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Setback on .40

Discussion in 'Cop Talk' started by Aux Bear, Oct 1, 2012.

  1. OK, I'm an Aux. Deputy and have never fired my duty weapon on duty. Years ago, when I started on the force, we fired and re-qualed with the prior years duty rounds and now we use fresh target rounds. I've read a lot here about bullet setback and the related hazards of rechambering a round repeatedly. Well I'm now in year 3 of carrying the same duty rounds and even with due diligence of rotating rounds in the mags I think that by now I've gone through at least one rotation on every cartridge. Anyone ever check their rounds for setback? Anyone know what the minimum O/A length should be? I'd like to check my rounds and see if I've exceeded the safe minimum. Hell, I'm about ready to chuck the whole 100 rounds (G22 & G27) and just purchase new on my own dime. It would be nice to at least fire them off for target use provided that they are safe to fire.
  2. Pete7072


    Aug 23, 2012
    We shoot our duty ammo that is in our magazines and our weapon when we qualify. We do this to avoid bullet set back. There is a chart in our range with 5 bullets in the casing, and a number under it. The number indicates how many times the bullet has been chambered. As the number goes up, the bullet is pushed further down into the casing. I will try to get a picture of it to show you. We qualify twice a year. I never re-chamber the same round twice. When I unload my duty weapon, I move that round down to the bottom of the magazine. I don't unload my duty weapon often, but that's what I do when I do unload it. I also rotate my magazines. Call me crazy... I guess.

    Your ammo should be fine, as long as the same rounds did not keep getting re-chambered. When you re-chamber a round, the ramp pushes the bullet back into the casing, after a certain amount of times, it will push it back so far, that the round is unusable. Neighboring departments have a barrel in their locker room . You point your weapon at a pile of old body armor, un-chamber, and leave the round in the barrel. You should definitely speak to your department about getting an extra box of duty ammo for this reason. They issue you it, they should pay for it.

    Last edited: Oct 1, 2012

  3. Paul53

    Paul53 Geezer Boomer

    Nov 27, 2011
    You should be able to get the specs by searching the web for your brand and specific round. I'm clueless as to how much setback becomes a problem. Do you have a tool to accurately measure the length of the rounds? It might be cheaper to buy one than replacing all your ammo.
  4. collim1

    collim1 Shower Time!

    Mar 14, 2005
    For a duty I would shoot your duty ammo and replace atleast once a year, twice a year would be better.

    Cheap insurance.
  5. razdog76

    razdog76 Heavy Mettle

    Sep 26, 2007
    Pressure is not something to mess around with!

    I unload my duty weapons very rarely to prevent this. If you have a level surface, you can stand all of the cartridges up and see if any are shorter by laying a straight edge on top.
  6. blueiron


    Aug 10, 2004
    The .40 round is very sensitive to set-back and I am convinced that an early Glock 22 I was issued instantly achieved entropy because of it.

    There is no magic distance that I am aware of at which one round becomes dangerous.

    Shoot up your ammo every year and get fresh rounds. Even if you have to buy them out of your kids' college fund, it is cheap insurance.
  7. I spent years making a living measureing parts. I have the precision tools needed, I just need the minimum number. I too have stopped unloading my weapon every time I put it in the safe. I had the habit of the mags and rounds in one safe and the weapons in another. Now the loaded duty weapons go in a single container. I have teenagers in the house and they are weapons schooled, but, I would be negligent if something happened while I was out. Unlike a "Regular" I pull details mostly on weekends and the special occasions and then there are the emergencies. So, my weapon use is impossible to predict. I did just over 80 hours each of the past 3 months and that may jump or slump as the needs of the county vary. Just reading the information here has me concerned about the possibility of me actually needing my weapon only to have a significant issue due to setback and me and or my partner paying a price. Thanks for reinforcing my concerns.
  8. blueiron


    Aug 10, 2004
    Minimum OAL is one thing, but attempting to predict the pressure maxima at a given point of set back, along a specific propellant burn curve is almost impossible without a Mann barrel, strain gauges, a universal receiver, and test instruments.

    It does seem anecdotally that the heavier 180 grain bullets have a distinct numerical representation in pressure incidents with the .40 cartridge.
  9. Pete7072


    Aug 23, 2012
  10. frizz


    Jul 6, 2012
    You are smart to be careful with this, especially with the high-pressure 40S&W.

    When you find the minimum O/A length for the specific brand and cartridge you have, a caliper is a snap to use.

    You can get a decent caliper for ~$30 shipped. That way you can check your new ammo if you want.

    I think when you have the slightest doubt about the safety of a round, you MUST ditch it 100% of the time. (With the 40SW, 200% of the time.)

    100 rounds of top-notch ammo is about $110 mail-order if you have to foot the bill, and that's worth it, in my opinion, to avoid the low low low risk of a ka-boom.

    Good luck, and may you never have to fire unless you are at the range.
  11. I have 4", 6". 12" and 24" calipers and Mics from 1" to 6". I made a living with them for years. Measurement isn't the issue. The "quick" question was what the majic minimum O/A length is. I want to check each of my rounds. The ones that I found set back I'll discard and the others I will test fire at paper. Haven't fired a Winchester Ranger through my weapon in years and would like some confidence that it will still feed them. (That's our prescribed/designated duty round and we cannot carry anything else.) I'm a IL certified firearms instr. and put 3-400 through my weapon every other week. Dept. furnishes WWB for training. Thanks to all that replied. I'll head down to my cop shop tomorrow and pick up a couple hundred Rangers.
  12. Ship A'Hoy

    Ship A'Hoy Trigger Control

    Feb 11, 2006
    My G22 stays loaded with Speer Gold Dots 180gr unless I'm going to the range. I will take the chambered round and put it in a seperate box. Once I have enough cartriges in that box of one-time chambered rounds I will fill a magazine and never chamber those again. Seeing that I practice almost once a week it takes me 45 weeks to go through all my carry ammo. I only do this for my G22. I'm not so concerned with my G21SF.
    Last edited: Apr 2, 2013
  13. old_pigpen

    old_pigpen Huh? What?

    Nov 4, 2007
    In a house
    Guys, thank you for this thread! I wasn't aware of the setback problem affecting the .40S&W. After 20 years of carrying 1911s, I bought a .40 M&P last year in preparation of rejoining my SO's reserve program. I haven't shot them, but I know some of my .40 round have been rechambered several times. I'm going to check them out today with a caliper.
  14. Java Junky

    Java Junky

    Jul 3, 2012
    Bear, I'm no expert, but wouldn't buyin'a box'a new Winchesters for a control measurement give you the numbers you need?
  15. The problem is that the OAL will vary between manufacturers, type of bullet, and even lots. Not to mention every round will have a slightly different OAL due to the way they're loaded. There just isn't a way to accurately gauge them after any kind of setback, you need the OAL from before you suspect setback.
  16. razdog76

    razdog76 Heavy Mettle

    Sep 26, 2007
    Hence I suggested comparing them with a straight edge. :thumbsup:
  17. So what # does a reloader use? They have to have a min. / max. O/A length that they work too. Maybe I should post this in the reloading forum......
  18. If you consult the manufacturer, they should be able to give you that information.

    A quick search shows that recommended min/max OAL is 1.085"/1.135" for .40

    However if your duty ammo is 3 years old, it should be replaced. Will it work, probably... but I would rather be safe than sorry, especially since a box is about $50.
    Last edited: Oct 2, 2012
  19. razdog76

    razdog76 Heavy Mettle

    Sep 26, 2007
    In this example, the force used to chamber each cartridge is unknown, multiply that by the number of cartridges. Now, if they each have been chambered several times, there are a lot of variables in this equation.

    Just to throw in another complexity, when I get new duty ammo, I visually inspect, and hand cycle each from the magazine to ensure all cartridges will chamber.