View Full Version : Headspace
08-07-2008, 01:03 PM
First off Iam new here and have been a person in the background. Great site. My qusetion is should a bolt in a 91 be loose with some for and aft play with no round in the chamber. I have one with a nice shiney bore but a loose feeling bolt.
Would like to shoot it with some cast boolit loads but not sure if it is safe. Do not know of any gunsmiths in my area to have it checked out. (Oregon} maybe somebody can help me out
08-07-2008, 01:40 PM
You can also allow for the extra headspace by fire forming brass with a light load and then not over re-sizing the brass. Basically you will be moving the shoulder forward a bit. BTW- My '91 has a bit of play too, but it's more in the design than wear and tear.
08-07-2008, 03:46 PM
Wow...I've been shooting M91s for 30+ years and now I find out they are "well known for developing headspace"! I never heard of that before. I'm well aware of the problem with softer Spanish M93s. Everyone seems to think all spanish M93s are soft but they are not.
To answer the question; yes the bolt will have some end play. This is because it cocks on closing and when closed with the striker forward it does not have a cocking lug to provide tension. A perfectly normal situation for the M91. I've measured the heaspace of numerous M91s and found them all to be quite close and well within military specifications of go, no go and field. Actually they are of closer talerance than most M98s. This is because they are a push feed action and do not have the controlled feed claw extractor. Thus headspace tolerances were held close because the extractor has to snap over the cartridge rim.
I have pressure tested Norma 7.65 ammo in one of my M91s and it does push 51,000+ psi (M43) just as Accurate Arms manual says it does. I've shot several thousand Hornady 150 gr .312s out of several M91s (I currently have 4 still in 7.65) over the years. A similar load with the same type of powder in AAs manual lists the same load at 48,800 psi. I have not used that AAs powder yet to see if that figure is close to what I get with the M43 but I suspect it won't be too much different. That load produces a pressure of 51,500 psi (M43) with a velocity of 2850 fps (cut down rifle with 24" barrel). That duplicates the Norma load. I've not experienced any indication of headspace increasing in that rifle or any other I've shot that and similar loads in. BTW; the Argentine milsurp ammo is also loaded right up there.
08-22-2008, 05:56 PM
Excessive headspace only pertains to factory length cases(factory ammo), and so isn't a problem for reloaders. Just load your first batch of ammo with the bullets far enough out there, pressing against the rifling, to keep the case head against the bolt face. This will prevent any initial case stretching. You can then set your sizing die to either neck size, or if you have chambering problems, minimum full length.
Just consider wildcat cartridges, and how we fire form the cases initially. It's just like that but to a lesser degree.
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