Is it worth buying a Magneto speed if you're shooting factory ammo?

[jdm911]

New to PRS and was wondering if it is worth buying a magneto speed to chrono Factory ammo? eventually i would like to reload, but for now i'll be shooting with factory ammo. Should I just use the info printed on the box? or should I invest in a magneto speed and chrono the ammo still?

Might sound like a stupid question to you professionals, but i'm new to all this so forgive me.

Thank you,

 

[SNAFU308]

The info printed on the box is just an indication of the velocity achieved in their test rifle or an estimate and isn't necessarily the speed you will get with your rifle. You should chronograph/confirm data for your ammo in your rifle regardless of if it's factory or hand loads.

 

[SubOptimal]

Do you absolutely need one?
No, you can start with the published data on the box, make adjustments for your particular barrel length (guess) and run that info through a ballistic calculator to get a base line set of data.
Range estimation if a unknown distance target and wind calls are far more important.
Once you have a base data set, you can true your data by just shooting and recording results. Muzzle velocity is handy to know but it is but one of the factors involved in making hits on targets.
The best, and most accurate data for YOUR rifle and Your load can only be obtained by meticulous record keeping and referencing and refining data over the long term.
That last is the rub. Barrels wear, lot numbers change characteristics of the ammo, some factory ammo is more temperature sensitive than others and, in the long run, it is the bullet that tells you if your data is good or bad. All the data in the world won't help you if you can't shoot well.

 

[CRT2]

Yes. Within the same lot of ammo I have chronographed 100 fps difference between rounds - match ammunition.

 

[Bradu]

If I did it all over again, a chronograph is one of the first things I would buy.

 

[04JRB]

Depends on what type of shooting. If I was just shooting 100 yards, then no. Once I started doing local club matches out to 650ish yards, I feel it was important to have one. The chrono / Magnetospeed gives critical data in order to plot decent dope for your ballistic program prior to truing that data up by actual hits/misses at targets at distance, it can save you a lot of time and ammo figuring it all out by data logging. Garbage data into the ballistics app, and garbage results down range. I have also noticed quite a spread in FPS on match ammo from the same lot like @CRT2 has.

 

[Olen_4504]

I picked one up once I decided to get into PRS (next week 1st match!) to get real world data on my factory ammo. roughly 100fps different than the box

message Fred at Bison Tactical on here. he's got good pricing on the magnetospeed V3.

 

[davsco]

yeah within a few hundred yards it's not that big of a deal, but as you reach out, having an accurate speed becomes vital. that doesn't mean you need to run out and buy one. if someone is chron'ing at your range, just ask them if you can run 10 shots thru it. or you can get an "old school" $100 chrono that isn't quite as easy to use and set up but still gives accurate data.

 

[Wrongtarget]

I only run factory ammo but this is a tool used regularly. Long term it will save you from guess misses lol

 

[W54/XM-388]

Based on what you can buy a used unit for, it will probably pay for itself in the long run by helping you waste less ammo shooting at various distances till you get your individual dope worked out.

 

[jdm911]

I picked one up once I decided to get into PRS (next week 1st match!) to get real world data on my factory ammo. roughly 100fps different than the box

message Fred at Bison Tactical on here. he's got good pricing on the magnetospeed V3.

What's his handle?

 

[jdm911]

What's his handle?

Nevermind I found it. Thank you!

 

[mercracing]

I would defiantly get one. Knowing exactly what your velocity is will save a lot of headaches and help you get more impacts.

 

[wigwamitus]

Yes !

Before I used the magneto speed, I used the "guess and correct" method. I would look at the box or the website ... and add/subtract 20 fps for each inch of barrel length difference, if known ... or I would just guess. Then I would shoot at 100yds and 500yds on my land and get close.
But still, when I went out to a neighboring ranch to shoot out to 1400yds, I would be off. A parabola is defined by three points, ideally farther apart. I still had to make adjustments and if I changed the MV that affected everywhere! Not where I hit, but where the ballistics calculator said I would hit. So there was a lot of back and forth adjusting trying to "zero to the parabola".

Now with the magnetospeed ... I pre-zero with the magneto speed on there for ~10 rds. Then zero at 100yds.

Then measure my height above bore as accurately as possible. And key the MV and the Height Above Bore into my ballistics calculator and then I am dead on from 0 to 1400yds or as far as I want to shoot. It has been a game changer for me ... and it takes less time and less ammo as well. I was an idiot for not getting one sooner !!!

 

[squib-load]

I have a sporter and have mixed feelings about it.

first.. its more consistent than my optical shooting crony which is very sensitive to lighting changes, shadows, gases if not placed far enough away.. etc.. and its too much hassle to set up a lighting box around it.

BUT the sporter effects my group size and POI severely.. POI shift is .8MIL .. thats right MIL .. on average about 3" high at 100 ... routinely on my 308.. a bit different on my 6.5-284N. the weight at the end of the barrel acts similar to a bench rest barrel tuner .. and a theory is also that the bullet interacts with the surface of the bayonet like an aircraft wing in ground effect generating lift...

that said here are my thoughts on if you NEED one

if you have a known distance range that you can get access to frequently and cheaply and out to AT LEAST 500 yards than you MAY not need it.. provided you are willing to go out and dope your rifle. In the military.. generally you don't normally see chronos... its all pretty much done with dope... and to be honest.. even with the best chrono data... actual dope is FAR MORE RELIABLE.. as it take into account/shows you the effect of positive/negative compensation (slower bullets you WANT to hit higher on a target) .. more info here http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm with factory ammo you can't control this as its a function of barrel timing and reloaders can adjust with seating depth mostly.. but powder as well.

shooting at long range will allow you to build reliable ACTUAL dope for that range and velocity can be trued/estimated by walking numbers back.. but if you can't shoot all the way out to your terminal ranges you won't be able to fully define your compensation.. that is why some of the best bench rest 1000 yard guys tune their loads at that distance and not shorter. for example.. lets say the following..

if you have a 25 fps velocity spread.. and the slowest rounds hit .5 moa high at short range like 100 yards.. that is positive compensation which is desirable .. but . it will be high out to a certain distance then cross back through the average trajectory line and begin hitting low.. at some distance. you can work the 'what if's' on a the JBM ballistics web site or a ballistic calculator. run a table out to 1000 yards in moa/min and INCHES at a velocity average. then run another with the velocity 25 fps slower.. but also put in a zero compensation that is .5" high at the 100 zero range. you will see a positive.. slower hitting higher compensation to a point then drop back down.. there will be a point where the 25fps slow rounds hit exactly where the fast ones do..

long and short.. there is no golden bullet other than many regular bullets shot down range at distances and conditions to be expected and doped into a log book.

chrono data can HELP get you on target but it can't contain all the answers...

if you do forgo a chrono and decide to dope.. or hell even with a magneto buy your ammo in big same lot quantities otherwise the data is useless as it will change sometimes significantly lot to lot...

 

[wigwamitus]

... the sporter effects my group size and POI severely ...

Oh yes, you cannot fully zero with the magnetospeed on there. It absolutely affects POI. The purpose of the magneto speed is to measure MV and it does that very well.
So can however "pre-zero" and get "into the ball park" with the magneto speed on there. Then once you have measured your MV with say 10-15 rds, you remove the magneto speed and finish zeroing.

 

[Olen_4504]

Oh yes, you cannot fully zero with the magnetospeed on there. It absolutely affects POI. The purpose of the magneto speed is to measure MV and it does that very well.
So can however "pre-zero" and get "into the ball park" with the magneto speed on there. Then once you have measured your MV with say 10-15 rds, you remove the magneto speed and finish zeroing.

what he said, i found this out the hard way

 

[squib-load]

you can not only not zero with it on.. you can't load develop either.. its a one trick pony.. velocity.

to really stir the hornets nest.. some f class folks I shoot with say that cranking that strap tight next to the muzzle will constrict and deform it.. effecting ES and potentially long term damage to the barrel itself..

not unlike the studies that show that the stress imparted by the set screw for AR gas blocks can be measured inside the bore of the barrel... but I am not going that far into the weeds... hehe

 

[wigwamitus]

... some f class folks I shoot with say that cranking that strap tight next to the muzzle will constrict and deform it ...

I've never strapped my magneto speed to the barrel. I strap it to the suppressors.

And it isn't that tight. Just tight enough not to move.

 

[squib-load]

@wigwamitus

once you have an actual confirmed zero and you know your POI shift with it on.. you can.. at least in my case .. strap it on and still ring steel with it.. I won't shoot for groups with it on...

you must mount in perfectly level and in the same spot every time.. if its rocked to 7 o'clock the rounds will go to 1oclock ,... rocked over to 5oclock rounds shift to 11oclock.. its like its literally bouncing off the bayonet.. which its of course its not physically touching the bayonet but the pad of air it compresses pushes it that way...

if the barrel has any taper at all.. it needs to be pretty damn tight.. I have had it walk on me. even tried a wrap of electrical tape under it and still manages to loosen up and walk if you don't crank down on it . the strap on the v3 is better than the sport however..

the only solution out there that covers all the bases.. accurate data, no effected by envionmentals, and doest effect the bullet is the lab radar.. but I have not won the lottery yet.

 

[LA260]

Best thing to do is to figure out a way to install the MS on the chassis or the stock instead of the barrel. That way you can shoot for groups, develop load, shoot at anything/anywhere without worrying about POI shifts. Something homemade like this that I'm using or you can buy a mount from the various companies that make them. I do realize that this may not work with every setup though

 

[squib-load]

@LA260

won't matter.. mounting it to the rail or stock.. the bullet passing over the bayonet will throw it .. it seems for almost everyone it throws away from the bayonet .. mount it at 6oclock the group goes up several inches.. turn it over mount it on the top ... group goes low same 3" ... mount it at 3oclock .. group goes left.. etc...

 

[LA260]

Interesting. I must be one of the lucky ones because 2 weeks ago I shot 20 rounds at a 10" round steel target at 1k yards with the MS attached as shown on the pic above, and then 25 rounds without the MS and as long as I held for wind correctly the rounds hit the steel in both cases.

 

[squib-load]

@LA260 so out of the 20 rounds fired with the MS on how many were hits.. how many of the 25 without were hits? what are you shooting. can't tell from the picture..

 

[Chalkeye]

Why is it such a problem if there is POI shift? Why are people so fixated on this as an issue with the magneto speed?

Strap it on and run ~5 rounds through, take it off and carry on about your day.

 

[squib-load]

@Chalkeye .. exactly.. to grab quick velocity data its fine for that purpose..

however.. there are many different uses in precision shooting for a chronograph ... and for many of them ..a MS just is not the right or easiest tool in the bag.

load development.. no-go.. groups data is not reliable however velocity data is.. so generally you have to velocity check you intended powder spread first.. shoot a ladder or OCW for grouping, then fine tune a load that shapes a group you can live with., zero with that load.. . then magspeed it again to finalize the loads velocity numbers to true it out over distance..

if you have a reliable optical chronograph or a lab radar you can do everything at the same time

 

[LA260]

@LA260 so out of the 20 rounds fired with the MS on how many were hits.. how many of the 25 without were hits? what are you shooting. can't tell from the picture..

It's a 260rem 2835fps 140ELD. I dont have an exact count of hits with MS vs no MS but the misses were either to the left of the target or to the right in both cases. The target was up on a hill with nothing but dirt around it so it was pretty easy to see the misses.

 

[427Cobra]

Yes buy one ASAP

I true my ballistics with mine attached at 800 yards, knowing exactly what the muzzle velocity is, I true the BC of the bullets to match what I dialed, I found my ballistics are fare more accurate/repeatable/trustworthy

 

[squib-load]

well its been well documented over on another site where a guy was designing a rube-goldberg mounting device to get it off the barrel and it didn't mater, his rounds still shifted away from the bayonet and on every rifle I own mine shifts and I can tell it the bayonet gets loose because if it rotates a little the group shifts in the opposite direction..

any who... don't care if your rifle defies the laws of physics or get into a pissing contest..

the op wanted to know if a MS is a good match for factory ammo.. and again.. its one tool in the box.. but at the end of the day.. if you are not doing load development and buy a big lot of factory ammo.. its better data to true and dope on an actual range than capture velocity only data.. in my opinion..

out

 

[Bradu]

I bought an MK machining mount for my magnetospeed to get it off the barrel while doing load development. I don't care about poi shift, it's the harmonics that made me decide to go that route. I don't know how much, if any difference it will make but for what I have spent on other equipment, I figured it can't hurt.