load performing oddly...

[armymedic.2]

my load for my .308 is 41.5 gr IMR 4064, with a 178 amax going 2615 fps. it is under 1/2 moa at 100, and seems to hold out to 800.

this has been a real performer for me, and has shot great thus far. just took it out to 1,000 for the second time, and i have the same results, WAY more elevation needed than i thought from what i have hard dope on to 850 yards.

800 hard dope=27
850 hard dope =30
900 hard dope= 36 but calculated 33.75
1000 hard dope =46 but calculated 41.25

also, my 900 and 1000 yard groups look nothing like my 850 yard group ( a lot bigger)

im wondering is my bullet de-stabilizing? why is it dropping so hard in the last 150 yards?

it is supposed to be going 1157 fps @ 1000....according to calculator

 

[Timo Turl]

Re: load performing oddly...

Using G7 (Litz) at 59F, 29.92Hg pressure, 1.5" sight height, 1:12 and 2615 MV puts you nearer to 1090fps....to get to 46 MOA implies a velocity at 1k of c1050 so well down on where it needs to be. Most seem to be pushing the 178 at 2700 for 1k.

Above depends on local conditions but are you using G1 or G7 function ? If the former, it estimates a velocity over 1150 which you also give below hence my query.

 

[KQguy]

Re: load performing oddly...

How do the holes look (1000 yd. shots),are they keyholeing?

 

[Queequeg]

Re: load performing oddly...

Are you showing pressure signs at that load? It is the minimum load listed for the 175 gr SMK in the 2011 Hodgdon manual.

Max load listed is 45.6 (compressed).

Pretty clearly your load is near the minimum velocity wise.

 

[armymedic.2]

Re: load performing oddly...

hey guys, no i am not showing any pressure signs with this load. my manual (speer #13) stated for imr 4064 43 was max for a 180 grain (no listing for 178). the group opened up at 42 and 42.5 grains, and was tightest at 41.5 so that's what i have been shooting.

I do not understand g1 and g7........
my local conditions were 67 % humidity, 29.75 baro, 200 altitude, a six mph wind quartering in from 10:30, and 32 degrees.

the bullet holes from the other day looked ok. certainly not sideways, but maybe a little wider than normal. i can't remember perfectly to be honest. was shooting steel today.

does that hard dope sound crazy to anyone else or is it just me?

7-800 42 inches of drop ----accurate fire
8-900 73.9 inches of drop----accurate to 850 (grouping around 10 inches at 850)
9-1000 95 inches of drop --- 4-5 foot group, i mena i have never shot that farbefore, but i can't imagine my form that is doing ok at 850 is complete shite at 1000. i dunno

 

[jmtyndall]

Re: load performing oddly...

You're pretty close to the sonic barrier at 1000 yards. The area right around mach 1 is a pretty unstable area for bullets as far as I know.

Also, a 10inch group at 800 should tell you something. If you're shooting 1/2 moa at 100, then something is going on around 800 yards that's causing you to lose that accuracy.

As for your drop. JBM is showing me that you're in the transonic velocity area around 930 yards at the temperature you gave. At that temperature, you're load needs to be around 2725fps to break 1000 before going subsonic. Also, I'm pretty sure you're going subsonic, because your drop is a little less than 1MOA off what I have calculated for 900 yards. Your 1000 yard dope however is 3MOA from what I have calculated. Not sure what ballistic program you used, but you might not have input the environmental conditions correctly.

Work your load up a little, and find another accuracy node higher than the one you're at now. Shoot to 1000 again and tell us how it goes.

 

[armymedic.2]

Re: load performing oddly...

ok will do, thanks for the insight guys. will report back with different bullet/and or powder after working up. i know i don't get another node under book max with 4064.

just saw on imr that they consider 45 grains their max compress load. gonna work some more with it then