Twist question for 7mm
- Thread starter Captcoop
- Start date
effendude
Gold $$ Contributor
I have had good success with 1-9" barrels, even with the 195 Berger with my 284 and 284 Shehanes. My 28 Nosler wears a gain twist Bartlein 9.5-8.5" and shoots well too. I live at 900' of elevation. It seems as though some shooters are favoring a slightly faster twist as of late.
Scott
Scott
FeMan
Gold $$ Contributor
I live at sea level and shoot a straight 284 in a 1:9 twist. On a few cold winter days, I have found my dope to be inexplicably low, particularly at 800 yards and beyond. Back checking with the Miller formula, I found my stability to be around 1.35 in those conditions. It isn't instability per se since it still wins matches with the right correction. I have chronoed the loads so I know it isn't that. I am ordering a 1:8.5 for the next barrel to see if it is due to marginal stability. In all other conditions, the 1:9 shoots lights out and predictably for me.
See any reason not to go with 8.5 twist from the start? I calculated my stability and 9 showed on low end for cooler Temps. Perfect in warmer conditions. I'm in need of 284 straight barrel for new build
Joe R
Gold $$ Contributor
I just ordered a barrel for a future straight .284 barrel, FWIW both Berger and Sierra recommend 8 twist for their .284 180grain bullets on their web sites. That's what I'm going with.
Kindest regards,
Joe
My barrels are 9s... Shot from Houston to Raton with no issues, using 180 Hybrids.
falconpilot
Gold $$ Contributor
Can't argue with Marks results! Good shooting buddy!!
Joe R
Gold $$ Contributor
Mark, given your shooting performance (an unreal 1,199 out of 1,200 points) I have to look up to see the bottom of your shoes. I think I better change my order on that barrel first thing tomorrow morning. Enough said.
Joe
smoking-brass
shoot straight....shoot often
I built a 280AI with a 8 twist barrel....I have had bullets blow up when I push them to fast. Go with a 9 twist ... I am next time.
FeMan
Gold $$ Contributor
I see no reason to start with something lower than a 9. The 9 shoots great groups, but I am really hoping that my cold-weather BC anomalies go away with something faster. I have a 8.5 now but won't be spinning it on until December or so.
This.
DennisH
Life Time NRA member
9 twist and RL17 are my choice for my 284. SUPER ACCURATE, will easily hold a 1/2 pattern at 300 yards.
Dennis
I took a path less travelled this year opting for a wildcat 7mm (284INCH) over a straight 284 for which I'd acquired a 1:9 Brux 30" last year. Took a few weeks to get it dialed in since there was NO load data for it (more case capacity than 7-08, less than 284) but once I settled things out I won it's first match outing @ 1,000 yards with a 200-15x shooting Berger 180 Hybrids.
2nd barrel's at the smith's now, it's a 1:8.5. My thinking is I'm at a functional node at 2,800 fps now but a bit more spin ought not hurt anything, particularly when I try a lower node maybe, to conserve this next barrel.
2nd barrel's at the smith's now, it's a 1:8.5. My thinking is I'm at a functional node at 2,800 fps now but a bit more spin ought not hurt anything, particularly when I try a lower node maybe, to conserve this next barrel.
Captcoop,
Use our TWIST RATE CALCULATOR to find what the optimum twist rate for your rifle should be at the ALTITUDE(s) you will be shooting at here:http://www.bergerbullets.com/twist-rate-calculator/
How to properly interpret your results can be found here :
http://www.bergerbullets.com/berger-bullets-twist-rate-recommendations-by-eric-stecker-bryan-litz/
The OPTIMUM TWIST RATES we now list on the bullet boxes and Quick Reference Sheets are based on a worst case scenario of 59 degrees at sea level . See Femans first post . He is experiencing this but has compensated . 1-8 twist rate would get back his lost BC at the altitude (sea level) he competes at.
Take care,
You won't catch me shooting in weather cold enough to compromise bullet stability. At 70, I feel as old as dirt, and as fragile as thin glass.
One of my next projects will be centered around a 28" 1:9" barrel (probably L-W50) and a SAAMI .280 Rem chambering. Some preliminary testing with a pair of Ruger 77MK I's, with Sporter and Varmint weight barrels, shows me that I think I'm going to like this project. Not intended as a mucho precision rifle, I just want to get out and stretch its legs at 4800ft ASL near here at my new home in AZ.
Beats NY in a fair number of ways.
Greg
One of my next projects will be centered around a 28" 1:9" barrel (probably L-W50) and a SAAMI .280 Rem chambering. Some preliminary testing with a pair of Ruger 77MK I's, with Sporter and Varmint weight barrels, shows me that I think I'm going to like this project. Not intended as a mucho precision rifle, I just want to get out and stretch its legs at 4800ft ASL near here at my new home in AZ.
Beats NY in a fair number of ways.
Greg
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