10 twist part 2

[runfiverun]

this is an abbreviated test today the weather would not wait.
load .308 rem brass 28,0 imr-4895 lint filler wlr primer.

50 yds 3/4w x 3/4high outside to outside 7 shots all touching 2 warming shots
one operator error flyer had to look over the scope to see my boolit hit the target[smilie=b:

same load at 100 yds 1" high 1-1/4 outside measurements 8 shots
with2 warmers no flyers sept maybe the one next to the one that opened it up
to 1-1/4 or it would have been 1x1 no matter
have lots of these and could have just about phoned in the 50-td and 100-yd
results.
no chrono today as i forgot to turn it off last time i used it
and the back-up battery i had was dead also [ note to self quit leaving batteries
in the truck all winter]:groner:
will run these at 200 maybe 3 when weather clears up again.

and will run another load halfway between the 28-37 load
at least velocity wise.

shot both groups twice today this is the average of botth groups
and when i said the rifle would shoot 100yd 1" groups this is the load i do
it with.
has worked all winter and was wanting to compare for the summer because
of something i am trying with lube..........more to follow..

[Larry Gibson]

runfiverun

Your load of 28 gr 4895 w/dacron filler with the 165 gr bullet is spot on as the "accuracy" load for most 10" twist 308s and many 12" twist 308s using 165-180 gr bullets. That is the load I'm going to use alongside the 38 gr load when I conduct the test for Bass at 50, 100 and 200 yards. Good shooting. Are you going to test at 200 Yards?

Larry Gibson

[runfiverun]

yep i am interested in how it does coming down through the sound barrier
i think moving air around a boolit does" stuff" and keeping the lube grooves full
helps the transition go smoother.
i hope bass runs this on his puter program so i can estimate how far it will travell
before it makes the transition and i will make a target that i can move away from that point.

[Bass Ackward]

i hope bass runs this on his puter program so i can estimate how far it will travell
before it makes the transition and i will make a target that i can move away from that point.



Judging from the last projection, it was off about 50 fps to the high side using a SAAMI standard OAL. So if it remains the same on the low end also, then you will begin to enter the barrier somewhere around 130 yards.

[Larry Gibson]

Bass

130 yards seems pretty short to me. the computed trajectory for 311291 at 1961 fps with 28 gr 4895 still shows 1403 fps at 250 yards. Am I thinking of a different load here with his 165 gr bullet?

Larry Gibson

[runfiverun]

joeb
showed the 311 boolit as having a higher b.c. then this boolit also
quite a bit higher down range.
with the 37 gr load i did have near 5 m.o.a. drop from 1 to 200yds though.
also with my filler my velocities are more like a 29gr load.

[Bass Ackward]

Bass

130 yards seems pretty short to me. the computed trajectory for 311291 at 1961 fps with 28 gr 4895 still shows 1403 fps at 250 yards. Am I thinking of a different load here with his 165 gr bullet?

Larry Gibson


Yep,

Your right. Joeb pointed out that I was in error reading the wrong line on the graph. I will correct it here since it involves runfiveruns test..

38 grain load with MV of 2116 should be

200= @1600
300= @ 1400

28 should be @ 1600 fps MV

200= @ 1200
300= @ 1085

[runfiverun]

so from about 150 to about 225 yds i should " see" something happening
if air is affecting this boolit?
any opinions here?

[joeb33050]

so from about 150 to about 225 yds i should " see" something happening
if air is affecting this boolit?
any opinions here?

I have some.
I don't much believe the "going through the sound barrier and accuracy gets bad" business, although it's much mentioned. Like Dacron ringed barrels, much agreement but very few examples.

I don't believe in the "pressure at bullet exit" or "muzzle pressure" and accuracy loss contentions.

I know that shooting small numbers of shots and groups proves very little. Both you and Larry suffer from "few shotitis." How about shooting some more groups, and less shooting the sh*t?

I know that the snowbirds are leaving as the traffic and congestion are going down. And, the temperature is on the rise. I opine that the snowbirds leaving is causing the temperature to increase. Lack of travelers with air conditioned cars, and of homes kept cool, is allowing/causing the temperature to increase.
joe b.

[Doc Highwall]

I know that when shooting a Palma match 800-900-1000yds that when I have been in the pits and when the bullets are going over your head they make a sound like a firecracker and when they go subsonic they make like a fluttering sound. When this happens accuracy goes to hell because the vacuum behind the bullets base is not consistent. This is why all if not most of your 22lr match ammo starts out at 1080fps or less so they do not have to go through the trans sonic range. You have to have the bullet travel ether subsonic all the way to the target or it must be above 1700fps at the target in order to have the least wind drift. I know it sounds contradictory,but all you have to do is look the wind drift tables and you will see what I mean.

[leftiye]

Joe "Jeeesh!"

[runfiverun]

joe
with the28 gr load i have shot at least 10 lbs of powder so far.
like i said i could have phoned the 50-100 yd groups in.
it is the farther groups and trying for over 2500 fps with accuracy that i am working on
i would have shot further than 100 but that is as far as i was going to shovel
snow to shoot. and am trying to figure out what i should be expecting
at 2and 300yds