as those who read me are well aware, i have an interest in small arms ballistics.
it should come as no surprise, therefore, that as funds permit i am trying to do a little long range shooting, to understand it and gain proficiency in it.
to that end i have developed a load for what would normally be my elk rifle, a 7mm remington magnum, that is more devoted to long range shooting, and by that, i mean shooting out and past 6 to 700 yards. the load consists of a 130 grain sierra boat tail hollow point (match king), in front of 61 grains of h-4350 powder, set off by federal 215 large rifle magnum primers, in winchester cases.
the load achieves about 3100 feet per second at the muzzle, and i suppose there is another 100 fps there if i wanted to sacrifice accuracy and case life solely in the interests of velocity. i do not.
i have been shooting at the range, using a great big homemade cardboard target, to determine the basic ballistic performance of the round. i have sighted in, or "zero'ed" the round at 300 yards, that being that the rifle/bullet combination shoot to a point of aim at 300 yards.
the round at zero'ed shoots 4.25" high at 100 yards, 5.25" high at 200 yards, "dead nuts on" at 300 yards, 8.75" below the point of aim at 400 yards, and 29" below the point of aim at 500 yards. i have one more target standard available to me at 600 yards, and i shall shoot that weather permitting.
i am using old sierra bullets trajectory tables while i am doing this, and it should be understood that sierra bullets has come under some criticism for its trajectory tables, some error being involved in their tabulation. they simply made some measurement and conceptual mistakes, some of which really rankle some people, but do not bother me so much: they are still pretty serviceable even with the error in them.
they do not have any tables for the 130 grain bullet i am using in the manuals that i have. they do, however, have a tables for their 140 grain spitzer boat tail, a bullet roughly similar in ballistic coefficient to mine. i have found that the table for the 140 grain bullet, at 3000 feet per second muzzle velocity, has trajectory values very comparable to the results that i am getting in my shooting. if you look to pages 820-21 in the 4th edition of the sierra handloading manual, you can look at the table to which i refer.
i am finding that in "old tilly," my elk rifle, the load as i am "manufacturing" it, is capable of roughly 1.5 to 1.6 minutes of angle out to 500 yards. now that i have the rough trajectory values down, i will do some tinkering with the load to see if i can improve that. i would like the rifle to shoot at about .6 to .75 minutes of angle over its range, as this would increase the utility of the load quite a bit at distance.
the next step is optics.
we will talk about that next time.
john jay @ 01.30.2011
p.s. anyone want to start the "john jay leupold scope" fund for me? laughing. i have a sock devoted to spare change for the purchase of a scope, but, i am not making much headway in building the fund.
i was at the range the other day, and a fellow was shooting an 8x24 power variable scope, set at 24 power (or magnifications), at 600 yards. it made a 6 inch target circle/bull look like a large dinner plate at 100 yards. he was shooting a .243 winchester, and at that distance, he could see the bullet holes from his individual shots, easily.
that magnification is as great as some spotting scopes were, just a few years ago. ah, progress.
as a point of comparison.-- most military sniping rifles were equipped with scoped optics of about 2.5 to 3 power (or, magnifications) during world war ii. it is quite obvious why snipers then were not engaging targets 1000 to 1250 yards then, as opposed to now. this comprehends infantry rounds up to 7.62x51mm nato.
some snipers are now shooting at targets/personnel at 1500 to 2000 yards, with .338 lapua's and .50 bmg rifles. that, my friends, is a long ways off, and far past what i contemplate, by a magnitude of 2 or 3 "distances." look at the drop table i have set out above for my 130 grain bthp 7mm bullet, and the drop between 4 & 500 yards, ... , and understand, that military snipers are simply shooting in another ballistic universe from what i contemplate.