI gas gives a bolt for a fraction of a second while unlocking.  Reduces the load on your lugs, increases the bolt's life.  I wouldn't want to remove it long term as a fix.

Was going to ask if it's brand new too.  I'd drop PWS a line, get its opinion.

I agree and is why I'd solicit a response here.  I googled the issue and another out there described the same thing and posted a picture that his bolt is not spinning quite all the way in.  Thanks for the number as it's really hard to explain the problem in typing.

 I worked in two arms rooms in the service and guard, so I know my way around these pretty well (although at the unit level, you really couldn't fix important things).   That doesn't mean much, but the obvious trouble shooting steps have been done.  A firing pin occasionally not coming all the way out, despite being wacked at full force, but protrudes full manually can point to a few things.  I don't mean to instruct as these things are obvious, but a bolt and bcg only allow for full pin protrusion in full lock up position,--by my primers, sometimes I'm not getting that.  This occurs when I don't use full force to load a round.  Again, this points to not quite going into full battery.    w
So going on down the line, why isn't it spinning fully, or is that little spring causing a slight separation of the bolt and BCG, which would also cause the pin not to protrude fully--that tiny bit may put me over the go/no-go threshold.

So read on if you want the rest of the story.

 Heres the odd part.  Again, full on chamber it will function 100%.  Here's the other time it won't function--lets, say I  don't quite seat the mag fully (ok I've done it at the range or while I'm hunting and trying to be quiet, and don't want to wack it in) it misses the round, but I notice because click--nothing.  So far not hunting but a few times at the range, and remember a DI yelling that you have to insure every mag is fully in, so I tap the mag and rerack and chamber a round--I can guarantee 100% it will not fire.  Click no fire, eject the round, put it back in the mag, and 100% it will fire and so will all the rest of the rounds.  I've never had that on any other weapon, now you can say "hey Marko, pull your head out of your ass and rack it like a man", but it's kind of a pain to sit in the cold waiting for yote to appear wondering if the first round will fire or not, that's not right even if I am a moron.  This will happen if I dry fire too.  So I take the spring out and so far it hasn't happened, that's why I look at the spring.

I don't, a spring with about as much pressure as a pen spring does not replicate DI pressure, does apply  just enough pressure to separate the bolt from the bcg.  My LWRC does not have a spring, and my PWS works fine with out it.  Just to add, I don't think it's the spring, but that tiny "off" I have appears to be worse with the spring in.  And as I stated in the OP, since this spring is in every build and works just fine, I'm soliciting others who might have the issue I have.  My LWRC has the bolt catch that is just undersized, and their forum has a nice thread on how that was detected for some, and addressed by LWRC.  Sometimes parts are out of spec and collectively is nice to find that out.  This rifle in question came from PWS without a piston, and they mailed me one pronto.  I will contact them.

Update,  I got in there with a strong light and mirror and noticed a metal sliver wedged  where the BCG face contacts with the lug lockup face.  This could cause my issue, or at least I'm hoping.   Would explain why a hard wack would close it up a bit.  Will reinstall the spring and go back to the range on Monday.

Understood, hopefully it's that metal sliver.  Substantive PWS info is relatively slim pickings so it'd be nice to know what you find.  Good luck Monday.

FWIW...I actually installed TWO bolt springs end-to-end on the back end of my bolt just to see what would happen. This was many months and range sessions ago and I haven't had any issues whatsoever. In fact, I've kept it that way ever since.

Marko16...I'll be interested also if the 'metal sliver' is the culprit.

Interestingly enough, my ADDAX/PWS/Bushmaster conversion (slightly different design) uses the original DI Bolt without a rebound spring. I've never had an issue with it. However, since PWS has seen the need to add it to the later design, I suspect it's required. The 'rebound spring' spring-rate is very light. A 'pen spring' is a good analogy.

I never thought of adding another 'rebound spring'. Given the very 'light' nature of the 'rebound spring', I can't imagine it has any major affect on timing of the Bolt release. Simply a little extra 'umpf' to move it out of battery.  

Best regards,

Old_Navy

A carefull once over is better than speculation, it works flawless with all parts attached.  I apologize for getting anyone worried about PWS.