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7mm-08 powders

08 Sep 2018
@ 08:18 pm (GMT)

Tom Dixon

So when I first got my 7-08 I tried a varget 162 amax load, the best velocity I could achieve at the time was 2450fps. I left it at that and have been using other bullets since. Now 500+ rounds later I have developed a new amax load with Vihtavuori N550, this is a much slower powder if the burn rate charts are to be believed. The N550 load delivers 2750 and shows no sign of pressure at that. I am using Winchester brass and CCI primers which are supposed to be quite hard so I could be over pressure?
Any way I was wondering is this big increase in velocity down to the barrel ‘breaking in’ or is this to do with my gun liking a slower powder. I know in the knowledge base Nathan recommends varget, but I seem to be getting better results with N550.

It’s a 21" 9 twist barrel by the way.

Replies

1
10 Sep 2018
@ 09:16 am (GMT)

Nathan Foster

Re: 7mm-08 powders
Hi Tom, I have tried N550 in the same manner. Sometimes you win, sometimes there is no major change to the accuracy / velocity / pressure relationships. But it sounds like this has been a great success. The N5 series does have a high energy content.

Certainly quite fast for a 21". Quite often it takes a 24" barrel to achieve this. Just goes to show, each rifle must be treated individually.

Just keep an eye on the primer pockets. If they begin to loosen, you will know that the load is too hot. Watch also for hot weather issues.
10 Sep 2018
@ 11:28 am (GMT)

Tom Dixon

Re: 7mm-08 powders
Cheers Nathan, so you don’t think that as the barrel wears in it gets faster? I developed the load in really hot weather so I should be ok on that front.

A cheeky request here, does anyone have quickload or similar? If so I’d love to know the numbers on the load, it’s 43.8gn of N550, 162 amax. It’s above the Vihtavuori book max but I find that the Vihtavuori data is really cautious ...
10 Sep 2018
@ 11:34 am (GMT)

Bryan Webster

Re: 7mm-08 powders
I have had great success with the 7mm-08 using Hodgdon's 414 powder on a rifle with a 20 inch barrel. Very good accuracy and velocities.
15 Sep 2018
@ 12:53 pm (GMT)

Kenneth Kephart

Re: 7mm-08 powders
Tom,
While a good powder, Varget is rather a fast powder for so heavy a bullet.
Hence why the Vithavouri 550 does so well.

Another fine powder is Alliant Power Pro 2000.
RL17 had better velocities, but higher ES/SD.

Over 20 rounds PP2000 gave me ES of 9, SD of 3.

Send me your barrel length and COAL and i'll gladly run through QL.

16 Sep 2018
@ 08:54 pm (GMT)

Tom Dixon

Re: 7mm-08 powders
Thanks Kenneth, The COL is 2.90", 2.215" to ogive. Barrel length is 21"

I think you're right about varget being too fast, i get really good performance in the 130-145gn bullets from N540 which is a bit faster than N550. We are having some difficulty getting some of the American powders in Europe just now so I will probably continue using the Vihatavouri powders.
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