7PRC Twist Rate

[escopeta]

Building a 7PRC for local hunter and he ordered a Carbon 6 barrel in 8Twist. My son is a high Master F class shooter and he said the 9 Twist is better for the heavies. He shoots a .284 Shehane, and 9 twist is what he uses. This will be a lighter weight hunting rifle on a Remington 700 magnum action. The shooter will probably start off with factory ammo. As the barrel is several months out it could be changed from 8 to 9 twist. So 9 twist better for general use with heavies?

 

[F Class John]

I guess it depends what you consider to be a 'heavy'. I'd say most F Class guys (and I'm guessing hunters?) will use an 8.5 or 9 for anything up to 184gr although the Berger 190s technically say they stabilize in a 9 as well but I think most would want faster and I know I had better luck with faster when I tested them.

Here's a good resource that actually tells you how stable a bullet will be all things being equal and you can enter different parameters.

Twist Rate Stability Calculator

Our newly updated Twist Rate Stability Calculator not only tells you what your SG is, but it also lets you know if you are reaching your optimized BC.

bergerbullets.com

 

[Sandstorm]

If your hunting id think a 165 to 180 gr bullet in a Accubond or similar would work stellar.
Your not thinking heavy as in over 200 gr. right.?

 

[DaveTooley]

I can't count how many 7MM hunting rifles I've built with 1-10 twists. Works great up to and including 160 class bullets. If I need heavier bullets in a hunting rifle I'll go 30 cal or skip right on to 338. YMMV

 

[Walt Krafft]

SAAMI twist for the 7mm Mag is 9.5. For a light weight hunting rifle I would go with that.

 

[B23]

My 7mm Blaser mag, which is a near twin to the new 7PRC, has a Hart 8tw. When I had it built I thought, maybe, I would try some 195's but all I've shot in it is a few 175's and the rest have all been 180's.

I'm having a 7PRC built for my daughter and it'll wear a 8.5tw finished at 22 inches.

If all you'll ever shoot is up to the 180's a 9tw will be fine, if you want to give yourself a little extra flexibility, get a 8.5tw.

 

[escopeta]

Only option for these Carbon 6 (McGowan)barrels is 8,9 and slower have 8 twist on order. Guess I will stay with that. Berger says 9 or faster for the 180’s. Guy has been shooting a a .280AI but wants something new. Will build what he wants.

 

[dthomas]

I think the cartridge is designed for an 8 twist, so if that is what he has on order he might as well just keep it as an 8 twist. As John said in f class i use a 9 or 8.7 twist for 180-184 bergers.

 

[escopeta]

Will be running a 26” with brake, so will see how it works out when I build and shoot in several months.
Thanks all

 

[sifer1]

i need some help here. so i've got a 7 prc with a 1/9 twist. but shooting factory so far does nothing.
any suggestions do work a load for it. maybe a heavier round and what powder to use??
thanks in advance

 

[Mike TackleBerry]

It depends on the bullet weight, but an 8T is absolutely perfect for the .284 heavies, like the 190 LRHT. 9T for the 190s wouldn't be sufficient; you want a gyroscopic stability factor of 1.50 or higher.

 

[FrankG]

It depends on the bullet weight, but an 8T is absolutely perfect for the .284 heavies, like the 190 LRHT. 9T for the 190s wouldn't be sufficient; you want a gyroscopic stability factor of 1.50 or higher.

Bullet weight is only part of it... bullet length dictates twist is the most primary driving factor. If you go to a solid with the weight being the same as a cup and core bullet... the solid is longer and hence forth will need a faster twist rate.

velocity plays a small part as well.

For up to 180gr bullets... a 9 twist is plenty. The 183smk need a little more twist but I have fired them in a 284Win running them at 2900fps out of my 9 twist and shot in the .4" range but again I would use a slightly faster twist for those. I'll say 8.5 minimum. 190 ATIP's Your looking at a 8.25 minimum for twist on those. Hornady recommends 1-8.

Also how the barrel is made... twist rates can vary or inconsistent especially in button barrels and production barrels.

Later, Frank
Bartlein Barrels

 

[STOMP442]

Elevation plays a big part as well, where I am at a 9 twist works well for up to the 180s with no problems. That 7PRC was designed to shoot the 180+ bullets. That was one of its big selling points. I would stick with an 8 and eliminate any worries.

 

[Tangent]

I was looking at Tikka's 7PRC rifles recently and they are 1 in 8.

 

[effendude]

I've ran 175, 180 and 195 Bergers out of my 284 Shehane rifles, (2 F-Class and 2 hunting rifles) all with 1-9" Bartlein barrels. Theoretically, the 195's shouldn't have shot as well with the Shehane speeds but a wall full of taxidermy begs to differ. Elevation here in MN is 900', Africa was 2-3000'. I'm rather lean towards a faster twist if building another 7 in the future just because Berger keeps making heavier bullets! I did purchase a Tikka 7PRC and it has a 1-8" barrel and it is a solid .5MOA rifle with the 175's. Any future 7's will have 1-8" barrels. The 175 Elite Hunters and the 180 Hybrid bullets are both hammers on game up through elk, kudu and wildebeest.
Scott

 

[Mike TackleBerry]

Bullet weight is only part of it... bullet length dictates twist is the most primary driving factor. If you go to a solid with the weight being the same as a cup and core bullet... the solid is longer and hence forth will need a faster twist rate.

velocity plays a small part as well.

For up to 180gr bullets... a 9 twist is plenty. The 183smk need a little more twist but I have fired them in a 284Win running them at 2900fps out of my 9 twist and shot in the .4" range but again I would use a slightly faster twist for those. I'll say 8.5 minimum. 190 ATIP's Your looking at a 8.25 minimum for twist on those. Hornady recommends 1-8.

Also how the barrel is made... twist rates can vary or inconsistent especially in button barrels and production barrels.

Later, Frank
Bartlein Barrels

I was referring to cup and core. I see no benefit to running a solid in a .284 cartridge, especially for hunting (If it's required by state law, then you use what you have too), which is what the OP is mainly referring to.