Concern about twist rate for Berger 105 Hybrids

[snakepit]

I'm with Jim on this. I didn't switch to the 7.75 twist because of some formula that told me that the hybrid was "marginally stable", but because I was experiencing some unexplained flyers with the 8 twist. Let the target tell you when it is time to change. Good shooting...James

If you have enough data by now could you tell us how the 7.75 twist is shooting compared to the 8 twist.

 

[DJ111]

I have had no issue shooting them in 8" twists with a Dasher and BRX. Shooting them at 1100' elevation between 50-90 degrees. I have not tried a faster twist yet but have no reason to change either.

 

[Alex Wheeler]

Ya, but they weren't in the 10 ring Tom.
Guess whats going on next year? More 7.5" twists...

 

[johara1]

I started checking twist in my 8 to 1 barrels and the best shooting one is 7.9 to 1. The difference is with the same components and the same lot head to head, 8 to 1 barrels shoot .1 + and 7.8 to 1 shoot - .1 @ 100 will shoot agg. 3.071" 1000 5 shot groups and will agg. 5.5 " for 10 shot groups with a light gun. This year with a LG. and 8 twist ….. average to big with flyers ………. jim

 

[lloydx2]

Maybe need to try 1-7.5 twist Jim?

 

[Dubya]

The OAL of the Hybrids has more to do with the BC, but are we over looking the bearing surface, which contacts the
bore. My VLDs and Hybrids bearing surface are close to the same (0.360 plus/minus 0.001/0.002) and work with an 8 twist just fine.


Gary.

 

[johara1]

Maybe need to try 1-7.5 twist Jim?
[/quote


I had great success with the 7.8 but i was just saying that the little bit faster twist than a flat 8 seems to do better but it will not shoot as good as a 7.8. I have had the 7.8 barrels shoot in the .040 range @ 100 and 2" @ 1000…….. jim

 

[Dubya]

johara1, are using a .236 or .237 bore?

 

[johara1]

johara1, are using a .236 or .237 bore?

I never saw a difference, but i don't know anyone that checks it,or knows how to. What is written on the back of the barrel are feel good numbers that get cut off…….. jim

 

[Dubya]

LOL, ok thanks.

Gary

 

[dixieppc]

Over the past year, I purchased several different brands of 1-8 twist 6 mm barrels to be used on my 6 mm BRX rifle. Berger recently came out with their update stability calculator that now states a 1-7.25 twist is optimal for this bullet and cartridge. It seems odd as I could not even find a 6 mm barrel with less than 1-7.5 twist. Just curious what result people were having using a 1-8 twist barrel on their 6 BRX with the 105 hybrids. Also curious if anyone tried a 1-7.5 twist and had better results than the 1-8. Just wanted to ease my mind that I don't have 4 barrels that are not going to give me optimal accuracy for my BRX.

Thanks,
Joe

I have a 6mm 5R, .237, 1:8, 28" Heavy Tapered SS Bartlein that actually measures out to 1:8. It is chambered for .268 neck, .120 freebore in straight 6br. I am still in the process of finalizing the optimal load/seating depth using the 105 Hybrids, Varget, Lapua Brass and 450 primers.

So far, my best SD and Grouping is coming in at a MV of 2850 at environmentals of 85f and 1515' alt. Plug this into the Berger calculator and you get a SG of 1.45 which is at the upper edge of "Marginal Stability". However, this thing is showing real potential at 200' load testing so far.

Just for the hell of it, I plugged 3200 for the MV into the Berger calculator and SG moved to 1.5 which is the lower edge of "Comfortable Stability". So it appears that MV also dictates optimal twist rate.

If I had it to do over again, I might opt for the 1:7.75 or even 1:7.50 but I think my 1:8 is going to do just fine if not do me proud at 600' competitions.

Regards......

 

[LRPV]

Use your actual measured bullet length instead of the generated value of 1.29 and see how it comes out with your other numbers.

 

[dixieppc]

Use your actual measured bullet length instead of the generated value of 1.29 and see how it comes out with your other numbers.

Actual bullet length to 2 places is 1.25 which moves my SG from 1.45 to 1.6 which places me well into the "Comfortable Stability" region. I'm Happy.....

Regards....

 

[Blaster-37]

You guys working with the Berger Calculator should try adjusting your velocities and temps, interesting. As all good shooters know, the target is the bottom line as it never lies.
greg

 

[blairf]

Tag for later

 

[savagedasher]

Saturday we shot 1018 yd gong match. The winds 10 to 15 mph from R to L head winds to start. Second round they went to15 to 20. Third round 25 to 35 . I had a Dasher 8 twist on my left I was shooting 7.5 dasher on my right was a 284 . The 8'' twist was getting large amount of bullet movement. The 284 was less . My 7.5 had the least amount of vertical.
600 yds I feel 8 twist is fine. 1000yds 7.5 or faster works better in the wind Larry