Latest thinking on 7mm twist rates for 180 hybrids; Freebore and Neck Thickness

[WindSurgeon]

I am getting back into the game and building a new F-open rifle. My last gun was a .284 is set up for 180 VLD's using .188 FB and .313 neck. I still own the PRT reamer for this chamber. The barrel was a 1:9 twist. That gun was built in 2013 and was a tack driver, but it is finicky and exacting when it comes to the case dimensions it shot. In other words, a lot of work. The necks were all turned to .311.

I'd like to shoot 180 Berger hybrids. Has any of the thinking changed related to twist rates and chamber dimensions. Would like to run a no turn .284 Lapua brass. Any thoughts would be appreciated. Thank you.

 

[rardoin]

If you want to have the option of running the 184gr Hybrid I suggest at least .220" (or even up to .250") freebore. Even with the 180 I would take the .220" minimum. I agree with a no turn...not needed. I would spec a .320" neck. My .284 Win shot the 180/184 hybrid well, .320" neck, .225" FB reamer. I had plenty of room to keep the base of the bearing surface away from the neck/shoulder junction and plenty of bullet in the neck.

 

[greisdor]

You would be better served to get 284 peterson brass.

 

[ShootDots]

What Robin said @rardoin is excellent advice. The only difference I have is I like a turned neck. I use a .313 reamer with a .225 freebore in a Sherman and I turn my necks to .012.. I also shoot the 180VLDs (can't find a Hybrid to save my life) and I have an 8.75 twist.

 

[Kracken McGraw]

If you don’t mind me stepping on this thread. I have read a lot here that a 8.5 to nine twist barrel is recommended for the 284 Win. If you go with 180 grain plus bullets, Would a 8 twist be detrimental? This would be for 2500+ elevation, seems like the 8 twist barrels are a little easier to find on the shelf.

 

[jeffp400]

straight 284, 8 twist, .237 f.b. .315 neck with .002 clearance. f open 184's .050 off lands. it likes this load but having extraction problems. going .004 clearance.

 

[Kracken McGraw]

You would be better served to get 284 peterson brass.

What did your necks measure outside with loaded bullets on the Peterson brass, if you don’t mind?

 

[greisdor]

My JGS reamer is .320 neck. The largest peterson loaded was .317. I then skimed the brass after two firings so that bullet seating pressure was the same. They are now .3145 and are shooting great....

 

[1shot]

I run a .313 neck w/.225 FB in an 8.5 twist. It has served me well.

Lloyd

 

[KenOath]

..319”-.320” neck for no turn Lapua brass, if your running 180 Hybrids you’ll get away with .208” fb but .220”+ will give you the 184 option, 9tw...

 

[FeMan]

If you don’t mind me stepping on this thread. I have read a lot here that a 8.5 to nine twist barrel is recommended for the 284 Win. If you go with 180 grain plus bullets, Would a 8 twist be detrimental? This would be for 2500+ elevation, seems like the 8 twist barrels are a little easier to find on the shelf.

9 twist stabilizes the 180 and 184 at sea level just fine. Spinning faster will increase the effective BC somewhat, but I have heard that the faster twists may not group as well. I don't shoot well enough I guess to be able to tell. I run 9 twist in F-open and 8.5 in my tactical and hunting 284s. All shoot better than I do.

 

[1shot]

9 twist stabilizes the 180 and 184 at sea level just fine. Spinning faster will increase the effective BC somewhat, but I have heard that the faster twists may not group as well. I don't shoot well enough I guess to be able to tell. I run 9 twist in F-open and 8.5 in my tactical and hunting 284s. All shoot better than I do.

I started with a 9 twist in my 284 Shehane. I'm in Ohio and where I shoot is 1,200 ASL. The rifle shot "OK" with 183 SMK's but not great. I took the rifle to Byers Colorado which is 5,500 ASL and it was on fire!! Shot a PB with a boatload of "X's".With that new info, I went back home and screwed on a 8.5 twist and the performance was the same as the 9 twist gave me at the higher elevation.
I hope this helps,

Lloyd

 

[kev77]

You would be better served to get 284 peterson brass.

Why Peterson

 

[greisdor]

Peterson 284 brass is as good or better than Lapua and you don't have to neck it up. I have been shooting them for a year now and they are still tight even with the hot loads I shoot.

 

[Don Shelton]

Peterson 284 brass is as good or better than Lapua and you don't have to neck it up. I have been shooting them for a year now and they are still tight even with the hot loads I shoot.

I also use Peterson brass for my Shehane and have over 9 firings on some of it...I also turn the necks to .013” and have no issues... I used Peterson in my 308 and now use it in my 6 Bra also

 

[KenOath]

Lapua will have straight 284 brass on the shelves this year apparently, finally!

Not that necking up is a big issue but one step removed none the less..

 

[WindSurgeon]

I started with a 9 twist in my 284 Shehane. I'm in Ohio and where I shoot is 1,200 ASL. The rifle shot "OK" with 183 SMK's but not great. I took the rifle to Byers Colorado which is 5,500 ASL and it was on fire!! Shot a PB with a boatload of "X's".With that new info, I went back home and screwed on a 8.5 twist and the performance was the same as the 9 twist gave me at the higher elevation.
I hope this helps,

Lloyd

Thanks Lloyd. I am in Minnesota at 970 ft elevation. Sort of average, and I plan to shoot the Berger 180 or 184 hybrids.

 

[1shot]

Thanks Lloyd. I am in Minnesota at 970 ft elevation. Sort of average, and I plan to shoot the Berger 180 or 184 hybrids.

If you don't already have a barrel, I'd go with at least an 8.5 twist.

Lloyd

 

[Kracken McGraw]

What OAL length measurements are y’all getting in the .284Win. with 180 and 184 bullets loaded? Thanks!

 

[Sandstorm]

My 284 Shehane is at 3.280 coal..with a 240 freebore -.014 out with a 180 HYB
9 twist Brux with a 32 inch 1.250 pipe and a No turn neck