DTAC 115 and 6XC, 6SLR, 6CM, 6 dasher, 6 crusader, ?

[zipollini]

Could somebody list some of the pros and cons of driving a DTAC 115 with the following case sizes when considering shooting at ranges of between 100 and 1300m ?

6 XC
6 SLR
6 Crusader
6 CM
6 Dasher
6.5 X 47 Lapua necked down to 6mm
???

Since people are driving the DTAC 115s @ 3200fps using RL-17 in a 6XC case and they will already fit every mag. and the brass is available, is there any real reason to look at the other case sizes now ?

Thanks in advance

 

[watercam]

Funny thing about 'everyone' - I haven't met them yet! My experiences with the 6XC were not so grand. Don't get me wrong, it worked very well for me both XTC and Long Range but the best velocity I obtained w/ 38.5 gr. of Re17 was around 2950. I believe a 5R barrel would have helped a bit plus a 30" barrel instead of the 27" I went with. I now shoot a .243 w/ 107s @ 3150 fps and will live with the shorter barrel life. Interestingly I am getting that velocity with only 42 gr. of Re17. I could get more but don't really need it.
The 6x47 is essentially the same case with the others having slightly less capacity but all good, solid performers. I would go the easiest route (I hate wasting barrel life developing loads and fire forming cases). Folks w/ stock 6BRs do very well in both disciplines as well. All it needs to be is accurate and still churning around 1400 fps @ 1000 yds.. The rest is wind reading skills.
Wait 'till you try Palma!

 

[zipollini]

I'm looking at this article by German Salazar

http://www.accurateshooter.com/cartridge-guides/6xc-for-competitive-shooting/

Per the above article

"Reloder 17 Shoots 600-39X in First Match at 500 Yards


On July 20, 2008 shooting his 6XC at the Phoenix Rod & Gun Club, the author confirmed that RL17 can deliver real-world, match-winning accuracy. Shooting a 500-yard prone High Power match on the NRA MR65 target, using iron sights, German Salazar posted a very impressive 600-39X score. The three relays were shot with three different loads of RL17 in progressively “hotter” increments: 40.6 grains (3215 fps), 41.2 grains (3290 fps), and 41.8 grains (3311 fps). He shot 200-14X with the low load, 200-15X with the middle load, and 200-10X with the hottest load. German felt the middle load was the most consistent. (NOTE: these loads are all with moly-coated bullets–you should reduce the load by at least one full grain for “naked” bullets”.)

German explains: “Ask any high power shooter and he’ll tell you 600-39X is quite an achievement with iron sights on the new (smaller) MR65 target at 500 yards. I can say with assurance now that this powder will shoot accurately in the 6XC. Last week, using H4831sc, shooting the same 6XC rifle, at the same range, with the same course of fire, I shot a 598-29x. I do think Reloder 17 helped me shoot a higher score this week, with 10 more Xs. The extra velocity afforded by RL17 reduces wind drift considerably, and the elevation held very consistent, particularly with the first two loads.” Even at the hottest load, 41.8 grains (3311 fps) of RL17, German did not observe sticky bolt lift or other notable signs of pressure. So far, then, what we’ve learned about Reloder 17 is “all good” — in the appropriate cartridge, it will boost velocities dramatically, and it can deliver competitive accuracy in High Power competition."

 

[johara1]

I use the 115 DTAC's in a Dasher and yes RL-17 will go 3050 and it shoots around .200 at 100 yds. and under 5" at 1K ,but you need a drop tube. With RL-15 it will shoot in the mid ones @2925 at 100 yd's and shoot in the 3's @1K. No first place for speed,you make the choice......jim

 

[rcw3]

Just my opinion for what that's worth. The 115's are big horsey bullets and a case the size of a .243 Win. or so is ideal to push them (i.e. 6mm Super LR, 6CM, 243 Win, 6mm Crusader). The others will push them, but it's a little like towing a horse trailer with a passenger car.
Robert

 

[watercam]

zipollini,
I too read German's article and he is a fantastic source of information on any number of things related to long Range shooting. I am only saying that my experience, and that of the match shooters I shoot with, could not match his results. It is a great cartridge but if you notice John Whidden's success with National Championships, he has been shooting 105 gr. VLDs w/ a .243 and a hot load to reach 3200 fps+. Sheri Gallagher won in 2009 with a 6.5/284 for Long Range. David Tubb won this year but I do not know what cartridge he was using, it may have been the 6XC.
What I am saying is that it is a lot more about the shooter and an accurate cartridge that stays well into supersonic speeds at 1K yds. than any one particular Super Cartridge that spells success on the range.
I hope you get a rifle built soon and join all of us on the line. I am not able to shoot nearly as often as I would like to due work issues but I love it, hope you do to!
Mike T.

 

[NateG]

I can't say I'm a huge fan of the 115. According to Litz's numbers (which I trust a lot more than most manufacturers BCs, for a variety of reasons), the 115 has a BC that's only slightly higher than the 105 Hunting VLD--or the target, before the meplat was changed--slight enough that you can probably drive the 105 enough faster to offset the BC advantage.

However, at the speeds you're talking about, you'll probably make a puff of the hunting jackets. (Never had a problem at 3050 with a BRX, but 3300+ is another world) However, the new 105 Hybrid is probably the best bet for big 6mms. (little ones, too) It's got a (very) slightly higher BC than the 115 and a thick jacket.

I've seen some ludicrous BCs quoted for the 115s, and I think they're full of it. (Or, they're a product of the mis-fit between the G1 drag curve and long range bullets) Either way, I'm not impressed by the ballistics* of the 115s. Now, a "modern" 115 with an i7 form factor of about .950 (about average for the new hybrids) would be awesome. My back-of-envelope numbers say a G7 BC of about .294 or G1 of about .574. That would be worth shooting.

*which is a far cry from saying they won't shoot well, or aren't good in the wind at that speed. Just that the shape of the 115 isn't very sleek, and that it leaves plenty of room for a better design.

 

[zipollini]

Nate - I don't have Litz's book yet (it's on my list). What does he list for the earlier DTAC 115's and the new pointed Hbn version as far as G1 and G7s ?

The numbers that I keep bumping into are a G1 of .585 listed here

"BALLISTICS: The 115-grain DTAC has approximately 10 points lower BC than a 142gr 6.5mm Sierra. Everybody's BC calculations vary so I believe this is the best way to evaluate it against the 142gr 6.5 Sierra. (Also if you look at the Berger 115gr 6mm keep in mind that Bergers BC's are not conservative at all.) This means that if you shoot the DTAC 115 at 3000 fps verses the Sierra 142 at 2950 fps then the drift at 1000 yards is virtually the same.

[Editor's Note: Henry Childs has confirmed the BC figure David is proposing. We suggest you use a .585 BC for the 115gr DTAC.]"

in the article here - http://www.6mmbr.com/6XC.html

I've also bumped into a mention that the newer pointed version is around .590.

Dave Tubb just posted this the other day on this site

"If you are shooting the 115 DTAC's close to 3100 fps then your initial starting G1 BC # will be approaching .600.
Many fail to recognize data from a 1000 or 1200 yard tests using the oehler 43 system will give better information than if shot at closer distances.

Current production DTAC 115's will have a better BC # than current production berger 115 vld's"

 

[zipollini]

This is great info guys. Keep it coming. I'm absorbing as much as possible here as well as spending waaaaay too much time reading and doing research. I hope it pays off .

Thanks again

 

[spclark]

Since people are driving the DTAC 115s @ 3200fps using RL-17 in a 6XC case and they will already fit every mag. and the brass is available, is there any real reason to look at the other case sizes now?

Don't know what people you're referring to in that statement but I for one would be very wary shooting next to someone reporting 3,200 fps out of a 6XC using DTAC 115's out of a magazine.

Early on in my experience with a new 6XC-chambered long range rifle in late 2008 I was getting 3,100+ fps using the DTACS of that era. This was with the latest (at that time) 6XC chamber reamer supplied by Hugh Henricksen, 30" Bartlein 5R 1:7.8 barrel chambered & 'smithed to the action by Carl Bernosky.

With RL-17 & the new Norma brass, 'Russian' primers and Tubb's supplied hBN-coated 115's, that brass was worthless for another reload.

I had great results before with the same 115's in a 26" 1:7.5 PacNor, not good at all with the Berger 115VLD.

 

[spclark]

It is a great cartridge but if you notice John Whidden's success with National Championships, he has been shooting 105 gr. VLDs w/ a .243 and a hot load to reach 3200 fps+.

Correct.

Once I'd realized the 115's weren't going to work in my rifle (see previous post) I moved back to the Berger 105VLD & immediately saw the performance I new this rifle was capable of delivering.

David Tubb won this year but I do not know what cartridge he was using, it may have been the 6XC.

Reliable info I've received (I wasn't there) is that David won using one of his T2k's chambered for .338 Norma Magnum.

I've seen 6BR's shot great at 1,000 yards, but not when the wind blows. I'm getting 3,100+ fps with Berger 105VLD's (looking forward to trying some of the new Hybrids next week) with simply astonishing accuracy.

I could shoot cleans with this rifle in every match... were it not for my limitations.

I trust the limitation to shooting 115's well is barrel twist, not case capacity. You need 'enough' horsepower with the right 'chassis' for the task; any more is gonna cost you in the long run.

 

[DTubb]

USED a 6XC WITH 115'S FOR THIS YEARS(2011) LONG RANGE EVENTS EXCEPTION BEING A 308 FOR PALMA.

 

[spclark]

David, congratulations on your LR Championship win & thanks for setting me straight on that.

(so much for my otherwise reliable source :-\ )

Were you using your 115's for High Power Week also?

(You coming up to Winnequah again next week? Be a might cooler than you're probably used to....)

 

[Bob3700]

I have to say that I tried to get the 115 DTACs above 3000 fps with the 6mm MMX in a 30 inch Bartline (7.5T) tube. At 3000fps, the brass lasted three reloads and primers fell out of the cases.

For me, that is why I went to the 243 SLR. It has the extra capacity to launch those DTACs between 3050 and 3100 fps without high pressures and very good accuracy.

The older 105 Bergers were accurate, but you had to work on seating depths a bunch to find it. Perhaps the new hybrids will be another great option.

We will have to see.

Bob

 

[NateG]

Nate - I don't have Litz's book yet (it's on my list). What does he list for the earlier DTAC 115's and the new pointed Hbn version as far as G1 and G7s ?

The numbers that I keep bumping into are a G1 of .585

I don't have the book in front of me, but Berger lists the 115 as .545 (G1) and .279 (G7). The DTAC is similar (looking at the shapes tells you they can't be very different in BC, with the same diameter and weight), however. --I just found a Litz BC for the DTAC: .276 (G7)

The problem comes when you compare an averaged-over-the-flight G1 BC to a top-band (high speed) G1 BC.

Geekery follows...

The G1 drag curve (and therefore BC) is calculated for a blunt, short, flat based projectile. The G7 reference projectile, however, is much more similar to the LR bullets we shoot. The G7 standard takes into account that the drag coefficient of LR bullets drops at high speed--The G1 drops off too, but not as quickly. Therefore, matching a bullet to a G1 BC at high speed (2600+fps) will greatly overestimate the BC at the lower speed portion of its flight. (sub 2000fps) This results in things like the 115s being quoted as having excessively high (.58+) G1 BCs.

The 115s can shoot extremely well (I've gotten trounced by them more than once, and will again), but they have a relatively high drag shape. (For sleek, LR bullets, that is.) The G7 form factors are about 1.0, when the newer designs are more like .950 or so. What that means is that the usual "heavier bullets drift less" rule of thumb can fail since the lighter bullet has a lower drag shape. Combine that with the higher speed the lighter bullet can be launched at, and the big bullet loses it's ballistic edge.

 

[rcw3]

USED a 6XC WITH 115'S FOR THIS YEARS(2011) LONG RANGE EVENTS EXCEPTION BEING A 308 FOR PALMA.

Congratulations on you long range win - exceptionally well done!

No question you can wring a lot out of a 6XC.

Rumor has it (and we all know how rumors can be) you were using a blend of powders (H1000 and H4350) with the 6XC. Any truth to that?

Robert

 

[Bob3700]

John Whidden shoots a straight 243 with the 105 gr Bergers. Now his velocity is quite high (don't know what his brass life is like) but his results are outstanding. Surely, part of the results are due to is superior ability to read the wind but that 105 at warp speed can't hurt.

I am going to give the 105-107 gr bullets a go in the SLR because as good as the 115 DTACs have been to me, there just might be something better I have not tried yet. This is the better mouse trap syndrome I am sure.

Bob

 

[spclark]

I am going to give the 105-107 gr bullets a go in the SLR because as good as the 115 DTACs have been to me, there just might be something better I have not tried yet.

Bob, I don't think you'll be disappointed once you start with Berger's 105VLD, how they perform for me in my 6XC is the standard by which I measure other bullets.