Range Report Tubb Magnetospeed Mount - good results

[leftyk82]

I've been to the range multiple times with this setup and it's worked well, been repeatable and I can say I recommend it to others. I've owned the Wiser Precision version of this concept but never anything from MKM, though the idea is the same.

The measurement from the bayonet to the center-line of a 6.5mm bore is 1.125 inches. I've gotten consistent readings with the Sensitivity Setting at 9. I have only used it with the suppressor so I can't say what might change when used with a brake or bare muzzle. If I didn't tighten the screws down with a hex, the mount would walk due to the forces of recoil. But, once tight, everything stayed put.

Edited to add:
For those using the mount far away from the end of the steel rod, like shown below, I've found best results by keeping the large set screws loose while inverting the rifle with the muzzle towards the sky, holding the rod with your hand and positioning the mount in its correct alignment, then tightening the set screws. This will prevent the bayonet from acting like a fulcrum and pulling away from the center line of the bore if tightened on the horizontal plane like on bench.

If you are not using the full length of the rod, say on a shorter barrel, I don't see the above as an issue.

 

[bassmaster07]

Is it changing POI? They say that this type will not change POI but I have a hard time buying that.

 

[AIAW]

Is it changing POI? They say that this type will not change POI but I have a hard time buying that.

How would it affect POI? It's not touching the barrel in any fashion - which is why Tubb designed it this way.

 

[leftyk82]

No POI change.

Worth noting that I’m using a 24” barrel and a 7” can. So there is a good amount of length to use.

 

[ShtrRdy]

I thought the main POI change was due to the muzzle blast glancing off the blast shield on the bayonet and pushing the bullet.

 

[AIAW]

I thought the main POI change was due to the muzzle blast glancing off the blast shield on the bayonet and pushing the bullet.

Never personally heard of that happening. With the spacing the bullet would be well past the bayonet before the gas had time to alter trajectory.

No contest compared to having the bayonet strapped directly to the barrel though. I see POI changes with it directly attached to the barrel, but it is consistent. I use a LabRadar most of the time if it isn’t too windy.

 

[leftyk82]

Also haven't heard nor experienced that.

If I miss my target while my barrel and muzzle device/suppressor are still free floated without a fulcrum, it's my fault.

 

[ShtrRdy]

Several years ago a guy posted a target which showed POI when the Mag-speed bayonet was attached at 9 o'clock, 6 o'clock, 3 o'clock, and 12 o'clock positions. The POI moved opposite of the bayonet mounting position.

If you look at high speed video, the muzzle blast moves as fast as the bullet exiting the muzzle.

 

[DTubb]

The distance of the Magneto from the centerline of the bore is the key to consistency (lack of group deflection). Depending on the diameter of the bullet distances for full circle accurate measurements can vary from over .6 to 1.1". I am not as concerned about the gas blast as the bullet's frontal shock wave bouncing off the Magneto back into the body/tail of the bullet. Using a muzzle brake or a can retards gas blast issues. If the Magneto is set too far away from the bore the readings can be effected ( again bullet diameter dependent).

 

[ShtrRdy]

The distance of the Magneto from the centerline of the bore is the key to consistency (lack of group deflection). Depending on the diameter of the bullet distances for full circle accurate measurements can vary from over .6 to 1.1". I am not as concerned about the gas blast as the bullet's frontal shock wave bouncing off the Magneto back into the body/tail of the bullet. Using a muzzle brake or a can retards gas blast issues. If the Magneto is set too far away from the bore the readings can be effected ( again bullet diameter dependent).

I never thought about the bullets frontal shock wave bouncing off the Magneto and into the bullet. That's a good explanation.

I was recently measuring the velocity on some rounds and noticed better shot grouping when the Magneto was attached to the barrel. Does anyone know if I should increase powder charge or decrease powder charge to get better grouping with no Magneto?

 

[LawnMM]

In my experience the actual effect on group size is minimal and the effect on POI varies based on things Mr. Tubb mentioned.

I do like the mount though and I'm going to try one on my new chassis.