MAC went auto today...

[COHIBA]

while shooting a MAC today, open bolt M11 made by RPB, the thing ran a burst of about 3-5 rd.s.
it went so fast i couldnt tell how many, just a kind of bang,bang, buuurrrp. 1st time it has ever happened. the gun is a semiauto and has never had anything done to it. its a 1 owner gun that was bought NIB in the early 80's.
any idea what happened?

[SDC]

Open-bolt guns are susceptible to this sort of thing with inconsistent ammo (usually reloads); if the ammo you were using wasn't powerful enough to push the bolt back to its full "open" position, the sear can't catch the bolt, so you get "BRRRP". Another possible reason is a build-up of crud on the sear or the sear support pin; if the sear can't freely rotate to re-engage the bolt after each shot, the bolt is just going to "run-away", and dump every round until the sear DOES catch it. HTH.

[COHIBA]

i was using factory fiocci ammo. i am cleaning the gun now and looking for problems but dont see any. this gun isnt one of those rattletrap gunshow macs. it has had less than 500 rds in its life 100 of those were today. do you have a link to an exploded pic or scematic so i can see what parts your talking about.

[Pappy John]

I don't have an intimate knowledge of the innards of the Mac, but I've seen it happen in the past with a friends weapon...on an indoor range...stitched a line up the ceiling. :what: Can you say "roof repair"?:(

[Topgun]

uh....what's the.....exact......reload recipe to avoid in order to make sure it doesn't go full auto?

:evil: ;)

[COHIBA]

the mini mac .380 has a cylical rate of 1600 rpm. that equates to 26.98376843595984734 per second. how did your buddy even get off paper before the mag ran dry. i was shooting at an ammo box and tore it up before the bolt caught. i didnt even grasp what had happened till i heard the brass hitting the ground like it was dumped out of a cup.

[Hkmp5sd]

how did your buddy even get off paper before the mag ran dry

I have a Cobray M11/9 with a cyclic rate of 1200 rpm. Thats a 32 round magazine in about 1.5 seconds. If you aim it at the bottom of a full size silhouette and fire the entire magazine, everything after the 3 round is anti-aircraft fire. If I attach a foregrip, about half the rounds hit the silhouette before I'm shooting clouds. Using a suppressor, I can drill the entire magazine in COM.

If you were able to hold your semi-MAC on target when it went full-auto, it makes it sound even more like you were shooting some weak cartridges.

[COHIBA]

it is very mild to shoot. that may be due to the fact that it is only a .380. the fiocci ammo has never seemed weak in any other cal.
i was using the fake suppesor at the time and shooting from a carport at a ammo box about 15 feet away.

[Jim Keenan]

In addition to the other possibilities mentioned, wear on the sear or the sear notch on the bolt can also cause the same thing to happen.

Jim

[COHIBA]

jim, i dont think that the little bit that the gun has been shot would cause that kind of wear.

[Jim Watson]

I would be more concerned that the BATF would consider it an unregistered machine gun. I recommend getting it fixed pronto or scrapping it discreetly.

[COHIBA]

i really dont see that as a problem, but, thanks for your concern.

[standingbear]

give harvey a call on the phone,he can sell you(QUALITY) replacement parts and perhaps enlighten you somewhat on the rpb macs.he will talk you arm off,hes a good guy.its a good idea to fix your open bolt for safty reasons too.

[AK103K]

Is it possible that its just dirty and/or over lubed? My old AR7 used to give 3-4 round bursts pretty regularly when dirty. I'd clean everything real good and look for wear or something out of place, there may be a broken part.

[denfoote]

I would be more concerned that the BATF would consider it an unregistered machine gun. I recommend getting it fixed pronto or scrapping it discreetly

i really don't see that as a problem, but, thanks for your concern.

I think now that you have admitted on the open internet that you do indeed possess an unregistered full auto weapon, you had better put this closer to the front burner than you seem to be doing!! Even if the weapon legitimately malfunctioned, it will be up to YOU to prove that when the ATF agent comes calling!!!! BATF's position will be that you illegally modified the weapon. Say bye bye to all your other guns when that happens!! :rolleyes:

I'm sure they monitor these gun boards!! ;) Crushing it before they get to your door is indeed an option!! :(

[Jason Demond]

Man, some guys get all the luck!:(

[COHIBA]

you know i think i even posted my address on this site along w/ my phone # and fax.
if you will read a bit closer i dont think i ever said this was my MAC.

[yankytrash]

denfoote, Jim, others thinking about destroying perfectly good examples of weapons just because it's glazed with old coagulated oil -

that's not how it works. Sorry to burst the internet-tripe bubble people've been inflating, but it's just not. I know from two occasions of personal experience that they are more helpful than most local smalltown sheriffs, and many others with daily dealings with the ATF can tell you the same.

They're not after Joe Shmuck (nothing personally aimed at you Cohiba :D ) with a broken pistol who's honestly trying to fix it, they're after the bigger boys that're possibly letting those "broken" guns onto the street. Sure the entire organization is just plain wrong, but for most of the ATF employees, it's just a job.

Hell, the ATF actually helped me get some "assault" weapons back from a local sheriff seizure, even though drugs were involved. If you believe in black helicopters, you probably won't believe that.

"Oops, G17 went full auto, don't know how to fix it and better not ask. Let's mash it under the truck tire as we're peeling out of here..."
"Uh oh, FAL's sear and hammer are worn and it went full auto. Don't have the money to have a smith replace them, and better not ask nobody, so let's chunk it in the river."
"Oh well, my grandfather's WWII Reming Rand 1911 went full auto today. Don't know a dang thing about 1911 trigger groups, and better not ask anybody, so let's go throw it on the chop box."

:rolleyes: Please.

[Hkmp5sd]

yankytrash,

'bout time you showed up around here. You been hiding or on vacation? :)

[yankytrash]

Naaa, the huntin bug bit me in the butt so hard I never thought I'd break free from my blood-thirsty coma. Found out that my eyes were gettin messed up from staring at TFL all day/all night, so I had lay off the net for awhile. When the battle is between big bucks/fat turkeys and the internet, I had to drop the net.

The shock I was in for when I came back to TFL and it was closed!:what: Thought I lost y'all. Spring Gobbler ain't for another month, and apparently IPSC shooters are afraid to get wet, so I can stare at THR a little while longer before my next disappearence...:D

[Jim Keenan]

As long as someone raised the issue, I thought BATF had seized those open bolt MACs long ago. They put out a notice in all the gun magazines to turn them in to avoid possible prosecution, as they were considered "readily convertible" to machineguns.

As to a gun accidentally going full auto due to wear or whatever, BATF is not concerned, they will tell you to get it fixed, that is all. Now if you deliberately altered the gun with the intention of making it full auto, that is another story.

At one time, I doubted that ATF or any other LE agency monitored these sites; today, with all the terrorist scare, I am not so sure. But it will always do well to remember that maybe 500 million people can read what you say here, and not all of them wish you well. Posting on a site like this is not like chatting with friends; it is like going on Larry King Live with a megaphone.

Nuff sed.

Jim

[SouthpawShootr]

They put out a notice in all the gun magazines to turn them in to avoid possible prosecution, as they were considered "readily convertible" to machineguns.

Gosh, I hope not. I still see these things from time to time on Gunbroker.com and other auction boards. They're usually ridiculously expensive and the seller makes a point of saying that the gun is legal and was made before production was halted. I've never seen notices to turn them in, but then again I was in high school during the early to mid-80's and was pursuing other interests. :D

I have read time and time again that ATF did prohibit new manufacture of these guns because of the reason you cite. But my impression was always that earlier manufactured guns were grandfathered.

I have a regular plain vanilla closed bolt SWD M11 semi. I bought it just to have, because the price was good, and pre-bans in decent shape are getting fewer and farther between.