[Bob_The_Student]

Update: bought used "flat bolt" (what he wanted) and changed all parts mentioned above (ejector, extractor, bolt, recoil spring) and still have same issue. I now have rifle in my possession to disassemble and give it look. I'm now going after Ebeebys thought with binding bolt release.

I'm going to check gas system also. He said he did but...

 

[curly1]

The piston should be good if you can hear it freely moving when you tilt it down and up.

 

[Bob_The_Student]

I disassembled the rifle and I backed the gas piston nut out with my fingers is that OK? Does it need to be staked? Or just a good tightening with the wrench? The bolt catch does seem a little "gummy" I'm going to shoot some acetone in that area and try to degrease/ oil out of there and then re-oil it. I want to see if it operates a little smoother.

 

[USAAF]

Was the nut finger tight or just a bit loose? If you use the wrench be very very very careful you do not over tighten the castle nut. It is very easy to crack the piston housing. If cracked you will not be able to weld it in any form.(as it will crack again shortly.) Barrel replacement required. Just make it snug. you can also stake it in place too. Have you replaced the magazine release with a new type 4? Have you checked the magazine plunger assembly for damaged or broken springs. If these get clogged with dirt the can cause the magazine catch to drop.

 

[Bob_The_Student]

I easily back out the nut, so it was loose. The mag release looks real good not a lot of movement with mag and locks nicely. I cleaned up the rifle and lubed it and used 2 of his mags and did multiple "manual" mag dumps and had no issues. I know it's not the same as shooting it but I wanted to see if I could replicate. I did have a feed issue, a couple of times, when I rode the bolt on purpose. The recoil spring seems real strong and I don't see anything in the way of a burr on the action (feed ramp, chamber, etc...). The bolt stop/release seems to be smoother and not "gummy" as it was previously.

 

[Bob_The_Student]

Shot the rifle today. STILL NEED HELP!!! It fired one round and didn't feed just like before. However, this is what I believe is happening... it feels like there is a "rub" about midway when bolt is traveling rearward. What I think is happening this "rub, obstruction, etc..." is slowing down the bolt enough that it isn't cycling all the way to the rear. Therefore, I think that the bolt is not able to catch the rim of the next cartridge in the mag because the bolt is sitting on top of the cartridge instead of dropping or allowing the cartridge to pop up to catch to chamber.

Any thoughts? What is the best way to figure out where the "rub" is? Should I use chalk or something? Any other ideas? I open for any other thoughts. I also thought about swapping the slide out and seeing if that's the problem. I don't know!

Appreciate any other thoughts.

 

[lambo35]

Take the action out of the wood, remove the recoil spring and trigger group, tip the barrel down 180 degrees from upright, see if the bolt and slide close smoothly and lock in battery, now rotate the barreled action 180 degrees to the muzzle up position, does it rotate completely to the rear okay? Now try the same routine with the action in the wood, any interference?

Chuck

 

[Bob_The_Student]

Lambo35, no obstructions either way. In the stock same result. I did try it after recoil spring was removed and left trigger group in. I noticed when I tilted it towards the rear of the receiver the slide/bolt would stop in the area I felt the "rub" yesterday. I posted photos below. Is the hammer my issue? Notice the wear? I posted photos of 2 new hammers for comparison. I also included of photos the way the trigger group is now. I have not disassembled the TG until you guys look at it and say this or that looks like this or that is wrong.

To me it appears that the bolt is rubbing the hammer and wearing a "half moon" in to the current hammer. If that's normal give me another place to look. Do the springs look good and correctly installed. Again I have not touched the trigger group it is how it was when this problem started. Thanks

New hammers:

Problem?

 

[Bob_The_Student]

of course it wouldn't let all photos fit.

Sorry for the huge photos that is a different file format.

 

[scooterwrench]

Only thing that jumps out at me is the hammer spring is coil bound. That would create enough friction to keep the bolt from sliding freely. Try removing two coils(don't think one will be enough)from the spring and see if that helps.
Lightly grease the hammer and bottom of the bolt. This is a high friction area.

 

[Bob_The_Student]

What do you mean it's bound? And the wear on top of the hammer is correct?

 

[scooterwrench]

When a spring is fully compressed the coils stack together and the spring is coil bound. I cannot compress any further,it is mechanically locked. That spring looks like it may have been replaced in the past and not fitted to the rifle. Probably installed by a parts changer. The hammer spring adds to the recoil spring tension until the the bolt passes over it. The pressure of the piston may not be enough to overcome the tension of the recoil springs and the hammer spring if it is too strong. Remove the recoil springs and install the bolt. Drop the hammer and see how much effort it takes to slide the bolt back and cock the hammer and how much drag there is once the bolt passes over the hammer.

 

[scooterwrench]

Excessive hammer spring tension will accelerate wear on both the hammer,bolt and bolt guides.

 

[lambo35]

Try exchanging [with a friend, gun shop or?] your entire trigger group with another and fire ten or so rounds to see if there are any functional differences between the two trigger groups. This may help isolate where the problem exists, trigger group or barreled action.

Chuck

 

[Bob_The_Student]

Drop the hammer and see how much effort it takes to slide the bolt back and cock the hammer and how much drag there is once the bolt passes over the hammer.

This seemed normal. Didn't notice anything that seemed like it was extra "effort".

Try exchanging [with a friend, gun shop or?] your entire trigger group with another and fire ten or so rounds to see if there are any functional differences between the two trigger groups. This may help isolate where the problem exists, trigger group or barreled action.

Chuck

Changed entire TG and same issue... fired and next round barely moved forward to chamber.

 

[lambo35]

Have you tried using some USGI ammo? Did the bolt ride over the cartridge an close or did the cartridge keep the bolt from closing ?


Chuck.

 

[daveccarlson]

I had a vexing and baffling failure to feed on the last round issue... Turned out the magazines had the follower spring installed the "wrong way," which I didn't think was possible...?

 

[Bob_The_Student]

Have you tried using some USGI ammo? Did the bolt ride over the cartridge an close or did the cartridge keep the bolt from closing ?


Chuck.

Bolt does not close.

 

[lambo35]

Bolt does not close.

Bob, does the bolt jam on top of the the cartridge past the rim or?
With a calipers measure the distance of the bolt face from the bottom lip that catches the cartridge rim to push it forward to the center of the firing pin hole. The Kuhnhausen manual, pg.114, shows the distance should be .305" -.005"R. A nos .U. Underwood bolt that I have measures right on spec. A measurement of less than .300" would be too short and out of spec, that bolt should be replaced with one that measures within the above specs. I hope this helps.

Chuck.

 

[Bob_The_Student]

I have changed the bolt this is another bolt recently purchased. The owner wanted another flat bolt so that's what he got. The original was an Underwood the new one is a Winchester I believe.

If I remember correctly the bolt is riding on top of the cartridge and past the rim of course. It seems the next round is just slightly pushed forward until it rides over the top and bolt jams open.