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7mm RUM/180gr Berger Disappointment

 
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Old 09-15-2008, 11:12 AM
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7mm RUM/180gr Berger Disappointment

All,

Spent the money for the 180gr Bergers a couple of weeks ago and have been working up a load. I'd really like to take advantage of the high bc of these bullets, and I've never heard a dissenting opinion of Berger bullets in general. Upon the advice of Carlock and others I tried Retumbo and US869. I laddered both of those powders and found that US 869 gave significantly higher velocities than Retumbo, up to almost 3200fps before the cases showed signs of pressure. The ladders showed some sweet spots, but because of the higher velocities I got with the 869 I decided to try loading some test rounds with that powder. I loaded 5 rounds each at 99, 101, 102grs respectively. Groups started out at almost 2" and went up from there. I only fired three rounds at the 102gr level before I gave up. To say I'm very disappointed in the Bergers would be an understatement. I thought I had everything set correctly, including seating them almost two thousands into the lands. I know it's not me as I can hold 3 160gr Accubonds inside 1/3" at 100 yards with that rifle. What did I do wrong? The only thing I can think is that the twist rate is not fast enough in this bbl to stabilize that heavy of a bullet. Has anybody had any luck with these bullets in a factory 26" bbl? How about the 168gr Bergers or Sierras? Any advice would be much appreciated.

Hicks
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Old 09-15-2008, 11:35 AM
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Re: 7mm RUM/180gr Berger Disappointment

I'd try a few just touching the lands and see how that does.
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Old 09-15-2008, 11:56 AM
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Re: 7mm RUM/180gr Berger Disappointment

My 300 WBY likes them (210's) .010 off the lands..averages 1.5 in at 300 yards.
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Old 09-15-2008, 03:17 PM
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Re: 7mm RUM/180gr Berger Disappointment

You didn't say what rifle or barrel you are shooting, but my first inclination would be that you don't have fast enough twist.

Berger reccommends a 1 in 9" twist. Most factory barrels are 9.25" and slower.
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Old 09-15-2008, 04:45 PM
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Re: 7mm RUM/180gr Berger Disappointment

My 26" barrelled 300 Win. Mag. Likes them about .020 off the lands and you might want to come down a bit with the powder charge. My best groups are 3 grains below max. Max isn't always the most accurate load.
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Old 09-15-2008, 05:29 PM
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Re: 7mm RUM/180gr Berger Disappointment

Hicks,

I hate to rain on your parade but......try going with the lower velocities and see what happens.......

Also, if the group size opens the farther you jump them into the rifling, excessive velocity is definitely indicated.

I tried 150 Bergers in a 270 AM and was sorely disappointed. The problem was explained to me very well by one who knows.

His words described something like wringing out a very wet towel. That's what the bullet looked like as one end entered the rifling and the other didn't. All groups were very bad and some bullets didn't make it to the backstop.

They work wonderfully in a 270 Win @ 3000 or so and a 10 twist. Between the tight twist of a Lilja 3 groove bore and velocities in the 3500+ range the jackets just wouldn't take it.

I'd really like to try some of Berger's "thick" choices and see what happens.
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Old 09-15-2008, 06:35 PM
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Re: 7mm RUM/180gr Berger Disappointment

I doubt its a stability issue. True that most 7mm's are 1 in 9.25" and Berger does recomend a 1 in 9"

However, my 7 RM is a rem 700 w/factory tube and a 1 in 9.25" and it shot the 180g VLD at 1/2 MOA and 2825fps, bullets were seated right at the lands. I am only 700 ft ASL so if there stabilizing out of my 7 RM at near 400fps slower, it just wouldn't make sense that its a stability/twist issue...

Try that Retumbo and seat them at the lands or in a bit and report back.

Some guns just dont like a particular powder/bullet combo, but will love another powder with the same bullet.
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