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How many rounds to test reliability?

Discussion in 'Handguns: Autoloaders' started by PPS43, Feb 6, 2011.

  1. PPS43

    PPS43 New Member

    Jan 3, 2011
    I often hear the advice to train with FMJ and carry JHP. It is usually followed by recommendation to shoot just enough JHP to make sure the gun feeds them reliably. But when I do the math to figure out how many JHP that would be, I'm getting a very large number.

    Let's assume 0.2% stoppages (carry gun should be reliable, right?). The rule of threes says that "Given no observed events in n trials, a 95% upper bound on the rate of occurrence is 3/n".

    So it looks like I need to shoot 3/0.002 = 1,500 rounds with no stoppages in order to be 95% confident that the rate of stoppages is no more than 0.2%.

    Even to get 0.5% I still would need to shoot 600 rounds, and 0.5% is already crappy reliability in my opinion.

    How many rounds do you shoot before concluding that the gun feeds them ok?
    Last edited: Feb 6, 2011
  2. rellascout

    rellascout member

    Dec 22, 2004
    I personally shoot 500 to 750 rounds of ball ammo out of a would be carry gun to test basic function and reliability. I then will shoot 100 rounds of the JHP of my choosing. If it chokes on these I move on to the next JHP of choice. Rinse and repeat.

    Needs to feed 100 round without a hiccup before it goes on the belt. I then fire another 50 rounds every 3 months assuming there have been no stoppages with the ball ammo.

    I also try to shoot the same grain ball ammo that I am shooting JHP. For example 230 gr 45 ACP or 124 gr 9mm.

    Nothing really scientific about it but I feel confident what is on the belt is going to run if called upon.
  3. Bonesinium

    Bonesinium Member

    Sep 11, 2010
    Ideally, you would like to shoot as much of it as possible, and your numbers work out. But of course that is unrealistic. Money is a factor and we all can't afford to shoot infinite amounts of ammo. So here are my thoughts.

    If my firearm is functioning properly without failures when shooting FMJ, then I know that it has the potential to function consistently without failures. If I test 100 rounds of a JHP, and it functions without failure, then it should hopefully function as well as when shooting the FMJ. Of course this in inherently flawed, but sometimes you just don't have the resources to do much else.

    So to answer your last question, I shoot 100 rounds.

    Is that enough? Not nearly as much as I would like, no. But until someone starts paying for my ammo, there it is.
  4. The Lone Haranguer

    The Lone Haranguer Elder

    Jul 30, 2006
    Johnson City, TN
    About 100 rounds of hollowpoints should establish reliability. If the gun truly has a problem, it will probably show up within the first magazineful.
  5. sarduy

    sarduy Senior Member

    Apr 13, 2007
    United States of America
    just get 4 boxes of FMJ and 2 boxes of the jhp you will be using.

    make sure you mix them in the mags also... if they all shoot fine, you are good to go.
  6. mongo4567

    mongo4567 Active Member

    Oct 3, 2008
    I consider 150 trouble-free rounds to be the minimum, at least 50 of them must be the ammo that I'm going to carry.
  7. wow6599

    wow6599 Senior Member

    Apr 6, 2008
    Wildwood, MO
    Just what I do - couple hundred FMJ and 25-50 JHP is good for me. But.....I also like Remington GS' as my JHP choice, and they seem to feed 100% of the time - in any caliber, in any gun. YMMV.
  8. cheygriz

    cheygriz Senior Member

    Dec 28, 2002
    High up in the Rockies
    To me, a reliable gun/ammo works under all conditions!

    I like to clean the gun, remove all traces of lubricant and shoot a minimum of 200 rounds without cleaning or lubing.

    If it passes, I thoroughly clean and lube the gun and feel comfortable carrying it with the test ammo.

    Why remove the lube??? Some gun/ammo combos will work very well in a clean, well lubed gun, but fail under adverse conditions. If it's a reliable combo dirty and unlubed, you can pretty much trust it.

    BADUNAME37 Senior Member

    Aug 10, 2008
    I've been known to take a new gun and shoot two or three cylinders of ammo and calling it good.

    That has been more in recent years due to the cost and (un)availability of ammo.

    Most all of my guns I have worked up loads for which inherently requires shooting a fair number of shots just to find which ones work best and are most accurate. On some occasions, that, in itself was enough for me to be satisfied that the gun will work when I need it.

    I typically clean a new gun very thoroughly, looking for anything that may be loose or any parts that may not be quite right. I had a brand new, just out of the box 642 that flung the cylinder rod the first time I opened it. Unfortunately, I had to send it back to S&W. I was a bit disturbed at those series of events which, in my opinion, should not have occured, especially on a gun that has technically never been shot (except for factory testing).

    It worked out well, as, while they had it, they did an action job that made every trigger pull of all five rounds smooth and equal in feeling. I can actually feel the separate processes going on as I am slowly pulling the trigger. And, the trigger is extremely smooth feeling. When the internal hammer drops, there is very little (if any) trigger play. They also chamfered the cylinder holes so my speed loaders load quickly. The chamfer is barely noticeable.

    All in all, I am satisfied with what they did for about $80 additional dollars.
  10. rellascout

    rellascout member

    Dec 22, 2004
    Wrong forum... look up it states Handguns: Autoloaders

  11. Doghandler

    Doghandler New Member

    Jan 15, 2011
    West Branch
    "Nothing really scientific about it but I feel confident what is on the belt is going to run if called upon."

    Do you load your own belts or do you have a Butler prepare your belt for you?

    like Batman

    just askin

  12. Shadow 7D

    Shadow 7D Mentor

    Nov 30, 2008
    Frozen North
    Well, it all depends on...

    YOU, how many rounds do YOU think it takes???
  13. schmeky

    schmeky Senior Member

    Mar 17, 2006
    West Monroe, Louisiana
    Some professional gunsmiths say 1,000 rounds with -0- malfunctions.
  14. Jaywalker

    Jaywalker Active Member

    May 28, 2003
    PPS43, I believe your calculations assume flawless ammunition, and while it's pretty good, it isn't that. In order to reach any confidence level, including 95%, you'd have to do it with the same lot of ammunition and magazine, as well, and for me, that's just not in the cards.

    There are two main parts of reliability - the firearm and the ammunition. For a new semi-auto pistol I'll shoot maybe 200 - 500 rounds of practice ammunition, to smooth the burrs and rough spots that come from today's manufacturing process. Then I'll buy 300 rounds of "duty" or "social" ammunition and expend 200 rounds of it in practice to ensure that lot works reliably. If it doesn't, I buy 300 rounds of a different make/lot and try that. If I like a lot and change lots (common, as I make subsequent purchases), I'll just function test it. It helps to avoid ammunition that has a poor feeding reputation, such as the 147 gr 9mm HPs.

    It's not perfect system, but I've been doing for 30 years, and it works for me. Also, I mark my magazines, and if failures happen, I toss the mag, and don't bother to try to fix it. Compared to ammo testing, magazines are cheap. FWIW.
  15. 451 Detonics

    451 Detonics Senior Member

    Jan 4, 2011
    I load a very wide 125gr semi jacketed hollow point in 9mm and a 200gr semi wadcutter in 45. If my guns will feed and shoot those two loads I know they will feed anything. I do run 50 or so rounds of DPX to make sure however but I have yet to have a gun fail to feed them.

    Of course carrying a revolver 90% of the time solves that problem nicely.
  16. Jim K

    Jim K Elder

    Dec 31, 2002
    I always recommend at least 200 rounds of the carry ammo with no failures. In other words, if a failure occurs at round 150, correct the problem and start the 200 over. And with an auto pistol that is 200 rounds with each carry magazine.

    There is no point in firing a bunch of ball ammo if that is not what you will be carrying. The gun needs to work with what you will use in it, not what is at home on the shelf.

    I know some will say 200 rounds is not enough; others will say it is too much. I consider it a reasonable compromise. I recognize MRBF and all that for statistical purposes, but a gun that fails on only one round out of a thousand is one too many if it is the first round. You will be too dead to care if the next 999 rounds would have worked just fine.

  17. Steve C

    Steve C Senior Member

    Jan 5, 2006
    On guns that I've had a long time that have had no problems with JHP's that I've hand loaded or bought I only run a mag or two through them when I pick up a new brand or offering of the latest JHP type available.

    I may shoot 6 rounds of a particular new revolver ammo type just to see where it prints but don't worry about feeding in a Revolver of course. All the testing is about giving you confidence. Its been my experience that if there's going to be a problem with a particular type of ammo it will show up in the first mag or two.
  18. sidheshooter

    sidheshooter Participating Member

    Dec 30, 2007
    I follow the Ayoob doctrine of 200 rounds of carry ammo, through all mags to be in rotation, with no failures. In my (limited) experience of things, all modern service guns in service calibers should easily sail through this requirement. Some of my 9s (Smith 3953 and 2nd gen 19 come to mind) have fired into the low thousands with no failures at all. I'm pretty sure they'll feed the next round too...
  19. Wags

    Wags Member

    Dec 4, 2004
    On the lake Ohio
    I thought the rule of thumb was 200rds reliably with what you carry/shoot the most? The more rounds the better I suppose before it's strapped to your hip for carry.
  20. earlthegoat2

    earlthegoat2 Senior Member

    Aug 28, 2008
    SE GA
    This is why I am amazed that people dont stick strictly with revovler for concealed carry. Just the purchase of one will save you a couple hundred or more dollars on function and reliability testing. Most all auto will have at least one jam in the first 100 rounds because of faulty ammo, bad shooting form, or just because you are working some of the kinks out of the gun.

    I think all the advice given is good adivce but I know most people dont do it. Many people on this forum may do it but the average CCer wont. I think the vast majority of CCers do not do an adequate test with their new firearms. Revolvers can jam up but it is whole lot less common. When they do jam it is for good though until you can get some tools.

    Just as with everything pertaining to carrying a firearm there are compromises that are going to be made. Maybe they are good maybe not so good. If I carried an auto I would put 150 or xxxx many rounds through it with one magazine and then if I carried a spare I would just load it up and carry it and take my chances if I ever needed a reload. Just me. Then again I dont know if I will ever be carrying an auto.

    I have heard a few gunsmiths say as few as 150 rounds on several occasions. If you take into account the myth and the legend of the "500 round gun break in" that companies like Kimber have promoted in one way or another over the years then you should not start your function and reliability testing until after this so called "break in"

    The truth is though is that "break in" is function and reliability testing.

    Im not a math wiz so I dont really understand your formula up there but all I know is that if my gun shoots 1 round and functions fine it is 100% on one round. If it shoots 99 out of 100 it is 99% and so on. It is more about feel with me. If I feel that my next round is going to fire and my pistol is going to function fine I will carry it then.

    My HK P7, which is well known for it flawless function, gave me a failure within the first 10 shots I fired out of it. I swear it was the fault of the ammo because the casing at the mouth tore and folded back on itself as it was being fed into the chamber. How reliable can you expect ammo to be then? I never had another failure in over 1000 rounds fired after that and since I am fairly certain the one failure was ammo related I was confident in calling it a 100% gun. Ammo on the other hand, not so much.

    Used guns can also play a part in function and reliablity testing. I tend to think guns with more rounds through them will be more reliable in future use. Not always the case, I know, so dont go there. Point is if I have a used pistol and I fire 100 trouble free rounds out of it, it is good to go for me.

    Bottom line is you have to test your gun with the ammo you are going to carry in it. Maybe we should all carry FMJ so we can practice with what we use more economically. I have done it before with my nightstand guns. I used a GI 1911 for years as a bedside gun and had it loaded with FMJ because that is all I ever shot out of it. I was confident enough with FMJ and 45 ACP that I sure did not lose sleep over my choice. I always had the snubby there too with 158 LSWCHP I could have reached for.

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