From: toby@u.washington.edu (Toby Bradshaw)
Subject: Re: Why no falling blocks in bench-resting ?
Organization: University of Washington, Seattle

In article <35o2ir$hf4@selway.umt.edu>,
James F Johnson <uncia@selway.umt.edu> wrote:

#Why are bolt guns preferred over other actions for supreme accuracy ?

Action stiffness and bedding control, scope on the receiver instead
of the barrel, precise and repeatable breeching, excellent camming
power for extraction, excellent gas handling in the event of
case rupture or pierced primer.

#Specifically, why aren't falling blocks as good or better ?

You might be able to fabricate one that would be as rigid as
a bolt gun with comparable breeching precision and camming
power, but it would be harder to manufacture, I would think.

You could eliminate the scope mount and bedding problems
by going to a barrel block.  Having a falling block action
behind a bedding block kind of defeats the aesthetics of
a single shot, though :)

#You see so much about sleeving actions and doing away with mag cut-outs
#etc. in order to make turn-bolts stiffer.  Wouldn't it be easier to make
#a stiff falling block ? Wouldn't it be easier to get proper lug engagement
#etc if those lugs just slid up and down, as opposed to back and forth and
#round and round ?

The lugs on a bolt gun (properly trued and lapped) are perpendicular to
the axis of the bore.  They go nowhere but straight along the lug
abutments.

A bolt action is the path of least resistance where accuracy is
concerned, more so perhaps with "practical rifles" than something like
a rail gun.

-Toby Bradshaw
toby@u.washington.edu

From: toby@stein3.u.washington.edu (Toby Bradshaw)
Subject: Re: Single Shot vs Bolt Action
Organization: University of Washington, Seattle

In article <199311090432.AA14579@ns1.nodak.edu>,
Todd Enders A262 857-3018 <enders@warp6.cs.misu.NoDak.edu> wrote:
#     Please define near-equal and long range.  The above mentioned single
#shot pistol will shoot 1/2-5/8" 10 shot groups, scoped, sandbag rest, at
#100 yd. It will do this day in and day out.  I surmise that a single-shot
#behchrest rifle, with a good barrel, prepped with the same care as its bolt
#action counterpart *should* be able to group in the 'teens at 100 yd.  It
#*may* be more difficult, given that there is not a lot of experience building
#one, but I still see no inherent reason why it *can't* be done.

There is no currently-available falling/rolling block action that is
likely to give groups in the teens on anything like a regular basis.
Plenty of rifle cranks have tried, as single shots used to dominate the
benchrest game (or its predecessor) and have been resurrected sporadically
since for competition and live varmint shooting. Besides the practical
problems Bart mentioned, falling block and rolling block actions have some
inherent problems. Case head support is not as consistent as a bolt action
because the lockup is not as tight, and cannot be made as tight with a
falling block.  Likewise, extraction is poorer because of the lack of
mechanical advantage.  It is difficult to mount a scope on a bedded
surface, i.e. the scope is almost always mounted on the barrel in falling
block and rolling block rifles.  This is bad for accuracy.  You might be
able to work around it by using a barrel block for bedding, but the
inherent lack of rigidity in action/barrel/bedding of the short
single-shot actions plagues them from an accuracy standpoint.  A
single-shot action might be constructed to resolve some of these problems,
at the expense of negating their advantages (comapact size, light weight,
etc.).  Somebody clever might even be able to come up with a decent
locking system and some leverage for extraction, too.  But it would be
much more complicated than a bolt action with equivalent potential.

-Toby Bradshaw
toby@u.washington.edu