Truing Ballistics for Reloads

[jwrowland77]

I was just wondering if anybody has heard of the following.

I use a MagnetoSpeed chronograph. For the load I use for 600yd matches, I get a velocity of around 2700fps for a 175gr SMK. However, when I put in the drop that I actually see at the 600yd mark (and it hasn't mattered what temp I've shot in, I've seen the same amount of drop at the same place over a wide range of temp), and try and true my ballistics table, it's truing the MV up to about 2850.

Is this normal? Just wondering and trying to learn and understand.

 

[Fredo0621]

What program are you using? Shooter? Applied Ballistics?
I doubt your getting 2800+ and what is your dope to 600?

 

[jwrowland77]

I'm using Ballistic AE

The first time I shot my sighters at 600yd, I used what the program said of 15MOA up. Well, after getting it settled in, it's 13.5 which is 81" drop.

 

[jwrowland77]

For my 1000yd load, I use the same bullet, different powder but get 2750fps, and I only have 315" of drop. I adjust up 31.5 MOA.

 

[Fredo0621]

All my data shows at 2700ish a 175 smk should be around 95" of drop at 600. Looks like the magneto is off or you are deifying the laws of physics. Either way that load is smoking!
Care to give the details of your rifle and load?

 

[jwrowland77]

See that's what I was getting, should be around the 88" mark.

Rifle is a Rem 700 SPS varmint, 26" barrel.

Load for 600yd load is:

IMR 4065 44.5gr
175gr SMK.
CCI 250 (I use these for my 7mm RM as well)
Win cases.
OAL 2.81.

So I guess the chronograph is a little slow or so.

I've shot this load in Tulsa, Memphis, and Little Rock all with the same adjustment of only 13.5 MOA up adjustment. (13x6=78, .5x6=3) for a 81" drop. I've shot it in weather from 50 up to 100 degrees. Low humidity high humidity. It all stays around the 13-13.5 MOA up adjustment.

And the thing is, is I've gone higher charges with zero high pressure signs, the higher loads just weren't as accurate as the 44.5 load.

I used Hodgdon website to get my load data.

 

[Fredo0621]

My custom 700 was a SPS varmint in its previous life which is probably the best bang for the buck out there IMO. Anyway you have a very long throat which helps aid in the pressure dept but I have never seen that velocities that high with 4064. WIN brass is generally faster bc it can handle more powder than say LC or Lapua. You might want to post this over on snipershide.com and I'm sure someone over there could help as well. I'm kinda baffled.

 

[jwrowland77]

I've never been over there. I might have to check it out. I mean hey, it gives me sub-MOA groups at 100 and 200 so I'm pretty happy with that.

The 600 and 1000yd, I'm still learning all the lovely wind games. Lol

 

[jwrowland77]

I have a load to that gives me 2750fps using Lapua brass and 2000-MR. That's my 1000yd load.

This past weekend I tried it out and my app told me 35 MOA up, but I only had to adjust 31.5. Which is only 315" drop as compared to what it should be of 350"

 

[Fredo0621]

2000-MR is my go to powder for .308. I'm slanging 168 berger hybrids at 2840ish from a 22 in. Bartlein with 48.2 gr of 2000MR in Lapua brass. Check out there website it caters to the precision rifle shooter. You might just have the fastest Remington barrel ever made.

 

[jwrowland77]

Lol. I doubt that but it sure does shoot well. Lol

 

[jwrowland77]

I just wish I could figure why my chronograph says one thing and the truing ballistics says another. I know I'm not overpressure. I do know I'm on max end though on the chart.

 

[jwrowland77]

Well, I posted it over on snipers hide as well just to see.

 

[Fredo0621]

They will be able to help. Lots of guys run magneto chrono and should help you out. I want to know as well.

 

[rcmodel]

Bullet Ballistic Cofficients are not set in stone either.

Same bullets:
One barrel & crown sets them off wobbling slightly for quite some distance, maybe 100+ yards, until they settle down and become perfectly stable.

Another barrel & crown starts them almost stable right out of the muzzle and they stabilize at 50 yards or less.

Guess which bullet has the real highest BC?
Even though they came out of the same box.

If your rifle shoots them flatter then the BC & velocity indicates it should?

Maybe that's the reason.

rc

 

[jwrowland77]

I'm learning all kinds of new stuff over the last couple of days.

I'm going to guess the rifle that stabilizes the bullet faster.

 

[rcmodel]

Yeppers!

If you get the opportunity, lay down behind a long range rifle and train your spotting scope right beside the rile and barrel.

Then watch the bullets spiraling off down range for quite some distance until they settle down and fly right.

It's a real wonderment anyway one can hit anything at long range!

rc

 

[jwrowland77]

Lol. It is pretty cool to see the bullet trail when I have to spot and score for matches.