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Jump?

 
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  #1  
Old 07-21-2013, 09:45 AM
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Join Date: Feb 2008
Location: Star, ID
Posts: 272
Jump?

New STW toy. Started with 160 accubonds and H1000. Loads of 76.0, 78.0, and 80.0gr, started with a F215.

Groups shrank from 1.5" to 1.0" at 100 yards as I went up in charge. Despite 85 degree temps, I had no pressure signs. At 80.0 gr my velocity was 3260 with an ES of 11.

I would like to play with seating depth at this point, but my magazine caps me around 3.61". I started at 3.605". I couldn't find a Hornady 7stw case for my guage, so I took a few loaded 76.0gr rounds and pulled the bullets and powder, then simple lightly seated the bullet into the empty cases and then chambered them. 3 of 4 bullets seated right at 3.82".

I usually don't jump Accubonds more that .02", so .215" seems like a lot. I don't find much problem jumping TSX's a bunch.

Anyone else using this much jump on an accubond in an STW with sub-moa performance?

I know SAAMI spec is 3.600". Is this a lot of jump compared to where most of you find performance?
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  #2  
Old 07-22-2013, 07:22 AM
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Join Date: May 2012
Location: N.D.
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Re: Jump?

Quote:
Originally Posted by bkondeff View Post
New STW toy. Started with 160 accubonds and H1000. Loads of 76.0, 78.0, and 80.0gr, started with a F215.

Groups shrank from 1.5" to 1.0" at 100 yards as I went up in charge. Despite 85 degree temps, I had no pressure signs. At 80.0 gr my velocity was 3260 with an ES of 11.

I would like to play with seating depth at this point, but my magazine caps me around 3.61". I started at 3.605". I couldn't find a Hornady 7stw case for my guage, so I took a few loaded 76.0gr rounds and pulled the bullets and powder, then simple lightly seated the bullet into the empty cases and then chambered them. 3 of 4 bullets seated right at 3.82".

I usually don't jump Accubonds more that .02", so .215" seems like a lot. I don't find much problem jumping TSX's a bunch.

Anyone else using this much jump on an accubond in an STW with sub-moa performance?

I know SAAMI spec is 3.600". Is this a lot of jump compared to where most of you find performance?
I'm loading at 3.650" into a bore that has a 3.8" and change ( I really don't care so I never got specific) throat with a 140 accubond and rl25. You want this caliber to jump at least a bit, especially with the tougher bullets.
I bet you would really crap a kitten if you had a 7rum. They usually have a 4.1" throat and a 3.6" saami spec. for cartridge length. The one I had was jumping an even half inch and shooting 1/2 moa.
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  #3  
Old 07-22-2013, 07:57 PM
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Join Date: Feb 2008
Location: Star, ID
Posts: 272
Re: Jump?

We'll I guess I'll play a little more with charge weight on the H1000 and if I can't get groups tight enough I will pull out other powders.

Barrel is only a 10 twist, so I'll have to stick with 160 or under, but want to keep as much BC as possible or I would try the TSX, they seem to shoot well with a lot of jump. I will rebarrel unless I can get a solid 800 yard gun out of this.
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  #4  
Old 07-23-2013, 07:30 AM
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Join Date: May 2012
Location: N.D.
Posts: 2,964
Re: Jump?

Quote:
Originally Posted by bkondeff View Post
We'll I guess I'll play a little more with charge weight on the H1000 and if I can't get groups tight enough I will pull out other powders.

Barrel is only a 10 twist, so I'll have to stick with 160 or under, but want to keep as much BC as possible or I would try the TSX, they seem to shoot well with a lot of jump. I will rebarrel unless I can get a solid 800 yard gun out of this.
I've also got a 10" twist 7stw. For a while that was the norm for twits who thought they could get a bit more speed out of this cal.. Use a 9 " twist so you can go to 175-180 grain pills and keep the bbl. length up if you want the last few fps. I've shot the 160 abond in a few rifles and the 140 has turned in better groups in every one so far. The bc isn't very different considering the weight difference and the 140 will outrun the 160 by 200 fps in most bbls.
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