first carbine unboxing

[W5USMC]

Saw bunch of listings for that corrosive French ammo on GB just the other day.

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[Matt_X]

I just went over the magazine engagment and cycled a bunch of dummy rounds through the midway Underwood.
FWIW the magazines seem to have only a little play when the bolt is closed.
That's becausae the follower is pressing on the bottom of the bolt. If you are checking them with the bolt open, yes there is a lot of play. Examine the fit with the stock removed and its easy to see.

On this carbine I also observed about 5 thousanths verticle play on the right side of the magazine catch. Just eyeball guess as I don't think I have any feeler gages at the house right now. I'll look in the AM. When this carbine has FTFs, its on the right side, 2nd to last round, in one of the new Korean mags. I can solve it by pushing up on the magazine while cycling. Later this wekend I'll compare with my SG to see if its the mag or the mag catch or just that combo.

[ssgross]

First...regarding to hitting very high at 25 yds...when I took the rifle out of the case to clean tonight, I made note of the sight position.
Attachment 120993Attachment 120992
First pic is how I found it. Second pic shows there is a small gap where it could slide down further, but I don't feel a detent when I push it all the way down flush. Which is the 100 yd setting...is it the first line, or pushed all the way down flush?

Now, about the mags. The two I used were marked "AI" on the back. The third I haven't used at all is stamped "U". The AI's seem a tad more loose than the U, which is still pretty loose. Here are pics of the mag well and mag catch. Mag well seems straight. mag catch doesn't seem worn.
Attachment 120994Attachment 120995

Short video showing how loose the mags are.


Flipping upside down, the front-back movement is all in the mag. the side-side seems to be a somewhat loose trigger group pin. I recall up above I commented the trigger group was a bit loose, and heard back this was normal.

my bench is a bit wobbly, but you can see the horizontal play at the trigger group pin area. I don't think this horizontal movement is the issue. The mags clearly sag in the well, especially with rounds in them. Been reading on the upgraded mag catches. Looks like it should solve the problem. Unfortunate. I'd like to keep this original-as-it-came.

[W5USMC]

Which is the 100 yd setting...is it the first line, or pushed all the way down flush?

1st line is the 100yd setting, all the way down flush is not a setting at all.

[Matt_X]

Here's what I did to resolve the FTF. Maybe it will help.
First I knew the FTFs were only from the Korean made mags that I had brought to the range.
I didn''t know if it was both or just one of them.
As mentioned above I had already examined the mag catch and observed a little bit of vertical play on the right and recalled the FTs were always on the right, at least sometimes the second to last round.

Second I checked the mag fit into the assembly with the stock off. Then loaded each of the magazines with 15 dummy rounds and cycled them. I did this with all four mags that I had brought to the range. I did this mostly to be sure I wasn't throwing the results by hand cycling at different rates or short cycling.

After getting a FTF from one of the korean made mags on the second to last round, I repeated the test with just 5 rounds in both. This time checked using different cartridges.
So this got me to another FTF from the 2nd to last round.

Then I measured the nib to top hieghts a couple differnt ways on all 4 mags. I also measured the lip openings, and dissassembled all four to compare followers and springs.
In my case I found the magazine had a shortest nib to top height (1.455"), and the narrowest lip opening of the four magazines. The straight section of the nib opening also bowed or bent downward. That could explain why the bolt usually caught the cartridge but then over rode it as it continued further.

To increase the hieght over 1.5" and increase the feed opening required a little bit of sheet metal shaping. After doing this, retested by manually cycling the dummy rounds again.
Ran perfectly!

At this point I should mention something I've observed about cycling rounds through the carbine. When the round is chambered, the bullet bites into the rifling just a little. After cycling it may get pulled out a little. I know changing the seat has effects on the pressure development, so if you are cycling live rounds, check that the round is still within spec before using.

I'm using dummy rounds. I have 10 that are made up with rubber primers to cushion the firing pin and recently got some 1943 and 1944 dummy rounds with no primers. I thought the bullets older dummy rounds might not pull out when cycled, but after enough cycles, they did.

Since I do alot of dry firing, I made a little gage to check the overall length. When dummy cartridge is too long, I gently squeeze it back to spec in the bench vise. Obviously don't want to do that with a live round! My rule is no live rounds in the workshop where I'm working on or dry firing a firearm.

[ssgross]

It should be at least 1.5 inches.

all three are between 1.500 - 1.505, and the nibs are nice, square on the bottom, and pronounced.

Here's what I did to resolve the FTF. Maybe it will help.

interesting. I thought my failure to feed's were from the nose of the round wedging in the chamber. I could be wrong. Yours looks like the bolt slips off the back of the round after pushing it partway. I need to see if I can manually reproduce the problem - will either remove the firing pin or disassemble some rounds and make dummies.

[Matt_X]

Definately seems to be worth the effort to trying to replicate the FTF and from there see which of the causes or are the most likely.

I recently saw some late WW2 era dummy rounds for sale on-line, either as whole box or in groups of 10 cartidges. Let me know if you want to look through for the website.

[painter777]

Since you've got the Mags handy, try cleaning and servicing them.
I'm not saying this is your current issue, but it's a great time to rule out a Mag being 'The Problem'.
I can say out of a mixed box of over 50 NOS and used I found issues with about 20-25% of them.

Have you had the Mags apart to clean and lube?
To check or swap internal springs?
To check for sharp corners on the side edges of the Follower and to see if the rear wall of the Follower is at 90 degrees to the top?
To see if the top of the Follower is sitting level?
Feel for sharp raw edges on the top side feed lips that may put drag on a round being stripped. I use a worn out piece of 220 to smooth the side feed lips or a fine wet rock.

Look inside the Mags Tube for scratched raw areas with finish missing. A sharp burr on the edge of the Follower can hinder the Spring, killing some energy.

I try to wipe away any extra oil from inside so it deters dirt from hanging on.
Then spray with Silicone and stand upside down to drain any extra.

Here see for yourself. Norchwich93cmp has a video on tuning mags:
HTH's someone.

Safe Weekend All,

** CLICK ON WATCH ON YOUTUBE**

[ssgross]

Have you had the Mags apart to clean and lube?

Yep. I took them out of the grease wrapper, cleaned flushed all the hard grease out of em with mineral spirits and gave a good scrub in an out. dried, re-oiled, and assembled. I took a pencil and pushed down on the followers in various places. They each went all the way down, and all the way back up, level all the way no matter where they were pushed down. I did just order 2 of the new Korean made ones that people say are really good, as well as a NOS replacement mag catch of the newer type - which people are calling the m2 type but what people on this forum clearly proved was meant for all M1/M2's in ordnance dept docs.

Do your's giggle as much as mine?

[USGI]

I know you have new mags, but while you're waiting for your other new stuff to come and if you have a good caliper, measure the distance between the nibs and the very top of your mags. It should be at least 1.5 inches. Take a look at post #22 on the last page of this older thread. - Bob

https://www.milsurps.com/showthread.php?t=73505&page=3

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