tobnpr said:
Most likely though, the bolt stop at the top of the trigger
Hey tobnpr, bet you a beer it is the sear/spring.
Because of this:
I will add that the trigger does have a lot of back and forth play in it.
Actually it is probably a combination of both.
If the sear/spring has the proper tension, the trigger should be held firmly in place. Well, maybe firmly is the wrong word, but it should have enough tension not to flop around.
Easy enough to test, hold the trigger forward and try and remove the bolt. If it comes out, it is probably the stop on top of the trigger, if it doesn't, it is probably the spring.
Another thing to look at, some people advocate putting a spacer between the sear/spring and the action, as a way to try in improve a heavy trigger. It screws to the bottom of the action just forward of the trigger. (You can see the tip of the screw in my photo, the circular thing at the left edge of the photo.
This post over on Gunboards shows how the trigger can be improved:
http://forums.gunboards.com/showthread.php?163034-m91-30-and-shims&p=1278464#post1278464
Please note, I am not advocating doing anything listed, but his photos show what you can look for, and also shows pretty well what the Mosin Nagant trigger looks like under the wood, and gives you a good understanding of how it works.
And when you take it out of the stock to check it out, be really careful of the trigger pin. Those have a way of falling out and vanishing.
This problem does not mean the rifle is unsafe, unless the sear/spring is so bent or weak that the sear doesn't properly engage the cocking piece on the bolt. Is the trigger really light? If so, clear the rifle and cock it, then whack the side of it a couple times with the heel of your hand, as hard as you can. Also, bang the butt of the rifle on the floor a couple times.
As long is the sear doesn't release, it is probably safe to shoot.
As to the headspace, if it is a Soviet rework 91/30 it is most likely fine. You can buy the gauge set of
Amazon for ~$50, or you can make them yourself using a nickel or a washer. The 7.62X54R headspaces on the rim, so the gauge is just a metal disk.
Here are the thicknesses, as reported by Yankee Engineering
here
Military 7.62X54R MN
Go - .064
No-Go - .071
Field - .076
Really, all you need is the
field gauge. If you are rebarreling a rifle, you would need go and no-go, but all you want to check is to see if it is under the max spec.
You need a metal disk that is .076" thick, I have heard of people using a nickel or a washer that is about the correct diameter. You can also do a quick and dirty headspace check on a rimmed cartridge by putting tape on the base of a cartridge or spent case, keep adding layers until it doesn;t close, then measure the thickness of the rim plus tape, and see if it is under the field dimension listed above. If you reload, you can also check with a deprimed case and a spent primer. Barely seat the primer, then chamber the case, and let the bolt seat the primer as far as it can go. Then measure the rim thickness plus primer protrusion. and compare with the field dimension.