Rimfire grouping query

Rimfire bolt action rifles, lever action, pump action and self loading rifles. Air rifles.

Re: Rimfire grouping query

Post by No1_49er » 22 May 2018, 5:28 pm

There's a couple of things to establish in this query.
OP says it is an old CBC bolt action, to which he has fitted a scope. OP also says that a little way down the track he cleaned the bore and it didn't look too pretty.
Starting with the barrel, and not knowing its history, I'd be inclined to keep cleaning, keep cleaning, keep cleaning; even if he wears a bronze brush out doing so until he can push a patch through like it's sliding on glass. Then inspect the bore with a good light to determine how good the rifling is.
Next, look at the barrel crown with a bit of magnification help. Depending on how it's been cleaned in the past there may be some evidence of wear - grooves or dings.
A very thorough clean of the breech area and the bolt with something like brake cleaner to get rid of the last vestiges of old bullet/gun lube.
My favourite lube for actions/bolts after a thorough clean is Birchwood Casey Moly Lube (Dry Film Lubricant). Slippery as the proverbial.
Then there's the matter of the scope.
We don't know what it is, whether it has parallax adjustment, and if not what is the parallax preset to: the web site for the scope may have some info' as to what the parallax has been preset to. The focus could also be an issue adding to the problem.
A previous poster has given a fairly good method to set it up, but should also have mentioned that the reason for pointing at a blank sky (whether that be clear blue or cloudy grey/white) is so that you can not intentionally focus on the object in view. Also, that when making those two turn adjustments he should be looking at anything other than the scope. His eye must relax its focus to "normal". Having made an adjustment he then looks through the scope again. Should be looking to infinity and not AT the cross hair. When the focus is good, the crosshair will immediately appear to be sharp as soon as looking through the scope - no conscious focusing. Once set, it is set for good, for HIS eyes. No need to adjust again.
Only then can he determine whether or not a parallax error will manifest itself. Easily done. Place the rifle on a bench rest (of any sort) so long as the view of a target at the chosen distance can be viewed without touching the rifle. The "target" is then viewed at the same time as moving ones head left and right/ up and down. If the target appears to move then there is a parallax error, which will make his group "loose"! No movement, parallax good AT THAT DISTANCE.

A bit long winded, but hope that helps.
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