On a Mosin I would be concerned about the firing pin depth more than headspace. If your firing pin is out of adjustment it could puncture the primmer. I have 3 and all are fun to shoot and accurate. The best and quickest way I've found to remove the grease is boiling the the receiver in a tall kettle of water and brush out the bore until clean. Just dont do this with the woman of the house around.
That is decent advice.
I have bought, sold, rebuilt and shot probably more than 100 Mosin Nagants of all types and countries of origin from $9.95 Ufixem Russian/Polish/Hungarian/Romanian M44s from Century and several other jobbers to Type 53s, and have NEVER repeat NEVER found any Mosin Nagant with headspace issues.
Somebody said if the "bolt matches...." They are NOT Mausers! If the bolt matches I am MORE skeptical of the honesty of the seller than if it DOESN'T.
MOST Russian conscripts were completely illiterate.
They cleaned them in the field by stripping them, and putting all the metal parts in a barrel and boiling the heck out of it, and after a while, they dried them, oiled the heck out of them, and put them back together in their stock....WITHOUT matching ANYTHING. A bolt? a Receiver? A Mag and trigger housing? They couldn't tell or CARE if they matched when they came out of the barrel and slapped them together in their stock...they just had to have a complete CLEAN rifle by the time they got inspected next....
If your Mosin Nagant saw ANY service at all, it does NOT match. PERIOD.
MOST "matching" Mosins were "force matched" later, probably after they made it into the states, although some were probably done later pretty nicely by former commies who figured out they could get more dollars out of the 'Capitalist Pigs." . Yeah at first with the stupid "electropencil," so you could spot them, but later a LOT of "Mauser guys" replicated the numbers with decent punches to sell them at a higher price to the rubes...on a lot you can STILL see the grinding marks under the numbers if you look closely...but the EASIEST way is to compare the size and fonts...if they are NOT exactly PERFECTLY matching other punches on the receiver, it was "forced" sometime later in it's life.
At least the FINNS ground the numbers and markings off a lot of refinished parts, refinished them NICELY and didn't remark them....
And OUR US troops who were issued Remington and Westinghouse Mosins Nagant M91s which were the BEST ones ever made when we "invaded" Russia with the Allies in 1919? The "Tight Bolts" that were found to be a problem in the cold were fixed easily by throwing away the Remington or Westinghouse bolts and replacing them with "any" bolt from any captured Red Russin Mosin Nagant....which worked in ANY kind of weather....
MATCHING bolts are important in any old military rifle that shoots RIMLESS rounds because they headspace on the NECK, which can change with throat erosion, so they bring a PREMIUM to collectors (8x57, 7x57, .30-06, etc....)
One of the reason RIMMED rounds are so much BETTER for bolt action MILITARY rifles is that it is SO hard to MESS with headspace..no matter HOW much the rifle is shot...
The ONLY Rimmed round you might want to check is a shot alot .303...that screw on bolt head on some Enfields CAN be "set back...." (I've never had one do that, BUT I have heard guys I trust say they have...)
As to the advice above... I HAVE had to adjust a few bolts because of that....
The Mosin "multi-tool" to take apart the rifle and/or the bolt (which was almost NEVER done by the troops....)has measuring cuts to measure the firing pin protrusion, and I HAVE had to adjust a few, which is done with the screw in the very back of the bolt...
But EVERY one I have had to adjust, had the "cheater marks" out of whack which warned me to check...
When they adjusted the firing oi n at the factory, they punched "cheater marks" through the adjusting screw into the sides of the back of the bolt....if the lines line up, it PROBABLY is OK. If they don't, it has been changed since the factory and you should check.
Every Mosin I have rebuilt, or put together from parts, or suspected for any reason, I did a "Polish Headspace Test" on....
Load it with any surplus BRASS cased ammo, bungee cord it tightly to a tire/wheel, tie a string or a wire to the trigger, walk back 30 feet or so, and pull the string....
When it fires (and doesn't blow up) eject the round, and INSPECT the BASE with a glass..(ignore any splitting or cracking in the neck or even higher up in the case, Russian and Combloc brass annealing was NOT very consistant....)
The signs you are looking for is the last 1/4" or so in front of the rim...IF you have headspace issues, you SHOULD see stretching, cracks or other stress marks in that area...
Like I said, I could give you a better description if I had EVER found one that qualified.
I did this three times with each of them, and if I saw no evidence of bad things, I removed the string, and put a mag through it slow fire from my shoulder confident it wouldn't blow up to test for accuracy, then at least two mags through it as fast as I could with stripper clips to check function before I decided to keep it or sell it, and gave a good description of the firing test to the buyer. (Plus the HEAT from the rapid fire allowed me to clean a LOT of crud out of the barrel TOO....LOL)
That is NOT to say somebody WON'T find one with headspace issues someday...I haven't is all it means.
BUT I have bought more than a FEW for a song that the seller said "had Headspace issues" because they had "tight" chambers that wouldn't chamber a round without hammering the bolt home that I turned into shooters and resold...



Headspace NEVER "tightens..." from wear.... it LOOSENS.....
A tight chamber is a BUYING point on a Mosin...you WILL get it cheap, and a little REALLY fine valve polishing compound on a 20 ga swab on the end of a section of cleaning rod in your drill will remove a LOT of the green junk guys have accumulated in the chamber that got there from shooting green lacquered steel cased ammo in HOT chambers, and get it working SMOOTHLY....
BTW...because of my experience with this, I won't shoot ANY of the green laquered steel case x54 stuff I bought cheap back when and put back through ANY of my Mosins....unless Socio-Economic collapse FORCES me to use it, AND if I haven't TRADED it already to other Mosin owners for Chickens or Goats or eggs or something....



