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100 yard Bmag 15gr vs 25gr + barrel tuner

2K views 15 replies 8 participants last post by  nodak 
#1 · (Edited)
When I bought my Bmag I also purchased a rubber donut barrel tuner. It was only $9.00 and figured I would try it.



People that load center fire ammo are actually adjusting the loads which in turns adjusts the harmonics of the barrel. They trial and error until they find the right load for their gun. That load might not work as well on another gun of the same make that has slightly different harmonics. The idea is you want the nodal point of the wave to be at the end of the barrel. You can't see it so you trial and error to get the best groups.

The first time I took mine out I had the barrel band on but did not mess with it, just guessed. I put up some nice 20gr groups of 1/4" and .3". The second time out I had 20 mph winds and could not match that feat. like .5" to 1"

Today I wanted to test the new 15 gr ammo vs the 25 gr

25 gr - So so groups like .8" to 1.8" at 100 yards. Barrel band was at the end.
15 gr - A little better but like .8" to 1"

Then I pulled the band off the gun to see.
25 gr - maybe a little worse not a huge change
15 gr - worse 1.1" to 1.7"

Not very impressive shooting.

I decided to put the tuner back on and moved it in 4" from end.

15 gr Huge difference. All of a sudden it was easy to group, felt like a laser.
I shot 4 groups of 5
.29"
.32"
.33"
.55"

I have not bedded my stock. And my Bmag is probably not the great shooter as it looked from my first range results. It does not become the laser until I adjust the tuning doughnut. I did not attempt to get the 25 gr with more than one tuner setting, maybe next time. I think I'm going to stick with 20gr and 15gr for now.

If your Bmag is not getting less than 1" groups at 100 yards I would suggest giving this a try. You might be lucky at get one that does not need it or some have changed the harmonics by fooling with the action screw torque.

If you bed the gun torquing the action screws won't have the same effect, which is good if you don't want to worry about the tension changing the groups.

I'm sold on the tuner. I think with rim fires they are needed if you want to see what your gun can really do.

Here are some pics of todays groups.




 
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#6 · (Edited)
Great post. I've never tried one of these, but read about them for years. I hand load all my centerfire and you're right on.

Question: was your test on a sporter barrel or heavy barrel?

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A new Bmag with bull fluted barrel not the thin barrel. The stock is a non bedded boyd beavertail. It came with the gun, not an after market.

Here is the gun.. Scope 6-24x Athon FFP.

 
#7 ·
I’ve had one of these for years but never got around to testing it much. I kinda forgot I had it. If I remember correct they say place towards muzzle on free float barrel and towards receiver on non floated
 
#8 · (Edited)
I've had one of these for years but never got around to testing it much. I kinda forgot I had it. If I remember correct they say place towards muzzle on free float barrel and towards receiver on non floated
That is correct, I think that is just a rough guide. Really have to test it inch by inch. I've not tested every spot, seem to run out of time at the range. In a perfect world you don't need one, you happen to have a gun that matches the ammo well.
 
#10 ·
Potentially, yes.

The whole reason why these can have any affect on rimfires is because, unlike a centerfire, you can not taylor fit the ammo to the gun so if ammo changes from lot to lot the placement of one of these devices can vary well change too.

I think it's important to remember, one of these devices will never make a poor shooting barrel, shot well.
 
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