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"When" Should a Bolt be Replaced?

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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Topic: "When" Should a Bolt be Replaced?
    Posted: Jul 08 2017 at 4:57pm
That's the question and I don't think when the gun stops shooting or blows-up is a satisfactory answer.

Most of the guns we see have been to the arsenal at least once. The bring-backs and those in pristine condition haven't been fired all that much. The ones that have tripped thru the arsenal have surely had the bolts replaced out of necessity or precaution. So...how long will a GI bolt last and what deformities and to what degree of wear does one warrant replacement? Cracks for sure, but that's a no-brainer. I want to pick-the-brains of the experts here.

The used bolt trade is relatively huge. Some of this stock will show signs of light peening, but many don't. Where could all of these bolts have come from....carbines that are no longer serviceable, or from guns in which the bolts were replaced because the bolts were deemed worn-out?

I will be happy with a suggestion that would point me to a thread, some manual or part thereof that can define the bolt inspection process. And..of course, any comments from the floor here.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote m1a1fan Quote  Post ReplyReply Direct Link To This Post Posted: Jul 08 2017 at 6:25pm
The U.S. .30 Caliber Gas Operated Carbines - A Shop Manual by Jerry Kuhnhausen

Page 23-32 - Out of batttery, potential issues, etc...
Page 108-118 - Bolt Inspection, life expectancy, headspacing, etc...

Here: http://www.uscarbinecal30.com/bolts.html

And of course my favorite here:

http://www.uscarbinecal30.com/operation.html

What I've been told by my armorer and others is that when replacing a bolt, ALWAYS (there's that word again), have the headspace checked by a qualified gunsmith.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 08 2017 at 11:30pm
TM 9-1276_1947 describes the inspection process, but pretty much just says look for cracks and measure firing pin protrusion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 6:30am
Originally posted by W5USMC W5USMC wrote:

TM 9-1276_1947 describes the inspection process, but pretty much just says look for cracks and measure firing pin protrusion.


47 and 53 say about the same thing......burrs and excessive wear. I understand that the most likely place for burrs are at the front face of the right bolt lug and the rear skirt. "Excessive wear" is subjective and ...is any burr at all grounds for rejection? I feel like that is subjective as well.

Cracks are obvious and not subjective. A burr-is-a-burr, but is a slight mark a disqualifying burr? Maybe it's a common sense thing. Maybe one has to handle enough of these to know. I know I would not toss a bolt just because it had a few wear-marks on it and maybe a relatively small burr as long as the carbine functions smoothly. Obviously, armorers had the luxury of replacing bolts just for precautionary reasons. Civilian owners don't have the luxury of an endless supply of fresh bolts.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 10:32am
Agree, "Excessive wear" is subjective. I will continue with the "if it ain't broke, don't fix it" rule for my carbine bolts. They all still chamber, fire, extract and eject.     
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 11:35am
That's more-or-less the approach I take. Maybe I was seeking some definitive answer as to where things get dangerous and how problems may manifest themselves..........short of an explosion in your face.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 1:12pm
Well, if the locking lug's contact surface of a bolt is "excessively worn", that wouldn't be "subjective" would it?

What would a definitive test for such "excessive wear" be? Just because it chambers, fires, extracts and ejects doesn't mean it's good to go. These things had specs for a reason.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 1:24pm
Seems to me inspection for cracks as mentioned in several other posts would be #1 followed by checking headspace and then checking firing pin protrusion.

How often does folks do all this?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 1:58pm
Originally posted by blackfish blackfish wrote:

these things had specs for a reason.
So what spec measures excessive wear? There isn't one. The only spec mentioned in the Technical Manual is the firing pin protrusion measurement. 
Straight from the TM:
41. Functional Check
a. Test bolt for freedom of movement in its guideways in receiver.
Check freedom of movement of firing pin in bolt, fit of tang in slot,
and protrusion of nose of pin from face of bolt when in forward position.
Firing pin should move freely in bolt. Fifth echelon organizations
inspect firing pin protrusion with firing pin protrusion gauge
(41-G-194-125). (See fig. 33.) Before proof or functional firing, nose of
firing pin should protrude 0.048 to 0.065 inch.
b. Test functioning of extractor and ejector. When ejector is depressed,
it should be flush with face of bolt. A free ejector should not
extend beyond the front lip of bolt, as it is likely to cause obstruction
to feeding.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 3:45pm
Anytime statements like some, not much, too much, a lot, hardly any and excessive are used, they are subjective. It's been my observation that the first place the bolt is going to show signs of damage is likely to be where the hammer strikes on the left side of the rear skirt. That's where one will notice varying degrees of mushrooming. This damage is far more prevalent in a commercial carbine wearing a soft bolt, but I've seen it on USGI bolts to a lesser degree and they never stopped shooting.

Maybe a proper answer is to replace the bolt when there is evidence of mushrooming. Not some, excessive, or a little...but ANY signs. I have no idea what the life of the bolt is and they were likely changed so often in a war-era environment that it never mattered. If you have a carbine now and shoot it often...it matters and you don't have an armorer to take it to for a free fix. You have to decide on your own.




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Post Options Post Options   Thanks (1) Thanks(1)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 6:47pm
Like I said earlier "if it ain't broke don't fix it" but make sure you wear good shooting glasses with ballistic lenses! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 7:24pm
One should never be afraid to shoot his gun, but I do find myself taking a peek now-n-then to make sure the bolt is rotated and locked.Big smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 7:27pm
Originally posted by W5USMC W5USMC wrote:

Originally posted by blackfish blackfish wrote:

these things had specs for a reason.

So what spec measures excessive wear? There isn't one.



Of course there is. It's just not listed in your TM.

You need to refer to the original drawings for the part's specifications.

Determining whether your part conforms to its original design is purely objective. If so, any wear present is not "excessive".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 09 2017 at 10:35pm
[/QUOTE] 

Of course there is. It's just not listed in your TM.

You need to refer to the original drawings for the part's specifications.

Determining whether your part conforms to its original design is purely objective. If so, any wear present is not "excessive".
[/QUOTE]
You are kidding right?? The Technical Manual was published for those that used and maintained the Carbine.  Although I was not an armorer, I was a Maintenance Officer for with over 30 years in the Marine Corps and happen to know a little bit about maintenance in general in the military. Regardless of the equipment being inspected, repaired or maintained the TM is the reference. Not the original drawings. Original drawings are for manufacturers, not a reference for inspection or maintenance.  

Remember the M1 Carbine was not and is not a match grade weapon, it was designed to function when covered in dirt, sand, water and whatever else it was exposed to.   
Over analysis leads to paralysis.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 9:24am
Quote
You are kidding right?? The Technical Manual was published for those that used and maintained the Carbine. Although I was not an armorer, I was a Maintenance Officer for with over 30 years in the Marine Corps and happen to know a little bit about maintenance in general in the military. Regardless of the equipment being inspected, repaired or maintained the TM is the reference. Not the original drawings. Original drawings are for manufacturers, not a reference for inspection or maintenance.


Check out references like SA's Inspector Training Manual (1951). SA was the first state-wide carbine inspection and rebuild faciltity post-war. That's about as deep into maintenance as you can get.

Terms like "excessive" wrt wear mean nothing absent context. For maintenance purposes, the implied context removing all ambiguity is the original part specification.



Your TM provides just a gross overview of the overall process, not much detail. Note all the gage inspections to remove parts having faults not detected by visual inspection from the pool. And the SA manual, actually used for this process, describes all these gage inspections but leaves all detail to, wait for it, the drawings!

So the actual drawings must have had some relevence to carbine inspection and maintenance over 50 years ago, but apparently not so much anymore.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 10:36am
Agree that the TM that I referenced only provides a gross overview with not much detail but that was the point I was trying to make, keep the inspection simple and if it still works use it.  I would like to see what is written in TM 9-1005-210-35 dtd june 69. this is what I believe to be the latest published actual Army TM which is a Field to Depot level maintenance manual. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 11:24am
One could take the position that any noticeable damage at all warrants a replacement, which was likely the position taken at the arsenal. I am also sure that bolt would yet have more life left in it past that point. I think I was searching for that "point" at which one would replace the bolt....and it may well be forever a subjective matter. A small dent, ding or mushroom is not likely going to cause the bolt to fail, but there has to be some point at which it would and it may simply be in the eye of the beholder.

I think the bolt is going to show physical damage B4 it goes out-of-tolerance on any point one could measure and compare to a specification. Below is a picture of a bolt showing rear skirt damage. I consider this degree of damage as light and bothersome, but is not affecting operation. You can catch the edge with a fingernail. You can find well-fired bolts that look much worse than this, yet continue to function. How much worse can this get and not be a concern?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote RClark9595 Quote  Post ReplyReply Direct Link To This Post Posted: Dec 09 2017 at 8:47am
I worked for years in a large automotive automatic transmission re-manufacturing plant, the parts for a rebuild went through an assembly line and inspection process much like the carbines did for re-build at arsenal. One thing that proved impossible was teaching people how to judge wear without some sort of go no-go gauging. It finally came down to if there is any visible wear anywhere, replace the part, that's my 2 cents worth, and I don't think things were much different at arsenal, because people all look at things differently and judge differently, their last job may have been at McDonald's. Before we said just replace it if there is any wear noticeable, I would be called to the line constantly to judge a part or parts for an assembler. I'm sure arsenal had the same problem, in my opinion, if it's your carbine, you're the judge, how much wear will you except? I would say depends on how critical the part is to the safety of the gun, and bolts to me at least are high on that list.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Charles Quote  Post ReplyReply Direct Link To This Post Posted: Dec 09 2017 at 12:39pm
This seems like the place to ask, what is the significance of two punch marks on my S'G' flat bolt?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Dec 09 2017 at 4:06pm
May depend on where they are placed. Proof-mark or hardness test. I have an IBM round bolt that looks like someone was playing tic-tact-tow on top of the right lug.
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