Magnetospeed Surprises

fuzzy39

fuzzy39

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So I've had my Miagnetspeed for a while but have not bothered to set it up until yesterday to check over some loads. First up I tried out some of my max 270 WSM loads I had worked up with IMR 7828 and 150 gr Accubond LR bullets. The load just starts getting a little sticky with extraction every few rounds so I intend to load down a grain. Anyway, I was hoping to see 3000fps but to my surprise I was averaging 3150 fps. I was pretty excited.

Next up was my 358 Win with 158 gr Hornady XTP bullets and a max load of R7. The latest Speer manual listed a top Velocity of 2850 fps and with the 20 inch BLR barrel I was shooting with I was hoping for about 2700. Surprise, surprise..... 3007, 2985, 2994, 2881!!! Crazy.

Last up was another 358 Win load with a 200 gr Hornady SP in front of a max load of Tac powder (John Barsness' data). He had quoted velocities of around 2700 fps so I was hoping for similar. Again a surprise .... but of the slow kind. Only one shot broke 2500 with the others from 2485 and higher.

Needless to say, my Magnetospeed will be out with me every time from now on!!!

And, I did have all these loads worked with lower powder amounts. I only tested the max loads.
 
Speed and pressure are directly related. You can measure velocity.

If velocity is higher than the book, pressure is probably over book too.

A well made rifle may not show pressure when operating at proof round pressure.

I consider 3000 MAX with 150 gr bullets.
 
Ganderite said:
Speed and pressure are directly related. You can measure velocity.

If velocity is higher than the book, pressure is probably over book too.

A well made rifle may not show pressure when operating at proof round pressure.

I consider 3000 MAX with 150 gr bullets.
Click to expand...

Thanks Ganderite. 3000 fps was what I was targeting so I'll back off a full grain to start then re-measure. It goes to show the importance of using a chrono!
 
the problem with book velocities, is that they vary so much from manual to manual. Which manual do you trust, when both list the same components?
 
Yes, over the years since I acquired a dependable chronograph, I have had some interesting surprises.
Book numbers are very seldom what you will see from your rifle, using the book loads.

I remember when Hodgdon introduced a powder labelled H205, many years ago. It seemed like a good
choice in the 7x57, Hodgdon listing a given load with the 150/154 grain pills that delivered 2800+ at
safe pressures. The load produced very good accuracy in my #1AB Ruger, so I loaded up a box or two
of 154 Hornadys, and went hunting. With this load over the next 3 years I shot 3 moose, 4 muleys and
2 Whitetails, plus one very decent size Black Bear. No long shots, longest was about 240 yards, one
shot did the job in every case.

Imagine my surprise when I finally got a chance to run this load across the chronograph and found it
loping along at just over 2300 fps!! My other clue was the condition of the recovered bullet from a moose.
The shot was about 55 yards, and expansion was not as much as I expected.

In other cases, I have had starting loads that were obviously hotter than expected. One memorable
starting load in a "new to me" rifle that I expected to see 2950 fps or so, showed 3210 fps!! This was
well above what I considered a working load in that particular chambering.

It is just a good idea to take most book velocities with a grain of salt until they can be verified. Dave.
 
stubblejumper said:
the problem with book velocities, is that they vary so much from manual to manual. Which manual do you trust, when both list the same components?
Click to expand...

I would think that's a simple feature associated with differences in chamber dimensions, how fast a particular barrel is, what method they use for measuring pressure, ect.

The variability from gun to gun would likely account for that - not to mention the fact that manuals have largely decreased max loads over the years. What is safe today is middle of the road according to some books from 30 years ago.
 
Suther said:
I would think that's a simple feature associated with differences in chamber dimensions, how fast a particular barrel is, what method they use for measuring pressure, ect.

The variability from gun to gun would likely account for that - not to mention the fact that manuals have largely decreased max loads over the years. What is safe today is middle of the road according to some books from 30 years ago.
Click to expand...

The fact remains, that I have seen variances of over 150fps from manual to manual. In some cases, I have not been able to reach the velocity listed in some fairly recent manuals without pressure signs, and yet I routinely exceed some manual max loads by over 100fps, with long case life, and no pressure signs of any kind.
 
fuzzy39 said:
Thanks Ganderite. 3000 fps was what I was targeting so I'll back off a full grain to start then re-measure. It goes to show the importance of using a chrono!
Click to expand...

You're likely going to have to back off more than a grain.

Once you reach maximum specs it takes more powder to gain velocity, until you are in the danger zone. Then a grain can be enough to create a nasty spike.

I use a lot of IMR7828, both in regular cut and ssc. I use it in cartridges with similar capacity to bore ratios to your 270WSM. It's a relatively forgiving powder and manages to give some very decent velocities, without pressure spikes by lengthening out the pressure curve. Good stuff.

TURF THE LIBERALS IN 2019
 
fuzzy39 said:
So I've had my Miagnetspeed for a while but have not bothered to set it up until yesterday to check over some loads. First up I tried out some of my max 270 WSM loads I had worked up with IMR 7828 and 150 gr Accubond LR bullets. The load just starts getting a little sticky with extraction every few rounds so I intend to load down a grain. Anyway, I was hoping to see 3000fps but to my surprise I was averaging 3150 fps. I was pretty excited.

Next up was my 358 Win with 158 gr Hornady XTP bullets and a max load of R7. The latest Speer manual listed a top Velocity of 2850 fps and with the 20 inch BLR barrel I was shooting with I was hoping for about 2700. Surprise, surprise..... 3007, 2985, 2994, 2881!!! Crazy.

Last up was another 358 Win load with a 200 gr Hornady SP in front of a max load of Tac powder (John Barsness' data). He had quoted velocities of around 2700 fps so I was hoping for similar. Again a surprise .... but of the slow kind. Only one shot broke 2500 with the others from 2485 and higher.

Needless to say, my Magnetospeed will be out with me every time from now on!!!

And, I did have all these loads worked with lower powder amounts. I only tested the max loads.
Click to expand...

I have had very similar surprises! I also run all my loads that I develop through my Beta Chrony. Just recently I purchased a MagnetoSpeed Sporter Chronograph and I am very eager to try it out this July. I am developing a 150 grain Nosler Partition load for my 270 Winchester (using IMR 7977 powder) and a 150 grain NPT load for my 30-06 Springfield (using Hodgdon's Superformance powder)
 
If you're consistently getting higher velocities from different rifles, you might want to cross reference those loads with a different chronograph, just to be sure yours is honest.
 
This summer I will setup both my optical chrony and my new MagnetoSpeed Sporter chrony and see what the difference is. It should not be much ... say 10 fps since the optical chrony needs to be placed 5 yards from the muzzle. I will post my results once I do more testing.
 
An update on my testing of the Magnetospeed Sporter that I have recently purchased.

I have field tested for about 18 hours at the gun range. Short story is that I am extremely pleased with its performance for the following reasons:

1. Extremely easy and quick to setup and use (60 seconds or less)
2. Very accurate and consistent readouts (never failed to readout velocity in hundreds of rounds)
3. Worked very well with rifles that have muzzle brakes and rifles that do not.
4. Easy to reattach to a bunch of different rifles at the range benches (sporter barrels and heavy barrels).
5. Works very well with light and heavy loads in the following calibers (270 Win, 30-06 Springfield, 308 Win, and 26 Nosler)
6. Very useful verifying factory ammo velocities (Hornady, and Nosler)
7. Instrumental in verifying the velocities of reloaded ammo.
8. Easily withstands the muzzle blasts with only minimal "pitting" in the hard poly-carbonate edge of the bayonet.
9. Works will in the summer's heat and sun and hot barrels.
 
Dmay said:
So how do you determine this?
Click to expand...

Well ... for my reloading purposes ... the charge ladders that i build with controlled materials and processes ... when i plot the velocity results on an Excel graph ... they form a linear pattern or a low order exponential curve ... and not a scatter pattern ... like my optical Beta chronograph. I do realize that this isn't a formal scientific method of analysis ... but for me it is better than what i had before. I also have boxes of Hornady factory ammo that i use as a reference. I would expect results to within my own defined error range for those advertised velocities. ... i do realize that there are a lot of variables that i am not controlling ... Anyway ... i wish i had access to real equipment ... like Hornady
 
Dmay said:
So how do you determine this?
Click to expand...

I've checked my magnetospeed against other magnetospeed units and a Lab Radar unit. Of course, I was using the same rifle with handloads assembled to the same recipe. All three magnetospeed units measured velocities averaged over 5 shot strings within 25 fps of my unit. The Lab Radar set up was right in the same velocity range.

Magnetospeeds work very well IMHO.

I have used several different types of velocity meters in my years of shooting. Everything from shooting through screen cards attached to electrodes which compared the difference in the time it took the bullet to pass through the first and last screen to Chrony types, which were much better, Lab Radar set ups which are excellent and the Magnetospeed units, which IMHO are ideal for my purposes, because of their compact size, reliability, consistency and price.

OP, heed Ganderite's warning well. He knows what he's talking about. Velocities can only be increased by increasing pressure or extending the pressure curve. The ratio of powder to velocity curve IS NOT PROPORTIONAL. I had to point this out very stringently to a young reloader today. He's hell bent on extreme velocities and hasn't done his due diligence on how to achieve them safely.

New, late manufacture rifles are very strong because the materials they're made from are better than anything made previously. They don't require heat treating for one thing. Still, is your face or eyesight worth an extra 50-100 feet per second??
 
I have field tested my MagnetoSpeed Sporter chrony at the gun range for 4 full day sessions using my 270 Winchester and 30-06 Weatherby Vanguard S2 rifles. The MagnetoSpeed Sporter chrony preformed flawlessly and is easy to use, install, take off, and clean. It is a great value in a chrony.
 
Depending on your cartridge, each inch of barrel length equates to a loss/gain in fps and you either add it or subtract it from the test barrels maximum velocity.

Example

308 Winchester

Test barrel 24" Max Velocity is 2934 fps for Max pressure of 61,000 psi

Standard Cartridges with 2800 to 3000 fps loss/gain 30 fps/inch

Your barrel 28" ... which is 4" inches longer than the test barrel ... will have a gain of 4 x 30 fps over the test barrel

so your barrel will have 2934 fps + 4 x 30 fps = 3054 fps for Max pressure of 61,000 psi

http://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length/

They have a graph by the inch
 
Carbon12 said:
Depending on your cartridge, each inch of barrel length equates to a loss/gain in fps and you either add it or subtract it from the test barrels maximum velocity.

Example

308 Winchester

Test barrel 24" Max Velocity is 2934 fps for Max pressure of 61,000 psi

Standard Cartridges with 2800 to 3000 fps loss/gain 30 fps/inch

Your barrel 28" ... which is 4" inches longer than the test barrel ... will have a gain of 4 x 30 fps over the test barrel

so your barrel will have 2934 fps + 4 x 30 fps = 3054 fps for Max pressure of 61,000 psi

http://bulletin.accurateshooter.com/2015/06/308-win-barrel-cut-down-test-velocity-vs-barrel-length/

They have a graph by the inch
Click to expand...

More like 20 fps ... or so

“The Berger Reloading manual says for the 308 Winchester, ‘muzzle velocity will increase (or decrease) by approximately 20 fps per inch from a standard 24″ barrel’.”
 
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