Thread: How much clearance is needed

Between the scope and a rail .
Will a barrel expand more than say 0.06 of a mil if it gets hot therefore pushing the end of a rail or mount up onto the bottom of the bell of a scope , therefore mucking with the group
I'm not talking whiz-bang calibre here just 30 06.?
I can easily fit a piece of A5 twixt both but seems to touch both the bottom of the scope bell and mount
When looking it sideways it looks , fuzzy, but when you have a proper look there is a definite gap

What do you all think? maybe move it forwards a couple of mill just in case but then want for proper eye relief. Old eyes.

wouldn't think it would matter.. on a savage I had in the past you could literally just slip a piece of paper between the scope bell and the barrel and that thing got hot as anything and never touched

Wouldn't change it unless you notice any shift

Excellent
set it up today then looked and thought
F.......
I'll give it a go as it is.
Thanks.

I had a scope which had a paper thickness gap and eventually figured out that it was getting hit every shot by the barrel moving and the flex in the rifle. Was on an AR but pretty sure all barrels flex and move to some degree.
But as others have said, if it makes both difference to the zero, then there is no issue. But it may affect it over time if the barrel is moving and hitting the scope.

I'd think that the whole unit would expand as one. So the action would move with the barrel.

I would be more concerned about getting some vegetation wedged in the tiny gap while out hunting.
Not realizing it was in there and it effecting the point of aim.

Originally Posted by Sideshow

I'd think that the whole unit would expand as one. So the action would move with the barrel.

Heat expansion yes. This should be fine, but barrel whip, especially if it is a thinner profile barrel. Though generally this is further down away from the action where the barrel thins down. My usual guide is as long as piece of paper moves freely between them you should be fine. If it gets "blurry when you look at the gap, cut a hole in a piece of cardboard about 1 inch round and have a light behind the rifle. Hold the card up to mask the entire unit except for wher the bell end of the scope is close to the rifle and see how much the light comes through the gap....

The whip in the barrel goes the whole length of the rifle like a wave it is not just in the barrel think of a small earthquake when you fire a shot

Cheers was going to try it today buit though fine it is blowing a gale so would be hard to tell if the thing was moving or if it was my shooting, will wait for a calmer morning.

Originally Posted by akaroa1

I would be more concerned about getting some vegetation wedged in the tiny gap while out hunting.
Not realizing it was in there and it effecting the point of aim.

Or a drop of rainwater spanning the gap.

Interesting thread.

My contribution is what if you've got a heavy scope in a mount with inserts like the optilok ? Could muzzle jump allow the scope to flex down in the mounts for a moment ?

You might be able to see if there has been contact by looking at the finish on the scope and barrel after a few shots; see if its gone shiny.

I bet a paper thickness will be just fine. Whatever clearance is OK round the fore end will be OK above the barrel too.

on my 30/06AI the scope was bloody close to touching about .02 or so I could see a shiny spot on the barrel and I had noticed the shots wander when it was hot, the barrel was also touching the fore stock so I relieved the fore stock and shimmed the scope +.02 will see how it goes on Sunday.

Watch this video I know it's a .50 BMG but the recoil wave happens in all rifles to some degree, https://www.youtube.com/watch?v=AZL7MN7ERRQ