Want to speak with the most knowledgeable expert on Harmonics

[Larryh128]

I use a 208g A-max, (now ELD Match) bullet with 41.5 grains of Varget for long distance (loaded hot, not dialed in for accuracy) in my thin barreled Savage .308. About 2,430 fps. In testing with the same ammo, I got a 1-7/8 group out of 10 shots at 100 yards. (embarrassingly poor). At 215 yards it still shot 1-7/8". I moved out to about 500 yards and shot a 2-1/8 " group with 7 shots. I would like to try 1,000 yards but have no place close with the room. Harmonics? Bullet going to sleep? I want to repeat this with the Hornady ELD bullets which should be very close. Have to wait until the corn is harvested to get out to 500.

My main hunting rifle in 300 WSM groups about 3/4" at 100 with either a Berger or Barnes VLD. At 300 yds it's still 3/4". At 400yds about 1 1/4. We all like 1 hole groups at 100 but after initial sight in, I never shoot that close."

 

[tn6br]

Get ahold of Mike Ezell. He is a very competent gunsmith and knows a lot about barrel harmonics and tuner related questions.

@gunsandgunsmithing

 

[VaRandy]

For those that were really interested in my problem, I will try to make it clear with text.

I have a 65 lb .408 Wildcat built on an MacMillian 50 heavy stock that is weighted, Wearing a 36 inch barrel, the 1.4 inch barrel was heavy enough that it was recommended it be built with a V block up against the receiver. a 10 inch one was made to go across the 5 inch wide forearm.

Moving ahead to now, I am trying to lighten it considerably and change it to a more conventional Mac A-5 Super Mag that I has finally come in. Presumably, if I needed that V block on the original, I would still need it on the replacement. That would be ridiculous on a tactical this size, so what would happen if I put only a 1.5 inch band somewhere between 3-4 inches from the receiver. Likewise what would be the difference with two bands spread out evenly? Solid long V-Block versus one or more thin bands. Harmonics?

I need to have at least one out there to mount the front of a large external adjusted scope that requires 8.25 inches between the feet to get my desired click value. I also need to get the front sight even on plane with the rear which in on the integrated action.

Second question is value of the full V-Block versus bedding the barrel all the way to the end of the forearm. Without a block, wouldn't there be a force attempting to lift the heavy barrel AT the action.

Action is 1.5 inches, not 2.0. Not interested in shortening the barrel because I want to shoot with the 2 mile and more group of crazies out west!

 

[dcali]

If you constrain a rifle differently (as in use a full length V block vs pillars vs glue in or something else) you can expect the barrel to vibrate differently as a result. The greater the difference in stiffness of the various mounting options, the more it will matter. On a normal sized rifle, I would be surprised to see a dramatic difference between a v block and pillars. But maybe a little. But on a big one like that, it's possible that the compliance of hte stock factors in. I'm speculating here, if that's not clear. You'd really have to test to find out for sure.

Also, because the inertial loads that drive those vibrations are in large part determined by mass that is offset from the bore (scopes and stocks), you can expect significant differences from that as well. A rifle in a 20 pound stock isn't going to react the same way a rifle in a 10 pound stock.

In either case, it's hard to say which will be better. I know that's not terribly helpful, but it's about as good as you can get without spending a whole lot of effort testing and figuring.

It sounds like your problem is more a matter of how much strength you need to keep the rifle firmly attached to the stock. You can count on it messing with vibration if you change it, but you sort of need the thing to hold together, so you have to do what you have to do.

 

[Bart B.]

Readers may want to check out posts 14 and 15 in:

http://forum.accurateshooter.com/threads/predicting-transonic-stability.3862971/#post-37008199

Here's more info on Mann test barrels used by arsenals testing ammo;

http://www.odcmp.org/1001/mann_inc.asp

https://www.google.com/search?q=man...i=RGdSWbipH4qKjwSpw7OwDQ#imgrc=y4ROwtwtgYXZ7M:

 

[fgregorio]

Mate, if the stock is fibreglass, it won't have the rigidity to sustain consistently the bending moment between the band and the v block. I would suggest an alloy custom job with either a barrel clamp as the attachment of the barreled action to the stock, OR, a forend clamp in conjunction with the existing v block. If so you need a VERY rigid forend in an alloy stock. If it is all about dropping weight instead, I would flute the barrel and bolt. For these mods, I would add a barrel tuner as a means of controlling the barrel vibrations. I can elaborate on the vibration control if it helps you and if it fits in this thread

 

[simo hayha]

For those that were really interested in my problem, I will try to make it clear with text.

I have a 65 lb .408 Wildcat built on an MacMillian 50 heavy stock that is weighted, Wearing a 36 inch barrel, the 1.4 inch barrel was heavy enough that it was recommended it be built with a V block up against the receiver. a 10 inch one was made to go across the 5 inch wide forearm.

Moving ahead to now, I am trying to lighten it considerably and change it to a more conventional Mac A-5 Super Mag that I has finally come in. Presumably, if I needed that V block on the original, I would still need it on the replacement. That would be ridiculous on a tactical this size, so what would happen if I put only a 1.5 inch band somewhere between 3-4 inches from the receiver. Likewise what would be the difference with two bands spread out evenly? Solid long V-Block versus one or more thin bands. Harmonics?

I need to have at least one out there to mount the front of a large external adjusted scope that requires 8.25 inches between the feet to get my desired click value. I also need to get the front sight even on plane with the rear which in on the integrated action.

Second question is value of the full V-Block versus bedding the barrel all the way to the end of the forearm. Without a block, wouldn't there be a force attempting to lift the heavy barrel AT the action.

Action is 1.5 inches, not 2.0. Not interested in shortening the barrel because I want to shoot with the 2 mile and more group of crazies out west!

would you post pics?