Cold natured rifle

[Virg461]

OK guys, I have a question about temperature.

I have an MAS 45, which is a .22 cal trainer based on the Mauser design. they were built in France for a few years starting after WWII.

Anyway, it's a great rifle, built like a tank, weighs almost 9 lbs. It's been shooting great, especially with Wolf Match.

However, I had it out last week when it was pretty cold (about 28) and I couldn't get it to shoot worth a flip. It went from the normal half inch groups at 50 yards to 2 or 3 inches.

I checked to make sure everything was tight, couldn't find anything amiss, gave up and went inside to warm up. That night I started thinking about the way the barrel was set into the stock. The action is held in place with two screws that go through the steel trigger guard. However, the front sling attachment screw goes right through the fore end of of the stock and screws into a piece that attached to the barrel itself and holds the barrel down into the stock.

The next day was just as cold. I shot a few with everything as is, and the groups were all over the place. I unscrewed the sling attachment, and the next group of five I fired went into one ragged hole. Off to the left and down about an inch, but a very tight group. Next group was even better.

I've shot this rifle many times, but never in weather this cold. Is the wood stock contracting in the cold and throwing me off, or the barrel? It's obviously the cold weather, as I've never shot this rifle with the screw loosened. In warm weather, its never been a problem. Anyone else seen anything like this?

 

[BrocLuno]

SO it's in the house and warm until you take it outside to shoot? Does it just go off from the get go, or start to string away as it cools outdoors?

Most likely the wood is drying out in the freezing weather - freeze drying. It's shrinking and pulling the barrel one way or another - putting tension on the barrel. Of course the metal is reacting too. But I bet if you pulled the barreled action and made a homemade mount for it with a free floating barrel - you could shoot tight groups all day. Put it back in the stock and it'll act differently.

You can try to work out some way to stabilize the stock by soaking it with penetrating epoxy when it's the driest. That should get it as good as it will be. You could maybe relieve that front screw area and make a resilient bushing that will give a bit as the stock moves?

 

[Picher]

The fault may not be the rifle, but the ammo. Some types don't like cold temperatures.

Rifles also may have temperature issues, but not by design, mostly by maintenance. Many gun oils, especially as they age, congeal in cold weather, slowing firing pin striking. With rimfires, solid ignition is more important than with centerfires, which have more consistent priming.

You should disassemble the bolt, clean it well with Gun Scrubber or brake cleaner, then lightly lube with a cold temperature lube, preferably moly.

 

[Virg461]

Picher,

I hadn't considered the ammunition, but that's food for thought. It's interesting, though, that as soon as I loosened the screw, the groups tightened up.

I can't help but think that there was some sort of binding occurring as either the stock or barrel contracted in the cold.

I suppose an interesting test would have been to tighten the screw back up to see if the group size worsened again. Maybe just releasing the "tension" when the rifle is at stable temperature is enough.