This velocity is impossible isn't it? I'm at a loss.

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fuzzynuts54

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Ok well I still haven't had a chance to chrono the latest loads but according to jbm they are not at all what they should be.

.300 win mag .308 cal 208gr amax, 79.5gr of h1000, cci magnum rifle primers, 3.500 oal.....2225fps???!?! WTF?

Now I know I need to chrono the amax load it but I haven't had the weather so I've just used the jbm online to calculate and I know it's not the perfect way but it should be pretty close, plus I wanted to sight in my new scope yesterday.

So here's the data/specs. .300win mag. Sight height 2.0". Range 123yards. 41'f, 700ft elevation, humidity 100%, 29.92hg.

I zeroed my 150gr smk loads 1"high. They are chronod at 3300fps and the drop tables confirm that. My 208amax's hit 3" lower than the smk's.

I shot 3 groups of each and alternated between loads to be absolutely shure. The amax's were absolutly consistenly 3" lower than the smk's.

According to jbm the muzzle elevation is 4.295moa to achieve 1"high at 123y with the 150smk at 3300fps in these weather conditions.
With the same muzzle elevation (and same point of aim) jbm says these amax's are only going 2225fps. Is that possible with 79.5gr of h1000? Is my powder misslabeled? Could this be an anomoly related to the differing recoil or the barrels "node"? I'm puzzled....
 
Are you somehow trying to use the holes in the paper for the two bullet weights to calcualt drop and therfore velocity?

If so, forget it.

The holes in the paper tell you where the rifle shoots. A Chrony tells you velocity.

A whole bunch of things determine elevation, with velocity having nothing to do with it at short range.

If you zeroed at 100 and at 500 with each and compared the drops of each, you could get a rough idea of velocity. But only rough.
 
You would be better to shoot at 2 distances and use the drop between the 2 as your data.

Example:
Shots at 100 are 3" below POA. Shots at 200 are 5" below POA so there is a 2" difference from 100-200

Using that data you can estimate a velocity.
 
".300 win mag .308 cal 208gr amax, 79.5gr of h1000, cci magnum rifle primers, 3.500 oal.....2225fps???!?! WTF?"

It sounds about RIGHT for 210 Grain bullet in 300 Win Mag, I leave rest for Xperts - Biggs

Edit: Reg - Canuck , it's some one's custom long range competition load for their own rifle specs- ( Amax bullets) I expect it to be around 2400f/s
 
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Biggunners said:
".300 win mag .308 cal 208gr amax, 79.5gr of h1000, cci magnum rifle primers, 3.500 oal.....2225fps???!?! WTF?"

It sounds about RIGHT for 210 Grain bullet in 300 Win Mag, I leave rest for Xperts - Biggs
Click to expand...


Depending on rifle, however I am going a lot faster in mine. I would say 2800fps should be a good estimate in a 24" barrel, and perhaps a tad faster with that much H1000.
 
I was reading on US forum the other day about a few fellows throwing 210gr Bergers at 2800 with 30-06's, using RL-22. They had load data from one of those $200+ ballistic programs showing their loads were under 60 000 psi. Never done it myself, mind you.

I doubt 2800 with a 208 is out of reach with a 300 win mag. Not at all.
 
I should have mentioned, it's a 24" barrel. Mixed federal/winchester brass, assorted by weight. 79.5gr is just starting to define the edge of the primers.
This particular load was not the tightest grouping (77gr was) but it was the top of the node. 77grains was another 2" lower yet. According to the loading data 79.5 is over max and should be 2850fps or more.

I honestly can't see the velocity being this low. I can't see it being barrel harmonics because this is the high end of the node. At this point I really want to conect it to the recoil. There is a distinct difference. The 150gr smk is quite sharp, while the 208 is more like a slow moving train.
I'm just kinda playing detective with this. I know the chrono will give a positive answer but for now speculating is kinda fun.
 
Quickload estimates 2900ish with that load in a 24" barrel.

Unfortunately QL has several versions of the 300 WM in it all with different velocity outcomes but going on the average above.

Guessing that the barrel node is putting the bullets lower than your known load. If the known is letting the bullet from the muzzle when it is in its high vibration and the new is letting it out on the low vibration the difference is quite possible.
 
A velocity calculation based on bullet drop at such short distances is almost useless. There are way too many variables and measuring errors, as well as human error that can really screw up the results. Hence, the "impossible" results.

Get a chronograph if you want to know the velocity.
 
dan belisle said:
I nudge 3000 fps with 200gr bullets in all my regular length belted 300 mags (308 Norma, 300 Win Mag, 30-338, 300 Wby). 2900 with 207 shouldn't be too tough to do with the right powder. FWIW - dan
Click to expand...

I can also nudge 3000fps with the 208 AMAX with Retumbo in my 110BA (a nicely compressed load). I do have a "fast" barrel and it has always been able to exceed posted velocities for a given charge weight.
 
A 'drop' comparison at just one range with two different bullets is absolutely useless for predicting velocities. It really won't tell you anything useful at all; different bullets and loads generate entirely different dynamics in a rifle, and those will affect your POI much more than velocity, especially at very short ranges like 100 yards.

My 44 magnum (rifle), for example, prints subsonic lead loads well over 1 foot HIGHER at 100 yards than jacketed full-intensity loads. They just affect the rifle differently.

If, however, you were to plot out the drops from a single load over several ranges, you could make a meaningful estimate of the MV. You'd need a baseline at 100 yards, then data at several other ranges; ideally moderately far ranges: 500+ yards is where things really start changing quickly, and will give you the best data. Then, with the known trajectory of your loads plotted over these ranges, you could figure out a rough MV using the known BC of that bullet.

But simply comparing the POI between two different loads at 100 yards is really less than useless for predicting MV. It's completely random data that's entirely meaningless without additional data points.
 
But like I said both these loads are the top of the node, not one at the top and one at the bottom. I'll take human error out of this also, this wasn't one shot from each load, it was 3 shots with smk - 3 with amax - 3 smk - 3 amax - 3 smk - 3 amax. All groups measure 1-1/4" and less.

I don't get the argument that 100y isn't far enough. 1 bullet of known velocity and bc is being launched at 4.295 moa and everyone agrees that the program can calculate it's point of impact. The next is a known bc and a known point of impact. It's velocity should be just as easy to calculate so long as there are no other variables. Well what are the possible variables here? Barrel harmonics and recoil charachteristics but I feel I've ruled the barrel harmonics out also.

I'm not arguing this, just analyzing ad this is what I conclude. Oh and one more note, this is shooting prone off te bipod, not sandbags. The bipod definatley affects the motion of the gun when recoiling much different than sandbags.
 
My H1000 + 220gr Nosler Partition load hits 2850 out of a 24" barrel, so your numbers seem extremely low.
 
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