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Slide/Frame Fit Question

Discussion in '1911 Forums' started by mholl26, Jan 25, 2010.

  1. mholl26


    Sep 23, 2007
    Which semi-custom maker has the best slide/frame fit and smoothness? I am particularly comparing Wilson CQBs and Ed Brown Kobras, but would like to know other outstanding examples.
  2. bac1023


    Sep 26, 2004
    I would probably say Wilson out of those two, but you're splitting hairs either way.

    Frankly, the barrel fitting and lockup has a lot more to do with accuracy than the slide to frame fit.

  3. Quack

    Quack Rent this space

    Jan 7, 2002
    NE Ohio
    from what i have Brown > Wilson, but my TGO-1 (Springfield Custom Shop) was better than either.
  4. mholl26


    Sep 23, 2007
    I do covet one of those.
  5. tous

    tous GET A ROPE!

    Jan 7, 2001
    Plano, Texas, Republic of
    As bac noted, conistent return to battery is the more critical factor when it comes to not just both accuracy, but repeatable accuracy.

    Regarding the slide fit to the frame, we all know of the myth, perhaps we can consider a bit.

    Besides the desired back and forth motion, a slide can move in five other dimensions: it can roll (rotate around the front to back axis,) it can pitch (rotate around the side-to-side axis) and it can yaw (rotate around the top to bottom axis,) it can move side-to-side (perpendicular to the desired back and forth,) and it can move up and down. The slide nominally moves down due to gravity. A properly fit slide limits these potentially adverse movements, thus, the rails on the frame should fit the slots in the slide almost exactly.

    How exactly? I have many folk brag about a 1911 with a 'tight fit' where they can barely move the slide back and forth. Why they boast about it puzzles me. Any friction between the slide and frame retards the slide's velocity in both directions and to compensate I either need a zestier cartridge, a weaker recoil spring or both just to get the danged slide to ... slide. A weaker recoil spring combined with excessive friction may well cause the slide to have insuffcient velocity on return to pluck the next cartridge from the magazine and return the slide to battery. Not only do I have an unreliable pistol, I have a pistol where the dynamics of the firing cycle are changing as friction wears away the snug places.

    Why is the immovable slide a good idea again? :headscratch:

    Again, how tight is good enough? Recall, we want the to minimize all BUT the back and forth movement and we want the engineered back and forth motion to be as efficient as possible, thus, a properly fit slide fits the frame ALMOST exactly, but not so exacty as to cause friction when the parts move. Consider, if I have a 0.10" gap between rail and slot, the slide can move adversely (pitch, roll, yaw) that much, but the slide moves freely. If I have a 0.001" gap between the rails and slots, the roll, pitch and yaw is significantly reduced and the slide can still move freely. If I have no gap between rail and slot, the roll, pitch and yaw is eliminated, but the slide can't move without excessive friction.

    What I try to achieve is the best compromise between no adverse motion and a slide that moves freely. Remember, the botom of the slide bears on the frame just below the rails (right above the plunger tube,) the top of the slide slots bear on the top of the frame. A proper fit means that the slide contacts both of these bearing surfaces approxmately equally. The larger the bearing surface, the less chance of adverse motion. The frame rails should extend to just about the bottom on the frame slots, but without drag. Side to side isn't a big problem. There really isn't a force during operation that moves the slide that way.

    Once all of the potential adverse motion has been minimized, attack the friction. I generally use progressivly finer lapping compounds on a snug slide/frame until the slide moves smoothly, I have 100% contact or as close as I can get on the bearing surfaces and ... if I tip the pistol nose up at about 45-60 degrees with the slide forward, the slide will slide on back with little of no drag; the same if I tip the pistol nose down.

    Consider, if the slide is properly fit as described, there is no so-called "break in" period because everything moves optimally already. No need to wear down parts that drag because the parts don't drag.

    That's just me. I know other folk have different approaches.

    Last edited: Jan 26, 2010
  6. Cobra64

    Cobra64 Deals in Facts

    I've been told by a master pitsolsmith / competition shooter that barrel to slide lockup is the most critical aspect for accuracy.

    Some of the 239s are rattle traps with the slide back, but in full battery the barrel is under slide tension and locked up tight. The 239 is an extremely accurate little pistol.
  7. :wavey:Mr. Tous, Thanks for all the good information.
  8. Brass Nazi

    Brass Nazi NO BRASS FOR U!

    Jul 4, 2005
    Yep, I have seen very tight guns that would not shoot worth a crap and have seen a few rattlemasters that could be used in bullseye.
  9. tous

    tous GET A ROPE!

    Jan 7, 2001
    Plano, Texas, Republic of
    Indeed. :thumbsup:

    Anyone who has examined Colt Gold Cup pistols find that they hardly pass the 'if I can move the slide it's not a good pistol' dogma. Colt fit them with room to breath, yet few would argue with the results.