6 Dasher Twist Again

[Rset]

I am currently shooting a 28" 8 twist Dasher with very good results.
Will be buying a new barrel and was looking to finish at 31" with a 7.5 twist.
Is there any advantage, or disadvantage in moving to the new barrel as described?

 

[Dusty Stevens]

Longer barrels whip more and weigh alot more. I guess it matters what discipline you shoot it in

 

[jvw2008]

Are you expecting more velocity out of the 31”? Even if that happens, I would be concerned about the weight and whip trade off. You might check Lilja’s article regarding barrel stability versus diameter and length.

 

[Rset]

Longer barrels whip more and weigh alot more. I guess it matters what discipline you shoot it in

Shooting F-Class. With the 28" barrel, still have 1.8# to stay under weight. assuming 1.25" straight

 

[Rset]

Are you expecting more velocity out of the 31”? Even if that happens, I would be concerned about the weight and whip trade off. You might check Lilja’s article regarding barrel stability versus diameter and length.

Weight should not be an issue. Currently have 1.8# to make up with the extra barrel length. Whip I may have to look into, bit seems most f class shooters are running a 30" or more. Using a 1.25" straight

 

[Rset]

In addition to the extra length, I am also wondering about twist. With the higher velocity of the Dasher, is a twist faster than 8 required, or desired?. Would be shooting heavy for class weights. 105 hybrid +

 

[big john 5394]

7.5 twist and 30 in bbl is great for a dasher and we have the new 109 berger should shoot with that combo. I have been using that combo and its working with good results.

 

[dmoran]

@Rset
31" 6Dasher barrels is what I use and prefer. Reason being, can hit the upper nodes with a little less powder, hence pressure. That is the reason why I went from 28" to 31" barrels many years ago now. Typically around 1/2-grain less powder to hit the same speeds that 28" barrels achieve.
Going to a 7.5-twist will yield more bullet stability for the heavier/longer bullets.

Just my 2-Cents...

 

[swd]

I've gone to 7.5" on all my 6mm's for more versitility with different bullets. Barrel whip just isn't an issue to worry about with F Class rifles. Length is an wasy way to add weight and a little speed. Go for it.

 

[BenPerfected]

I've gone to 7.5" on all my 6mm's for more versitility with different bullets. Barrel whip just isn't an issue to worry about with F Class rifles. Length is an wasy way to add weight and a little speed. Go for it.

I have been shooting both 7.0 & 7.5 twist straight barrels. Hard to see any difference on paper as there are too many variables to measure the results on paper at 500 yds.
Ben

 

[Whitehunter]

@Rset
31" 6Dasher barrels is what I use and prefer. Reason being, can hit the upper nodes with a little less powder, hence pressure. That is the reason why I went from 28" to 31" barrels many years ago now. Typically around 1/2-grain less powder to hit the same speeds that 28" barrels achieve.
Going to a 7.5-twist will yield more bullet stability for the heavier/longer bullets.

Just my 2-Cents...

Like your reason dmoran. Had this on my mind for a couple of years. Found a Krieger barrel I had that is 1.350 for 6" tapered to 1.1" at 31" with a 8 twist. Will use a BAT M action for semi-heavy gun, free bore will be .104 for the short custom bullets. Is the rumor true short bullets for short benchrest shooters in long range 600 and 1000 yard (LOL)

 

[Boatschool02]

Will offer the opposite opinion.
I would not intentionally add overall firearm weight at the end of the barrel (or forward of the balance point) unless it was a tuner.
1.8lbs under weight on a 6mm is borderline inconsequential.
If this were a 300WSM, it'd be a different situation altoghther.
You could buy a 1.350 tapered barrel or add weight to the butt, etc.
-
Asking someone what barrel length they recommend without asking which powders they tune for is a recipe for mediocre outcomes.
-
Give your smith the freedom to cut off as much as they deem necessary from the muzzle end.

 

[Rset]

@Rset
31" 6Dasher barrels is what I use and prefer. Reason being, can hit the upper nodes with a little less powder, hence pressure. That is the reason why I went from 28" to 31" barrels many years ago now. Typically around 1/2-grain less powder to hit the same speeds that 28" barrels achieve.
Going to a 7.5-twist will yield more bullet stability for the heavier/longer bullets.

Just my 2-Cents...

My reasoning as well on the length. Thank you for the reply.

 

[Rset]

Now that we have some input on length and twist. Let me ask about free bore.
Shooting 105 Hybrids now in a barrel that I have no idea what reamer was used and shoots great.
Assuming I stay with the 105 or possibly the new 109, what free bore would you suggest?

 

[Rset]

Give your smith the freedom to cut off as much as they deem necessary from the muzzle end.

Can always have length removed. Part of the reason I thought about going longer in the first place. Thank you for the input. If it doesn't feel/shoot right, I will make adjustments.

 

[dmoran]

Can always have length removed. Part of the reason I thought about going longer in the first place. Thank you for the input. If it doesn't feel/shoot right, I will make adjustments.

Actually it's easier to lengthen the throats/free-bore via way of a throating reamer (very commonly used).

I'll suggest at least a .130" FB.
Myself use a .160" FB and shoot Berger 105-VLD's primarily or heavier/longer bullets.

 

[Ranger188]

This is the article Jerry was referring too. A little long but a good read.
There comes a point that you are not gaining as much fps per inch the longer you go.
Especially with a cartridge that burns a faster powder. If you were running
a big magnum, then a longer barrel would yield a good fps per inch.
Most 600 and 1000yd BR shooters are using a 28 inch barrel.
They are not doing it for the hell of it.
Now the short range guys (100-300)are running 22-23 different needs.
https://riflebarrels.com/a-look-at-the-rigidity-of-benchrest-barrels/

 

[Whitehunter]

Now that we have some input on length and twist. Let me ask about free bore.
Shooting 105 Hybrids now in a barrel that I have no idea what reamer was used and shoots great.
Assuming I stay with the 105 or possibly the new 109, what free bore would you suggest?

The 105 hybrids do better with a longer free- bore. I shot a .135 free-bore on a Dasher at the G.B.A. 600 yard Nationals to set a heavy gun single target group record of 0.715" for 5 shots. This was shot with a 16.5 pound light gun and 28" barrel. Using 105 Hybrids that measure close to the new 109 Hybrids, powder used was RL 15. When I spoke of the 1.350" barrel for 6" tapered to 1.1" finished at 31" was to add weight to center of stock. The taper is to reduce the whip from a longer barrel. Will be using a MB Action that weights 38.5 oz's for more weight in center of stock for 10 shot groups. The size of barrel should keep heat lower than a H.V. to help on group size. If the gun is muzzle heavy I can add 2 pounds of lead to MBR stock with no problem for a weight of 22 to 23 pounds total on gun with scope. The 10 shots is for benchrest 1000 yard and 5 shots for 600 yard.The free-bore will be .104 for the shorter custom bullets and Like Donovan spoke of I can lengthen free-bore to .135 for Hybrids if the short bullets don't work. "MISSISSIPPI"