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Old July 10, 2013, 02:29 PM   #1
Machineguntony
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Using a powder charge below published data on a machine gun

Today I called up one of the dealers who sold one of my NFA guns to me.

Here was his advice, which I am not sure of, and I wanted people's opinion.

I bought an MP5, and the dealer said that all NFA guns are 30+ years old, and one day will be 100 years old if properly taken care of. Also, because these guns are machine guns, and are subject to higher amounts/volume of fire, he advised to preserve the gun and prevent wear an tear, to shoot the lowest pressure that will cycle the gun reliably.

He said start with the minimum load data, and reduce by 1/10 of a grain until the gun starts to not cycle, then use the grain count that last reliably cycled the gun.

This sounds a bit iffy to me. First, wouldn't it be dangerous to go below the published powder specs? Does shooting really stress the entire gun? I understand some parts have a limited lifetime of use, and then can be replaced, such as the barrel or the bolt assembly, but is this also true of the lower (which is the part legally considered the gun)?

As to going below the powder specs, my fear is that on a machine gun, especially if it is silenced, so that there is more backpressure, a bullet gets lodged, due to insufficient energy to push the bullet past the barrel, but the case is ejected and next round is loaded. The next result must then be a kapow to the face and a trip to the hospital.

Lastly, is it possible to have a squib that results in a bullet being lodged in a barrel, yet there being enough pressure to eject the case and cycle the action? My guess is yes because it appears (again, I'm merely speculating) that there would be less force required to cycle the action than to expel the bullet from the barrel. Anyone have any data on which requires more energy/force?
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Old July 10, 2013, 02:40 PM   #2
JD0x0
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Most submachines guns (ex. MP5, M10) are designed to run with +P+ ammo, they tend to cycle better, and on a full auto weapon, it also tends to increase the cyclic rate, aka rate of fire.

In WW2 some of the Japanese MG's and sniper rifles used "reduced pressure" ammo the purpose was mainly to reduce muzzle flash, although it probably reduced the amount of barrel heat in the MG's.

I doubt reducing powder charge will add significant life to a weapon, unless you plan on dumping huge amounts of rounds, in a short period of time, where the barrel could potentially overheat. The weapons were designed to be run hard, and they were built that way. Most older MG's have barrels that are able to be swapped out quickly. The German MG42 would unleash hundreds of bullets until the barrel was ruined, it would be swapped out in a matter of seconds, and continue dumping rounds toward the enemy until the next barrel needed to be replaced.
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Old July 10, 2013, 02:43 PM   #3
Buffalo444
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No, data, but when an ammo dump or other ammo storage facility catches on fire, it is casings that start flying everywhere, not bullets (bullets weigh more than casings). However, one would believe in order to properly cycle the action, it would take a force equal to or greater than the force needed to fire the bullet in order to cycle it (or it wouldn't be a very good gun). While I do think *in theory* the advice he gave had some merit, I would just stick to shooting plain target/surplus ammo, no fancy +P+ stuff. I know you should be able to have 99% of the stuff on your gun replaced/repaired easily enough, and receivers *can* be welded back together and you can have a normally functioning firearm again.
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Old July 10, 2013, 04:03 PM   #4
boondocker385
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I don't know about the suggestion, but my friend reloads for a Thompson (full auto) and loads them within published data with no issues. He has over 20k rounds through it.
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Old July 10, 2013, 04:16 PM   #5
Slamfire
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Quote:
I bought an MP5, and the dealer said that all NFA guns are 30+ years old, and one day will be 100 years old if properly taken care of. Also, because these guns are machine guns, and are subject to higher amounts/volume of fire, he advised to preserve the gun and prevent wear an tear, to shoot the lowest pressure that will cycle the gun reliably.

He said start with the minimum load data, and reduce by 1/10 of a grain until the gun starts to not cycle, then use the grain count that last reliably cycled the gun.

This sounds a bit iffy to me. First, wouldn't it be dangerous to go below the published powder specs? Does shooting really stress the entire gun? I understand some parts have a limited lifetime of use, and then can be replaced, such as the barrel or the bolt assembly, but is this also true of the lower (which is the part legally considered the gun)?

Considering an MP5 is a 9mm auto gun, even though I have not seen one, I doubt you will ever crack the receiver, which is the registered part, with standard pressure loads.

But, in the main, the guy makes sense. Everything is built to a designed fatigue life. Well, most everything. Portable small arms are going to be built to a light duty life, so you can expect that after enough rounds, something is going to crack or fatigue. Fatigue life is directly related to the amount of stress put on a metal object. The more you bend it, the shorter the fatigue life. Whatever the part, it will be something that is load bearing. In AR’s you shoot an AR long enough you will get cracked bolt lugs. You shoot a M14/M1a long enough and you will crack bolt lugs and crack the rear end of the receiver. The bolt rebounds off the receiver heel and given enough hard impacts (under 10,000 rounds) the sidewalls of the receiver crack. I have been told the life expectance of the M92 aluminum frame is around 35,000 rounds.

Given that few firearm parts have an infinite fatique life, cutting loads is a great idea to increase the fatigue life on everything. The less pressure the longer the life. Just that simple.


Quote:
As to going below the powder specs, my fear is that on a machine gun, especially if it is silenced, so that there is more backpressure, a bullet gets lodged, due to insufficient energy to push the bullet past the barrel, but the case is ejected and next round is loaded. The next result must then be a kapow to the face and a trip to the hospital.
You can use fast powders in your 9mm, such as Bullseye or W231, and I really doubt you will ever have the situation where the pressure functions the gun but does not expel the bullet. Now if the action does not cycle, then maybe something is stuck in the barrel, but I can’t believe a powder charge with enough pressure to cycle the action reliably, (in a blow back by God!) will stick a bullet.

I would be interested in hearing if this has happened to someone.
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Old July 10, 2013, 05:12 PM   #6
jmorris
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My minor loads for USPSA/IDPA will run in an MP5 but not the MP5SD, the ported barrel bleeds off too much gas.

They are built like a tank, don't worry about ammo killing them (unless you load squibs or doubles).
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Old July 10, 2013, 10:25 PM   #7
BuckRub
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I've also shot MP5s that were 10 MM. I wouldnt shoot reduced loads.

Last edited by BuckRub; July 11, 2013 at 05:19 PM.
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Old July 11, 2013, 10:54 AM   #8
oldpapps
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I don't have a 'full auto'.
I do have classic and vintage (some very vintage) weapons.

My (useless and very opinionated) view is that I want to be able to shoot that old beast for a long time. To do this, I specially load soft wimp loads that are far from being taxing on the weapon. Example: Marlin .38S&W, 5 shot top break revolver. This is an 1880's black powder weapon. I won't even fire factory .38S&W stuff. Is this weapon anything more than a curiosity? A very light loading of 231 under a lead 9MM 124 grain bullet (don't look for accuracy with a bullet that is .005 undersize). This is an extreme, but you get the idea.

I agree that for 'just play time' shooting, lightened loads that function the action would be in order.

I also don't think that a listed 'Maximum load' is a challenge.

Load with care and enjoy,

OSOK
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Old July 11, 2013, 11:18 AM   #9
Jim Watson
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Quote:
Lastly, is it possible to have a squib that results in a bullet being lodged in a barrel, yet there being enough pressure to eject the case and cycle the action?
This has happened. It is extremely rare, to the point I do not worry about it in semi-autos, but in a full auto, it would be very destructive. Low probability, high consequence.


There is a risk attendant to reduced loads in full autos, especially open bolt designs.
It is quite possible to have a load which will cycle the bolt far enough to pick up and fire the next round out of the magazine, but not far enough to sear up. So it won't quit shooting when you let off the trigger and you have a runaway gun until it empties the magazine or jams.

Some guns are more tolerant than others. A friend had a Thompson that would function properly on midrange target loads, SWCs feeding, no runaway.
It had just enough recoil to hold the muzzle level, no climb. You could hold it with one hand and it would fire at a low cyclic rate, chug, chug, chug, holding itself level and on target. But that was a lucky combination of gun and ammo. I would not count on it.
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Old July 11, 2013, 06:06 PM   #10
AK103K
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I owned and regularly shot an MP5 for almost 30 years, and never fired a single reload out of it. Lots of commercial standard, +P, +P+, and a lot of NATO and military surplus from a number of countries, including a good bit of "SMG" rated ammo. While I dont have an accurate count, I can pretty much guarantee you, the number of rounds through it was in the six digit range. We shot "cases" through it pretty much every weekend, for most of the 90's.

In all that time, the only thing that ever broke, was the roller retainer on the bolt. I did have to have the bolt carrier welded up (hard weld) early on, because Flemming didnt do it when it was converted, and a timing issue developed. Vollmer did it for me in the early 90's, and it was fine after that.


I also had a SWD M11/9mm and it didnt farewell with the "hot" stuff, but once the upper was replaced, it too went another 25+ years without a hitch, and it actually had more rounds through it than the MP5. The MAC did have a fair number of reloads through it as well, but probably less than 10%.

This is what a little under 2000 rounds of hot Spanish SMG ammo did to the first upper. The bolt knob also sheared off and had to be replaced. I stopped shooting any of the SMG rated stuff though it after this, but lots of NATO and +P without issue.



The replacement upper on the gun, which lasted another 25+ years.




Personally, I wouldnt shoot reloads in the MP5. The way they appreciated in price over the years, it wasnt worth having something go wrong trying to be cheap. My gun was one of the few that was a "registered receiver" gun, in which the receiver was actually the registered part. Unlike most of the later "trigger pack" guns, if something happened to the receiver, mine was done if it couldnt be repaired. I wasnt as worried about the MAC, but still felt it wasnt worth the bother (or risk), especially since ammo was plentiful and still reasonably cheap, up until just before Obama go in the first time.

One thing you need to keep in mind with the full autos is, there is a lot going on and quickly when you shoot them, and all it would take is a lapse of attention and one wrong move or decision due to turn it into scrap.
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Old July 23, 2013, 08:18 AM   #11
Slamfire
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I found the answer to my question here:

http://thefiringline.com/forums/showthread.php?t=524007
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Last edited by Slamfire; July 23, 2013 at 01:36 PM.
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Old July 23, 2013, 09:15 PM   #12
jmorris
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I trust my reloads much more than a lot of ammo that people buy. I have firearms that cost more than a few thousand dollars that have never fired a round that I did not put together.
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Old July 24, 2013, 03:05 PM   #13
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There are some local guys here in town that load all their 9mm for use in full-auto guns with lighter, 95 grain .380 bullets... mostly because they can get the .380 bullets for less dough. In some droughts (like this nasty one), any component that is compatible with 9mm but isn't 9mm is also likely to be easier to obtain.

I've never thought about the intangibles of loading for a fully automatic gun, but I can see where it does introduce new concerns. The idea of sending another round immediately behind a failed one is a very obvious concern that just never occurred to me. I can certainly see why you started this conversation.

As much as I absolutely LOVE firearms and consider myself knee-deep in this hobby and lifestyle, I can't generate interest in full-auto no matter how hard I try. Between the all-too-strict Federal hoops and the crazy market for the guns themselves (not that I blame those in the market, it's simply supply & demand) and barely even touching on the expense (and/or time, to us handloaders) in feeding them, I don't believe I'm making any kind of bold prediction when I say I'll probably never own one.
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Old July 24, 2013, 09:25 PM   #14
jmorris
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I understand that sentiment. My mother in law was there at one of our machinegun shoots the day after the 4th of July.

She asked "what was the point?". I just told her that 15 people were doing nothing more than firing about $2000 less "fireworks" off and having more fun than watching them blow up in the air.

That and the fact that very few can do it makes it something that folks want to do.

Look at it this way, can you say your kids Grandmother has ran a full auto?
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Old July 24, 2013, 11:30 PM   #15
Sevens
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Haha, I *almost* can. I can tell my girls that their Grandmother has run government issued, government property M16A1 and M16A2 rifles at 200 and 300 yards on the Viale range at Camp Perry. Unfortunately, she ran them one round at a time, in semi-automatic fashion, but these were taxpayer owned select-fire rifles. And the earlier ones didn't have a 3-round burst option, IIRC. Hydramatics, H&R, Colt and others.
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