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7.5 or 8 Twist for 115 DTAC

Brandon05_88

Brandon05_88

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Jan 5, 2011
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Charleston, WV
I know this has been addressed before because I searched and read the topics a few times. I seen most people say 8 twist will work most of the time but 7.5 is what's needed. I plan on going with a .243 Win match chamber and 26-27" barrel. I normally shoot between 20-90 degrees F and 500-3000 feet elevation. I do plan on shooting past the supersonic range from time to time. I already have an 8 twist Krieger waiting for this build. Should I go with a 7.5 just to make sure of stabilization at subsonic speeds and peace of mind in colder weather?
 
Re: 7.5 or 8 Twist for 115 DTAC

Very intereted in hearing some responses as well. I recently purchased a Bartlein 1 in 8 for a similiar build and was wondering the same thing.
 
Re: 7.5 or 8 Twist for 115 DTAC

If you dont go with a 7.5", I believe you'll end up
wishing you had.
 
Re: 7.5 or 8 Twist for 115 DTAC

Some 7.5s can be touchy from what I have read others have had good luck with them. It sounds like it might be a crap shoot. A lot are going to the 7.8s for the 115s.

I shot 115s in a true 1-8 Kreiger without any problems at 1450ft elevation in the summer. Never shot them in the winter months.
 
Re: 7.5 or 8 Twist for 115 DTAC

I'm shooting a Rock 27" barrel with a 1-7.5" twist chambered in 243 Win Match by GAP, it shoots fantastic with the 115 DTAC's.
If I was you I'd go with the 1-7.5" twist.
 
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Re: 7.5 or 8 Twist for 115 DTAC

Some say the 1:8 works great for them. A few say it doesn't. Why take the chance?
The 1:7.5 is the choice for the 115s hands down. Unless you have a free 1:8 lying around, what is the use to try and force it? Use a 1:7.5 or 1:7.7 and call it a day. Shoot it, set it back, shoot it some more. DONE.
 
Re: 7.5 or 8 Twist for 115 DTAC

Shiredude, that's exactly what I was thinking.

raptor, the range I usually shoot at is 572' ASL, 20-30 deg in the winter. I believe with an 8 twist, things could get ugly.

Mike, that's kinda my thought of why chance it. I'm still on the fence about melonite, so setting it back may not be in the plans.

Now, I just need to get rid of the Krieger 8 twist I have.
 
Re: 7.5 or 8 Twist for 115 DTAC

I have a McGowen 8 twist in a standard .243 that shoots the 115s just fine. I load them with RL25 at about 3,080 fps and have shot them out to 600 yards so far with great results. From what I've seen of other people's results, though I'd go with the 7.5 twist if starting over.
 
Re: 7.5 or 8 Twist for 115 DTAC

A 7.5 twist will for sure handle the 115's. An 8 twist maybe. Why leave it to chance. If you want to shoot 115's I feel the 7.5 is for you. The 7.5 will shoot the lighter bullets just fine. I have (4) 7.5 twist that shoot the lighter 70 gr. Ballistic tips just fine.
Semper Fi
 
Re: 7.5 or 8 Twist for 115 DTAC

The information I received is that a true 1x8 will work fine but if it errors towards 1x8+ you might have an issue. I went 1x7.5 and dont look back for a second, still handles the lightweight varmint bullets just fine so no reason to use a slower twist.
 
Re: 7.5 or 8 Twist for 115 DTAC

Given the AO I usualy shoot at (800'ASL, high humidity NE), I stayed safe & went 1:7.5" twist for my GAP built .243WinMatch DTAC launcher. Same powder as mscott, RL-25 & netting me 3100 (no pressure) from 26" Rock tube. It's like my 7WSM's little badazz brother!
 
Re: 7.5 or 8 Twist for 115 DTAC

With a 243 a 1-8 Krieger will run the 115 regardless of conditions, and a hair faster than a 7.5. The only problems people run into are with button barrels that are not truly 1-8, or with slower rounds. Keep the Krieger and rock on. I've run through two 1-8's and one 1.75. I will be sticking with 8's from now on, unless I happen to get a deal on a 7.7 rock, and it will only be because of the deal not the twist.
 
Re: 7.5 or 8 Twist for 115 DTAC

Thanks for the replies everyone.
I've decided to go with a 7.5 twist Bartlein 5R, and I've already secured one. I just wanted to know for sure that it 'will' work versus 'usually'. I'd be pretty pissed to go through everything only to settle to shoot another bullet. Like I said earlier, I want enough stabilization to shoot past supersonic speeds, and I was doubting the 8 twist for that.
 
Re: 7.5 or 8 Twist for 115 DTAC

My wife (LH_Gina) has a 7.5 twist Krieger and shoots 115's like a laser at 1000 and then some. My 8 twist Krieger has shot decent groups at 300 with 115's but havent gona any farther with them. I primarily shoot 105's. I'd say the 7.5 is a safer bet. My new barrel is a 7.5 that hasn't been put on yet.
 
Re: 7.5 or 8 Twist for 115 DTAC

The guy I got my Shilen 8 twist from sold me a opened box of 500 115s with it. He only loaded 20, but he said he just couldn't get them to shoot and wanted to try something else. I am tempted to load some, but I'm just not interested in pushing things hard in this barrel since it shoots the 105 Amax so well. I would go with the 7.5 or 7 if you are focusing specifically on that round.
 
Re: 7.5 or 8 Twist for 115 DTAC

The faster the twist the more likely it is to stay stable through the transition because the bullet is turning more rpm's so I think you are defiantly better off with the 7.5.

Dustin
 
Re: 7.5 or 8 Twist for 115 DTAC

I'd run a cut rifled 1-7.5 for the 115's and a 1-8 for 105-108's
 
Re: 7.5 or 8 Twist for 115 DTAC

I had an 8 twist but decided to get a 7.5 for my 243 and shoot the DTAC.
I think it is a better choice.
Berger has a 115 VLD and they recommend 1 in 7 or faster.
 
Re: 7.5 or 8 Twist for 115 DTAC

Great...I have a Schneider 8tw with his 5pc(I think thats what he calls it) rifling about to go in for a 115dtac build but you guys have me worried now. I shoot at 2200 feet almost exclusively. Am I going to regret this?
 
Re: 7.5 or 8 Twist for 115 DTAC

I run Bartlein barrels in 8 twist for my 115gr DTACs in 243. I run them right at 3,000fps. 2500ft 0F to 100+F. No issues what so ever.

I recently ran a reamer in one and converted it to 6mm Crusader to run fire form loads through. Pushing those just over 3,000fps, and a few at 3050fps without issue.
That rig is about to have a new 8 twist Bartlein screwed on. I don't expect any issues running it faster but guess I will see what happens.


 
Re: 7.5 or 8 Twist for 115 DTAC

7.5 for heavier than 105's, no question. A true 8 might work, but a fractional 8 is suspect.
 
Re: 7.5 or 8 Twist for 115 DTAC

My wife shoots a 7.5 with 115's and I have a 7.75. Both great to 1400 with the 115's. Why risk it if the 115 is the choice?
While I haven't tried them, if you plan on the Berger's, I have heard they need the 7.5...

Good Luck
 
Re: 7.5 or 8 Twist for 115 DTAC

Depending on the bullet (length of the bullet with the 115's) it might shoot in a 1-8 and it might not. The 1-8 twist is on the edge of working. Besides the length of the bullet there are other factors to consider.

What velocity can you push them out of your gun?

What elevation do you normally shoot at? Do live in Denver, Co or do you live down in Florida?

What environment do you shoot in? Average temperature, air density etc....

My old 1-8 twist barrel would shoot the DTAC's o.k. but when I tried the Bergers it didn't shoot them (to be fair I only tried one loading but the accuracy went sour from shooting 1/3moa groups with the 105's and 107's to shooting around 1 1/8moa).

According to my twist calcs. the Bergers need a 1-7.75 min. or right around there (going from memory right now). That's why I tell guys if shooting 115's go with at least a 1-7.5 twist barrel.

Again if your shooting in Denver you might not have any problems but if you take the gun to a range and the elevation is say 800' and your in denser air conditions, lower temperatures (lower temperatures have an effect on velocity of your ammo say a 70 degree day vs. shooting on a 35 degree day) etc.... the gun might not shoot as good.

My 7.5 twist barrel chambered in 6x47 Lapua will shoot in the flat .200's if you steer it right. Even at a 1000 yards I got compliments from several people that the gun was shooting sub 1/3moa even at that distance.

A little faster twist doesn't hurt you like some think it might. I tend to error on the faster side because of the above reasons. Even if you shoot a lighter weight bullet in the gun if the ammo is good with little run out and good quality bullets you usually don't see a huge negative impact on accuracy.

Later, Frank
Bartlein Barrels
 
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MTETM said:
Re: 7.5 or 8 Twist for 115 DTAC

My wife shoots a 7.5 with 115's and I have a 7.75. Both great to 1400 with the 115's. Why risk it if the 115 is the choice?
While I haven't tried them, if you plan on the Berger's, I have heard they need the 7.5...

Good Luck
Click to expand...
What barrel length are you running ? I have a choice between a 26-inch Barrel or 24-inch Barrel they're both bartlein 5r
 
Wow... this is an old thread.. Those bbls long gone. These days my wife shoots a 24 in BRX with 110 or 115. She still uses a 1:7.5 at 24 inch Benchmark bbl. We are at 2800 elevation. This has worked from 1000 to over 8000 for us.
 
aauya said:
What barrel length are you running ? I have a choice between a 26-inch Barrel or 24-inch Barrel they're both bartlein 5r
Click to expand...

I just put together my first 6cm. 26” bartlein 5R. My component should be here in the next few days (including some coated dtac’s to test). I’m really hoping the .183 saami fb is a good match for that bullet. I’m guessing 2950-3k FPS I should be able to reach fairly easy. Mine is a 1-7.5 twist.
 
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Mvgratz said:
I just put together my first 6cm. 26” bartlein 5R. My component should be here in the next few days (including some coated dtac’s to test). I’m really hoping the .183 saami fb is a good match for that bullet. I’m guessing 2950-3k FPS I should be able to reach fairly easy. Mine is a 1-7.5 twist.
Click to expand...
shouldnt be that hard to hit in a 6 creed considering you can in a 6XC
 
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I just took the plunge, and tried the DTAC 115's. I got a 1-8 proof barrel, and shoots under half moa. They are way better than the Berger 105 hybrid I was shooting. More consistent out of everything I've tried. Sticking with DTAC 115's.
 
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On the contrary, I actually find myself leaning to the slower side as I’ve found that they shoot better in my own personal experience.

I know that logic says to run a faster twist than what you think you’ll need, but I have more than a few loads that are supposedly “very unstable” and they shoot better than any 7 or 7.5 I’ve shot.
 
I had stability problems in cold weather with a 1:8. I did a bunch of testing and it seams like Tubb is spot on. They stabilize in a 1:8 at 0 DA. At negative DA they start to do goofy shit in the wind for me. I have one more 1:8 barrel to wear out, and then I am going to try a 1:7.5". I just use 105's in the 1:8 barrels when it's cold.
 
I have 2 6comp match rifles, one 1:7.5 and one 1:8, the dtacs work fine in the 1:8. That rifle, however, seems to prefer the 105s. I haven’t shot them further than 300, but I would imagine the gap widens with longer ranges.

There have been problems with hitting pressure prematurely and suddenly with the 1:7. That’s what I found when I selected my 1:7.5, I’ve never owned a 1:7 to be fair.
 
jakelly said:
I have 2 6comp match rifles, one 1:7.5 and one 1:8, the dtacs work fine in the 1:8. That rifle, however, seems to prefer the 105s. I haven’t shot them further than 300, but I would imagine the gap widens with longer ranges.

There have been problems with hitting pressure prematurely and suddenly with the 1:7. That’s what I found when I selected my 1:7.5, I’ve never owned a 1:7 to be fair.
Click to expand...

My decision was easy. A 1-7.5 bartlein was the only available option at the time. (Won a barreled action from Impact Precision, so I took what I could get before I ever researched available bullet options.)
 
PAYDIRT said:
Can someone explain why you wouldn't just go with a 1-7 and not worry?
Click to expand...
I have never had a 1:7 in 6mm, but I have seen many knowledgeable people post that the 1:8 is the place to be if you can stabilize the bullet you want to shoot. Faster than 1:8 and they claim you have potential issues with pressure, velocity, bullets coming apart, and accurate barrel life. I got tired of not being able to shoot the DTAC bullets at cold weather matches and decided to try a 1:7.5. The numbers work there and hopefully it is less finicky than a 1:7. If I have issues with that barrel I will be going back to a 1:8 and just continue to shoot 105 or 107 bullets in the cold.
 
Hi MakeSawdust! What temps were u running into problems with. Or, having trouble with the DTACS. Thanks
 
I just went with a criterion remage 1-7 grabbed a load right out of hornady manual for the 105's to play with before I tried to "find" a load, doubt I'll do load development after shooting this load.
 
What's the optimal fps that these should be ran at. I got mine right now at 2858. Getting dime groups at 100 yds. Haven't took them to a grand yet. Just wondering, if I'm running mine to slow, or should be faster. Thanks
 
Why not ask David Tubb? No one knows as much about the DTAC as he does? At one time I knew but cannot recall now.
 
Before ordering a new barrel I thought what twist for my new AI-AT 6cm. I decided to go 1-7 26 in Bartlein spun up by Dave Tooley. I have yet to put it on still shooting the 1-8 twist from 2 years ago. Here is i found the 1-8 shot the 105 Hybrid, 108-ELD-X Really good. The 1-8 didn't shoot the 110 SMK or 115DTAC as good as the lighter bullets. So I went 1-7 and am looking forward to seeing how it shoots.
 
Get a good Smith to chamber your barrel, and you’ll be fine with a 7/ 7.5

This is a brand new Bartlein 5R barrel. 1:7” Lwft Hand Twist. Loaded 100 rounds to break her in (no cleaning between shots #gayness) today and check for pressure (none). 50 rounds of Hornady 108gr ELD and 50 of 115gr DTAC RBT. 10-shot groups. H4350. Chambered by Sawtooth Rifles. He chambered my
4-groove Krieger 1:7.5” Right Hand Twist and at 1600 rounds still hammers with both 108gr and 115gr

Simple, Pick a good Smith ?

1865347C-275A-49A8-89A7-6B44E99A860A.jpeg
 
1/7 26" Criterion in a bone stock Rem 700. 105's with H 4350 Just grabbed a load from the Hornady book.
IMG_6977.JPG
IMG_6996.JPG
 
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