Failure of bolt to lock open after last round?

Information on Malfunctions and Care of your Model 8 & 81
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cantgrowup
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Joined: Tue Apr 23, 2019 9:27 am

Failure of bolt to lock open after last round?

Post by cantgrowup » Sat Jul 18, 2020 5:19 pm

Shot my .25 Rem Model 8 for first time and tried Hornady 117 JSP with IMR-3031 at 21.0, 22.0, 23.0, 24.0, and 25.0 (5 rounds loaded for each but I fired them in 2 and 3 round batches). The rifle was ejecting and chambering at each load, but the bolt would not lock open after the last round until I got to the 24.0 rounds and it only did it once. It did not lock open after the 25.0 gr loads. If I manually pull the bolt to the rear on an empty magazine, the bolt will lock open but I have to do it with some force.

So, before I try increasing the loads above 25.0 grains to get more recoil (realizing that 27.0 gr is the max), I'm wondering if there is an easy adjustment to the gun itself to facilitate better lock-up after the last shot. The gun has a new mfg internal magazine W-spring and a New Old Stock follower. The Model 8 "bible" says that if the bolt fails to lock open on an empty magazine, it is a broken magazine indicator, but my magazine indicator and spring are still intact, and the bolt will stay open if pulled to the rear hard enough. Could it be that the magazine indicator spring is compressed after 97 years and not providing enough upwards force? I could try to bend it out a little but that would risk breaking it off.

Suggestions?

cantgrowup
Posts: 54
Joined: Tue Apr 23, 2019 9:27 am

Re: Failure of bolt to lock open after last round?

Post by cantgrowup » Sun Jul 19, 2020 6:56 pm

No comments? :roll: Come on guys... you are supposed to be the experts on keeping these ol' Model 8s going. Nobody has commented yet. I'm thinking that it may be a problem with the magazine indicator spring being "bent" after a century of constant stress. I now have 8 of these rifles and they will not be "safe-queens". I'm interested in keeping them firing for as long as I can. After they go "kaput" for the final time, I can sell them to Cracker Barrel to hang on the wall, but for now, I'm going to shoot them like John Browning intended! An antique gun that doesn't shoot is just a hunk of junk metal.

I've googled videos on re-tempering flat springs and it suggests a method for restoring the "spring" to a bent flat spring. It says heat it to a cherry red and then drop in water. And then you have to re-temper the spring by heating slowly over a flame and then letting it air cool. I assume that before I do any of this I should attempt to straighten the "age bent" spring to a flat condition before re-tempering.

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Phyrbird
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Re: Failure of bolt to lock open after last round?

Post by Phyrbird » Sun Jul 19, 2020 11:01 pm

CGU
Is the mag ind spring riding on to of the bolt carrier rail, that's usually what causes weird stuff with the empty lock & cycling new rounds? It's supposed to be in the tiny slot just under the rail.
The spring should be fairly straight when not in the action. Look to see if both tabs on the spring are worn.
There also could be a issue with the little tab on the back of the mag follower, or the end of the mag indicator that catches the bolt.
That's my 2c worth & I'm stuck to it.
Phyrbird
SOKY

cantgrowup
Posts: 54
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Re: Failure of bolt to lock open after last round?

Post by cantgrowup » Mon Jul 20, 2020 7:41 am

The small side tab on the magazine indicator spring is in the correct slot in the receiver. The spring itself is slightly bent where it is inserted into the magazine indicator itself, most likely just from being in compression for 97 years. The weakened spring is still trying to lift the indicator and lock the bolt, but it just doesn't have enough strength to lock it open after the last shot. That is why I am thinking about straightening the spring to a flat condition again, then heat treating the spring to return the temper.

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Phyrbird
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Re: Failure of bolt to lock open after last round?

Post by Phyrbird » Mon Jul 20, 2020 1:18 pm

CGU,
I did the heat treat several times. Worked once, on an old rimfire single shot, made from a piece of hacksaw blade. Curled ends for the pins it fit. Point is unless you get VERY lucky with the metallurgy of the part & the temps involved you get a fancy paper clip most times.
I heated to cherry red, quenched in 30w oil, then drew color of the whole part to just past brown almost blue, then quench in cool water to set the temper. Getting the color draw even for the middle & the ends of any part like this is more art & luck than science. Unless of course you have a precision tamp controlled furnace.
Even then it may only work for a while then fail. A better idea may be find one second hand.
Know what imean?
Phyrbird
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Rifleman
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Re: Failure of bolt to lock open after last round?

Post by Rifleman » Mon Jul 20, 2020 4:30 pm

Can't say if this could be your problem CGU', but when my first Mod 81 300 Savage was giving me more headaches than a noisy neighbor, ie. failure to eject, failure to lock after last round, improper ejection, most of my problem had to do with a warped and damaged Bolt carrier latch spring and a damaged bolt carrier latch. After replacing them, I was still having some problem at times with the bolt not locking back after last shot. The magazine indicator spring looked ok and was in place when I reassembled, but then I noticed when the bolt failed to lock back after last round, the tab was out of the slot. I put it back where it should be, fired five rounds and it would not lock.

After putting it back several times, I noticed that the slot where it was supposed to be had some hard 'gunk' in it that didn't allow the tab in the spring to fully seat. The recoil would evidently jar it out, all I could assume. It looked alright upon reassembly and repositioning it several times. When I previously fully stripped and cleaned the rifle, the slot just didn't get properly bathed. Used a sharp pointed awl and hoppes 9 to clean, reassembled and never had the problem again, ie., it stayed put. I didn't disassemble the bolt either and a dirty ejector chamber was casuing some problems with ejecting, cleaned it as I should have from the get go and no problem.

As far as 'heat treating' the spring, I tend to go with what Phrybird said. Not saying you don't have the expertise to do so, good deal if you are, but springs are a 'testy' bunch. Things can go south pretty fast and easy with them if not done right when tempering. A guy I know ruined several before he gave up and bought a fourth and used it 'as is' in a handgun. Numrich did have some available last week or so as I was looking on the sight for 8/81 parts, looked today, out of stock. Good luck with your fix.

cantgrowup
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Joined: Tue Apr 23, 2019 9:27 am

Re: Failure of bolt to lock open after last round?

Post by cantgrowup » Sun Jul 26, 2020 7:25 pm

Okay... Physician heal thyself. I took the Model 8 apart again and studied the mechanical workings of the individual parts. The magazine indicator lever is pushed upward up by the magazine follower and after the last round is responsible for locking the bolt back. Since this was a NOS follower that I installed, I merely bent the little rear tab on the follower up a bit so that it would push up on the magazine indicator lever more.

Then I reloaded some more Hornady RN 117gr (#2550) rounds (5 each) with 23.0, 23.5, 24.0, 24.5, and 25.0 gr of IMR-3031. Firing one round at a time from each batch to see if it would lock the bolt back, I noticed that 23.5gr was the minimum load that would lock the bolt back after each single round loading. So.... I shall try that load from now on. It also seemed to be the most accurate.

I noticed that the little flat spring on the magazine indicator lever is only to provide a constant downward force so that it keeps the lever down .....until it is pushed upward by the magazine follower after the last shot.

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