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barrel harmonics

29 Sep 2016
@ 06:19 am (GMT)

Brendon Greig

There was a post the other week about muzzle breaks which got me thinking about the affects of suppressors and muzzle breaks on the harmonics of the barrel I guess that in a simple way they must put some tension on the barrel when firing as they are catching expanding gasses exiting the barrel as well as the weight on the end of the barrel changing the vibration my rifle shoots about an inch and a half to the left with the suppressor on compared to without
This got me to wondering if there are any bullets that wont shoot with a suppressor/muzzle break but will without or vice versa due to the changes in harmonics affecting bullet travel down the barrel


29 Sep 2016
@ 12:41 pm (GMT)

Murray McGehan

Re: barrel harmonics
Brendon, Generally with can's groups will sometimes open up slightly and of course point of impact will change, sometimes quite dramatically. The point of Impact change is not really an issue as long as the amount of change is consistant and dialed into the scope to compensate.
With a properly installed muzzle brakes, generally the change in point of impact is a lot less than you see with cans, that is if you see any change at all. There are many rifles that have had brakes fitted and group size hasn't changed, some actually show improvements but this is more due to the shooter not being flinching because of the impending recoil.
The biggest disadvantage of brakes are the extra barrel length and the increase in noise.
29 Sep 2016
@ 08:27 pm (GMT)

Nathan Foster

Re: barrel harmonics
Yes, tricky business because people will often mix up human error with harmonics.

At the worst, I have seen POI shifts of several inches at 100 yards without human error. So in this case, we see some major changes in harmonics. And yet when performing load development, the load that worked best without the can, also worked well with the can.

I have seen suppressor manufacturers make claims that a suppressor can correct harmonic ills, but I have not seen this fully play out, not in a consistent way. But I have seen cans compensate for poor shooting technique. They can also help overcome poor bedding to a smaller extent as less torque is placed on the action. But adding one variable to fix another is not exactly ideal. That said, it can be useful if the rifle is of a less than optimal (for accuracy) design, such as featuring a two piece stock.

Again, its very hard to say whether outcomes will be good, bad or no change. Murray stated he has seen increases in group sizes. This can be caused by trapped heat, making the barrel more malleable and prone to increased whip.

It would be more correct to say that suppressor may have an effect on harmonics, but that we should not assume that this effect is always positive. It may go either way. However, a suppressor can help compensate for human error.

The suppressor bore diameter and concentricity will also have an effect.

Collet tension / fit is yet another major factor. I once worked up a good load for a rifle without a can, checked it with the over-barrel can and all was well (group same size but different POI). I was about to give the rifle back to the client but a news report came through about a cop with a loose suppressor who hit the wrong guy. So I went back to the range, loosened the unit a half turn and my group shifted 6" to 1 O'clock. So here we see some major harmonic influence.

Brakes are different again. I often see what you might call a transferal. Mechanically, we again see "a change" which could be good or bad or neurtal. As for human error, a shooter may claim that his rifle kicks far less, but if you watch his body closely, he may actually flinch quite badly from the concussion slap to the face. This is were we see a transferal, removing a problem from one area but creating a new problem. The effect on the shooter is vastly dependent on the actual brake design which goes back into the post you initially mentioned.

As we increase the power of a cartridge in an un-braked or un-suppressed rifle, there comes a point where human error becomes ever more evident. The slightest (micro) change in body position and tension may send shots off by 1 to 3" at 100 yards. We simply cannot manage this level of recoil with absolute repeatability. We may also be suffering concussion after several shots if chasing extreme accuracy. At this recoil level we have little choice but to adopt a can or brake. Once fitted, not only is the shooter relieved of excessive force, but also the action and stock.
30 Sep 2016
@ 07:18 am (GMT)

Brendon Greig

Re: barrel harmonics
Thanks Nathan have been thinking about this for a while so thought I'd post it for comments cheers


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