115 DTAC questions
- Thread starter JerryK
- Start date
I've pushed the 115 DTAC to 3100+ fps using 6XC & Reloder 17 but decided it wasn't worth it. At 2950 the 115 shoots just fine thanks out to 1k & I can reload the brass again many times.
If you truly want 3100 you'll likely need more case volume; look into 243AI, 6Rem (as suggested) or maybe a 6mm-06, 6mm-284, 6mm x 55.... You can look forward to significantly decreased barrel life for the extra 100+ fps though.
There are cartridge diagrams on several potential candidates posted here:
http://www.6mmbr.com/cartridgediagrams.html
If you truly want 3100 you'll likely need more case volume; look into 243AI, 6Rem (as suggested) or maybe a 6mm-06, 6mm-284, 6mm x 55.... You can look forward to significantly decreased barrel life for the extra 100+ fps though.
There are cartridge diagrams on several potential candidates posted here:
http://www.6mmbr.com/cartridgediagrams.html
6CM ---- DAT115 & Sierra 107s
Reamer used was the 6CM LR a version of a 243 Winchester improved.
Action: Panda Big Bore
Bench rest mode with a Night Force NSX 12 – 42X scope. The rifle weight is 15.5 #.
Winchester 243 Brass was prepped and sorted into lots by weights. Neck diameter new is 0.269”, The neck were turned to a sized diameter of 0.267.5”, loaded is 0.269” and fired is 0.273”. Sierra 115-grain bullets touch the lands with an OAL of 2.915”. Berger 115-grain bullets touch the lands with an OAL of 2.972”.
May 14, 2010 Sacramento 100 yard chronograph – 59 degrees – 71% humidity
Bullet --- Powder----- Charge --- MV ---- ES --- SD --- Primer --- Group size --- Comments
S115 ---- H4831 ------ 4X.5 --- 3151 --- 20 --- 07 ---- CCI-BR --- 0.434” ------- jump 15
S107 ---- H4831 ------ 4X.5 --- 3195 --- 27 --- 09 ---- CCI-BR --- 0.289” ------- jump 20
Reamer used was the 6CM LR a version of a 243 Winchester improved.
Action: Panda Big Bore
Bench rest mode with a Night Force NSX 12 – 42X scope. The rifle weight is 15.5 #.
Winchester 243 Brass was prepped and sorted into lots by weights. Neck diameter new is 0.269”, The neck were turned to a sized diameter of 0.267.5”, loaded is 0.269” and fired is 0.273”. Sierra 115-grain bullets touch the lands with an OAL of 2.915”. Berger 115-grain bullets touch the lands with an OAL of 2.972”.
May 14, 2010 Sacramento 100 yard chronograph – 59 degrees – 71% humidity
Bullet --- Powder----- Charge --- MV ---- ES --- SD --- Primer --- Group size --- Comments
S115 ---- H4831 ------ 4X.5 --- 3151 --- 20 --- 07 ---- CCI-BR --- 0.434” ------- jump 15
S107 ---- H4831 ------ 4X.5 --- 3195 --- 27 --- 09 ---- CCI-BR --- 0.289” ------- jump 20
Don,
I did find some info on the 6 mm CM. The other cartridge that I looked at was the 6mm Super LR. Actually, they both look ballistically the same, a 243 with a 30 degree shoulder. My preference would be toward the Super LR as it has a much longer neck.
I would think that the Super LR would be more versitle for different bullet wts (105s to 115s) with that longer neck. Also the longer neck would reduce the torching effect some over the short neck version.
Either will probably deliver the accuracy and velocity. The LRs longer neck appeals to me.
Bob
I did find some info on the 6 mm CM. The other cartridge that I looked at was the 6mm Super LR. Actually, they both look ballistically the same, a 243 with a 30 degree shoulder. My preference would be toward the Super LR as it has a much longer neck.
I would think that the Super LR would be more versitle for different bullet wts (105s to 115s) with that longer neck. Also the longer neck would reduce the torching effect some over the short neck version.
Either will probably deliver the accuracy and velocity. The LRs longer neck appeals to me.
Bob
All three of my 6x47 Lapuas will push DTAC or Berger 115s to 2970fps w/o loosening primer pockets with N160. All three have 30" bbls. Maybe it's the small primer casehead, but whatever the reason, it works, and works quite well.
<3000 fps doesn't seem to grow LR pockets in the various brands of 6XC brass I've been shooting, in my rifles. It's when I venture beyond 3050 I have issues.... The DTAC 115's seem to work well enough just under 3k I don't feel compelled to go any farther.
SR vs. LR in any case that has the option? I'd prefer to use the former when available; my first 100 of the new Lapua Palma brass should be arriving tomorrow or Tuesday, just in time to load a few rounds to try next week at Midwest Palma.
Were the option for SR available in something I could use for 6HAGAR (.25 / .30 Rem parent case) I'd be a happy camper....
SR vs. LR in any case that has the option? I'd prefer to use the former when available; my first 100 of the new Lapua Palma brass should be arriving tomorrow or Tuesday, just in time to load a few rounds to try next week at Midwest Palma.
Were the option for SR available in something I could use for 6HAGAR (.25 / .30 Rem parent case) I'd be a happy camper....
SP Clark,
Consider yourself lucky to get over 3000 fps with an XC and have primer pockets last more than 4-5 reloads.
You are also running the pressures up there to get that velocity. That is OK, it is just not for me. Been there, done that.
I have several shooting buddies with T2K rifles and they are hard pressed to get beyond 3000 fps with a 107 SMK! Primers are flat and cratering at anything over 2950 fps with their Schneider bbls. 115s are out of the question for them.
The 243 Super LR has already delivered 2980 fps with the 115 DTAC with a load that is several gr. of powder below max. Accuracy is great so far at 100 - 300 yds. I do need to take it to 600 yds and see how it groups.
Am not looking to be a velocity demon here, just shoot the 115 DTAC in it's sweet spot (2950-3000 fps) and do it with less than full throttle loads.
I have a couple of 1K matches scheduled this summer, we will see just how well it does.
RGDS
Bob
Consider yourself lucky to get over 3000 fps with an XC and have primer pockets last more than 4-5 reloads.
You are also running the pressures up there to get that velocity. That is OK, it is just not for me. Been there, done that.
I have several shooting buddies with T2K rifles and they are hard pressed to get beyond 3000 fps with a 107 SMK! Primers are flat and cratering at anything over 2950 fps with their Schneider bbls. 115s are out of the question for them.
The 243 Super LR has already delivered 2980 fps with the 115 DTAC with a load that is several gr. of powder below max. Accuracy is great so far at 100 - 300 yds. I do need to take it to 600 yds and see how it groups.
Am not looking to be a velocity demon here, just shoot the 115 DTAC in it's sweet spot (2950-3000 fps) and do it with less than full throttle loads.
I have a couple of 1K matches scheduled this summer, we will see just how well it does.
RGDS
Bob
I am getting 3180 from a straight 6mm Remington 30", 48.3 7828 SSC and 115 DTAC at 3.150 OAL. Accuracy is excellent and pressure moderate for this case. My Winchester cases hold 56.9 H2O. All signs are that case life will be good. Barrel life? We'll see. Top loads push pretty close to 3300 but case and barrel life at that pressure would be poor.
JERRYHM said:
Jerry,
There is a current theory (as there usually is) regarding neck length and the way propellant gases erode the throat. The essence is, if I have it right, that a longer neck takes the brunt of hot gas exiting the case body and spares the throat. There might be something to it. 6mm Remingtons seem to have a little better barrel life than .243 Winchesters despite burning more powder and operating at higher pressure.
If you don't like that theory, wait a while, there will be another.
Steve.
you are correct on the long vs short neck theory. The longer necks coupled with a 30 or 40 degree shoulder angle are supposed to angle the hot plasma gases away from the throat of the bbl. I believe the originator of the theory called it the TP or turbulence point. The fellow was actually a rocket scientist and the theory was based on rocket nozzel design.
So when you look at cases like the 243 with 20 degree shoulder, they are deamed bbl burners. Many cases copy the 6mm BR due to it's long neck and 30 degree shoulder angle (6XC also) not only for accuracy but longer bbl life.
In the end, cartridges that burn a lot of powder for their bore size are going to be hard on throats. You do what you can to minimize wear and prolong bbl life.
Someone is always coming up with the next better mouse trap to try to increase bbl life. Friction proofing bullets, salt bath nitriding bbls, long case necks, 30-40 degree shoulders, you take your pick.
Bob
you are correct on the long vs short neck theory. The longer necks coupled with a 30 or 40 degree shoulder angle are supposed to angle the hot plasma gases away from the throat of the bbl. I believe the originator of the theory called it the TP or turbulence point. The fellow was actually a rocket scientist and the theory was based on rocket nozzel design.
So when you look at cases like the 243 with 20 degree shoulder, they are deamed bbl burners. Many cases copy the 6mm BR due to it's long neck and 30 degree shoulder angle (6XC also) not only for accuracy but longer bbl life.
In the end, cartridges that burn a lot of powder for their bore size are going to be hard on throats. You do what you can to minimize wear and prolong bbl life.
Someone is always coming up with the next better mouse trap to try to increase bbl life. Friction proofing bullets, salt bath nitriding bbls, long case necks, 30-40 degree shoulders, you take your pick.
Bob
Bob3700 said:
That's been my experience too with mine. That's one of the reasons I sold my original Schneider 6xc barrel in favor of replacement Pac Nor 1:7.5 twist. I never tried the DTAC in these with any loads over 3k fps either, as they work fine for my needs around 2850-2900 & reasonable loads. I actually prefer the Berger 105VLD @ 2975 after a couple of seasons.
The >3k was in a 30" Bartlein 1:7.8 twist I had chambered for 6XC & mated to a Quadlite. First test loads (RL-17 & Norma 6XC cases) is what gave me the way high speeds. I've backed off significantly from there for match loads. I can get +150 fps in the longer barrel with lower charge weight.
SPClark,
I too have a Quadlite action and that is what I have a Bartline bbl chambered up for the 243 Super LR.
Initial testing of the Bartline bbl 7.5T and 30" long has given me 2980 fps with the 115 DTAC and very rounded primers.
The exact same bbl chambered for the 6MMX (first version of the XC with 20 degree shoulder) could get to that velocity but primers were pretty flat. The pressures were up there and brass (Primer pockets) didn't last real long. I too tried the Norma 6XC brass but it is heavier and produced higher pressures along with the velocities. I had to give the brass up cause it was actually enough larger at the case head that I had hard bolt openings. My reamer was ground for Rem 22=250 brass which is about 1 to 1.5 thou smaller at the head.
The MMX with 115's was very accurate at 600 and 1K so I kept shooting it.
Well, the worm has turned and I am giving the Super LR a try. Just looking for a load that gets the 115 DTAC up around 3000 fps and is easier on brass while keeping the accuracy.
Will try the 105 Berger and 107 SMK as well just to see where the x count is highest.
Let the games begin.
Bob
I too have a Quadlite action and that is what I have a Bartline bbl chambered up for the 243 Super LR.
Initial testing of the Bartline bbl 7.5T and 30" long has given me 2980 fps with the 115 DTAC and very rounded primers.
The exact same bbl chambered for the 6MMX (first version of the XC with 20 degree shoulder) could get to that velocity but primers were pretty flat. The pressures were up there and brass (Primer pockets) didn't last real long. I too tried the Norma 6XC brass but it is heavier and produced higher pressures along with the velocities. I had to give the brass up cause it was actually enough larger at the case head that I had hard bolt openings. My reamer was ground for Rem 22=250 brass which is about 1 to 1.5 thou smaller at the head.
The MMX with 115's was very accurate at 600 and 1K so I kept shooting it.
Well, the worm has turned and I am giving the Super LR a try. Just looking for a load that gets the 115 DTAC up around 3000 fps and is easier on brass while keeping the accuracy.
Will try the 105 Berger and 107 SMK as well just to see where the x count is highest.
Let the games begin.
Bob
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