Home Forums Hunting & Shooting Gunsmithing M1909 Argentine Mauser - Lug Set-Back (Again)

Gentlemen:

I posted this question on the Gunwriter's forum, but this is a better place. I've followed a number of threads about lug set-back on the 'Fire, AR, and a few others, and there really doesn't seem to be a lot of consensus: some have experienced it, some haven't, and some just heat-treat an action from the get-go in order to avoid it. But what I haven't seen an answer to is this:

If there is set-back, after firing a round is the bolt handle stuck or hard to lift, much like it would be if a load is too hot? Or is it only caught when measuring headspace from a fired round? I hate to be a pest about this, but I have a M1909 that often has a sticky bolt even with loads that I know are loaded to lower pressures and I'm wondering why. After reading some of these threads, I'm beginning to suspect that set-back might be the issue, although also from what I understand about the only way to tell for sure is to pull the barrel and examine the action face.

Thanks

Lug set-back involves excess pressures hammering the bolt back into the recesses which creates a concavity in the mating surfaces of the action. Generally there is a small bump behind the bolt lug due to the upset of metal.

The brass in the chamber has been fireformed in the chamber and therefore is a little bit bigger than when inserted (yes there is some spring-back in the brass, but it is still bigger) and the combination of the little bump behind the concavity and the bigger brass makes the bolt difficult to lift. It will also be a little tight when closing on that fired brass.

On Mausers small incipient cracks can often be seen radiating forward from the rear back corners of the bolt lug after set-back has occurred.

Thanks. I appreciate that. I can't see anything on the lugs: no bumps, no cracks. I don't get it. I'm going to fire some factory 140-grain Core-Lokts and see what happens. I know the 175-grain RN loads I shot through it are ambling along at about 2300 fps using Ramshot Hunter - nothing even marginally hot - but the bolt wants to stick. From what I understand, M1909s are a little harder to cock than M70s or commercial M98s - and this is true of another M1909 I have that was built with a hardened and trued action - but this is significant. I'll see what the factory rounds do. So far it's a mystery.

Thanks again.

The cracks would be on the bolt body beside the trailing edge of the lug and may not show. A simple mag particle peek will see the crack before the eye can.

You are not likely to SEE anything, even if you have set-back. The details you describe say your rifle has lug set-back.

I'not seen any cracking of the bolts on mausers but I have seen numerous cases of setback of the lugs in the receiver. Most often, this occurred in actions which were loaded real hot and/ or had been opened up for a magnum cartridge. The upper locking lug seat ended up with a ridge corresponding to the ejector slot in the left lug. I suppose this could be corrected by machining and re-heat-treating but I would not bother. GD

I have read a bit on the heat treating of the action on the 1909, basically some receivers are "soft" resulting in lug set back often at lower pressures. They can be tested , Rockwell harness etc as well as be re-heat treated to a harder standard.

A sticky bolt lift can be caused by many things. One of the best ways to verify setback is to pull the barrel and inspect the lug seats.

Mausers are tricky to diagnose due to their split upper lug. When the lug seats set back, a ridge is left due to the ejector slot cut through the upper bolt lug. This can lead to a false "good" reading if you try to use a headspace gauge. Because, as you rotate the bolt into battery, the bolt lug contacts the ridge and is forced forward into the gauge. The gauge being hardened steel, doesn't compress and will read like the headspace is fine. However, if the bolt would be allowed to go into full battery, then the excess headspace would be apparent.

In all the Mausers I worked on that had setback, not one had the bolt lugs set back or cracked. The setback was confined to the receiver's lug seats. The only Mauser bolt I saw with a cracked lug was an FN commercial. This due to the fact that the entire bolt was heat treated again after the swept bolt handle was welded on. Early commercial bolts were repurposed military bolts that had the new handle stick welded on. Then the bolt was re-heat treated. This of course resulted in a bolt that was too hard.

Mike--just checking.

You have tried different brands of brass?

Define sticky bolt? Is it simply hard to cock? Hard to lift the bolt only after firing? I take it this is chambered in 7x57? New bolt handle?

Thanks for all the comments.

Yes, 7x57, and yes, two different brands of brass.

I picked up this rifle as a foul weather rifle since it was in a B&C stock. I fired a little over half a box of Prvi 158-grain factory rounds and noticed then that the bolt was a little hard to lift after firing. I needed the bolt handle lowered a bit to clear the ocular, so had a new handle installed. I took it back to the range and fired a fouling shot using a 154-grain Interlock in a Hornady case. I almost couldn't get the bolt open even though the round is loaded moderately. I then fired a few more low velocity loads (175-gr @ 2300) loaded in Prvi brass, and even though the bolt wasn't nearly as sticky as with the Hornady load, it was still hard to open, about the same as the first day I shot it. As I mentioned before, from what I understand 1909s are a little stiffer than a commercial Mauser on cocking - borne out by how easy my Zastava M98 is to cock, not to mention my M70s - but this one is even harder to cock after firing.

I guess the only way to really know is, as you mention, to pull the barrel and check.

Thanks again.

Sounds to me like when you had the handle installed, they softened the cocking cam on the bolt. Pretty common.. Worth inspecting. If that doesn't do the trick, then pulling the barrel may indeed help determine what's up.

The fellow who did it is a pretty well-known custom gunsmith who specializes in Mausers, but it's certainly possible. I just need to think about whether or not I want to put any more cash into it as it currently sits. Of course, unless the action is ruined it could always become the basis for a custom or semi-custom build.

In any event, I certainly appreciate y'all's comments and the sharing of your expertise.

If the bolt lift is difficult after firing but not as difficult when empty, The lugs have probablyset back. The way to know for sure is to pull the barrel and have a look. GD

Definitely would listen to z1r & greydog...you have probably done this but just in case. The unusual seems to come with the exclusive crap I buy used.

chamber smooth & round?
measured the throat for seating?

Oh, I'm definitely paying attention. You can count on that!

Yes, the chamber is fine. Actually, and oddly enough, I have two other rifles that will chamber a fired round from this 1909. I have not, though, measured the throat for seating.

Did not intend to imply the bolt lugs actually get set back much, but rather they crack. I can find several bolts here that look like your picture just before the lug calves off. I can also dig out bolts that show tiny incipient cracking either through the lug or in the bolt body.

I do appreciate the commercial mauser information as several have been FNs.

Lets examine what happens when you have lug setback.

I think what you get is excess headspace.

I had a good friend who was a gunsmith (now deceased) who had lug setback on a military FN action. The caliber was 25.06. He had a tendency to load his ammo on the hot side of things. the lugs had rather severe setback if I remember correctly. And what he did was remove the barrel and then did what was necessary to reheadspace it. It worked fine thereafter.

Wow! That was superficial.

Headspace is not the biggest worry. It may remain within SAAMI specs with a serious issue extant. After shooting a round the bolt lift is difficult because the case has grown to fill the space and the "ridge" described by z1r (back side of the concavity as I described it) cause serious difficulty in lifting the bolt. Excess headspace is not an "if then, therfore" situation at all.

I appreciate everyone's comments. One more question (or maybe a compound question) and I'll let it go.

Ignoring cost/benefit entirely, assuming we're talking about lug set-back, can this issue be fixed? If so, who would do it and any ballpark as to cost?

Thanks

Two steps:
Determine if the action is hardened. Since cost:benefit is not in the question, have it rehardened if needed.

Have the barrel receiver lugs reground to clean up the divot/ridge and have the barrel set back a thread or two and remembered.

I have not had one done in a long time, but it used to be cheap.