Best Twist for Bart's .790 Boat Tail?

F

Frank Green

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I saw a posting asking this question and I've been asked a few times this week on the phone here at work.

According to my numbers and even talking to another bullet maker we feel that the bullets with the .825-.840 length jackets a 1-14 twist is to slow. I come up with a 1-13.6 as min. assuming a 3200fps. for a average velocity.

If a 1-14 is really on the ragged edge you might find on some days the gun shoots just fine and some not. Why? A few factors come into play. One is velocity (doesn't play a huge part but does play a small part) also weather conditions. Both temperature and wind and elevation weather at sea level or 5000 feet. If it is really windy and the bullets are not properly stable it can make the groups run bigger.

The .790 length bullets a a 1-14.33 is min. at the same velocity.

I tell guys a little faster twist won't hurt you shooting good quality bullets.

I know Lou M. shot the .790 Bart's in a 1-13.5 twist barrel.

Everyone talks about how bad the wind was at the Cactus this year and how Lou killed everyone. Did the combination of a little faster twist and the .790 bullets help him out? Was it a combination of the seating depth?

Maybe Bart can give us his thoughts on what his bullets might like for twist?

Keep in mind all that there are a lot of variables in this stuff.

That's why for my first barrel I split the difference between the 13.5 and 14 twist and made mine 13.75.

Later, Frank @ Bartlein
 
Bart's BT

Billy Stevens has had great success using the 13.5 twist barrels. Richard Milton shot the .790 BT's and won the 200 yard LV agg at the Crawfish last weekend with a 14.75 twist barrel. He shot a 14 twist in the HV 200 and finished second with it. If he could have shot anything decent at 100 yards, he would have been in the hunt for the 2-gun. Good shooting....James Mock

PS I just talked to Richard and he told me that he did not shoot the BT's. He shot the Ultra's instead. Sorry for the mistake, but he told me that he was going to shoot the BT. The concensus of those who have tried them that the 13.5 twist is best. James
 
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Frank

I have been using 13.5 twist barrels for going on 5 years.
The main reason I went to them is because on occasion, when I shot 1-14 twist and Fowler Bullets on .825 jackets, I would put a round on the target and the darned hole would appear to be quite a bit bigger than it should. I would sometimes take the time to go and examine the hole, and sure enough, the bullet appeared to have not gone through the target straight.
About that same time, (you probably remember this), Lester Bruno started trying 13.5 barrels with the boat tail he had then. It looked very promising. Then, he aquired the 00 die he has now, and those bullets, and that 13.5 twist, allowed him to set the World on fire that year, especially with his Rail Gun.
I figured ole Lester had stumbled onto something, so I bought some 13.5 barrels,and used Barts Ultras. They shot very good.
Then Lester sent me some of those 00 Boat Tails, (sort of an Ultra with a Boat Tail), and that is what I have been shooting for over 3 years.
I never get that first shot that looks twice as big as it should anymore.
Barts Boat Tail Ultra on the .790 jacket is a little fatter in the o-give at the lands than the Bruno, and it measures about .0003 bigger just forward of the boat tail-shank junction. It would seem 1-14 would be ideal if a 1-13.5 works great with the .825 jacket bullet, but like you said, a tad faster twist sure won't hurt anything if the bullets are up to snuff.........jackie
 
Hey Jackie! Thanks for the reply. I was the one that did the twist rate calc. for Lester when he started making his own bullets and suggested going to the 13.5 twist back when we we're at Krieger. We made him the first 13.5 twist barrels and he went to the next super shoot back in 99 or 2000 and won everything.

Thanks for the input. Always look forward to your comments and thoughts and the things you do!

The thought on the 14 twist barrels and longer bullets is they are not as stable enough and when you get in even slight wind conditions it will play with the bullet a little more. Hence what you saw etc....

When Lester first talked to me about what was happening and I told him to send me a couple. I forget what the original calc. was but it was something around 13.7 give or take a little. I thought the 1-14 was to much on the edge and suggested bumping it up to a 13.5. The rest seems to be history.

Have a good weekend! Frank
 
Frank

Frank,

I personally think the 13.5 twist is about prefect for BTs. My goal when I started this project was to come up with a bullet specifically for the Bartlein and Krieger barrels. In my testing I found very few bullet dies actually make a good BT. I have flat-base bullets that are proven winners that shoot terrible as BTs. In my opinion the addition of the BT changes the center of gravity too much for most bullet dies. I think the BTs are slightly tougher to stabilize and need a little extra help. Shorting the jacket to 790 combined with the extra twist of a 13.5 barrel is the way to go.

As for seating depth… it can make all the difference in the world. The majority of shooters don’t realize the difference a couple of thousands can make.

Bart
 
Frank Green

Frank, thank you for starting a great post, very informative. The other gentlemen who contributed, I applaud you.

:D
 
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