What twist barrel would I need to stablize a 7mm. 180gr. JLK bullet at 2,600 to 2,700fps. ALT. 500 TEMP. 25-75 deg.
Thanks,
John
Thanks,
John
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Gunsmithing Barrel twist for 7mm. Wildcat
- Thread starter BigBuckInBama
- Start date
Re: Barrel twist for 7mm. Wildcat
I used JBM and your inputs @ 2550fps with a true 1:9tw and it came out to 1.31 for a stability coefficient.
I used JBM and your inputs @ 2550fps with a true 1:9tw and it came out to 1.31 for a stability coefficient.
Re: Barrel twist for 7mm. Wildcat
Although the 1:9 works fine in my 7WSM and my brother's .284 winchester for the Berger 180s, we are running them at a minimum of 2,800 fps (my brother's .284; 2,900 in my WSM), I would be inclined to go 1:8.5 or possibly 1:8 for a velocity below 2,700 fps, especially if you are going to be running it in the winter when the air density is higher.
JeffVN
Although the 1:9 works fine in my 7WSM and my brother's .284 winchester for the Berger 180s, we are running them at a minimum of 2,800 fps (my brother's .284; 2,900 in my WSM), I would be inclined to go 1:8.5 or possibly 1:8 for a velocity below 2,700 fps, especially if you are going to be running it in the winter when the air density is higher.
JeffVN
Re: Barrel twist for 7mm. Wildcat
Thanks for the replies. I'm playing with a (747) 7x47 Lapua. I've got it to 2,700+ with 180gr. JLK this summer without any trouble in a 30" barrel 1:9tw, is fine in the summer but I think is going to be to slow this winter.
Thanks,
John
Thanks for the replies. I'm playing with a (747) 7x47 Lapua. I've got it to 2,700+ with 180gr. JLK this summer without any trouble in a 30" barrel 1:9tw, is fine in the summer but I think is going to be to slow this winter.
Thanks,
John
Re: Barrel twist for 7mm. Wildcat
The KLK and Berger are close enough to being the same length sa ask Berger they say that only a 9 twist is needed for a 180gr 7mm projectile but a little faster twist can not hurt you could use an 8 twist. In the 7X47 Lapua i would use a lighter projectile though you are realy asking a lot pushing them from the small case capacity i would look at using a 162-168gr projectile.
The KLK and Berger are close enough to being the same length sa ask Berger they say that only a 9 twist is needed for a 180gr 7mm projectile but a little faster twist can not hurt you could use an 8 twist. In the 7X47 Lapua i would use a lighter projectile though you are realy asking a lot pushing them from the small case capacity i would look at using a 162-168gr projectile.
Re: Barrel twist for 7mm. Wildcat
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BIGBUCKINBAMA</div><div class="ubbcode-body">Thanks for the replies. I'm playing with a (747) 7x47 Lapua. I've got it to 2,700+ with 180gr. JLK this summer without any trouble in a 30" barrel 1:9tw, is fine in the summer but I think is going to be to slow this winter.
Thanks,
John</div></div>
Wow, that makes me wonder what's possible with lapua 308 palma brass necked down to 7mm.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BIGBUCKINBAMA</div><div class="ubbcode-body">Thanks for the replies. I'm playing with a (747) 7x47 Lapua. I've got it to 2,700+ with 180gr. JLK this summer without any trouble in a 30" barrel 1:9tw, is fine in the summer but I think is going to be to slow this winter.
Thanks,
John</div></div>
Wow, that makes me wonder what's possible with lapua 308 palma brass necked down to 7mm.
Re: Barrel twist for 7mm. Wildcat
I shot some 168gr. Berger VLD at 2,800 and the 162 AMAX at 2,900 it is a nice little round.
John
I shot some 168gr. Berger VLD at 2,800 and the 162 AMAX at 2,900 it is a nice little round.
John
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