Magneto Speed Alternate Mounting Options effectiveness.

[dave300]

So, I have a question that I hope anyone whom has "used" a adaptation of the Magneto Speed can speak to.
At the 2015 or 2016 SHOT show (cant remember) I spoke to the MS folks about the shift/harmonics that the MS causes, and why not build an mounting/adjustment rod as suggested in this and other threads?
Instantly and with authority, I was told that the shift/POI is partially caused by the muzzle blast conflicting with the actual bayonet and that the alternate mounting option I was suggesting will still have the same issue with a shift/POI as if the device was attached to barrel. More so with smaller profile barrels.
Can anyone who has "used" one of these devices, home made or otherwise speak to the above?
I sure would like to get my MS back in action if the shift does not actual take place, as it is quit a lengthy drive to shoot for me, and then follow up with a second trip to shoot without my MS attached to zero and confirm drops.
I think I will cross post this to gather as much info as I can and try to report back here.
Thanks

 

[Mr.BR]

BS muzzle blast follows bullet ,whatever vibes MS induces after bullet left the muzzle you don't care unless is some super fast full auto fire we are taliking about,its about weight on the muzzle.

 

[Ricker]

I use the MPA Magnetospeed adapter which mounts to the chassis. When using the MPA mount there is no point of impact change on my gun. I have also used the MS on barrel and there a slight POI change high and left for my gun.

 

[squib-load]

I think also its a bit caliber/velocity dependent

I have a MS sport that I use on a .308 5.56 and 6.5-284 norma rifles.. the .308 is a schneider modified m40 taper 24" .925 at the muzzle heavy barrel, the 6.5-284 is a CBI remage and the 5.56 is a 18" odin match barrel on a match AR shooting 77SMK... every one of these rifles show a POI shift.. dramatically, and load dependent will show, sometimes, a much different group pattern as well

for example

in my .308 the POI shift is .8 mil high.. routinely and repeatable .. i can dial it in or hold off.. every time.. group size on a dialed in load are generally about the same size as I am in a good node.. BUT.. my positive compensation (the slow rounds hitting high with the MS off) shows up just the opposite with the MS on.. the slow rounds hit low...

on a bad load.. I have seen the exact opposite.. worked up a load with the MS on.. got a group and velocity SD I liked. it showed positive compensation.... loaded 25 up and shot them without the MS and the behavior was 180 degrees out ..


with my 6.5-284 I just got a new barrel screwed on.. shot a velocity ladder from 53 grains to 56.6 grains and a velocity swing of 2940-3140 and with the MS on 5 of the 7 in the ladder were in a .6moa ragged hole.. took the MS off and shot the same 7 load velocity ladder and the group was 2" across and not a single round touched... it changed the harmonics that much.. POI shift was about .6mil again.. 3" high

similar behavior with the 5.56

one theory is that when the bullet passes over the bayonet there is aerodynamic interference called ground effect being imparted on the bullet... like an aircraft wing.. it generate more lift if its close to the ground due to the increased drag of the air between the wing and the ground. happens at about 1/2 the wingspan.. so a 100 foot wingspan aircraft generates greater lift and sees ground effect around 50ft and down.. increasing as you get lower..

similarly if the bayonet is not perfectly level ..as is the case 99% of the time with a sport because it does not have angle compensation.. this too seems to increase the effect of shift.

I no longer work up loads with the bayonet on.. I will do a velocity ladder, 1 sometimes 2 shots per load density just to sanity check velocity/pressure/safety ... graph it so see if there are any flat spots that might look good for a node.. but usually just go back and either run a traditional ladder at longer range in a velocity that I am interested in or do a OCW type test..

the other thing the MS does is screw up the positive compensation that you look for.. i.e. slower rounds hitting higher on target.. a desirable effect for long range loads that bench shooters use tuning devices to fine tune .. seating depth works to a point.. but with the MS on.. sometimes I see results 180 degrees out from MS off..

long/short.. mounting it off the barrel will take the harmonics issue out of the equation but there will still be interaction with the bullet and POI shift and groups will probably still be effected..

 

[squib-load]

@Mr.BR

the muzzle blast in the second frame would be going under the bullet between the bullet and the MS .. and depending on caliber and powder choice the dump pressure and muzzle blast could be even bigger.. and that WILL effect things.. dramatically ..

and your pics are with a brake on.. dumping the gas to the side.. the effect is worse with all the dump gas and unburned gas explosion leaving the barrel following the bullet down range

don't believe me.. if you have a MS.... shoot 3 shots with the bayonet at 6, the rotate it 90deg and shoot another, then rotate 90 again.. the group will move opposite the bayonet.. every time and by the same amount... weight stays the same.. barrel harmonics are the same.. just the angle of the bullet over the deck of the MS changes..

 

[Mr.BR]

Have no tried rotating it ,but considering the attachment method it hard to replicate. On the Barrel tuners we built and tested a fine thread 0.5mm per turn make gun go in and out of tune in less than a quarter turn on some loads.

But my bett on group move due to MS orientation is on the barrel whip that is happening well before bullet exits , where the weight is relative to the bore matters ,am not buying aerodynamics as MS first has a cut out second enough clerance.

I typicaly test loads without MS and after group testing pop on the MS for speed verification with remaining rounds , depends how anal you want ot be with group testing when are they small enough , for my tactical practical .284win rig 0.5moa is good enough . I have a 28' long modified TRG contour cut rifled barrel , not much displacemnt with MS typical 1.5x bullet hole , and gun tends to group better with most loads with MS atached than without LOL ,my friends Rem700 on the other hand has considerable group shift

For me group testing is about low ES ,SDs and geting the temp /velocity data ,as am using relatively temperamental powder Reload Swiss RS60 -aka RL17 in US , groups are fine with most loads as its very easy to get 0.5moa that i am ok with.


Diy riging a MS mount will see if anything happens.But like said am very sceptical of aerodynamic related shift theory

 

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@Mr.BR

yes.. there is certainly the barrel tuner effect.. but there is the aerodynamic interference with the bayonet face as well.. again.. if it was just weight.. rotating the bayonet would not change anything (the weight is in the same place.. turning a BR tuner moves the weight back and forth) the the group always goes away from the bayonet.. at any angle.. 180 off the face of the bayonet.. 100% of the time on my 3 rifles I have used it on

 

[squib-load]

@Mr.BR I don't know what caliber you are loading for.. I tried R17 in 6.5Norma.. it was a bit explosive for my tastes and it didn't take much to see pressure spikes at velocity less than 3000 on a 26" barrel.. went to r- 26 and got north of 3150 without pressures signs and called it quits.. very impressive powder .. the creed moor guys are getting up to 3k in that rifle with r26.. I went back to the 3050 node .. shoots great .. I have been told R26 was designed for speed and R23 has superb temp stability just slightly less velocity but more than r17 and short cut...

 

[Mr.BR]

was .284 win now .284shehane in Long action repeater ,Reload Swiss RS60 simmilar to Rl17 ,its quite temp sensitive but once you get used to it and have lots of data its quite predictable and gives plenty of velocity .Me and my shooting partner have been using it for 4 years now .

@Mr.BR

yes.. there is certainly the barrel tuner effect.. but there is the aerodynamic interference with the bayonet face as well.. again.. if it was just weight.. rotating the bayonet would not change anything (the weight is in the same place.. turning a BR tuner moves the weight back and forth) the the group always goes away from the bayonet.. at any angle.. 180 off the face of the bayonet.. 100% of the time on my 3 rifles I have used it on

Look at the barrel vibration gif, that is all happeing while the barrel is traveling down the bore and barrel whip will change shape if you put weight left or right of the bore , Why would you assume that is not the case .

Barrel tunners are circular so realisticaly only move weight forward and afft in very precise maner , there is no off bore bias with them.

 

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@Mr.BR

because I know aerodynamics and while your finite analysis of barrel whip explains some things.. it doesn't cover the aerodynamic friction that occurs to a body traveling at mach 2-3 passing less than .3" from a interference surface...

 

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@Mr.BR
also had been seen many times in the design of muzzle breaks and suppressors..

if I recall correctly.. for best accuracy there needs to be .020 for clearance and it must be perfectly concentric. or guess what.. it deflects the bullet.. even if it doesn't strike the brake

in this example.. the aerodynamic lifting body (bullet) is unbounded on one side.. and in aerodynamic 'ground effect' on the other..

 

[squib-load]

now.. include the hypersonic gases exiting with the bullet and the explosive wave formed by the combustion of the expanding unburned fuel to the picture and you have quite a mess

 

[squib-load]

The projectile was discovered to experience a marked pitching moment, initially nose-downwards at the high end of type C reflection interactions, then more strongly nose-up with contin- ued decreasing ground clearance, as the pressure distribution over the rear of the projectile was increasingly distorted by the build up of high pressure behind the series of shock/ground interactions.

 

[squib-load]

how does that scan... I say thats definitive..., scientifically gathered data...

 

[Stpilot12]

So back to reality.... Been playing with the MK Machining Magneto Speed rail mount for about 2 months. My rifle averages 1" low with the MS strapped to the barrel. With the MS mounted to the rail I have NO shift in POI or difference group size whatsoever, like its not even there.

 

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@Stpilot12

my AR has less POI shift than my 2 heavy barrel 308 and 6.5-284 rifles...

1 because with the AR the barrel isn't tapered and the bullet isn't flying into a rising ground plane, 2 it has a brake and therefor not as much muzzle dump gas to interact with the projectile while its over the drag surface.

3 I get less effect if I adjust the bullet to be higher over the bayonet than the recommended .25" but velocity data becomes less reliable and I get E messages.

my theory is that muzzle gas interaction is a player, and that explains why folks with brakes and cans see less effect

additionally, if the bayonet is kept perfectly parallel which is possible with the v3 and off mounts but not possible with the sport on tapered barrels the rising surface accentuates the bullet deflection as specified in the research

but as you can clearly see in the research, a bullet shot over a fixed surface within a caliber definitely is acted upon by its shock wave

its not my paper but was referenced in designing future hypersonic 'things' if you get my drift

here you can see clearly that at a height of .75 of projectile diameter the shockwave reflections are interfering with the body, and the tail is loosing lift pointing the bullet up, at 1.77x diameter the reflection passes behind the projectile

projectile shape effects mach cone shape, effect varies with ogive shape/ bullet length / velocity / atmospherics etc... for example here.. if the bullet were much longer, even at 1.77x diameter height, the reflection would hit the tail of the bullet.

expanded view of hight to diameter distance and effect of lift/drag at the boattail

in the words of Anchorman ... ' its science..'...

 

[squib-load]

@Mr.BR

I was doing testing and break-in on a new barrel for my 6.5-284.. it dumps a lot of gas and un-burned kernels of R26 because they gave me the wrong twist rate and the bore feels a bit oversize as well.. its on its way back to be looked at.. but here was an interesting fiding

my previous barrel from the same maker would group .25-.35" groups at 54g and a 53.8-54.2 spread at 2 seating depths would group inside .5 so a very nice node at 3050fps... this new barrel is 150fps slower at that same powder load so something is off with the barrel.. any who..

the last range trip I decided after 50 rounds to shoot another velocity ladder x2 since nothing was grouping with this barrel and I didn't know it wasn't mfg right yet.. . one for velocity data from 53.5-56.5 which is normally over 200FPS spread... the results were bizarre talk about tuning device...


I fired some fouling rounds the first 3 grouped just around .5" and the next 3 were a diagonal string almost an inch.. not looking good

strapped on the bayonet and shot the first 7 round string, on the left target. shot 1 I didn't hold low with, forgot the shift, and 4 forgot as well.. the rest were shot holding 1 mil low at the center of the target, shift was right about .7mil .. but look at that group...

a 200 FPS spread and with the 2 shots superimposed back into the group by dropping them 1 mil.. I can cover 5 of the 7 shots with a quarter

the target on the right was the same loads and seating depths shot again with the bayonet off... its all over the place...

the barrel was allowed to cool fully between groups.. now some of that could be the barrel fouling since the powder is burning dirty .. no pressure seems to build with the wrong twist and possibly slightly oversize bore diameter.. also its melonited, a first for me on a precision barrel and that is supposed to be slicker but this barrel tends to slow down after some shots not speed up like most. again I am figuring its fouling but look at that group or lack thereof..

POA is the center of the target with no hold..

and you can see my optical crony struggling with the lighting conditions magneto speeds on the left optical on the right. on the right target optical only

 

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