Gun ''MTBF'' - relevant?


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P95Carry
July 21, 2005, 10:47 PM
HDD's in puters usually have a figure for MTBF - Mean Time Before Failure - measured naturally in hours.

I wonder tho if there are any figures for our guns - measured here in ammo thruput. I know some rifles utilizing hyper velocity rounds will maybe have a barrel life of 2,000 rounds let's say but leaving those aside, what about our ''Regular Joe'' guns??

Cheap will often one can imagine yield a lower figure - maybe a Lorcin would not pass the 100 round mark! But consider every day fair quality items - good 1911's, 92F's, SIG's, BHP's, CZ's etc, then good qual' revo's as well, for handguns .... and say regular rifles like 700's M77's - average hunting stuff. Maybe even add in actually shotguns, which get hammered by clay shooters.

It is unlikey we will see much problem with the rifle category as thruput might be actually fairly modest (leaving the semi's such as SKS and AK) but handguns, well - many of us put huge ammo quantities thru - in the multiple thousands.

So - what are your thoughts as to a ''gun MTBF'' on average? Let's think mainly handguns. What would you expect, assuming adequate maintainance and ignoring random breakage - for reliable longevity? The stage when a gun is past useful.

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Third_Rail
July 21, 2005, 11:01 PM
The military conducts tests that include mean failure time, etc. Interesting reports.

NMshooter
July 21, 2005, 11:55 PM
From personal experience the H&K USP .45 is only good for the advertised life of 30k rounds.

Typical .357 magnum revolvers usually develop cracked forcing cones at about 5k - 6k (with factory jacketed .357 ammo), which on a crush fit thread barrel means you throw it away at that point.

A quality 1911 should last 50k before any parts breakage, the slide should last about 80k, and the frame 150k.

Typical sidearms can be expected to last between 20k and 50k rounds.

Supposedly my 9mm Glock will outlive everything else, but I have a lot of shooting to do before I have proven that to myself. :)

But I think MTBF includes both breakage and failure to function, so you are probably looking for completely different numbers.

I am no expert, so YMMV.

heypete
July 22, 2005, 01:41 AM
It depends on what kind of failure. Castastrophic failure? Probably not very likely with most modern-production guns.

Various bearing parts (barrel, sear, etc.) wearing out? Probably after numerous thousand rounds.

I've shot about 7k-10k through my Glock 19, ranging from Speer Gold Dots to the dirtiest of Wolf ammo. Bore's still bright and shiny, with only minimal wear marks. The only minor failure that happened was that the take-down lever and spring spontaneousy fell out, necessitating a purchase of $8 worth of parts (as opposed to $30 parts/labor from the local armorer -- I can DIY way cheaper).

Most quality guns are over-engineered, and probably will outlast you. I look at the new M1 Garand that the FedEx guy just delivered today, and I think I'll be able to give it to my grandchildren...and I'm only 22 now, unmarried, and without children. :)

No_Brakes23
July 22, 2005, 02:56 AM
The military does this with various forms of Ordnance.

For instance, the barrels on the AV-8B's 25mm GAU-12 are only rated for 5,000 rounds before they get chucked. (That's about 84 combat sorties assuming it expends all 303 rounds each time, so it isn't as short as it sounds.)

But A/C guns are carefully monitored, I am not sure how the service life of rifles and pistols is determined.

Moonclip
July 22, 2005, 03:41 AM
I had a commercial Bulgarian Makarov and the manual said it had a barrel life of 4000 rounds I think but I feel this is low and too hard to place. Too many variables such as how fast rounds were shot, did gun cool off? Or type and construction of bullets.

In seeing what worked and what didn't at an indoor range rental case GP100's were the durability champs and Beretta 92/96's were constantly breaking locking blocks and the occasional barrel,frame or slide cracked.

Glocks broke trigger springs and the occasional slide and 1911's generally did ok but for a cracked slide or frame now and then.

If people choose to flame me or not believe me so be it but anyhow I would not be too worried about it anyways. I'm not a big Beretta fan but if I spotted a 92 or 96 Beretta at a good price I would still buy it as I will not put as many rounds downrange as a rental gun and I will care for them better and the guns would not be fed commercial reloads as many ranges use.

When I told a Glock representative about the problems she immdiately got defensive saying the ammo was at fault, maybe so, but all the range guns were fed the same ammo, an even playing field and it was all copper plated and the Ruger P series guns while not glamarous never developed a cracked anything.

Zak Smith
July 22, 2005, 04:03 AM
MTBF = Mean Time Between Failure

MTTF = Mean Time To Failure

MTTR = Mean Time To Repair

MTBF = MTTF + MTTR

Availability = MTTF / (MTTR + MTTF)

Siewiorek & Swarz, 1992.

Proper definitions are important.

mfree
July 22, 2005, 09:22 AM
CZ's P01 is expected by NATO to exceed 30K rounds before failure, which likely means it'll last *much* longer than that. Looking at the quality of the steels and design involved, I'd believe it.

Tom C.
July 22, 2005, 10:59 AM
These numbers also translate into something else: probability of mission completion. In an combat aircraft, we were looking for a 95% reliability to complete a 1 hr. 45 min. flight with no failures, or about a 30 hr. mean time between operational mission failures.
With a handgun, I would be looking for a 99.9999% reliability to complete a combat fire mission, i.e., shooting an adversary to save my life or that of a family member. Would be interesting to see what that works out to as a round count between failures. The Army has numbers for things like this. This is where the requirements for the 9mm handgun came from.

entropy
July 22, 2005, 12:37 PM
Again, there are too many variables involved. Is an FTF/FTE a failure? Then I think 100 rounds is way too high for a Lorcin! :D The slide cracking apart and flying back in your face on an M92FS/M9? Depends on the ammo.I personally wouldn't worry about it too much. Far more failures occur because of operator headspace and timing than any other cause. Weapon quality, then ammo quality are the most determining factors, then operator headsapce and timing. If you are in the habit of leaning on you rifle with the barrel in the dirt, your MTBF will be very short, as will probably your lifespan. If you don't bother to check whether that squib load made it out the barrel, ditto. Did you check for spider nests down the barrel of your Remington 742 before you dragged it to the range the day before opener? Are you a homie who put some .38 +P+'s into the cylinder of an aging RG sunbbie 'cuz da +P's izz da bom, man!' There are just to many variables involved to get an accurate fix on the 'Average Joe's Gun's MTBF' ; the Military does exhaustive testing in a lab first, then on a Ransom rest or vise to destruction, then let trained operators abuse the weapons long before the average troop get his hands on one.

P95Carry
July 22, 2005, 03:13 PM
Zak Smith - thank you - indeed I was probably using MTBF a bit euphemistically!

Thx for replies - I am mainly considering shall we say (throw it away) catastrophic failure - when a gun becomes non-functional/useless and maybe not even economic to repair. Only really going for a ''feel'' of opinions here.:)

There is of course a middle ground too - even including a temporary failure due to something as simple as a worn mag, excessive crud - I am ignoring those.

jwmoore
July 22, 2005, 04:22 PM
heypete said: Glock 19... The only minor failure that happened was that the take-down lever and spring spontaneousy fell outI had that same failure at about 4500 rds, in the middle of a SIG forum shoot. Spring broke right in half. Needless to say, people weren't impressed. :D And I now have a complete set of springs in reserve.

~W

30Cal
July 22, 2005, 05:35 PM
Reliability predictions for mechanical things are generally based on limited historical data for generic part types or margin of safety can be used. In either case, it isn't very good.

Actual data from testing isn't very good either unless you have a statistically significant number of test samples (which would be crazy expensive for firearms).

Also very important are test conditions and how they equate to the actual world. A poorly designed test is worthless.

Rel predictions and testing for electonics is pretty good, especially for commercial parts where the ambient environment is almost always 70F and flourescent.

Ty

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