There have been many civilian commercial versions of the M1. Early on most used GI parts.  Later the use of GI parts diminished and many use distinctly different parts and receivers. Plainfield was one of the companies that designed its own receivers although they were compatible with GI barrels, slides, stocks, and trigger groups.  Small parts should be interchangeable with the exception of the hammer pins on the aluminum trigger group examples.

Start here for the history of Plainfield Carbines:

http://www.m1carbinesinc.com/carbine_plainfield.html

Serial numbers (yours would rate to around 1975 working back from the highest serial and number produced per year):

http://www.m1carbinesinc.com/carbine_Plainfield02.html

Models:

http://www.m1carbinesinc.com/carbine_Plainfield03.html

Receivers:

http://www.m1carbinesinc.com/carbine_Plainfield04.html

Parts.

http://www.m1carbinesinc.com/carbine_Plainfield05.html

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Military M1 collectors look down on the civilian variants, but there’s a degree of snobbishness and ignorance involved.  The many civilian variants have become very collectible in and of themselves as interesting variants of the M1 carbine, and a piece of Americana.

Plainfield also supplied military carbines including M2s to a number of foreign militaries and Plainfield carbines have been found in surplus M1 carbines returned to the US military.  The Plainfield carbines also saw service in Vietnam as many were purchased by the South Vietnamese who found the M1 and M2 carbines to be very well suited to both jungle warfare and theor smaller statured troops.

I've owned 3 Plainfield's over the years, 2 were good shooters. 1 I did have issues with but was able to get my money back.

The Plainfield I own currently is probably the most accurate of any of my current Carbines (I own 12  ). On mine I changed the recoil spring and redid the bolt with a USGI extractor and parts. That you either need a bolt tool or take it to a gunsmith WHO HAS THE PROPER TOOLS.

Bolt Tool

If it were me I would just buy the tool myself, and either sell it or keep it to use for cleaning. Odds are your bolt has neither been cleaned in all these years, that could be part of the reasons its having problems.

I would keep it, I have a policy of cleaning bolts every 2000 rounds. You can't just take the bolt down like a AR-15 bolt so every carbine I've bought over the years has needed that cleaned.

As to mags, my current Plainfield can be mag picky. Not knowing what mags you've ordered I would try these

https://www.keepshooting.com/mil-spec-m1-carbine-15rd-magazine.html

I've been using these for about a year now and have liked them.

Keep us posted, M1 carbines are fun to shoot and ammo costs have come down ALOT since this time last year, with some searching on Ammoseek you can find good deals

Never seen a rough chamber like that. I would clean it out good after changing the extractor and see what happens.

Glad to help.

I've had good luck with KCI mags also, 1 i used 3000 rounds before it wore out.

Before I would replace the barrel I have the Carbine inspected, it might just need polishing out. It "could" have been improperly reamed out when it was made years ago. I would contact a carbine specialist like Fulton Armory or Orion 7 and see what they say.

Fulton offers a "barrel refresh" service that sounds like what could cure the chamber on yours

https://www.fulton-armory.com/m1-garand-total-refresh-package-549-95-1.aspx

I've had that done on the last couple carbines I've bought and it's helped IMO

I would try some scotchbrite wrapped around a brush and a hand-drill to polish the chamber, those might be rough final finishing - may not be causing any problems for you but cleaning it could can't hurt.

Good KCI mags and possibly replace ejector, extractor and springs on the bolt if feeding/ejection problems persist

I would say most of my Carbines eject brass over my right shoulder about 3 feet away also

My Universal (early commercial carbine made in 1965) with relatively new extractor, ejector and springs - throws them right out.  Note this is with the KCI mags which run very well.




https://youtube.com/shorts/M4IgDBjquIU?feature=share

Sorry for your loss, OP.  The deceased had the good sense to get a GI parts compatible gun, so in the worst case you can screw a brand new barrel into your receiver.

Get an M2 magazine catch and use GI M2 magazines.  No more feed issues.  My Inland M2 runs like a top on PCI ammo.

Check the spring in that bad KCI mag, sometimes they get installed backwards

1980fps sounds about right for the length of the Carbine barrel





Plainfield's were made with a M2 style mag catch. As too "GI M2 mags", if your talking 30 rounders those have become very expensive over the years. Even then 30 round USGI mags could have problems  

Good. You might have a issue with the last round not loading if you load 15 rounds, stiff springs are the problem there. Most the time I only load 10 rounds in a mag anyway when I'm shooting my Carbines but that's me.

Agreed. I don’t have a Plainfield. But, you should use an M2 catch if you’re using a 30 rd mag.

my dad worked as a machinist at Plainfield when he came back from Vietnam......