Temperature, velocity and ballistic voodoo

Chuck

Chuck

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I was wondering what people's personal experience is with the degree to which Hodgdon's "Extreme" powders are immune to temperature change. I've been loading H-4831SC in my .270 and in summer I get 3170 fps from the 26" barrel. Today I got 3075 fps. The difference in temperature was probably 25 celsius in summer and about minus 10 today. To me this seems reasonable.

However, at the same time I shot a .30-06 today that I've never chronographed before. In fact I haven't had it long at all. With Hodgdon's max load of 60 grains of H-4831 I was getting 2470 with 180 grain bullets. This is basically .303 British ballistics, not a bad thing but not what an -06 should be. This was a great surprise to me since it is the same powder and primers I'm using in the .270 Winchester. Does anyone have a guess what variables might be at work here?
 
The powder in question is too slow for 180 gr bullets in a 30-06. Try same with H4350 and get 2700-2800. I've checked my son's 30-06 with 168gr TSX bullets in summer and winter and found a minimal difference.
 
Thanks for the advice. The only other potentially suitable powder that I have on hand is IMR-4064, or maybe H-380 (uncommon in the -06 but not unheard of). Until I can get my hands on some 4350 do you think 4064 would be worth a try?
 
IMR4064 is faster then IMR or H4350 yet the (safe) load in my manual yields less pressure and less velocity than the 4350. That's because it is too fast and you HAVE TO use less.

I've never used H380 but from the numbers it looks better.
Here's the Lee recipe:
H380
30-06 180gr jacketed bullet,
48 to 53grains (2490 to 2682 fps), 58440psi
3.3" OAL
 
W760 and it's twin, H414, are excellent powder for the 'ol'06, too.
It's in the same burning speed range as the 4350's.
I extensively use the W760 in '06 because of it's constance and availability. It shoot good in summer and winter in almost every '06 I tried it in (and I personally own three). Like the others cited above, it's best suited for 22inches and up barrels.
H380 is also a good choice, but it peaks a bit faster than the W760 and the other guys.
RL15, IMR 4064, Varget are good a choice with less than 21" barrels. It will cut the kick and blast without giving too much in velocity. But it's worthless in a long barrel.
 
My H4895 308 Win load was 10fps slower yesterday (45F) than it was when I developed it at 78F. It depends on the load and other factors...

Even the extreme powders have some temperature variation, but its much lower than that of traditional powders. No powder is immune to extreme temperature variations. Take a Varget load and let it cook for a bit in a really hot barrel, then fire it and compare your velocity to that of a cold barrel.

You might find this interesting:
http://www.shootingsoftware.com/ftp/Pressure Factors.pdf
 
Reloder 22 is the top 'go-fast" powder I have found for 180's in the 30-06. 60 grains usually breaks 2800 fps out of a 22" barrel and it does it at a low chamber pressure.


Other good powders are IMR 4350 , H4350, Reloder 19, W760/H414

I have found that IMR 4064 does loose a bit of velocity - about 2700 max - under the 180's but it has always been very-very accurate in every '06 I have tried it in.
 
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