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Question about bolt retention.

Printed From: The Carbine Collector's Club
Category: The Club
Forum Name: Safety/ Accuracy/Shooting/Ammunition/Care and Maintenance
Forum Description: What to Check, Reloading, Tips for Accuracy, Competitive/Recreational Shooting
URL: http://www.uscarbinecal30.com/forum/forum_posts.asp?TID=6215
Printed Date: Oct 01 2023 at 10:04pm
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Topic: Question about bolt retention.
Posted By: Angrysheep
Subject: Question about bolt retention.
Date Posted: May 27 2022 at 1:50pm
First time carbine owner.  Couple of questions regarding what is normal / acceptable wear for these interesting little guns.  Forgive my lack of proper terminology, I'm still learning this particular firearm.

Ok, so strip down to the bare receiver, no trigger assembly, no slide, and keep the bolt in place.......in battery.  Turn the receiver upside down, slowly hand cycle the bolt to the rear with light pressure.......

Question #1  Is it normal for the bolt to just fall out when this is done?  

The reason this happens on my carbine, is the metal that is underneath the track that the left bolt lug rides during recoil is very thin, sharp, and leaves a gap big enough for the left bolt lug to be briefly unsupported. Hence the falling out if flipped upside down when the bolt lug is over this area.

I do know that the irregular shape of this rail/track is to allow the bolt to be rotated for removal, but the metal in this area on my carbine appears to be missing more material than other pictures I've found online.  And it's thinner and sharper than magazine feed lips..... 

Question #2.  Is the edge along the left inside track that the left bolt lug rides on top of during recoil supposed to be so thin and weak?  Is it a result of high round count?  It doesn't appear to bear any significant structural role other than a guide and retention function.  Can it be "built back up" if needed?  It seems silly to have the life of the receiver be dependent on such a flimsy thin strip of metal.

Thank you for your time.  



Replies:
Posted By: jackp1028
Date Posted: May 27 2022 at 2:55pm
Hi and welcome to the forum from New Mexico!

It is normal for the bolt to fall from the receiver only when the left lug is positioned in the location shown in the picture below. You can see that the section is pretty thin as you described.






If the bolt falls out before or after the position shown above, something is wrong. See the sequence below.






If your carbine looks any different, please post pictures.




-------------
JackP


Posted By: Angrysheep
Date Posted: May 27 2022 at 3:21pm
Thank you so much for the reply.  Yeah mine is definitely missing some material.  I'm trying to figure out photo uploading.
https://photos.app.goo.gl/QKxtVDTcs1aRHewq9" rel="nofollow - https://photos.app.goo.gl/QKxtVDTcs1aRHewq9

Unsure if that will work. I have more pictures if it does.

Is there a way to solder or braze that area back up, or does that wreck the heat treatment of the receiver?




Posted By: jackp1028
Date Posted: May 27 2022 at 3:52pm
I've never seen that area damaged the way yours is. I don't believe it is due to wear. Is there any other evidence of damage to the receiver, bolt or slide? It may be the result of a previous out-of-battery discharge.

Although it looks pretty bad, your carbine may still operate normally as long as the operating slide is engaged with the right bolt lug and there is a magazine present to help guide the left lug past the damage. The bolt is actually well supported by the right bolt lug retained between the slide and the top of the right receiver surface. See if you are able to disengage it by hand when fully assembled. If not, it probably will be okay as is. I would not recommend welding or brazing. It probably would affect the heat treatment.      

-------------
JackP


Posted By: Angrysheep
Date Posted: May 27 2022 at 4:25pm
Everything else looks pretty good right now.  It's a Korean re-import Grand Rapids built Saginaw with an Inland 44 barrel and mixmaster parts.  

Bought from a pawn shop for use as a range toy. No idea on any history other than that.  It cycles snap caps fine, but haven't test fired it yet. 


Posted By: GotSnlB28
Date Posted: May 27 2022 at 8:28pm
I always examine shooters for burrs in that area as it can cause a bolt to break. I have stoned one off before. A quick search finds http://www.uscarbinecal30.com/forum/cracked-bolts-slides-and-receivers_topic3672.html" rel="nofollow - http://www.uscarbinecal30.com/forum/cracked-bolts-slides-and-receivers_topic3672.html but I have seen other posts over the years as well with it being the cause.



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