MarkIIVT

Vapdog and James B.

There is a section in the Speer manual either 11,12 or 13 that talks about "Modes" in external ballistics. The 3 phases are Modus violentus, modus medius, and modus terminus, if my memory serves me. It may be in a Nosler manul for all i can remember. But I rember reading it and being set with that "AH HA!" response. It seems that a bullet/barrel combination (and the various combinations of powder/primer/case/COl with in a bullet) produces flights of rotaional harmonic varibility. As I read and understand it some Modus violentus phase extend from 0-75 yds. on average, and the medius75-200, and terminus 200 out. SOME rifle/barrel/bullet combinations have an extended violentus ranges extending out to 125 yds. So the 100 yd range group will concievably be rotationaly varible more than the medius where the bullet settles down and the rotational harmonic becomes stable throughout the entire flight path of the bullet. Remember that the bullet is not shooting flat and in a line, but a spiral within an arc. harmonics are easier to judge when all things are straight and linear, but rotational issues throughout an arching flight get really complicated.

NOW, this may be a theory, but I believe that is why the Match bullets work over several ranges because the shape/jacket combos "dampen" the harmonics of the barrel/bullet combo. My 165 g SGK loads show this very thing, larger MOA at 100 yds and smaller groups at 200 yds. I shoot them at .70 MOA at 100 yds, and .35-.40 at 200 yds. So it explains my findings.

HOWEVER, there are probably more varibles I am not taking into account. MY 200 yd group BTW is in the RUGER ACCURACY forum on the 1 or 2nd page.

Dana

MarkIIVT

OK found it. It is in the Speer Manual #12, page 109. I was wrong on the names. It is
motus violentus. The area immediately in front of the muzzel. The bullet is not fully stabilized FULLY after the violent transition from the chamber to bore to free flight.

motus mixtus portion of the bullet path where normal stability occurs induced by the effect of gunbarrel and rifling.

motus naturalis, portion where velocity is dropping and is shedding velocity and stability, again becoming varible.

The arch described by the bullet path is parabolic arc, which is more complex than a simple cicular arc. Check more out on a google search of "Short, medium and long range ballistics"

Wolf killer

Bed the action, Float the barrel & Do a trigger job. Then take it back to the range.
If that does not help have a gunsmith recut the crown.

charlie brown

Have you tried different bullet seating depths? With my .223, The farther I set the bullet out the better it shoots. Can't remember exactly how much different (don't have my load log with me right now), but the difference was about .010" and made about 3/8" difference at 100yds. I would try different seating depths before doing major modifications to the rifle. It sure is a lot cheaper.

James B

The last group I shot yesterday came in at just under an inch. I took all the stock screws loose then tightened down the two rear ones real tight then just barely snuged the angled front action screw. This left a small gap between the barrel and stock that you can see open and close if you squezz them together. This seemed to float the barrel slightly. I didn't have my rear sand bag just the front one or I could have maybe cut it down to 3/4 or less. Anyway I think that load will be my deer load this fall. It was the Sierra Pro-hunter with 1/2 grain below the max of H414. I did play with the seating depth but not much as the magazine is shorter that the throat anyway. I may yet try a couple 140 grain bullets and twiking the 120 a bit more. I don't think I will be able to get the velocity I want with the 140 grains. At least not with any of the powders I have tried so far.

eldeguello

It certainly could! A lot of rifles do! The bullet sometimes has to have time to "go to sleep".

Deleted User

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James B

I finished free floating the barrel today. If I ever get another calm day I will take it out and try it again. I got a 3/4 inch group today from the 257 Roberts in my 700 Remington synthetic. It likes the Hornady 100 grain Interlock. It also shoots well with the 120 grain Nosler Partition. I should have the Roberts all ready by tomorrow for the Fall. I am reloading about 50 rounds of Ammo for it tonight. I may have to take it to a Gunsmith to adjust the trigger. I can ussually do my own Remington triggers but one of the screws is frozen. It will not turn for nothing.