Sticky bolt on marlin 39

[uscra112]

Oh, but it has to, or the cartridge wouldn't fire. The nose of my firing pin is stepped. The upper part does protrude, the lower part only comes flush with the bolt face.

Do you have any really low-powered ammo, like CCI Quiet, or one of the "subsonic" varieties? Can you make it jam up with that?

[Bazoo]

I mean the firing pin doesn’t come past the protrusions on the bolt.

The gun doesn’t lock at all with armscor or Winchester wildcats or shorts. I’ve shot 300 rounds of armscor or more. It has locked with minimags but upon cleaning the chamber, before tightening the headspace, had stopped.

I’d like it to shoot Remington ammo cause I have 5k+ rounds of it. It I also have a fair amount of the aguila, and it’s available here most often. It has only locked up once, and with my buddy shooting it, using aguila since I tightened the headspace. So I’m hoping it was him not closing the lever all the way.

[uscra112]

So I'm wondering what peak pressure your Remington ammo is actually loaded to. You can get the same MV loading a smaller charge of fast powder as you can loading more of a slower powder, but the peak pressure is higher. Counterintuitive perhaps, but some of my research suggests that .22 rifle ammo is loaded with something like Herco, not a superfast powder like Clays. I would not have trusted the old Remington not to have loaded the lot you have with a faster powder, for "reasons". . . . . . Like they were going bankrupt.

OK, hypothesis: High pressure load expands the rim thickness, and elastically deforms the action a little bit. Pressure released, the action springs back, trapping the expanded rim in a vise, (i.e. bolt face and barrel face.) Test by measuring before-and-after rim thicknesses.

Precedent: Savage 99s chambered for the .25-35 , a strongly tapered case, were notorious for very hard extraction if the cartridge were loaded hot. Receiver would elastically stretch, letting the cartridge lengthen. (Remember the 99 locks up at the rear of the bolt.) On relaxing the action would drive that lengthened case into the chamber, sticking it but good. (Almost a locking taper like the Morse used in tool holders.) Fix was to ream the chamber to an "Improved" shape with much less taper.

Rifles that locked at the front of the bolt, i.e. turnbolt actions, never suffered this problem.

[2152hq]

Another thing to check is for a cracked bolt.
Yes the Model 39A has the reinforced HS bolt, but they can crack as well especially from the hyper vel/pressure .22LR rds. Not often a problem but it can happen. Worth a look.
The cracks if they occur will be in the same locations as the bolts had them in the '97 and the early 39 from HS ammo use.
The thin web that separates the locking surface lug from the firing pin slot and the inside angle of the extension of that locking surface from the bolt.

Use a loup or magnifier and take a careful look at the area.
In the very least you can rule out the possibility.

[uscra112]

Hmmm. I wouldn't have linked the 39 to the 1890-1915 "boys' rifles" I collect, but it isn't really all that strong, now that you mention it. Nothing but that strut on the lever holds it closed, and that bolt is not exactly solid, what with all those slots in it.

[Bazoo]

I did check the bolt for cracks but not real well. I will check again. The new rem ammo is made by the Arkansas plant I believe. I talked to a woman there in regards to a different lot number that blew a friends gun up. Anyways.

There is in my bolt, where it locks, some wear in the form of metal that has moved from the lug and is slightly mushroomed off the sides. You can feel it with your fingernail. So I had excessive headspace. Bolt thrust is battering the locking lug. What causes bolt trust? Excessive headspace causing swollen cases. Fixed the headspace. What else. Chamber that is Uber smooth, not the case here. Chamber that has gouges? Mine does. My brass comes out scored. It extracts fine if it doesn’t lock up. It feeds fine. Could it be that there are burrs or high spots causing the brass not to grab the chamber walls and allowing the casing to push against the bolt face with excessive force? That’s what I’m thinking now, but I’m still studying in it.

Unless the rifle came from the factory with excessive headspace, something has to have caused it.

[Bazoo]

Well after reflecting and research I have an idea. The firing pin. The firing pin is proud of the bolts rear in its forward most position. The agi video (while nearly worthless) said the pin should be a couple .000 less than the bolt rear when no cartridge is present. I can imagine how that could help with bolt thrust, if the hammer, after crushing the rim of the cartridge also supports the rear of the bolt. But it also would give it a jolt at about the same time pressure was starting to rise or even peak. Maybe that’s just the bit of help it needs.

All of my research shows when fitted it should be below flush on the rear. It didn’t occur to me that might be an issue and could be the root cause, that caused the wear and the excessive headspace.

We shall see if it cures or helps the problem.

[uscra112]

Interesting hypothesis. In a lot of hammer-fired single shots we count on the hammer to back up the firing pin, but in this case it backs up the whole bolt!

Have you tried measuring rim thicknesses before / after yet?

Looking at my old pre-Microgroove 39, the pin is flush with no cartridge under the pin, but proud by about .005 after firing a round of Thunderbolt. (by Mk I calibrated eyeball.). How about yours?

What is the firing pin protrusion in front? Ought to be .030" - .040". Lean toward .030" if the gun has tight headspace. I set my .22 single shots to .035".

--------------------

On closer inspection under 10x magnification, my pin without anything in the chamber is also .005" proud at the top, flush at the bottom, at the rear. Hammer is bearing on the proud part. .

What stops the pin in the forward direction is the small rectangular lug on the bottom, forward of the one the lever hits to retract the pin. Preventing dry-firing damage to the barrel face.

[Bazoo]

My firing pin was probably .10 proud when all the way forward on an empty chamber. I removed material until it was flush or about. Fired it. Immediate improvement. It did still lock up but only a few times out of 80 rounds and not so hard I couldn’t work the action but enough it was noticeable.

So I went back in and removed maybe .004 more. I also dressed the top rear of the firing pin at an angle to better match the bolt. Though it’s still a bit proud there.

I also inspected the pivot area of the frame where the lever turns. The part that the outer portion of the lever rides against had some fouling. Looked like maybe a small speck of lead got smashed there. I wire brushed that and then polished that inner surface with 1000 grit paper.

Fired 3 magazines with no issues.

All of this with the Remington thunderbolt ammo.

[Bazoo]

One point of interest, is I’ve read many hours on several forums, and I cannot find anyone that’s had similar problems as I have. It mustn’t be a common issue. It could be a specific angle or tolerance that needs attention but it would take a smith that’s seen it before to diagnose it.

Could it be that speck of lead? Maybe. But each of the other things helped the problem. First, cleaning the chamber thoroughly, then tightening the headspace. Then shortening the firing pin. So, was it all these problems? If I had shortened the rear of the firing pin to begin with would I have still had intermittent locking up issues?

The firing pin still protrudes past the rear of the bolt after I’ve fired a case, so other than changing the angle, what else could it be affecting?

[uscra112]

Three mags of the Remington that was giving you such trouble? Wizard.!

That .10 protrusion sounds like too much to be just a tolerance stackup. Wonder if there might be different firing pins for different models, and you had the wrong one. Or an aftermarket one that wasn't right.

Still wishing to see before/after cases, although it looks like it's too late now to make any new ones. I have a Ballard that has the flat type firing pin, exactly like the 39. It is a little too short, so on firing the case head bulges a good .005 or more into the slot where the front of the pin should be supporting it, backed up by the hammer. , And that's with Standard Velocity ammunition. So it's a lead-pipe cinch that your HV cases were expanding, the bolt not being backed up by the hammer.

Took a long time, but it sounds like you have it licked. Write up a summary for the Marlin forum(s).

[farmbif]

I'm in the camp that says just shoot ammo that works well in it. the rabbit hole can get pretty deep trying to manipulate the gun to make it work with all brands and types of ammo. ive got 3 39a's and the newest golden likes winchester and cci ammo, one of the mounties shoots cci quiets real well. the other mountie will shoot anything its fed well but the takedown screw likes to loosen on it and when that happens it jams up.
but my problem child marlin rimfire is a 57m which will just not fire Hornady ammo, no way-no how, a trip to a real good gunsmith who knows what he's doing, rebuilt it with all the new parts I was able to scour out of many many google searches, guess what? it still will not shoot Hornady ammo, so it gets a diet of federal, winchester, cci and armscor 22 mag ammo.

[uscra112]

With ammo in such short supply, it behooves us to make our rifles work with what we have or can get. The days of just buying six or eight brands until we find one that works to our satisfaction and buying a ton of it are gone, at least for the present.

O.P.'s battle started with the fact that he has something like ten bricks of the Remington on hand, but couldn't use in his Marlin until he sussed out the problem. What with even the cheapest commodity ammo going for $100 a brick, the effort was worth the price of a new rifle.

[Bazoo]

I am all for using what the rifle likes in terms of accuracy, or even nose profile. This wasn’t a simple my gun didn’t like Remington ammo. It was locking the bolt/lever like that of a too high pressure round would. But it did it with Remington, aguila and CCI mini mags. I have 5k rounds of Remington between thunderbolts and golden bullets, and another 5k+ combined of mini mags and aguila. I haven’t tested any federal, blazers, or other cci I have.

The mini mags didn’t do it consistently. All my research over on rimfirecentral and marlin owners shows mini mags as ammo that is likely to work well in most everyone’s 39s. All my research shows that model 39 rifles aren’t overly sensitive to ammo other than for accuracy purposes. And we ain’t talking bout bad groups, but the rifle locking solidly closed and requiring extra force to move the lever. A rifle chambered in 22lr should “function” with all 22lr ammo, exception of course being made to specialty ammo. Not to mention all the other folks that shoot tubs of thunderbolts and goldenbullets out of their 39s without problems.

Some of the cases were bulged, and still some are, but not as badly. Pretty much expect bulged cases if your headspace is set at .046 (example and a guess) and you fire cases with rims .038. While not a target headspace, if my gun is at .046, it’s acceptable and should function. No pictures though.

Thunderbolts are cheap bullets, but goldenbullets are a notch above to my thinking. Aguila is on the same as blazers or even a bit above. Mini mags are above that but below target stuff. I don’t have any target ammo but I have a brick of Norma tac22. At 10 a box, it’s not my normal fodder. For that matter, mini mags aren’t either.

[Bazoo]

I fired 4 mags full today. For a total of 7 mags. 19 per mag, so say 20 cause I can’t add well. That’s 140 rounds without a problem. At least one mag of goldenbullets today. I lost track a bit. Hope that this journey helped someone else down the line.

[uscra112]

You must be over the moon! And you deserve to be!

[Bazoo]

I’m pretty excited. I thanked God for allowing me to get it sorted out. I have a much greater knowledge of my rifle now.

[uscra112]

Most of my career was spent in manufacturing, as an engineer. I will declare here and now that, while pay was a factor, and attaboys was another factor, what really motivated us was these Eureka! moments when we'd solved an intractable problem. Massive dopamine hits!

[Bazoo]

One reason I didn’t take it to a smith to fix is I wouldn’t have learned nothing. I enjoy learning. Doing something I haven’t done, or fixing something I haven’t fixed.

Not having a smith I trust is another reason. But if I did that every time my guns needed something I’d be always having something worked on. Learning minor gunsmithing is just part of the lifestyle.

[Bazoo]

I have acquired a no-go gauge. It leaves about .10 space of closing the lever on it. This with the lever I tightened the headspace.

I installed the I modified lever I have, which was a touch tighter than the original lever before I lengthened it. No-go gage will not close on it either.

Interesting that both levers (before I lengthened one) allowed the locking issue, but after I lengthened the lever it helped the issue. So headspace plays some roll, but obviously not as much as I had originally thought.

What really gives me reason to ponder, when I shortened the rear end of the firing pin, my problem got immediately better. The only thing I can figure, is the angle at which the hammer strikes the firing pin is changed such that it’s more squarely hit. Maybe that causes the bolt to move slightly? Maybe it was causing the bolt to wedge in the action?

The thing is, why do I not find anyone else with this issue? How could it be as uncommon as it seems, provided it’s so simple?