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New Carbine, New issue (to me) |
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Matt_X 
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Joined: Nov 10 2020 Location: Phila, Penn Status: Offline Points: 693 |
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 Posted: Oct 20 2021 at 10:08am |
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Dan, Were you thinking of this thread My Midway...w/ free bullet? Redtail wrote "It wasn't in more than 3/4-1 inch in, just to the the rifling as you can see..." By 1" was he was describing the chamber length? That was what I guessing. The dummy bullets I mention there were recently made and sold on e-bay. None show rifling impressions but did start to pull out over repeated use. (The photo I posted later in the thread is a mystery bullet that was in my house growing up. IIRC it was in an abelone shell along with matchbooks. Not even sure its .30 carbine although it has 4 grooves so I think its likely.) Since then I've received some 1943-44 WRA dummy cartridges with the tin coated bullets. http://www.uscarbinecal30.com/forum/ammunition-types-historical_topic5767.html I have only cycled them through once. |
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floydthecat
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Joined: Oct 13 2016 Location: Mississippi Status: Offline Points: 1792 |
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Posted: Oct 20 2021 at 11:48am |
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In any event, the round designed to fit the caliber should drop-in and freely pull-out. If it has to be pressed-in or prized-out, something is wrong with the chamber or the ammo. It’s called the “plunk test”.
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Rebel92
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Joined: Jul 20 2021 Location: Hattiesburg, MS Status: Offline Points: 541 |
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Posted: Oct 20 2021 at 10:23pm |
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sent you a PM
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floydthecat
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Posted: Oct 21 2021 at 6:32am |
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For the sake of others following here, lets share what you have discovered. Indications are that you have a 1.291-1.292 with the QH bolt and maybe a bit tighter with a SG bolt, but it does close. Slight pressure is subjective, it can very between a lumberjack and a surgeon, but indications are that you are within specs. A go gauge is 1.290 and your action should surely close on that.
You have both an envious situation yet perilous. As long as you don’t exceed normal brass lengths, no problem. Where you will possibly get into difficulty is out-of-spec brass or varying projectile shapes. It’s been documented that some chambers don’t like some profiles. A round longer than the action likes, or a profile that contacts the rifling could cause issues. You have pulled at least one bullet, which indicates the latter might be in play. I have lost track whether this is a “correct” carbine or not. If it is original, I would clean it up, leave it alone and shoot my shooter. If it is a shooter, I’d find another bolt that was shorter for that just-in-case situation, or be forced to measure the ammo that I fired in it. A chamber can get a little grungy, a case can be out-of-spec or a bullet profile it doesn’t like can show up. You might find yourself looking at the bolt lugs to make sure it rotated. I have an SG that measures 1.291. It’s a shooter and I found a bolt that head spaces 1.293, which makes me more comfortable. PS: I’d try to cancel the order for the field gauge, you won’t need it unless you plan to be evaluating carbines in the future for long head space.😁
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Rebel92
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Posted: Oct 21 2021 at 9:16am |
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Yes, it is a correct QH I will post pictures elsewhere on the forum in just a minute. ... It is not my shooter, but I would like to be able to shoot it occasionally. Would you recommend it I only shoot USGI surplus ammo, or is it just as likely to be out of spec as the commercial ammo? And would you recommend I pull a few bullets from commercial and or usgi/korean surplus?
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floydthecat
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Posted: Oct 21 2021 at 9:43am |
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A matter of personal choice. Personally, I won’t tolerate a gun that doesn’t shoot off-the-shelf ammo that is suppose to be designed to shoot in it, but we do know some carbines can have issues with some profiles. You can pick and chose ammo that for sure works, or go with a shorter bolt for longer head space that will likely shoot about everything. You can get a case gauge off epay for about $20, but that doesn’t catch the off-spec bullet profiles or rounds possibly exceeding overall spec length. I guess you have to determine just what brand of ammo might be problematic and avoid it. Keep an eye on the bolt. If it doesn’t rotate it shouldn’t fire, but it might and the least damage will be a cracked right bolt lug.
The carbine is most certainly in spec. Some commercial ammo might not be.
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Rebel92
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Posted: Oct 21 2021 at 9:46am |
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Okay, so essentially just shoot milsurp from the QHMC? I am okay with that, as I have acquired a lot of that. I only buy commercial ammo when I find it cheap (whatever that means in todays market). And I will be reloading my brass soon(ish)
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Rebel92
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Posted: Oct 21 2021 at 9:48am |
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and is the fine lapping compound un-necessary now?
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floydthecat
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Posted: Oct 21 2021 at 9:54am |
If you think the chamber is clean and a spec round passes the plunk test and you don’t have sticky-extraction, I don’t think polishing is necessary.
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Rebel92
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Posted: Oct 21 2021 at 9:57am |
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the plunk test would be done with a functional round? And just drop it in, and see how easy it pulls out?
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floydthecat
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Posted: Oct 21 2021 at 10:14am |
Correct. See if it drops in and bottoms without forcing it. Maybe have to use a finger-nail to pull it out. I push on it to insure seating, but it should slide out easily.
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Rebel92
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Posted: Oct 21 2021 at 10:19am |
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Something else I guess I had never noticed or thought to ask, does this look right? How far my homemade headspace gauge is coming out of the chamber?
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Matt_X
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Posted: Oct 21 2021 at 12:34pm |
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Basically yes. Take a look at the cutaway from the club's webpages I posted earlier. This one.  The lower arrow points the end of the barrel. The entire rim of the cartridge is outisde the barrel. The rim of the bolt is shown touching the barrel face although I suspect that's a slight clearance fit or else the bolt wouldn't rotate in as easily as it does. There maybe subtlties I'm missing. |
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floydthecat
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Posted: Oct 21 2021 at 12:40pm |
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Yep….hard to distinguish any difference in thousandths, but looks good.
I don’t think the rim is tapered that aggressively on the base in real-world ammo. Looked at that picture before and never noticed that.
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Rebel92
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Posted: Oct 21 2021 at 2:36pm |
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Well, FloydTheCat Did it again (Genius). Headspace came back and was within speck. Tried the Plunk test on both carbines with Korean Surplus and Armscor ammo.
On my inland, which shoots anything I give it, had both the Korean Surplus and Armscor seat and come out easily. (no surprise, have no issues at all with it anymore) Moved on to my QH (one with the perceived "issues"), and the Korean seated and slid out with no pressure with my tweezers. Next, I plunked the Armscor in it. I had to squeeze and pull with my tweezers to get the Armscorp out of the chamber. IT WAS TIGHT. So, I guess it really was the ammunition and how tight my chamber is. Very interesting results, but pleased that's all it is. Luckily I only have a few hundred rounds of armscor, which will be fed to my inland to conquer the turtles taking over my pond!
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New2brass
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Dan Pinto, Photo Editor Joined: Nov 29 2015 Location: CT Status: Offline Points: 4321 |
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Posted: Oct 21 2021 at 2:48pm |
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what is the serial number range of the two carbines? barrel dates if present
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Rebel92
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Posted: Oct 21 2021 at 2:54pm |
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Inland has barrel date of 11-43 serial number is 3072253 QHMC has an undated Rock-Ola Barrel, Serial number is 1881065 |
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New2brass
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Dan Pinto, Photo Editor Joined: Nov 29 2015 Location: CT Status: Offline Points: 4321 |
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Posted: Oct 21 2021 at 4:01pm |
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OK, so the Inland would have the late chamber. According to CCNL 334-3 we have seen in the serial range of 1875-1890 RO undated barrels, BA-9-43, Underwood 8-43 and RO 6-43 In another thread we were discussing the change in ammo case profile and chamber profile being changed in June of 1943. Rockola stopped dating barrels in 6-43 and this may not be a coincidence. I am wondering if your undated RO barrel may have been one of the first undated and somehow has the earlier profile which is causing the chamber to catch the later ammo a little but more? Only real way to find out is to slug the barrel. I am sure others can explain how and where to get he metal to do so, if you were interested in doing it. Basically I believe they found the later profile case should work in all carbines, but earlier cases would have malfunctions in later carbines. |
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floydthecat
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Posted: Oct 21 2021 at 4:05pm |
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Gotta luv the carbine world! A mystery at every turn, which makes it all interesting and fun.😁
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floydthecat
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Posted: Oct 22 2021 at 5:31am |
Armscor would be of the later design….I assume. Just guessing here and assuming no commercial manufacturers were producing ammo at that time, thus all commercial ammo would be of the later design and should fit either chamber? I think this is a case of the Armscor bullet profile just not liking the chamber in this carbine. It being a very little-fired and fresh chamber, the crisp rifling in the throat is grabbing it. I bet after some firing and wear, won’t be a problem at all.
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Rebel92 wrote: