- Location
- The Conservative part of Ontario
Safe Loads with Your Chronograph
There's really no excuse for
the serious shooter not to
own a chronograph these
days, with basic, accurate units selling
for not much more than the
price of a box of some "premium"
rifle bullets. Chronographs do all
sorts of things for us, but perhaps
their most important job is to make
handloading safer.
How do they do that? Well, any
handloader who doesn't own a
chronograph has read that speeds
vary in different firearms. There are
lots of reasons for this: tighter or
looser chambers and bores, different
components, different barrel
lengths, etc. But few of us really believe
it until we start using a chronograph.
And even then we sometimes
don't. I've lost count of the shooters
who've run their loads over my
chronograph and have been extremely
disappointed in the real
world speed, or those who've gotten
different results than I've published
in some magazine. More often than
not, they want to argue with my
chronograph, instead of accepting
the fact that "results will vary."
However, one thing is certain about
chronographing home-grown loads:
If the speeds from your firearm are
significantly higher than those of
similar loads in most loading manuals,
then the pressures are higher –
and probably too high. Too many
handloaders assume that such results
mean they own that happy something
called a "fast barrel."
Yes, some barrels will be faster or
slower than others – but if they
consistently show results a lot faster
than normal, then pressures are
higher than normal. Very few barrels
do this anymore. Instead the
problem (and it is a problem, one
that can blow your hand off ) usually
lies in either the lot of powder
or the particular bullet. Some lots of
powder can be significantly hotter
than others, and the best way to
find out is through the chronograph,
not traditional "pressure
signs." These signs – stiff bolt lift,
ejector-hole marks on the head of
the case, loose primer pockets –
generally only occur after pressures
are too high already, sometimes way
too high. So how much lower
should the load be reduced to make
it safe? You don't know unless you
have a chronograph.
Thirty years ago pressures didn't
vary much from bullet to bullet, but
today they do. Ultra-long copperjacketed
bullets such as the Swift
Scirocco tend to create noticeably
more pressure than the same weight
and diameter Hornady InterLock,
which generally has a shorter bearing
surface of less sticky gilding metal.
With a chronograph you can tell
when you're getting too much
velocity – and hence pressure.
Therefore, the safe handloader compares
previously published data for
the sort of load he's working
up – and he doesn't use just one
source, but several, one reason loaddata.
com is so valuable. If he's loading
for the .270 Winchester, for
instance, using a 140-grain bullet
and Hodgdon H-4831 powder, he
finds that most maximum loads for
the .270 stop at 3,000 fps or a little
less. So he knows that if his particular
rifle produces much more than
3,000 fps, the pressures are too
high, even if no traditional "pressure
signs" show up during his shooting.
One problem here is that some
loading manuals do not list muzzle
velocities from the barrels they used
during pressure testing. Instead they
work up the loads in a pressure barrel,
then shoot and chronograph the
same loads in a sporting rifle for
publication. These barrels usually
show somewhat lower velocities, because
they often have larger chambers
and bores than pressure barrels.
This is one reason I trust the muzzle
velocities listed by Hodgdon,
Nosler, Sierra and Western
(Ramshot) more than some others.
One big advantage in using a
chronograph to develop safe data is
that you don't ruin cases, as sometimes
happens when developing
loads the old-fashioned way. Primer
pockets don't get loose when you
look at the numbers, rather than
guess by bolt lift or how easily the
next primer seats. So in the long
run using a chronograph to develop
safe loads also saves you money!
www.loaddata.com
Bench Topics
John Barsness
•
Using a chronograph to develop loads will
prevent blowing primers, and maybe an eye.
There's really no excuse for
the serious shooter not to
own a chronograph these
days, with basic, accurate units selling
for not much more than the
price of a box of some "premium"
rifle bullets. Chronographs do all
sorts of things for us, but perhaps
their most important job is to make
handloading safer.
How do they do that? Well, any
handloader who doesn't own a
chronograph has read that speeds
vary in different firearms. There are
lots of reasons for this: tighter or
looser chambers and bores, different
components, different barrel
lengths, etc. But few of us really believe
it until we start using a chronograph.
And even then we sometimes
don't. I've lost count of the shooters
who've run their loads over my
chronograph and have been extremely
disappointed in the real
world speed, or those who've gotten
different results than I've published
in some magazine. More often than
not, they want to argue with my
chronograph, instead of accepting
the fact that "results will vary."
However, one thing is certain about
chronographing home-grown loads:
If the speeds from your firearm are
significantly higher than those of
similar loads in most loading manuals,
then the pressures are higher –
and probably too high. Too many
handloaders assume that such results
mean they own that happy something
called a "fast barrel."
Yes, some barrels will be faster or
slower than others – but if they
consistently show results a lot faster
than normal, then pressures are
higher than normal. Very few barrels
do this anymore. Instead the
problem (and it is a problem, one
that can blow your hand off ) usually
lies in either the lot of powder
or the particular bullet. Some lots of
powder can be significantly hotter
than others, and the best way to
find out is through the chronograph,
not traditional "pressure
signs." These signs – stiff bolt lift,
ejector-hole marks on the head of
the case, loose primer pockets –
generally only occur after pressures
are too high already, sometimes way
too high. So how much lower
should the load be reduced to make
it safe? You don't know unless you
have a chronograph.
Thirty years ago pressures didn't
vary much from bullet to bullet, but
today they do. Ultra-long copperjacketed
bullets such as the Swift
Scirocco tend to create noticeably
more pressure than the same weight
and diameter Hornady InterLock,
which generally has a shorter bearing
surface of less sticky gilding metal.
With a chronograph you can tell
when you're getting too much
velocity – and hence pressure.
Therefore, the safe handloader compares
previously published data for
the sort of load he's working
up – and he doesn't use just one
source, but several, one reason loaddata.
com is so valuable. If he's loading
for the .270 Winchester, for
instance, using a 140-grain bullet
and Hodgdon H-4831 powder, he
finds that most maximum loads for
the .270 stop at 3,000 fps or a little
less. So he knows that if his particular
rifle produces much more than
3,000 fps, the pressures are too
high, even if no traditional "pressure
signs" show up during his shooting.
One problem here is that some
loading manuals do not list muzzle
velocities from the barrels they used
during pressure testing. Instead they
work up the loads in a pressure barrel,
then shoot and chronograph the
same loads in a sporting rifle for
publication. These barrels usually
show somewhat lower velocities, because
they often have larger chambers
and bores than pressure barrels.
This is one reason I trust the muzzle
velocities listed by Hodgdon,
Nosler, Sierra and Western
(Ramshot) more than some others.
One big advantage in using a
chronograph to develop safe data is
that you don't ruin cases, as sometimes
happens when developing
loads the old-fashioned way. Primer
pockets don't get loose when you
look at the numbers, rather than
guess by bolt lift or how easily the
next primer seats. So in the long
run using a chronograph to develop
safe loads also saves you money!
www.loaddata.com
Bench Topics
John Barsness
•
Using a chronograph to develop loads will
prevent blowing primers, and maybe an eye.
