Slow twist 7mm

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Slow twist 7mm

Post by andym79 » 23 Mar 2019, 5:55 am

Hi guys I was just wondering if anyone runs a slow twist 7mm rifle?

By slow I am talking 12 or 13 twist, and would it stabilize Sierra Varminter 100gr, Speer 100gr TNT, Speer SPBT 130gr, Speer SPBT 145gr?

The online calculators say a 13 would work on all but the 145gr and a 12 would work on all of them!

Has anyone experience of shooting any of these or similar bullets in a 7mm?

I am considering building as slow twist fast shooting 7mm.

Thanks
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Re: Slow twist 7mm

Post by SCJ429 » 23 Mar 2019, 8:49 am

You can make up for a bit bit of twist rate if you have velocity, if you are shooting a 7mm Weatherby Magnum or 7 WSM you have a little more flexibility. The other thing is keep your bullets as short as possible, long VLD or ballistic tipped bullets need more twist rate. What caliber are you shooting.?
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Re: Slow twist 7mm

Post by Rod_outbak » 23 Mar 2019, 4:44 pm

andym79,

I've not fired a slow-twist 7mm as you are thinking of building.
However, I have fired the 100gn Sierra HP projectiles.

I have a 7mm-08 Tikka T3 Hunter Stainless Fluted, with a 22.5" barrel, a 1:9.5" twist, and a 3-chamber muzzle-brake(Trentech).

Usually, I load 120Gn Vmax projectiles; I find they nail pretty much anything I aim at, and are very predicatable/accurate out to ~400 metres(about my limit anyway).

July last year, I got around to testing some 100gn Sierra HP loads, which I had made up 5 loads from 45.0gns AR2208, up to 45.5gns.
The 45.0gn loads produced 14mm groups at 100 metres. The other loads were larger groups than that.
Best guess is they were roughly around the 3100fps(another thing I intend to check up on when I re-visit this again)
I didnt get around to trying any loads below the 45gns, but I intend to follow up on this in the next 12 months.

For a hunting/carry rifle, I'm pretty happy with 14mm groups.

Good luck on your build.

Cheers,

Rod.
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Re: Slow twist 7mm

Post by SCJ429 » 23 Mar 2019, 7:22 pm

The slowest twist rate I have is 1:17 but it is a 30 cal. It shoots 115 grain Bergers very well. My 7mm is 1:10 and I use 110 grain bullets in it.
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Re: Slow twist 7mm

Post by andym79 » 08 Jun 2019, 5:23 pm

Still thinking about doing this one any more thoughts?
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Re: Slow twist 7mm

Post by duncan61 » 08 Jun 2019, 6:38 pm

I have made 100gn Sierra HPs for my Sendero 7mm Rem Mag.With 56gn 2208 they are belting out at around 3300fps They group O.K. and make a mess of Kangaroo heads as you can imagine.The rifle twist on the Remington Sendero is 9/1/4 and it stabilizes 175gn pills.I loaded 168gn Sierra Matchkings and they shoot better than me at 1000 yards
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Re: Slow twist 7mm

Post by duncan61 » 08 Jun 2019, 6:44 pm

Are you going to build on the 7/08??? Anything larger would be a waste of case space.You are aware a standard .243 would be ballisticly similar with 100gn pills
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Re: Slow twist 7mm

Post by andym79 » 09 Jun 2019, 6:41 am

"Are you going to build on the 7/08??? Anything larger would be a waste of case space.You are aware a standard .243 would be ballisticly similar with 100gn pills"

When you put it like that it make the project sound lame! Though you are not far from wrong the 7mm is only going to push 250fps quicker with a lower BC!

So its a 243 AI but less than, but with the right twist and rig it would work very well.

My first thought was a 7x57r because I could do it in more than one rifle I have with a worn out barrel!

The other thought thought a bit crazy as it would be such a waste of powder was a 7mm STW for 3800fps. I can still use 140 gr in a slow twist 1 of those at 3300fps.
Last edited by andym79 on 09 Jun 2019, 7:27 am, edited 1 time in total.
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Re: Slow twist 7mm

Post by straightshooter » 09 Jun 2019, 7:24 am

Andym79
I am curious as to what it is you hope to achieve?
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Re: Slow twist 7mm

Post by duncan61 » 09 Jun 2019, 1:19 pm

If you have been on this forum for a while you will see andym79 is always asking about making different rifles.I did request once that we see some pictures of these projects.I find the topics interesting regardless and its much better than some of the political threads currently running
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Re: Slow twist 7mm

Post by SCJ429 » 09 Jun 2019, 3:24 pm

Any why don't you do a 7mm Grendel? Run even more twist than you originally thought.
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Re: Slow twist 7mm

Post by Stoney » 10 Jun 2019, 5:54 pm

duncan61 wrote:If you have been on this forum for a while you will see andym79 is always asking about making different rifles.I did request once that we see some pictures of these projects.I find the topics interesting regardless and its much better than some of the political threads currently running



+1 It's interesting to explore possibilities.
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Re: Slow twist 7mm

Post by andym79 » 10 Jun 2019, 6:09 pm

I could post quite a few pictures of the rifles I have done over the last few years they don't look that odd.

But I can put up a photo of all my wildcat cartridges, which would give you a better idea of the variety of things I have done.

6-222r
6.8x48r
30-357 max
338x45r
356r
408-444
416r

Plus there are a couple of non wildcats that are still not common.

22hp
218 bee
25-20
33 win
475 linebaugh
50 alaskan
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Re: Slow twist 7mm

Post by duncan61 » 10 Jun 2019, 6:17 pm

You dont have to do anything but I am genuinely interested,If I had spare loot and a workshop I would be making a large game rifle in 416 Rigby or 458 Win Mag
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Re: Slow twist 7mm

Post by SCJ429 » 10 Jun 2019, 8:25 pm

Live a little and make it a 450 Rigby Duncan.
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