Springfield Arms 1903 questions

[scythefwd]

OK, picked up a high sn# 1903 made in 1917.

I'm looking at this, trying to understand the geometries of the bolt and stuff.

Looks like the lugs themselves are squared off, so no camming forces applied there, but the safety lug (the third one towards the middle of the bolt) appears to be slightly ramped, and all camming force for the bolt is applied there against the reciever? Is this right?

Primary extraction appears to be handled by the bolt handle where it meets the body of the bolt (yeah, I know its one piece, but it was the best description I could come up with).

I'm not seeing any obvious way to manage firing pin protrusion in the design of the 2 piece FP. Is this possible? What should the protrusion be?

Thanks.
Scythe

 

[MEHavey]

The safety lug actually should have a distinct gap between it and the receiver when he bolt is closed.
All camming closure comes from the front two lugs. Put some black magic marker on the rear of those lugs
and see where it rubs off as the bolt closes.

 

[rcmodel]

Right.

And there is no need to 'manage firing pin protrusion' on any U. S. Military rifle ever made.

Tolerances are such, they manage themselves, thank you Uncle Sam for building each and every one to the same exact specs!

This isn't a Mosin Nagant you are dealing with here.

The third lug is strictly a Safety lug to prevent the bolt blowing out of the receiver in the event of a total front receiver ring failure, or simultaneous failure of both locking lugs.

It should be no closer to the receiver ring then .004" when closed, but much more then that is acceptable.

Closing cam force is applied by the bolt lugs locking into the receiver recesses.

Extraction cam force is from the bolt handle cam surface applied to the back of the rear receiver ring on opening.

While not as obvious as the extraction cam on a 98 Mauser, it is there and works quite well.

rc

 

[Jim K]

The safety lug does not do the primary extraction, in fact it does nothing at all, not even touching the receiver unless the primary lugs fail. Primary extraction is done by the cam above the bolt handle root interfacing with a cut in the receiver.

The firing pin stop, which controls firing pin protrusion is in the bolt sleeve where the firing pin cocking piece contacts it. Some folks think the firing pin stop is in the striker, but that is not true.

There is no adjustment to the firing pin protrusion, and there were no parts variations issued. IIRC, it is normally .065-.070".

Jim

 

[scythefwd]

Jim, I never said the safety lug does extraction.

RC and MeHavey - I'll pull out the feeler gauges and check. It sure as hell looks like its making contact. I'll blacken the lugs (a 3) with soot and see what rubs where. My locking lugs are square, so they're not the ones applying any camming force, BUT the cuts in the recesses in the receiver could be ramped to create the camming force vs. it being done with the profile of the lugs on the bolt. The safety lug and the slot it fits in the receiver is very much both profiled so that they would cam against each other...

I just picked this rifle up so I"m still looking at the how it works thing, not just how to disassemble it. Unfortunately its not a trivial thing to pull the barrel to see the profile of the recesses.

Thanks for the info. Like I said, I'll fire up a candle and blacken the lugs and see what goes from there.

Extraction cam force is from the bolt handle cam surface applied to the back of the rear receiver ring on opening.

^RC - I think we're in agreement with that.. its a pretty obvious camming surface providing that on this one.

This isn't a Mosin Nagant you are dealing with here.

- True, the tolerances are going to be much tighter, but its still 1917 technology that built this.. probably earlier since they didn't re-tool every year. Expecting .001 consistency is pretty much unheard of, especially with something "mass" produced.


EDIT - 1918 rifle/tech.. huge difference that one year made in these. This one is a high serial number in the 880k range..

 

[scythefwd]

Well, got home from work, took a flame and blackened the contact surfaces of the locking lugs and the safety lugs.

ran the bolt into the action, applied some reward pressure to the bolt (I had the guts out.. just the body). It appears only a little bit of both lugs is touching the recesses. About 1/4 of one, maybe 1/2 of the other, and the safety lug isnt touching at all, very small gap. Thinking of taking a little lapping compound and lapping the lugs until I have full contact of the locking lugs, which will also probably require a little bit of lapping on the safety lug to keep it from contacting (it may may not.. probably only need to take a micron off or so). Then reset headspace as need be... Or I can fire it as is...

 

[MountainBear]

Check the headspace. Get some ammo. Shoot the gun. Repeat steps two and three as necessary.

Frankly, 25% and 50% on the lugs is considerably better than I've seen on some of the new Remington 700 receivers I've worked on. Lapping in the lugs and then working on resetting headspace will be a complicated project. The barrel is cone breeched, and has a cut for the extractor. In order to fix headspace, you will need to move everything at least one full thread rotation so that everything lines up again (i.e. the extractor cut), and then use a chamber reamer to cut the chamber back to spec. That can be accomplished by hand reaming or using a pull through reamer.

Frankly, it seems like a situation where if the gun ain't broke, don't fix it.

 

[MEHavey]

About 1/4 of one, maybe 1/2 of the other....

That's good 2 Go, my friend.
Don't fix it.

 

[scythefwd]

Mountain.. saw how to chamber ream these in a video with Larry Potterfield.. looks like a pain. I'll leave it be after I get headspace checked.. for now lol.

MEHavey - oh, shes gonna get rebarreld some day.. probably into something like a 6.5-06 with an ackely shoulder geometry.. especially if I cant get this barrel to shoot.. Luckily I know a real gunsmith.. the type that actually fabs parts as needed. When I get it rebarreled, I'll have him lap the lugs then and then swap the barrel.. if you're gonna have everything off anyways, might as re-assemble it right.

Thanks for the info folks.. I really do appreciate it