A small tuner test

[Hi-NV Shooter]

Taking the Positive compensation at face value. 100% Positive Compensation is not achievable.
you can achieve partial PC and get slow and fast rounds to be close to same POI. but you will never get them to be same POI every time.

tuning as far as RF are about bullet exit timing. weight forward of the crown is used to speed up or slow down the bullet's exit. you want the bullet exit's so POI will be at the highest point. if you don't know the natural exit height the barrel will produce with no tuner you will never know if your tuner settings are causing POI to be below that height. you never want it to be below.

Lee

 

[Matt_3479]

Taking the Positive compensation at face value. 100% Positive Compensation is not achievable.
you can achieve partial PC and get slow and fast rounds to be close to same POI. but you will never get them to be same POI every time.

tuning as far as RF are about bullet exit timing. weight forward of the crown is used to speed up or slow down the bullet's exit. you want the bullet exit's so POI will be at the highest point. if you don't know the natural exit height the barrel will produce with no tuner you will never know if your tuner settings are causing POI to be below that height. you never want it to be below.

Lee

Hey Lee,

What’s the reason you want it at the highest poi?

So at 200 yards. Shoot without tuner. Mark the POI, then move the tuner until you find a tune that also has a higher poi.

 

[Hi-NV Shooter]

Hey Lee,

What’s the reason you want it at the highest poi?

So at 200 yards. Shoot without tuner. Mark the POI, then move the tuner until you find a tune that also has a higher poi.

Matt, If you are talking about a rimfire I would say it would be very challenging to get any consistent result at 200 yards. to even know if you are at the highest POI. IME tuned at 50 and then it is all about ammo performance. granted I have only shot at 100 yds.

As to why you want the POI to be at the highest point. again, going back to bullet exit timing. since the barrel is moving upward it has to reach a point where it will stop and start to go down. this point of transitioning is the most predictable(stable) exit point for the bullets to exit the barrel.
there is more formal terminology to describe this reasoning with sine waves and such. but for me this is the easiest way to explain why highest POI what you are want.

Lee

 

[gunsandgunsmithing]

First thing that is needed is a understanding of barrel harmonics and what a tuner does.

a 30 minute video on harmonics

Overall, a very good video. One thing he seemed to imply more than once that I don't agree with is he seems to say that moving a node to the end of the bbl gives best accuracy. A little physics though...you can't move a node to the end of a cantilevered beam, unless you have something attached to the end, ie a brake or a tuner that extends beyond the muzzle. BUT, we all know that guns can be tuned to shoot just as well without anything at the end or with a behind the muzzle tuner. So, what's happening is we are timing bullet exit to happen at the anti-nodes. He mentions them as the place of maximum muzzle displacement, which is true. This is pretty much the basis for my sine wave test. You literally see the poi move to top and bottom and coincide with a sweet spot at that point.

The other thing is not in the video but was mentioned by another poster too is positive compensation as being "how tuners work". Well, again, guns can shoot without tuners or with them, so I do believe in pc but that it's more of a side benefit of an adjustable mass at the muzzle vs "how" they work. A lot more goes into pc than simply screwing a tuner on. So, I don't hang my hat on pc as the goal but I do like to tune to the top of the sine wave when possible because of pc. I want very readable, predictable and repeatable group shapes more than anything else because any adjustments to the tuner are based on that. If you want the best accuracy, good loading techniques are still critical but yes a tuner can help with small velocity variations if you're tuned to the top, where pc is possible to achieve at least some of. I don't think we can get 100% of pc or if we could, our guns would be very drastically different in regard to shape and center of gravity in relation the the centerline of the bore.

Jim, thanks for posting that video though. It breaks things down pretty simply, so we can understand the basics pretty easily, of why tuners work. It gives enough to get people to think it through but not so much that it confuses. Many are only concerned in how to use one more so than why they work, but there are both schools of thought and it can only help to better understand what's going on.

As for tuner testing at longer yardages, I look at it simply like this. Yes, if you go from say 100 to 200 yards, the tune will be worth double as at 100 but the kicker is that wind is worth more like 4 times as much as it was at 100. The easiest way imho is to do initial testing at 100 on cf rifles, then confirm or make a small adjutment for longer range, if needed. Yes, pc is yardage dependent. But again, IMO, pc is only a part of tuning

 

[bsekf]

Most of the information above is "above my pay grade". Have been using Harrell's brakes and have been very happy....they work! Is the Harrell's tuner worth a serious look?

 

[JimSC]

Most of the information above is "above my pay grade". Have been using Harrell's brakes and have been very happy....they work! Is the Harrell's tuner worth a serious look?

I have 2 Harrel's and a Ezell , the one in this post is a reworked Harrels, some of the outer aluminum taken off to reduce weight and a unmodified Harrel on my Kidd semi auto. Both work for me

All a tuner does is allow you to move a weight back and forth on a barrel. In my opinion as long as you can repeat the setting and it does not move when attached and set is the key, to me the brand seems irrelevant. Perhaps the weight of the tuner itself comes into play, I am sure others will weigh in on that. My Ezell is on a F class .308 and does not seem to weigh anymore than the Harrels and works on the same principle. You screw a weight in or out and lock it with a setscrew, simple and effective

 

[grauhanen]

So which is it that explains how a tuner works -- the positive compensation theory that was linked in post #10 or the "stopped muzzle" theory offered in the video in post #18? Can it be both at the same time?

 

[Beiruty]

For 22LR, a tuner may work wonderfully, on other calibers maybe not. Why?
Consider Muzzle Energy vs rifle weight, or felt recoil. The rifle would have the barrel recoil before the bullet exit the barrel is virtually 0, that Positive compensation would work.
On high Muzzle Energy and low weight rifle, save your money.

Here is my test:

 

[JimSC]

looks like I will have to dust off my .308

 

[gunsandgunsmithing]

So which is it that explains how a tuner works -- the positive compensation theory that was linked in post #10 or the "stopped muzzle" theory offered in the video in post #18? Can it be both at the same time?

Tuners work by altering phase time. PC is a different but related subject with many more variables to it than simply hanging a weight from the bbl. As I said before, guns can shoot great with or without a tuner. How is that possible if PC is how they work?

 

[grauhanen]

Tuners work by altering phase time. PC is a different but related subject with many more variables to it than simply hanging a weight from the bbl. As I said before, guns can shoot great with or without a tuner. How is that possible if PC is how they work?

Rifles can indeed shoot well without a tuner. Of course it can be noted that, while it doesn't necessarily make an argument for PC (or simply hanging a weight from the barrel), RFBR rifles shoot better with tuners than without.

Can you elaborate on "altering phase time"? It's a term not used by Kolbe or in the Varmint Al explanations of tuners.

 

[gunsandgunsmithing]

Rifles can indeed shoot well without a tuner. Of course it can be noted that, while it doesn't necessarily make an argument for PC (or simply hanging a weight from the barrel), RFBR rifles shoot better with tuners than without.

Can you elaborate on "altering phase time"? It's a term not used by Kolbe or in the Varmint Al explanations of tuners.

In simple terms, shifting phase time is just moving the top or bottom of a single waveform either left or right, to coincide with bullet exit, in the case of tuners. This is exactly why such small adjustments matter so much and why there are multiple sweet spots, often more than one in a single revolution of the tuner. If you move too far at a time...the single most common mistake with tuners, you may well skip over sweet spots and never realize them.

 

[Shooter13]

Most of the information above is "above my pay grade". Have been using Harrell's brakes and have been very happy....they work! Is the Harrell's tuner worth a serious look?

I've only used 2 tuners, one is from @gunsandgunsmithing Ezell tuners, I found it to be the simplest and easiest to learn what I'm doing (along with a lot of help from Mike) so it might be work a look!

 

[CharlieNC]

Rifles can indeed shoot well without a tuner. Of course it can be noted that, while it doesn't necessarily make an argument for PC (or simply hanging a weight from the barrel), RFBR rifles shoot better with tuners than without.

Can you elaborate on "altering phase time"? It's a term not used by Kolbe or in the Varmint Al explanations of tuners.

Look at Kolbe's vibration charts where he shows the addition of a tuner shifts the bullet exit point to the rising section of the vibration cycle. While that curve exhibits little differences in frequency or amplitude, he uses this to explain positive compensation as the mechanism. He did not specifically discuss the "how" but the charts clearly demonstrate a phase shift in exit time as the reason.

 

[grauhanen]

Thanks, Mike and Charlie. The explanations offered help advance my understanding.

As an aside, I have to admit to confusion when many use PC to explain why tuners do what they do, while others say that it's not PC at all because their tuners need no further adjustment when they switch from 50 to 100. Perhaps it's a function of their rifles simply shooting well enough that tuners don't matter as much at longer distances. After all, it can't be nearly as straightforward to tune a rifle at 100 as it may be at 50.