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From: (Bart Bobbitt)
Newsgroups: rec.guns
Subject: Re: : Accurate .22 rifle?
Date: 19 Apr 1994 22:56:27 -0400

Norman F. Johnson ( wrote a very good bunch of words
regarding his rimfire rifle tests.

: Neither has had any kind of work done on it for improved trigger, 
: etc.  No cleaning of the bore was done between different batches 
: of ammo but 2 rounds were fired into the backstop to foul the 
: bore for each particular batch (for whatever good that does).  

Have you ever tried cleaning the bore very well, then putting 5 to 10
foulers through it before shooting 50 to 100 shots to test it?
You may be surprized at the difference.

: For the 513, 10 out of 41 types averaged (5 shot groups, 100 
: yards) 1.5" or less.  
: For the 582, 4 out of 41 types averaged (5 shot groups, 100 
: yards) 1.5" or less.  
: Neither rifle would do 1" average but each had two that averaged 
: just 1.25".  

What was the biggest 5-shot group size attained in the above tests?

The reason I'm asking about the biggest group shot with each combination
is that's the real accuracy level.  No rifle just shoots average size
groups; half the ones fired are bigger and the other half are smaller.
Very, very few are right at the `average' mark.  
The largest group it shoots with given ammo is the only thing
one can count on.  My guess is that if groups averaged about 1.5 inches,
a composite of five, 5-shot groups for one ammo type will be about 2 inches
or more.  Does your test data confirm this?

: Group size correlation between 50 and 100 yard groups was almost 
: exactly 1 to 2 on quiet days.

That's interesting considering .22 rimfire bullet drop differences for
normal muzzle velocity spreads will be more than 3 times as much at 100
yards as they are at 50 yards.  Plus the bullet's unbalance will cause
it to move a greater distance sideways travelling the last 50 yards than
it did the first 50 yards.  

: On windy days there was no kind of 
: correlation that I could detect.  Surprisingly enough, the windy 
: day groups were as enlarged in the vertical direction as they 
: were in their horizontal dispersion, perhaps because wind blew 
: the rifles as much as it blew the bullets.  

Vertical shot stringing due to wind is very normal.  It happens due to the
same reasons a baseball pitcher can throw curve balls.  With the bullet
spinning clockwise looking down range behind it, and the wind comming from
the right, there's more pressure on the top of the bullet which will push 
it down more as it goes down range; it'll strike low.  The opposite occurs
with a wind comming from the left.  Smallbore competitors notice this more
than highpower shooters; much lighter bullets going much slower.  Some
folks even use a 1:10 RR-LL rule of thumb; 1 click of elevation for every 10
clicks of windage, Raise if Right wind, Lower if Left wind.  (Goodness, I
just leaked out another secret.)

: Ammo type performance 
: was not according to the expected either.  

Not surprising at all.  You gotta try several lots of each brand/type to
see what shoots the most accurate.  A 3X difference between lots for a
given brand/type is very normal.

: As I get older I am more and more convinced that rifle accuracy 
: is less and less related to rifle cost. 

There's a whole lot of truth in the above statement.  Except to get to
the nth degree of accuracy, good stuff costs bucks.  However, reasonable
experiments with the right stuff will oft times surprise folks.  
: It would seem that 
: knowing the dimensional relationships and accomodating those by 
: properly constructed ammo (in the case of centerfires) and simply 
: trying different rimfire types in rimfire rifles will direct one 
: to satisfactory and sometimes surprising performance.  

Very well put indeed.


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