Originally Posted by toddc
My brake on my 7SAUM has 4 small ports on top. I threaded them all. Ended up with 3 plugged and 1 open for the most NEUTRAL shot. You could even run reducer bushings in 1 or several to further tune. I did this and also slightly cocked the side ports to counter twist in recoil with the longer bearin<script id="gpt-impl-0.6232750926957264" src="https://securepubads.g.doubleclick.net/gpt/pubads_impl_107.js"></script>g surfaces. I'm happy with my results.
That's probably the best way to fix this problem. We looked at other ways and to "Tune" the brake
threading one hole and using threaded bushings with different size holes was the best way.
Also to show how much effect the location had, we moved the ported bushing from the front hole to the back hole (4 top port holes) and there was a change in POI (the location appeared to effect the harmonics differently) accuracy seemed to be the best when the back hole (Nearest the receiver)was used for the top vent. This was probably due to the difference in the moment arm (Length)of the port to the receiver.
This led to the conclusion that if it made that much difference, We needed to compare the Tuned port brake to the same brake with all the top ports plugged for accuracy. Test showed that the brake with all the ports plugged shot the best group (More accurate even though it was very small).
This led us to the conclusion (At least with the test rifle)that the un opposed port, even though it resolved the muzzle rise/drop problem. was causing differences in the harmonics effecting accuracy and with the same loads and the same SDs and ESs. when all forces were in line with the bore, they seemed to have less negative effects.
I do feel that with good loads these effects can be negated/controlled to have little or no negative
effect on accuracy. Also keep in mind that the bullet is in the process on leaving the brake before any on these issues have much of a chance to cause issues with accuracy.
Neutralizing barrel flex has nothing but plus's for the bedding and the stock.
J E CUSTOM