Page 1 of 2 12 LastLast
Results 1 to 20 of 34

Thread: POF Roller Cam

  1. #1
    Join Date
    Aug 2009
    Posts
    79
    Feedback Score
    0

    POF Roller Cam

    Is there any benefit in running the roller cam in a DI carbine?
    I know I can't think of any benefit, but POF sells a kit for the DI gun.
    ΜΟΛΩΝ ΛΑΒΕ

    --"Fight back! Whenever you are offered violence, fight back! The aggressor does not fear the law, so he must be taught to fear you. Whatever the risk, and at whatever the cost, fight back!"-- Jeff Cooper

  2. #2
    Join Date
    Oct 2007
    Posts
    2,044
    Feedback Score
    14 (100%)
    I have one and haven't had any problems with it yet. My action does seem a bit smoother in its operation, however I don't see it as something you should go out and spend the money on with the expectation of it making your carbine "better" or more reliable. I won mine so it cost me nothing.
    Last edited by wahoo95; 09-24-11 at 10:26.

  3. #3
    Join Date
    Apr 2011
    Posts
    796
    Feedback Score
    3 (100%)
    From strictly a curiousity standpoint, do you believe that your rifle could, would, or could not function if the roller started to fail by becoming loose or whatever, to outright failing with actual parts seperation but remaining captured by the upper housing and carrier, yet still able to cycle perhaps until the next time things are taken apart?

    IOW, given that a conventional part can fail too, is the roller plausibly at least reasonably close to 'trustworthy' as the standard cam or even relatively as durable?

    Again, strictly curious on your thoughts as I'm not gonna buy one just to find out, but that doesn't mean I don't want to know.
    Last edited by GTifosi; 09-24-11 at 14:25.

  4. #4
    Join Date
    Apr 2009
    Location
    Washington State
    Posts
    473
    Feedback Score
    0
    One the earliest original designs had rollers, why would the designer leave them off of following designs if they were necessary?

  5. #5
    Join Date
    Apr 2011
    Posts
    796
    Feedback Score
    3 (100%)
    There's 'neccisary' and there's 'cost effective'.
    The two don't always go hand in hand at the manufacturing contract level, nor does the designer have the final say in such things.
    He may 'want', but the powers that be will 'have'.

    The bearing may or may not have been better, but certainly the pin as it exists now is significantly more cost effective and gets the job done adequately to a level where it doesn't hurt money wise to just toss it at X interval and put in another one.
    Last edited by GTifosi; 09-25-11 at 09:58.

  6. #6
    Join Date
    Oct 2007
    Posts
    2,044
    Feedback Score
    14 (100%)
    S
    Quote Originally Posted by GTifosi View Post
    From strictly a curiousity standpoint, do you believe that your rifle could, would, or could not function if the roller started to fail by becoming loose or whatever, to outright failing with actual parts seperation but remaining captured by the upper housing and carrier, yet still able to cycle perhaps until the next time things are taken apart?

    IOW, given that a conventional part can fail too, is the roller plausibly at least reasonably close to 'trustworthy' as the standard cam or even relatively as durable?

    Again, strictly curious on your thoughts as I'm not gonna buy one just to find out, but that doesn't mean I don't want to know.
    I think it would function about like a standard cam pin when it breaks. In all honesty, I cant see the new roller cam breaking as it "appears" to have less visible wear than a standard cam pin I have at the same 5k round count.

  7. #7
    Join Date
    Jul 2010
    Posts
    110
    Feedback Score
    0

    cam pin

    It does change the wear slightly on the upper where the pin unlocks.

    Has anyone ever just machined the wear into the upper?

    These pins luckily seem very solid manufactured, the tolerances are something I would never play with and it is well built. In saying that it does seem to have a failure mode that the pin doesn't. That is the roller could come off.

    If it locked, then it would maybe take some energy from the bolt group and maybe cause issue with the firing pin, there was a gun called the Hack 7 that had a round (not roller) firing pin that didn't rotate and was problematic.

    The square on the standard pin keeps this rotational tendency from happening. The roller cam and a DI system just doesn't sound like a lifelong marriage.

    I am scared of cam pins considering that is something thing that could kill you if it were to break.

  8. #8
    Join Date
    Oct 2007
    Posts
    2,044
    Feedback Score
    14 (100%)
    Quote Originally Posted by armatac View Post
    It does change the wear slightly on the upper where the pin unlocks.

    Has anyone ever just machined the wear into the upper?

    These pins luckily seem very solid manufactured, the tolerances are something I would never play with and it is well built. In saying that it does seem to have a failure mode that the pin doesn't. That is the roller could come off.

    If it locked, then it would maybe take some energy from the bolt group and maybe cause issue with the firing pin, there was a gun called the Hack 7 that had a round (not roller) firing pin that didn't rotate and was problematic.

    The square on the standard pin keeps this rotational tendency from happening. The roller cam and a DI system just doesn't sound like a lifelong marriage.

    I am scared of cam pins considering that is something thing that could kill you if it were to break.

    The roller could come off, however its no different than the top of a standard pin head shearing off...which I have seen. The roller like any other part could fail, however it appears to be under less stress by design when compared to the standard pins.

  9. #9
    Join Date
    Jul 2010
    Posts
    110
    Feedback Score
    0
    Did the head break where the stress relief groove is?

    I change them frequently, they get that sinusoidal wave mark on the side, that is where I thought they would break.

    I have always thought that the TDP should be tweaked to reduce the cam pin shaft O.D. by about .03" so the bolt would last longer. Bolts sometimes seem to elongate and crack around the cam pin on some high stress guns.

    wahoo95, call UVA and tell them that the football team doesn't get cheerleaders next year if they don't start a turnaround.

  10. #10
    Join Date
    Jan 2011
    Posts
    570
    Feedback Score
    1 (100%)
    Quote Originally Posted by mikeahe View Post
    I know I can't think of any benefit, but...
    ...But a piston AR company markets a product so it must be better? Naw dude.

    I, too, own a POF roller cam pin. I havent noticed any significant increase in the smoothness of the unlocking action and while it may reduce stress somewhat... I believe that regular cam pins manufactured by reputable companies have more history of reliable performance behind them than any piston AR company can conceive of. Again, solution searching for a problem IMO.

  11. #11
    Join Date
    Jul 2010
    Posts
    110
    Feedback Score
    0
    we're speaking technically here so there's no need to discredit a product by ignorant merits, is FN a stupid piston company,HK? is the AR 180 a stupid piston gun?

    Is the Pin HK added to the barrel extension that prevents the extractor from lifting while bolt is in the extension stupid? I truly think that is cool, that bails out so many bad situations with suppressed systems.

    The reason I initially tried it was imagining the loss of power when rounds are stripped from higher capacity magazines. The cam head is within the receiver slot at this point and I thought it was worth trying. In the end I don't know if it does anything over a lubed gun because there truly is nothing wrong with the existing pin.

    Frank (POF) was one of the first people to apply some of those all too cool coatings to production items and it was from his time in Aerospace, not in this eternally unevolving industry.

    I don't think you need to look at the piston line as an enemy breed, it's like you're fighting your brother saying he's totally genetically screwed. Stoner didn't do any more with DI after the project. Our (the AR) weapon is amazingly good because of the work we have done with the TDP, production, processing, and a commitment to making things better. Not because it was inherently the best from the very beginning.

  12. #12
    Join Date
    Jun 2011
    Location
    Back where I belong
    Posts
    1,544
    Feedback Score
    0
    Quote Originally Posted by armatac View Post
    we're speaking technically here so there's no need to discredit a product by ignorant merits, is FN a stupid piston company,HK? is the AR 180 a stupid piston gun?

    Is the Pin HK added to the barrel extension that prevents the extractor from lifting while bolt is in the extension stupid? I truly think that is cool, that bails out so many bad situations with suppressed systems.

    The reason I initially tried it was imagining the loss of power when rounds are stripped from higher capacity magazines. The cam head is within the receiver slot at this point and I thought it was worth trying. In the end I don't know if it does anything over a lubed gun because there truly is nothing wrong with the existing pin.

    Frank (POF) was one of the first people to apply some of those all too cool coatings to production items and it was from his time in Aerospace, not in this eternally unevolving industry.

    I don't think you need to look at the piston line as an enemy breed, it's like you're fighting your brother saying he's totally genetically screwed. Stoner didn't do any more with DI after the project. Our (the AR) weapon is amazingly good because of the work we have done with the TDP, production, processing, and a commitment to making things better. Not because it was inherently the best from the very beginning.
    Ok. I get where your coming from, in the technical sense. But, don't you think Stoner might have thought he finally got it the way be wanted it.

    The pin in the receiver extention, was not his idea, it was someone else's R&D. Roller cam, coatings,etc... evolving technology from other sources. And wasn't a piston was one of his designs?

    I agree with what you on the improvements made in TDP make the modern weapon great, don't you think he did a good job of laying the foundation?

    Not arguing, just sayin...

  13. #13
    Join Date
    Jul 2010
    Posts
    110
    Feedback Score
    0
    I think DI is one of the best systems, but I really can't tell if that is because we have done such a good job with it , and I too don't want to argue.

    AR18/180, is the true parent to modern short stroke/tappet piston guns.

    Stoner was around 32 when he did the AR10, he never did another DI system after the 15(retirement exemption with Reed Knight). Piston or DI, and rotating bolt are good parameters for a sound design and what their (stoner/sullivan/freemont) design legacy has shown us.

    Sullivan is still alive, and he is not the largest fan of DI. When I read the SAR article I was amazed at how much was just done on a whim but has never ever changed. The .223 round wasn't that well thought out but it does a fine job.

    In meeting people in this profession I come across 2 types of thinkers. 1 type is the type that says everything was very well calculated and basically perfect and if we vary we dont know what we are doing because we don't know what they were thinking when they did it originally, the other type is the type that puts all in question and occasionally misses the historical relavance of some designs and where they lead.

    They both have their issues. In the end if it works it works. Maybe looking past fouling and kinematics the DI system provides a more reliable cycle from the compressible flow type push of its "piston".

    The ultimax is the best gun ever invented hands down(my opinion but that is all that matters in this head).

  14. #14
    Join Date
    Jun 2011
    Location
    Back where I belong
    Posts
    1,544
    Feedback Score
    0
    I would like to get my paws on an ultimax.

    But yes, I agree. They were trying new things, and hey, thinking outside the box is what got us to this point. I don't know of any system that is perfect or could stand a few tweaks.

    Getting back to topic, I really need to try a roller cam in a DI. Just for my own curiosity.

  15. #15
    Join Date
    Nov 2007
    Posts
    11
    Feedback Score
    5 (100%)
    http://www.youtube.com/watch?v=6JmIQXkoog8

    Here is a interesting video, may show a argument for the use of the POF roller cam pin.

  16. #16
    Join Date
    Nov 2007
    Location
    New Mexico
    Posts
    1,486
    Feedback Score
    0
    I've got a POF roller cam pin in my Ruger SR-556C. The pin's been in the gun pretty much since new and I'm coasting up on 6,000 rounds fired.

    The stud or shaft or body or whatever you want to call it has the usual wear patterns from its interaction with the bolt carrier but the roller is looking fine. It is still tight on the shaft with no signs of loosening.

    I doubt there's any real benefit from the use of the roller but it doesn't seem to have caused any problems, either. I don't notice any increased smoothness in the action or anything like that. And I've still got a small amount of cam pin drag in my upper.

    Quote Originally Posted by armatac View Post
    Has anyone ever just machined the wear into the upper?

    The LMT MRP upper has an angled cut in the receiver just behind the cam pin recess.

  17. #17
    Join Date
    Jul 2010
    Posts
    110
    Feedback Score
    0
    brent31, yeah that video shows what drag there is, we should see a similar test done with one upper using a lubed cam pin and a roller pin. I'll do it if nobody else hasn't already but I don't really have the time now.

    That with a cam like move in the wear area (LMT MRP) apparently. I like, I like a lot. This maybe would help reduce "break-in" wierdness.

    I think this is something that just might make the DI even more reliable, atleast it should operate for a longer time if the ultimate failure mode is attributed to the system weakening due to loss of energy.

  18. #18
    Join Date
    Nov 2007
    Posts
    11
    Feedback Score
    5 (100%)
    brent31, yeah that video shows what drag there is, we should see a similar test done with one upper using a lubed cam pin and a roller pin. I'll do it if nobody else hasn't already but I don't really have the time now.
    I did try this in my LMT upper with a POF roller dry and could not get the BCG to bind like it did in the video.

  19. #19
    Join Date
    Nov 2007
    Location
    New Mexico
    Posts
    1,486
    Feedback Score
    0
    Quote Originally Posted by brent31 View Post
    I did try this in my LMT upper with a POF roller dry and could not get the BCG to bind like it did in the video.

    Can you take a video and post it here?

  20. #20
    Join Date
    Nov 2007
    Posts
    11
    Feedback Score
    5 (100%)
    I can try, won't be till the weekend.
    Last edited by brent31; 10-03-11 at 19:23. Reason: grammer

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •