I have a No.4 Mk 1 problem

[bernie]

I am cleaning a bunch of guns for a friend's widow, and fixing problems with them as I come across them, but this one has me stumped. He has a No. 4 that he bought years ago and never fired it. He told me at the time that it had a headspace problem. It had a No. 1 bolt head on it and when I tried it, it worked just fine as long as no cartridge is in the chamber. It closes just fine. However, if you put brass or a cartridge in the chamber the bolt only goes about halfway down until it will not move any further. He had ordered a No. 0 bolt head and it was on his loading bench, so I put it on thinking that might resolve the issue, but the same thing happens. Do you guys have any idea on what may be wrong with it. I know that it appears to be out of headspace, but what specifically might be the problem. I would like to get this fixed for my buddies widow as she said she really wanted all of his guns to work properly.

[mike24d20]

this may sound weird, but check to see if a part of a cartridge has split off in the chamber area. You can also do a chamber cast to determine exactly what the correct cartridge should be.

[Sunray]

It doesn't matter what the bolt does on a cartridge. It's what it does with a proper headspace gauge that matters.
This a military configuration No. 4, not a bubba'd rifle? Any chance it may not be a .303 Brit? That "No. 1" is what's stamped on the lug and it's not a No. 1 Mk III bolt head?
"...ordered a No. 0 bolt head..." Wrong one. Number should go up, not down. Try a 2, but that does not guarantee anything. First make sure the bolt head is screwed on all the way, as daft as that sounds. Happens a lot. Then check the headspace with proper gauges. No bits of tape, re-sizing to headspace on the shoulder, shims, chewing gum, rubber rings or any other silly ideas seen on the 'net.
"...if a part of a cartridge has split off..." Chambers a cartridge.

[Parashooter]

"...ordered a No. 0 bolt head..." Wrong one. Number should go up, not down. Try a 2, . . .

On what planet would a longer bolt head (#2) help with a suspected insufficient headspace problem?

Bernie, chop an empty .303 case off about 1/4" ahead of the rim and try it in the chamber. If the bolt closes OK, your problem is not insufficient headspace (with that specific rim's thickness). Could be debris in the chamber. If the bolt won't close on the chopped case, that's a pretty good sign of insufficient headspace, crud on the breech face, or some kind of extractor interference.

[John Sukey]

I tend to agree with mike. I have had that happen once. Fortunately I have a broken shell extractor.
You have no idea of what ammo was last used in the rifle.
Suggestion. A tight fitting patch from the muzzle might remove a broken case.
Another thought, use a bent wire from the chamber end Which may pull out a broken case.
Failing all that, it's a trip to a gunsmith who has the proper tool

[S.B.]

First of all, I would check the chamber carefully to determine if a broken shell case is stuck in there(used broken shell extractors are available from a number of surplus gun part dealers, that would be the easy fix. If nothing in the chamber, have a qualified gunsmith with head spacing gauges check to see if it needs his or her attention.
Steve

[Sunray]

"...an empty .303 case off about 1/4" ahead of the rim..." Tells you absolutely nothing.

[Parashooter]

"...an empty .303 case off about 1/4" ahead of the rim..." Tells you absolutely nothing.

Horsefeathers. Attempting to chamber the back end of a normal cartridge can eliminate the front end of the chamber as the source of the described problem. (And I still want to know how you imagine a longer bolt head would correct possible insufficient headspace.)