Ithaca Model 37 Troubleshooting

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PostPosted: Wed Feb 10, 2016 7:11 pm
twistedoak wrote:raven will know better ,
but that looks like a weak mainspring.
ammo type should not effect that
as far as ammo dumping you got it with a worn shell stop.
if you sense play in the lock up look at the slide stop.
I've had to replace them before when I had excess play.the area is very small where it contacts the slide and its a high wear area


I feel for you guys across the pond ,the parts were talking about are common and cheap here.
I have everything listed above in my spare parts box.

I also get the feeling your m37s are shot a whole bunch more then your avg m37 in the states.
over here m37s aren't considered range guns ,they are guns that get kept in a closet till small game season ,and put back after it closes



Twisted, I think you nailed it. The only other problem to a light strike is that it could be a broken spring. A broken coil spring can work fine some times and then the two pieces can "slip" and you have light strike.

If the bolt was really loose and it turned out to be a headspace issue, you would know it.

That's about all I can add to this conversation
--Jim
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PostPosted: Thu Feb 11, 2016 6:27 pm
ravengunsmith wrote: I've shot Kents (which is Gamebore here)
without an issue in my citori and they ejected fine (that has a tight Chamber, too)


Interestingly, I believe that the 37 has a "loose" chamber, certainly when compared to my BPS and I thought that the "low head",( under 10mm) was allowing over expansion of the hull which was in turn grabbing the chamber walls. High metal (16mm +) seems to alleviate the problem
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PostPosted: Wed Feb 17, 2016 7:04 pm
Mine are quite tight. all of them hate reloads.
--Jim
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PostPosted: Mon Jun 13, 2016 4:18 am
Well gentlemen to revisit the 'fail to extract' issue I am afraid that I have some more questions to put to you.
During a particularly long IPSC competition stage this last weekend I experienced the mother of all fails to extract. I was unable to finish the stage, so I made the gun safe and let it cool. when I eventually managed to remove the offending case I decided to keep it for later examination (photographs). I discovered that the magazine cap was a little loose despite being tightened at the start of the stage. This seems to be a recurring issue and, I believe, is central to the problem.
Upon examination, I saw that the case had bulged slightly, forward of the rim, had flowed into the extractor cut outs and had deformed behind the rim quite substantially. This seemed like a headspace issue, with the barrel loosening within the interrupted threads. I decided to research a little further as I had formed half a plan to fit a grub screw into the side of the mag cap to lock it in place. Checking the exploded views of the '37 from various sources, I was surprised to see the "mag nut pin" and its associated screw and spring. This is something that to me was hidden in plain sight, as I have always *assumed* that the ball detent was what prevented the mag cap from loosening. (to quote Jack Reacher, to assume makes an ass of u and me!) I would be grateful if anyone could shed some light on the fitting of these parts as my '65 does not have them, nor any place to fit them.
My research eventually found a Kings Ferry field maintenance manual which showed a different approach to the loosening mag cap.
In it, during assembly, it shows the yoke being hit by a hammer and wooden drift to contact the rear edge of the mag cap and so fix it in place prior to tightening the yoke screw. Is this common practice? It is contradictory to all other model 37 manuals that I have seen, which state "to dis-assemble screw the mag nut clockwise until it clears the barrel lug, then rotate the barrel" No mention of removing the yoke screw and drifting the yoke back first.
my '65 has wear marks from the yoke screw and yoke itself from where it has always been positioned, about 1/8" behind the mag cap when cap is locked into the barrel lug. I thought that maybe my ball detent was weak, but, research showed me that some mag caps are available without the dimples for the ball to engage. I thought that I knew '37s, it would seem not and I now seek further education from you all! Please note I am aware of the need to replace my yoke screw, it was 'wrong screwdriver' damaged before my ownership!!

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PostPosted: Tue Jun 14, 2016 10:20 am
what is the year again?
the loosening at the barrel lug may or may not have nothing to do with the stuck shell.
I say this because in theory the barrel threads are what set and lock in the headspace ,not the tightness of the mag nut.
excessive wear can cause headspace issues,however a misaligned yoke can also bind a shell in the chamber.
much like you describe

the mag nuts went though several variations mostly driven to reduce cost .
the biggest variation was the early pin type,i remember reading that one of the reasons they were dropped is because there were cases of people over tightening them.
in general use they all work fine.

the practice of pinning the mag nut with the yoke was adopted for high use guns by law enforcement., to prevent barrel removal
military guns required a fixed non removable barrel(after WWII)
the reasoning behind fixing the barrel is unrelated to the ability to fire the gun,but more toward swinging it like a bat or attaching a bayonet
how many shots did you fire?
I don't pin the nut on any of my hunting guns ,but if your sending a few hundred down range at a go ,i'd consider pinning it with the yoke.
i'd also check the tightness of the stock bolt often.

as far as the stuck shell ,
my first impression is to decide if the shell itself could be the oddball and a bad one .
then as I said above i'd check to see if the yoke was aligned properly
lastly i'd wonder if the gun was locked up completely when the shell was fired
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PostPosted: Tue Jun 14, 2016 2:01 pm
Hi Twisted,
My '37 is a 1965 model, field barrel featherlight. I believe that the loosening of the mag nut permitted the barrel to begin partial rotation. On the course of fire that I was shooting, I had fired about 20 shots rapid before the fail. During my reloads, the heat, even through the heatshield, was quite intense. With my speedloading technique, the gun is spun over rapidly and shooting continues after just a few seconds (some shooters keep the gun in the shoulder and load right way up)
The yoke on this gun was perfectly aligned, my barrel will not rotate if the yoke is mis-aligned (the tolerances are that tight)
My question about pinning the mag nut with the yoke arose after finding an Ithaca Gun Co. manual (Kings Ferry) that I had not seen before. It was neither military or law enforcement that I could make out, and included the model 87
I am fairly confident about the ammunition and the lock up. Also, the stock bolt on this gun is modified with a locking nut.
Thanks for your input and information

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PostPosted: Tue Jun 14, 2016 4:34 pm
The old style magazine nut you refer to was used from 1937 and phased out going into 1955. As stated before it was for the most part a cost cutting measure. A number of other short cuts took place that year including no checkering on field grade stocks, and simpler machining on the top of the receiver. I agree with Twisted Oak on the barrel line up. I have a 37 that the shells would bulge in the extractor cut outs and become firmly lodged in the barrel. The barrel would not bind in the yoke when installed or removed. I put the barrel on another 37 and it shot fine. I put the barrel from the second gun on the problem gun and had the same problem leading me to believe that the cut outs where not aligned with the extractors. After adjusting the yoke a number of times followed by test firing I was finally able to get things lined up just right and the gun will work with any barrel. As for the yoke assembly procedure you mention I have also heard of it but only for law enforcement use.
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PostPosted: Tue Jun 14, 2016 5:44 pm
This is very strange ,Gentlemen. Cutcher, you described my jammed case perfectly, but in my case it only happened when the gun was hot and the mag nut loose. I guess if the barrel moved marginally so that the extractors did not quite line up then we are approaching the cause. Prior to this jam the gun had fired about 100 rounds perfectly that morning, and the last jam before that was probably 400 rounds ago. I have been tightening the mag nut prior to shooting (it was always a little loose) So maybe the yoke pushed forward to the mag nut will cure the problem? I can but try.
I still don't understand why the ITHACA Kings Ferry NY maintenance manual is quite specific about this procedure, and yet you Gentlemen refer to it as military or LE. I tried to load up the manual for you to see but the site will not accept PDF files. There is reference in the preface about 1993 production guns and the sling stud, but that is the only date reference in the manual
Thanks as always for your time and patience with a puzzled Brit!
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PostPosted: Tue Jun 14, 2016 7:03 pm
Cutcher and twisted are both spot on. They know as much as anyone outside the factory.

Remember, it only take a few thou in any one place to get the entire firing/extraction mechanism to malfunction. If the yoke is too loose and the barrel heats up, that could be all it takes to cause that mechanism to foul. Especially the yoke. When I sold new Ithaca's I found out that shipping often caused the yoke to misalign and require a tune up. (UPS and FedEx are so gentle) I'd give you a torque spec for that screw but I have learned that every gun is a little different and to trust your eyes and how the barrel attaches and detaches.
--Jim
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PostPosted: Wed Nov 16, 2016 6:40 pm
As an update, the '65 has not had a jam since my last post and the '71 likewise. The '65 mag nut is locked into place with the yoke as per the KF manual but only when I have absolutely got the slot in the roof of the receiver perfectly in line with the top extractor cut out, problem gone!
The '71 did not have a yoke and the mag tube is non standard. I got a friend to pick me up a yoke when he was stateside. Of course it did not fit and needed to be packed out. I now position this yoke against the heat shield front mount as there, it holds everything solid. Again, nothing is locked up until the extractor slot and receiver slot are perfectly aligned. It seems to me that with just a little assembly care (and the advice of my peers across the pond!) the problems with my favourite shotguns have gone away. Thank you gentlemen!
PostPosted: Thu Nov 17, 2016 10:25 am
Thanks for the update...glad it worked out for you.
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PostPosted: Thu Nov 17, 2016 9:24 pm
For the interest of readers of this thread I have attached some screen shots of the KF manual discussed previously, the front page for reference and fig. 16, re-assembly of the yoke
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PostPosted: Fri Nov 18, 2016 10:16 am
Thanks..............
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