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tcoz

MagnetoSpeed's effect on POI

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One topic that always comes up when discussing the MagnetoSpeed is whether it has an effect and if so, how much on POI.  Most people don’t use it when they’re shooting groups but I want to share my experience from yesterday.  The 100 yard target was shot with the MagnetoSpeed attached and the 200 yard target was without.  The only change I made when going to 200 yards was dialing my scope up .4MIL which is exactly what my ballistic table called for after inputting the velocity determined by shooting the 100 yard target.  

 

The rifle is a Ruger Precision .308 and powder charge was 43.5gr of IMR4064 with a base to ogive length of 2.230 (.020 jump).

Obviously these results are for my rifle only and and yours may differ based on barrel harmonics but I wanted to illustrate that while the MagnetoSpeed May affect POI, it doesn’t always do so.

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ChuckS, at 100 yards group size (extreme spread) in inches and MOA is the same.  At 200 yards group size in MOA is half what it is in inches.

Edited by tcoz

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< a little thread drift>

 

I have used 1 MOA = 1" at 100 yards forever. But, being of unsound mind, when I see numbers agreeing to 3 decimal points, I get suspicious.

Solving backwards from your extreme spread, the only distance where 1.172" = 1.172 MOA is 95.493 yards... :D

 

< /a little thread drift>

 

 

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ChuckS, don’t overthink this.  I inputted 100 yards as target distance and the Bullseye Camera System calculated MOA from the targets.  For all I know the distance could be 95 yards or it could be 105 yards.

 

The purpose if the post was to illustrate that it isn’t a given that the MagnetoSpred chronograph will affect POI.

 

As you said, a little thread drift...:)

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I made a rail adapter for less than $40. Worked perfectly and never got an error reading in the 20+ rounds during load development.  And the beauty was no poi shift

20191001_215424.jpg

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On 1/10/2018 at 1:22 PM, ChuckS said:

< a little thread drift>

 

I have used 1 MOA = 1" at 100 yards forever. But, being of unsound mind, when I see numbers agreeing to 3 decimal points, I get suspicious.

Solving backwards from your extreme spread, the only distance where 1.172" = 1.172 MOA is 95.493 yards... :D

 

< /a little thread drift>

 

 

 

You are correct. No point in measuring to 3 decimal places if you're using 1"=1 moa. At 100 yards, 1.047" = 1.000 MOA. Doesn't matter for the point of the thread, but it's a valid point about that Bullseye software.

 

 

tcoz, it might be true that your rifle doesn't change POI very much with the magnetospeed, but it does change for a lot of other rifles. It's mostly about barrel stiffness vs weight of whatever you attach to it; same thing applies to mounting a suppressor, you should expect POI to drop. 

 

Look at the difference in group size though; if we're to consider the 5 round groups as valid, adding the magnetospeed approximately tripled your group MOA size. That's one reason most accuracy nuts don't like to work up loads with one of these attached to the barrel. 

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18 hours ago, jcarpenter82 said:

I made a rail adapter for less than $40. Worked perfectly and never got an error reading in the 20+ rounds during load development.  And the beauty was no poi shift

20191001_215424.jpg

Be curious about details on your rail mount adapter.

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6 hours ago, caspian guy said:

Be curious about details on your rail mount adapter.

Bought a qd rail adapter off Amazon for $5, heavy duty camera articulating arm for $25, 3" round aluminum barstock for $3. Drill and tap adapter and barstock so articulating arms can screw into. Drill through barstock and matching holes in magnetospeed, and finally attach. 

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10 hours ago, jcarpenter82 said:

Bought a qd rail adapter off Amazon for $5, heavy duty camera articulating arm for $25, 3" round aluminum barstock for $3. Drill and tap adapter and barstock so articulating arms can screw into. Drill through barstock and matching holes in magnetospeed, and finally attach. 

Thanks for sharing it. I like to chrono every shot during load development, and having the thing hanging on the barrel always stopped me from going down this path.  It's a neat solution to the problem I'll have to build something similar.

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21 minutes ago, caspian guy said:

Thanks for sharing it. I like to chrono every shot during load development, and having the thing hanging on the barrel always stopped me from going down this path.  It's a neat solution to the problem I'll have to build something similar.

There is 2 kinds of camera arms on amazon, this one is more rigid than the other

 

https://www.amazon.com/gp/aw/d/B06VYCVVVJ?psc=1&ref=ppx_pop_mob_b_asin_title

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I know this is an old thread but MK Machining has an adapter to take the mounting off the barrel and mounting with a rod that is attached to the forearm.  It attaches to a picatinny rail.

They run about $150.  Majority of my rifles are bolt guns so I am going to have to add a rail to the forearm.  There or a coupe of other ones out there.

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