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View Full Version : OH MY GAWD!! I blew my face off!!


rezman
February 09, 2009, 22:55
Heh heh, not really.

rezman here, nearly famous (in my own mind) starter of threads in the DIY forum that end up in Dumping Brass.

Finally got my gas tube on friday, so I set about modifying my locking shoulder on a new to me rebarrel job. This build (DSA type 1 with ?? 18" barrel, pin gauged out out at .256 no pressure, .258 would not close on no go. I called it .257. .257 with a 1.630 no go = minimum HS, I wanted 1.632 so minus .002 = .255 LS. I had a .259 from my original DSA rifle.

Got my Starrett reloding mikes out, they have blade tips. Measured along the LS to verify .259 at three points. Got out the permanent marker, blacked up the face, chucked it into my vice, and went to filing. Filed until all black was evenly removed. Stop, measure, repeat. If you do this be warned the first two filings of the blackoff removed about .001 per. The last one took about .002 off.

It may well be true the metal under the face is a little softer. Took my india stone to polish face and recut a little of the bevel. I ended up about .254. HS should be 1.633.

Reinstall LS. Off to the foothill behind my house. One round in mag, chamber round, hold rifle out in front of my body while holding slightly over my head, and BOOM!

OMG!! I blew my face off!! hehehe, not really, but the possibility sure crossed my mind. I don't want a 50k psi bomb going off in front of my face.

Shot x 3, checked brass for issues. No problem I can see. New barrel locks open on empty mag at gas #4. Shoots a little low minute of rock at 250 or so, but I forgot my sight tool. Fired the rest of box to verify function. So far so good.

I'll be watching the LS/bolt lockup interface for wear.

rezman

Brush511
February 10, 2009, 01:33
Did you file the locking shoulder at 11 degrees or 12 degrees? :devil:

ggiilliiee
February 10, 2009, 07:31
a blade mike ????....no way ..ehhehe ....this may be a first .....hehe your ready for the 11.5 club .....:bow:

http://community-1.webtv.net/ggiilliiee/HOMESURFACEGRINDER/

ce
February 10, 2009, 09:36
Take is easy, Hambone, next time don't be so skeered.

Yer face is a Maserati, it's a Maserati face.

rezman
February 10, 2009, 21:46
gigglee and ce,

I appreciate the response and defer to your seniority here at our hallowed files, and am sure you both have a vast store of knowledge, but do either one of you ever post something that doesn't need to be run through babelfish for a queens english translation?

In plain english, am I going to shoot my eye out or what??

rezman

ce
February 11, 2009, 09:41
No, man, the inherent safety of the design has you protected as well as any device intended to contain an explosion.

There was a dude up in Rio Rancho that blew up a FAL last year, and he got hurt, but we were unable to determine the cause, but it was most likely that his locking shoulder fell out, and he somehow discharged it anyway.

Rapid Rob was involved in that mess, we just read about it here, but never got all the details.

Why do you think everybody always asks;

Is it safe?

Try asking that from 10 people today, just walk up and ask;

Is it safe?

Anybody, it doesn't matter, just get them wondering, and then maybe they'll ask 10 people, and pretty soon, someone will have an answer.

IS IT SAFE?

rezman
February 11, 2009, 10:06
Now that I can get my peabrain around.

Thanks ce.

rezman

ggiilliiee
February 11, 2009, 11:17
its good to give it a little respect ..ive seen a buddys gun blow ....pretty ugly ...if hed had his face next to it instead of your method hed be either drooling into a gimbal mounted chin cup while losing full controll of his bowwels into the wheel chair resivoir and babbling uncontrollably ...you know ...kinda like BUSH .....
.. ...or daid ...3-4 inch twisted rather pointy schard blew off the side of the receiver ...gruesome to say the least ...1/16 out of batt and BOOOOOOOM OH GOD ....I CANT FIND MY LEGGS !!!...I CANT FIND MY LEGGS .......RAMBO "72":tongue: ...

seroiusly man any one who has the brains to actually use a "blade mike " to check parralel ...is first page in my book .....wouldnt worry a bit about your build ....as there was some real thought put into it .....:beer:

rezman
February 11, 2009, 12:15
Ditto on the muchas gracias gggiilleee.

rezman

justashooter
February 11, 2009, 15:38
should be 13* on the locking shoulder angle.

chromestarhustler
February 11, 2009, 16:10
sad days when this gets posted in building and gunsmithing and its a thread that attracts some replys that arent, so what.

ggiilliiee
February 11, 2009, 16:15
its 88 if ya look at it in a mirror in austrailia

and chrome ..hes one of the few folks that has used the correct tool to measure a lock shoulder ....especially after some file them ..one big mike anvil wont tell ya nothin ....i say he rocks ........and rolls

chromestarhustler
February 11, 2009, 17:13
yeah i got all the tools myself, just never been 100 percent convinced the locking shoulder wasnt just case hardened so filing on it seems like a bad idea since its cheap enough to just buy the correct one,

i love making parts and building stuff, but some corners you dont cut and some dimes you dont save.

rezman
February 11, 2009, 18:12
I used the blade mike cuz its what I got. The bonus points from giigglle were, well, a bonus.

It did make sense to keep the face parallel as I cut it down. Kind of like lapping both lugs of a garand bolt, not one at a time. Maximize the load bearing surface and all that.

CSH, I did my research before jumping into this. WEG has an L1A1 with a couple thousand down the bore, and he took like 7 thou off.

As far as just buying the right part, I have a sneaking suspicion the undersize locking shoulders you have to wait weeks for through a vendor, are just being modded by somebody else with a mill.

To each his own. BTW, if and when I do blow my face off, I'll be sure to post a pic for the boards amusement.

ggiilliiee
February 11, 2009, 18:28
i think all your gonna see is

"DEAD 600 YD MILK JUGS " hehehe ...


DIE MILK JUG, DIE ......:wink:

chromestarhustler
February 12, 2009, 08:44
yeah i guess depends who you bought it from. never thought a supplier would have machined down locking shoulders but i guess it is very possible. not a knock against you in anyway. and i would pray that your face never got blown off.

twistedneck
February 14, 2009, 22:39
Originally posted by chromestarhustler
yeah i got all the tools myself, just never been 100 percent convinced the locking shoulder wasnt just case hardened so filing on it seems like a bad idea since its cheap enough to just buy the correct one,

i love making parts and building stuff, but some corners you dont cut and some dimes you dont save.

At what point do you wear out the press fit in the locking shoulder?

And is it possible to file down the ls while it's installed? I have a .260 coming in from dsa and my current .255 is loosey. But this will be my third ls and I am worried about ms press fit loss .. Help appreciated

twistedneck
February 14, 2009, 22:41
Originally posted by twistedneck


At what point do you wear out the press fit in the locking shoulder?

And is it possible to file down the ls while it's installed? I have a .260 coming in from dsa and my current .255 is loosey. But this will be my third ls and I am worried about ls press fit loss .. Help appreciated

LtRiker
February 22, 2009, 19:26
I just talked to a guy today who blew one up. fired a couple mags and was on his last round when it blew the top cover off.
bot and carrier is jammed in the upper.
He was shooting some steel cased chinese and a part of the previous case broke off(about .030 worth) and his LS was loose enuff to allow it to close on this, when he fired it, the bolt jerked enough to split along the firing pin hole and the escaping gases blew the top cover off. The bolt and carrier are locked about 1/2 from being closed. A light tap woth a brass hammer allowed it to close, then I was able to cycle it open and out of the recevier. Carrier looks fine, LS is fubared and will have to be cut in half to remove.

we are getting a new bolt and top cover and LS and plan to try again.

he has had the rifle for over a year, no telling how many rounds are down the pipe and no idea who built it. Imbel GL upper on STG58 parts set that he bought at a gunshow about a year ago for $350.

twistedneck
February 22, 2009, 19:45
Originally posted by LtRiker
I just talked to a guy today who blew one up. fired a couple mags and was on his last round when it blew the top cover off.
bot and carrier is jammed in the upper.
He was shooting some steel cased chinese and a part of the previous case broke off(about .030 worth) and his LS was loose enuff to allow it to close on this, when he fired it, the bolt jerked enough to split along the firing pin hole and the escaping gases blew the top cover off. The bolt and carrier are locked about 1/2 from being closed. A light tap woth a brass hammer allowed it to close, then I was able to cycle it open and out of the recevier. Carrier looks fine, LS is fubared and will have to be cut in half to remove.

we are getting a new bolt and top cover and LS and plan to try again.

he has had the rifle for over a year, no telling how many rounds are down the pipe and no idea who built it. Imbel GL upper on STG58 parts set that he bought at a gunshow about a year ago for $350.

Thats one negative of a large chamber you only think about after the incident happens.

Lesson on this one? I love cheap ammo and plan to use more that's the benefit of a big head space, but how is it possible to catch a partial broken off piece of case? i guess his headspace was way to big, probably larger than a field gage