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  1. #1
    cnewcomer's Avatar
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    AMT Backup Discussion

    I have an AMT Backup .45, and I think it's a fine gun...if you're willing to tune it. I suppose back in the early days of the AMT it was decent enough for a cast offering, and it's my understanding that some were great off the shelf and some...well, not so much. What I'd like to do here is startup a discussion by those that own or previous owners of the AMT Backup. Whiners aren't necessary as there's plenty of that already out there. Let's discuss how to make the Backup good enough to rely on and carry.

    I'll start this off by talking about light strikes. I'm not certain if the models with the firing pin blocks have anything to do with it, and although mine is an earlier model, at some point the gun was sent to the factory to have one installed by High Standard. I removed it, as I felt it was neither part of the original design, nor at all necessary for this particular design. I also found that the firing pin spring was overly heavy. Amazingly so. The impact on the firing pin comes the force generated by the mainspring, and we all know how crazy heavy that danged trigger is! A super heavy firing pin spring calls for the super heavy duty mainspring to overcome it. I ordered all new springs from High Standard, and behold, the firing pin spring was much much lighter and about what I thought it should have been. My next step was to reduce the weight of the mainspring. I'm using custom springs that I cut to length to test. I couldn't begin to tell you the spring weight.

    Now the trigger is much friendlier, although still stout compared to say a DAO Boberg or similar true DAO pistol. I'll be testing various custom mainspring weights as I go along, and hope to discover a very reliable combination in order to reduce the trigger pull weight. I'm also eyeing the hammer, but will save that for another post.

    Oh, and if you've never removed and assembled the hammer and related parts, ya better muster up some patience!

  2. #2
    cnewcomer's Avatar
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    Here's a pic of a polished AMT Backup .45 feed ramp...


  3. #3
    Philco is offline Member
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    I owned an AMT Backup in .380 many years ago. It was without a doubt the worst firearm I ever owned. I was never able to fire a full magazine through it without a jam. I managed to trade it off and was glad to be rid of it. Never again!

    Reading your post it would seem you need to be a gunsmith to get your gun to function properly. I don't know about you, but life is way too short for me to spend my time trying to correct a sorry POS like the AMT Backup. Best wishes on yours. I'll never own another one.

  4. #4
    cnewcomer's Avatar
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    Looking for contributors, not whiners, but thanks for sharing.

  5. #5
    Steve M1911A1's Avatar
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    Quote Originally Posted by cnewcomer View Post
    Looking for contributors, not whiners, but thanks for sharing.
    Being a little more polite might work wonders, to get you the information you want.

    When you polished the feed ramp, I think that you forgot to polish the chamber, too. (Don't use a motorized tool for this, though.)
    I left the springs alone. Because the hammer "follows" the slide, the balance among the three springs involved should be maintained.
    Instead, I polished all of the sliding-contact surfaces in the entire trigger-action train.
    I also polished the trigger itself, since its edges were sharp and its surface was rough.
    The result was an "apparent" 12-pound trigger, even though it probably was closer to 15 pounds. (My scale stops at a real 12 pounds.)

    I replaced the issue grips with thinner, polished-dead-smooth, impregnated wood.
    The front- and back-straps of the grip were already rough enough, as cast, to provide good friction with my hand.
    Slim, slick grips made my presentations easier to accomplish, and quicker.

    I had Robert Mika make me a really good pocket holster out of artificial leather that was impervious to sweat.
    It has sticky rubber on it, to keep it in my right-front pocket.
    I use a Safariland-made, metal-skeleton magazine carrier for my reload, carried in my left-hand "cargo" pocket.

    I carried my AMT .45 Backup for about 15 years.
    While I was using it, and keeping in practice, I could make reliable head shots with it, out to about 20 yards...if I slowed down.

    Then arthritis struck. I can no longer comfortably use a tiny .45, and I can't make head shots at further than about 10 yards with it.
    So I've switched to a .380 ACP pistol. I can use that quite well.

  6. #6
    cnewcomer's Avatar
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    Tnx, Steve. Do you have a lead for those wooden grips?

    I needed to run more bullet separation tests today for another project, so headed to the range with my gear and took the AMT Backup 45 to toss more money downrange. The tests went well, and the AMT ran without incident with the exception of one 're'manufactured cartridge brand that has always given me some light strikes. And what do you know, it still does! However, the Speer LE 230gr Gold Dot's ran flawlessly. I had added the Wolff 'extra power' recoil spring for the Backup and I could tell a bit of difference when racking the slide, but it's not all that much heavier. Then again, I bought the AMT used so there's no telling what may have been changed over the years. I had also polished the internals, with the exception of the trigger itself, but got the rest of it looking like the feed ramp. I too had no idea what the pull weight may be since my scale only reaches 8 lbs.

    Since I do believe there's another avenue to look into the light strikes issue, I'll go there in the next reply.


  7. #7
    Steve M1911A1's Avatar
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    Quote Originally Posted by cnewcomer View Post
    Tnx, Steve. Do you have a lead for those wooden grips?...
    Yup.
    I made 'em.

    I bought some impregnated, laminated-wood slabs from Jantz knife-making supply, and went at 'em with files, a drill, sandpaper, and polishing wheels.

  8. #8
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    We'll see if this works for the AMT backup, but can say that I've had success with this in the past. And that's properly aligning the slide to the frame. It has also squared the hammer to the firing pin housing (or stripper, or block. I'm not sure what the actual name might be. The slide "strips" the cartridge from the magazine and shoves it into the chamber, kinda thing). If you've studied the alignment on yours and believe the hammer is partially blocked from full contact with the firing pin, this could be the remedy. In other words, the hammer still operates the firing pin, but not to its fullest capability.

    This image shows the rearward overlap of the slide. Although it's hard to see well, when the slide and frame are in proper alignment, the hammer appears be be fully seated on the firing pin block.



    I had already done a writeup on how to align the slide to the frame, so instead of rewriting it, I'll link the PDF file here. This was done on a Canik55 C-100 9mm with internal rails, but the process is the same.

    Is there no attachment function on this forum?

    Slide Alignment Link



  9. #9
    rustygun is offline Member HGF Gold Member
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    There are manufactures who make guns that you can unbox clean and lube, Shoot without any trouble, clean and lube, shoot again.

  10. #10
    Steve M1911A1's Avatar
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    Quote Originally Posted by rustygun View Post
    There are manufactures who make guns that you can unbox clean and lube, Shoot without any trouble, clean and lube, shoot again.
    Truth: The AMT .45 Backup was exactly such a pistol. It worked well enough, right out of the box.

    But because it was meant to be carried by a cop, in a pocket, as a backup pistol, its trigger action was purposely stiff and heavy. You just could not fire it by mistake or accident.
    It was meant as a "bad-breath-distance," "Get the heck offa me!" weapon, so that too-heavy, too-stiff trigger action was not a handicap to accurate shooting. It wasn't made for accurate shooting.

    But those of us who carry (carried) the AMT .45 Backup as our primary defensive weapon require(d) performance of it which its designer(s) hadn't intended.
    It was not intended for 20-yard head shots; or, for that matter, for seven-yard heart shots.
    In order to make its necessarily-crude action competent to handle those more refined tasks, it requires a bit of easily-accomplished, kitchen-table gunsmithing.

    It's a lot like modifying a G.I. M1911A1 into a competent carry gun.
    (Actually, the Backup requires a lot less modification and smoothing than ever did any G.I. M1911A1.)

  11. #11
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    Want to also add to the alignment process paper that the guide rod on this model is not independent of the lug or the frame's takedown pin. If you had to remove material from the barrel lug you'll need to do one of two options. Tig or braze material on the end of the guide rod (pin end) or remove material from the guide rods retaining shoulder. See the PDF link for details.

    Guide Rod Mod Illustration



  12. #12
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    Moving on to the firing pin itself, here is a link for diagrams and descriptions.

    AMT Backup 45 Firing Pin


    A trick to extend the pin length into the breech (first segment in illustrations), is to use a heavy metal wire gauge plate (plastic ones won't work). Using the firing pin, find the hole that fits best. Cut a piece of adhesive backed 120 grit and place it over that hole. Punch through it from the back side, then mount the firing pin on a drill and place it through the hole from the grit side (of course). Hold the plate square to the drill and grind away. You'll need to change the paper a few times but it'll eventually get to where you want it.

    Did I mention baby step fit tests?

  13. #13
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    Couple of pics...

    Guide rod after cutting shoulder:



    Completed slide to frame fit:

  14. #14
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    More shooting to report. This time with the Speer Lawman 230gr ball. Perfect. Rapid firing is much better with the lighter trigger. No light strikes and cycling is smooth and consistent. I'm amazed that this little powerhouse is fairly easy to handle, especially when using one of those rubber slip on grips.

  15. #15
    motopotamus is offline Junior Member
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    Quote Originally Posted by rustygun View Post
    There are manufactures who make guns that you can unbox clean and lube, Shoot without any trouble, clean and lube, shoot again.
    The hell you say

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