Comparison of the ballistic superiority of 6.5 CM

[doctnj]

I will start by saying I own 2 6.5 CM's. When I bought the first one, I really didnt understand what I was buying. I knew it was the new hot load and every one seemed to agree. And even better I was able to buy a limited produced rifle, giving it that "oooooh" factor. After that it was start out where most do. In the middle of the load tables and start searching for a round my rifle liked to shoot.

Didnt take long, mabey two trips to the range and I settled on a load that seemed to pile into a nice ragged hole. So check on that!

In the meantime I purchased a custom 260 with remy action. I.. make this short. The barrels are exactly the same as in same maker, same taper, same twist rate, and length. The 260 uses about 42.6 grains of powder and the 6.5 only uses 42.1 grains of the same powder. LESS IN CM BY .5 GRS.

So basically the same barrel, action, the exact same projectile. The only difference is caliber and therefore case shape and internal powder capacity.

She shoots the CM
I shoot the 260. I picked it I must say that 1. it is a nice shooting rifle and I already had 2 CMs

So here is my observation in real world loading and shooting between the two calibers.

CM takes less powder, produces more velocity out of the gate, is a flatter shooter there fore leaving quite a bit more elevation adjustment left in your turret. Just shooting at just a bit over 500 I am using 6 to 7 tenths of a mil more to hit the same target.

Not sure I can beat her when we get way out there. Gonna have to give her some bad loads or something. lol

[bodywerks]

That's one observation, I guess.
What were the actual velocities leaving the barrel? Or are you just assuming it based on your dope from each rifle? Unless you are 1000% certain that both of your rifles hold the same zero and that both scopes track straight n true, then you can't judge velocity based on your findings alone.
Now, if you strapped a magneto speed chrono to each and provided raw data, that would be different.
However, there are other factors that affect mv. You say both barrels are the same, same mfr, etc. But some bores run tighter than others, and a tighter bore, by even just a few ten thousandths, will also result in more velocity.
The 6.5cm is a nice chambering, especially for those that don't reload, but it's not a replacement for the 260 by any means, and my 26" krieger-barreled savage 260 runs faster than any 6.5 creed I know, showing hornady 140s running at 2925-2950 through my magneto speed, and my dope is either showing higher velocity or I need to check tracking again, as my POI is high compared to my dope, all the way out to 1200 yards.
That velocity was achieved using 43.2gr h4350, btw, and it takes 2.2mils from a 100yd zero to get to 500 at 2500asl.

[doctnj]

@bodywerks. I dont have time right now to go into all the stats. You do bring up some very good points. I did strap a magneto speed to the end of both rifles during OCW work up. The 260 with 42.6 gr of h4350 produced 2716 fps average while the 6.5 CM produced 3046 fps with only 42.1 grs of h4350 again average velocity. I have a second 6.5 CM that I just got back together and will re work it up. It will be interesting to see where it falls in line with the 260 as the old OCW that I used before it was torn apart does not seem to be the sweet spot any longer.

Looking back at my notes on my OCW work up on my Savage 6.5CM, the rifle that was just put back together, I had it loaded with 42.8 grains of h4350 but was only getting 2867 fps average MV out of it. But two things there, 1. I dont remember if that number was from the magneto speed or an old pos chrony I was using. and 2. that is factory barrel. Either way, its going to have to be re worked because what was a half moa before being torn down worked over and put back together is now 1 1/2 moa. NO GOOD!!!
My savage 338LM that went through the same process remained pretty close to old OCW. Dont know what happened to the 6.5. O well

[schnyd112]

3046? With what bullet? That is starting to get close to 6.5x284 velocities if you are shooting 140's. If you are getting that much more from a creedmore I am thoroughly surprised.

With my .260 i can get 2880-2925 fps from 142 smk's and 45.6 g h4831 depending on the weather. It really likes 45.3g with velocities in the 2850 range.

[doctnj]

I understand what you are saying about the MV being fast. I went back and looked at work up cards and at strelok ballistics program and yes that is the MV for that rifle. I had the MV that was directly measured with the magneto speed. Then over a period of time I took some actual results and entered them into the ballistics program to "true up" the MV by what the drop actually was at distance and so it does recalculate the MV to make the actual drop and calculated drop closer to each other. I will also say this. That many times her actual drop is still a mill or two less than the calculated drop even still.

[LongRange]

your not getting 3064fps with 42.1g h4350 and any bullet outta the 6.5CM...thats not enough H4350 to drive a 6.5mm bullet that fast...your chrony is off or the numbers were written down wrong and if the numbers match up in your ballistics app something is entered wrong there as well.

[yobuck]

your not getting 3064fps with 42.1g h4350 and any bullet outta the 6.5CM...thats not enough H4350 to drive a 6.5mm bullet that fast...your chrony is off or the numbers were written down wrong and if the numbers match up in your ballistics app something is entered wrong there as well.

Thank you, saved me a lot of 1 finger typing.

[stomp442]

I'm not buying that velocity either. Just not going to happen with that small case and that charge weight. Not even with a 30" barrel and R-17.

[Rob01]

Yeah that velocity is too high. Something is happening there with the chrono. And if you are using the dialed on data to reverse engineer a speed then you might want to check your scope tracking as it's most likely off.

[doctnj]

Yes I didn't explain it well obviously. The original number was 2816 or there about. Then after shooting the CM at distance and putting in actual vs computed the number I got was the 3000 what ever. Even my 260 had to be calibrated to get the dope to match up. But I still have to spin up more elevation on my 260 than the CM does.

[Rob01]

Yeah that's a scope tracking issue or some of your other data is off in the ballistic program like elevation. I put my magnetospeed velocity in JBM and when I dial it on the scope it's right there.

[doctnj]

Here is the wierd thing. The calculator on vortex website gave me the same numbers. I am leaning toward a tracking issue with her scope. I mean now with the reverse engineered velocity, the numbers are pretty darn clise. Is that something that should be fixed like by vortex, or just leave as is as long as the dope is good?

[Rob01]

If you are 100% sure you are putting in all the correct numbers to the ballistic program from environmentals and elevation to scope height and bullet data and not getting the right data then I would run a tracking test out to at least 10 mils(marks every mil) or 40 MOA(marks every 5 MOA) at 100 yards and see if you start to see any variances as the elevation is dialed on. A 200fps difference in chrono data and dialed on data reversed engineered is showing an issue somewhere.

[doctnj]

I want to go in depth on that idea rob. I'm in the middle of one other crisis and as soon as it is solved I want to sit down with you and learn how to do that. Would you be willing to help me?

[doctnj]

sorry Rob was in middle of issue last night. Friend was having a life problem. whew glad that is over anyhow.

Are you referring to the tall target test? I can prob. look it up but I will go ahead and ask. How many inches is one mill at 100 yrds?

[Rob01]

Yup a tall target test at 100. For mils the marks will be 3.6" apart and for the 5 MOA they will be 5.24" apart. Make sure it is 100 yards exactly.

[doctnj]

Yes the scopes I use are mills. Lets just say for the moment that its off a little. Should this be a warranty issue that vortex would fix or do we just continue to compensate with ballistic software?

[Rob01]

Yeah if you find an issue you should contact Vortex and have them take a look at it. They can hook it to their machines and see if there is an issue. Which scope is it?

I will say though if you are a tenth of a mill high or low at marks and don't see a consistent trend then that may just be the shooter/load. When you get higher up you will see if there is an issue. I had a few USO scopes that when I dialed 10 mils I was getting about 11.5 mils of actual travel. That's a problem.

[doctnj]

Well lets say that if we left the actual measured MV in the computer, she would have to dial down 3 or 4 mills at 500 yds. Less at closer range of course

[Rob01]

What scope is it? Yeah there sounds to be an issue but I was talking about doing the test itself and seeing rounds being a little off high or low by a tenth. Below is a tracking test I did on one of my scopes. You can see there are slight variances from actually shooting it and variances in shooter/ammo but it tracks good to the 10 mils. Also make sure you are level or you will see shots going off left and right. My shot at 8 mils was a little canted and you can see the shot out to the right but I shot 9 and 10 and then dialed back to 8 and shot again.

http://i.imgur.com/snjcxgH.jpg
http://i.imgur.com/DOYU6ZH.jpg