Berger 108gr. Boattail

[500Stroker]

My .243win chamber's freebore (don't know the exact length) has the 105 vld touching the rifling at 2.840"ish / 2.275" to ogive. So the boat tail/bearing surface junction sits at the shoulder/neck line.

Would the 108's require a longer freebore for optimal seating depth ?

Zero, my 6BRX has a .140 freebore and it has shot sub one inch 5 shot groups @ 600 yards with Berger 108's.

 

[500Stroker]

Well, darn it, someone should call up the NRA and let em know all those BR national records set with a Dasher and an 8-twist need to be revoked cause Berger says they are only marginally stable! lol...

I'm not disputing what Berger's calculator claims, but you can't dispute on paper results.

EDIT:. I'm not trying to disparage you, I'm just disturbing the sh*t a bit...

Food for thought, what if Berger is correct, perhaps there may have been more records set if those record setting shooters had been fly'n Berger 108's.

 

[LRPV]

Food for thought, what if Berger is correct, perhaps there may have been more records set if those record setting shooters had been fly'n Berger 108's.

Measure the actual OAL of one your 105 hybrids, plug that length into the twist calculator instead of just choosing the bullet from the drop down and see what it comes up with.

 

[500Stroker]

Measure the actual OAL of one your 105 hybrids, plug that length into the twist calculator instead of just choosing the bullet from the drop down and see what it comes up with.

I dont have a 105 to load, sold them all here.

 

[barefooter56]

Boys, I'll stick by what I stated early.
I just went back and ran the numbers on the Berger Twist Calculator and it stated that a 1 in 8 twist barrel is "Marginally" and recommends a 7.75 twist barrel for a Berger 6mm 105gr Hybrid bullet. I used 3050 fps, 59F, 700 ft above sea level.
Read it and weep but dont kill the messenger. LOL

500Stroker,
What was the SG number?

 

[500Stroker]

500Stroker,
What was the SG number?

1.48 SG - 105 Hydrid
1.67 SG - 108 BT

 

[snakepit]

Boys, I'll stick by what I stated early.
I just went back and ran the numbers on the Berger Twist Calculator and it stated that a 1 in 8 twist barrel is "Marginally" and recommends a 7.75 twist barrel for a Berger 6mm 105gr Hybrid bullet. I used 3050 fps, 59F, 700 ft above sea level.
Read it and weep but dont kill the messenger. LOL

I ran your numbers through the Berger Twist Calculator and came up with a Marginal Stability of 1.48. The range of the Marginal Stability Scale is from 1.0 to 1.49 so BC is being compromised by only 1% as stated in the results. Also if you would have just changed your temperature input 6 degrees from 59F to 65F your Stability would have been 1.50 and you would be Stabilized. I don't think this is going to affect your accuracy by using a 8 twist barrel. I know of a couple of shooters with 8 twist who were also in the top part of the Marginal Stability Scale who went to 7.5 and 7.75 twist and their results did not change. In a discussion with Bryan Litz of Berger I asked about this same topic and was told that I probably would see little difference with a stability number near the top of the Marginal Range as compared to the Stable Range.

http://www.bergerbullets.com/twist-rate-calculator/

 

[500Stroker]

I ran your numbers through the Berger Twist Calculator and came up with a Marginal Stability of 1.48. The range of the Marginal Stability Scale is from 1.0 to 1.49 so BC is being compromised by only 1% as stated in the results. Also if you would have just changed your temperature input 6 degrees from 59F to 65F your Stability would have been 1.50 and you would be Stabilized. I don't think this is going to affect your accuracy by using a 8 twist barrel. I know of a couple of shooters with 8 twist who were also in the top part of the Marginal Stability Scale who went to 7.5 and 7.75 twist and their results did not change. In a discussion with Bryan Litz of Berger I asked about this same topic and was told that I probably would see little difference with a stability number near the top of the Marginal Range as compared to the Stable Range.

I agree, I also played with the numbers on the Twist Calculator and you can make it do just about what every you want (within limits). Changing the AOL can also jump the SG. The numbers I plugged in are the Fall shooting conditions we have here in MO.
I compete with a number of shooters that fly 105's in 8 twist barrels with very good success.
I also agree with Bryan that we are splitting fine hairs and most likely can't measure the difference on the target.

 

[4xforfun]

The first time I tried the 108's was just a few days before the 2011 IBS 1K nationals. Shot small right from the git-go. 1st in LG group, 6th LG score, 1st LG overall, 1st in 2 gun overall. But, it was the dasher and the 108's that made it happen. I use at least a ten thou jam...I look for square land marks on my bullets, so the actual jam depends on the condition of your BBL.

Tod

 

[22DASHER]

The first time I tried the 108's was just a few days before the 2011 IBS 1K nationals. Shot small right from the git-go. 1st in LG group, 6th LG score, 1st LG overall, 1st in 2 gun overall. But, it was the dasher and the 108's that made it happen. I use at least a ten thou jam...I look for square land marks on my bullets, so the actual jam depends on the condition of your BBL.

Tod

What type of neck tension and load details did that barrel like with the 108's?

 

[4xforfun]

.271 no turn , .104 freebore chamber. 32.2 RL 15, .267 bushing, 450 primers and blue box Lapua formed with a false shoulder AND a hard jam.. I think I was at 2990 fps. I do remember having a brain shit(way more severe than your standard brain fart) and trimmed my brass at 1.50 instead of 1.54!! Didn't matter a lick!