Bullet test follow up parts break down and sight circle photo

Hey guys,
I did buy the carbine from the Bullet test post. The barrel is marked Saginaw SG General Motors no date stamp (Import marked). The receiver is a Saginaw #3257045. Magazine is marked K.I. Magazine release marked with an M. Trigger housing, hammer and bolt are Inland. Rear sight appears to be post war replacement SA with a shield with what looks like an M in it. Stock has been refinished but looks like a Saginaw with a faint RSG in the inside of the fore end. Handguard not market.

I have added a picture of the circle on the front sight. I think it is a machine mark, no numbers or letters inside the circle.


If anyone has a round bolt (complete) for sale at a reasonable price let me know.

Looks like the start or finish of the machine cycle... A WTB in that forum should find what you seek.

Another bolt will require fitting by a smithy. Bolts are not drop in parts.
Not all Saginaw barrels were dated. Saginaw, Grand Rapids didn't make barrels at all. That'd be the S'G' or IP(Irwin-Pedersen who lost the contract). stamp Saginaw.
There were 3 types of front sight. Milled, not all of which were marked, stamped and cast. Best to go here and rummage around the 'Parts' page. The 'M' might be a 'W' for Winchester. Just a guess though. Sights used by most makers had an 'N'. Might be an imporeter's mark too.
Remember, Carbines are fun. Even when they make our heads explode.
The U.S. Caliber .30 Carbines

I'm not doubting you, I too have heard that if you change any bolt in any firearm that you must have the headspace checked, but wasn't the whole reason for the M1 carbine to be so successful was because all of the parts were interchangeable safely no matter who the manufacturer ? Safely dropped in parts was the entire idea wasn't it?

My 2 cents worth. Originally acquired a Underwood barrel/ receiver/ bolt/ trigger group (barrel date 2-44) and scrounged parts until I had a functioning M1. The bolt that was with it was a round "A.I." marked. Later a friend gave me a complete "SG" flat bolt and I thought it looked better than the round, so I swapped them out. I manually cycled rounds through it fine & it locked up tight. First time I took it to shoot, I fired a few rounds through it holding it at arm's length, just in case.

No problems/ no gunsmith. I tend to agree with "jond41403" that parts were made to be "field expedient" in time of war.

I mean no disrespect at all towards sunray because his advice is 100% correct for 99.9% of all firearms that have bolts.the m1 carbine I would consider the exception because if I am not mistaken, the M1 carbine was the first of its kind to be designed with such strict manufacturing specifications, all parts including bolts we're supposed to be able to be swapped out without any worry of safety issues.it's one of those instances that seems to go against everything we were taught about firearms safety, but in the case of the carbine, it is supposed to be perfectly safe to do so. It's kind of like we are always taught to never put our fingers inside the trigger guard until you are ready to pull the trigger, but on an M1 Garand you have to put your finger in the trigger guard just to disengage the safety. I would do like boonie stomper did, after dropping in the new bolt, hold it out at arm's length at first until you get comfortable and confident with the new bolt

Head space checking should always be done. For Safety.

The only Carbines I remember not head spacing were (1) an early Winchester I rebarreled (2) a Winchester I bought with an odd barrel and an IP I rebarreled. None were a result of swapping bolts.

Can't remember ever having a Carbine that wouldn't head space due to bolt swap.

While carbine headspace is overhyped, those who are unwilling or incapable of understanding the physical relationships should be cautious - just as those who know nothing about electricity should probably get someone else to install their ceiling fan. Those lacking a basic understanding should always avoid taking advice from those who know less than they do. (unless, of course, you hear 'some guy' at a gun show say all is well, then you're good to go:madsmile:)

Since the carbine headspaces on the case mouth, if lacking headspace gauges, a 'better than nothing' check is to add shims to a fired round until the bolt won't close by hand - then mic this assembly. A Coke can is very close to .003" Chinese crap digital calipers are available at Harbor Freight for about $10.

For those who claim there cannot be an issue, perhaps they can answer these questions:

1. If every bolt worked in every carbine, then why did the Army acquire headspace gauges?
2. Has no one ever replaced a barrel after the carbine left the factory? How would you verify the new assembly was in spec - except by checking headspace?

For those on the other side:

1. Do currently available headspace gauges come with a calibration certificate ? (If not, then you're basically ****ing up a rope when concluding anything.)
2. Do you measure every round's case length before firing to make sure that it too is within spec?

Finally, who said this: Excessive headspace, due to wear, may be caused by worn faces of bolt, worn locking lugs on bolt, or worn locking shoulders in the receiver.

For those who lack an understanding of the basic concepts, here's a question to explore: what is likely to present more danger, inadequate headspace or excessive headspace.

Let's see, I have a 75 year-old M1 Carbine that probably was given to some foreign country at some point and re-imported, with no possible way of knowing who has done what to it except it obviously has had many parts swapped out, and I'm going to just drop a different bolt in it and shoot it. Okay, but tie it to a tree and tie a string on the trigger to shoot it. :)

Guys, I have had several carbines with long or short headspace. They have to be checked before firing with gauges. Arms length does not cut it. I can't believe grown men would say such a thing.