How or why does a hummer barrel shoot better?

[savagedasher]

Thanks for all the help. I know my 7.53 twist shoot better at long range the my other 3 -8 twist does. All are chambered with less then .0003 chambers . They are timed up. The bores are pretty straight. I'm working with several slugs that are 2'' long with half inch bearing surface on each end .I will be able to check the vacuum loss all the way down the bore. With out knowing the vacuum loss I will never understand the bore size difference from back to front. Larry

 

[BoydAllen]

I know nothing about vacuum loss but I can tell you that you can feel things when slugging a barrel that you cannot see with an air gauge, not that I have any air gauging experience but this was asked of one of the top barrel makers. I have done a little slugging, and a friend has done more, and it is a seriously underused technique for evaluating the potential of barrels. The differences in dimension down the bore are largely the product of finish lapping.

 

[savagedasher]

It is just like using a flow bench for matching and checking the flow on cylinder heads. I feel I can do the bore in a gun barrel the same way. I have piloted the twist now I'm working on checking the bore changes. Larry

 

[SS427]

I'm no closer today in being able to eyeball and pick out a hummer barrel, but it sure was an interesting discussion.

Today at 200 and 300 yards my 6BR kicked my 6ppc in the butt. (Both shooting 68 grain bullets at similar velocity.) Swirling winds, and because of how they run this particular range you can't set up wind indicators. Normally the 6ppc shoots a little better than the 6BR, but today it didn't seem to have a clue where the point of impact was suppose to be. The 6BR seemed to ignore the wind.

I wouldn't claim I have a hummer on my 6BR, but clearly it handles the wind better.

 

[GerryM]

Imagine steel ingot about 16 inches wide and 3+ft long close to the melting point{white hot] Then think of the things that have to be done to it to make bar stock.
Its rolled squeezed etc until its one long long bar then its ground to get the slag off The it goes to heat treat where it drawn at a series of temperatures.
Now you have this bundle of rods 16ft or more banded together with plain old heavy wire, Next think or overhead cranes moving the rods around.
Once they get to heat treat they have a lot of bends and sets in them. They are placed on a cradle on a big ass box {drawer} by another crane.
The bars are twisted and a lot of stress in in them they are rolled into the furnace to be drawn at different temperatures then quenched in water or oil
after they are moved from that big over head crane. they twist again mainly the outside ones, The inside rods have less stress due to having some suppor tby the other rods.
That's where the straightest bars are with less stress. They can be relieved again in a different process , Conveyer barrel furnaces.
That's EXTRA cost While being moved from the mill it is put into storage or sold directly to a customer.
At the barrel shops they usually check the bars fro straightness and cut out any bends that exist. still there are stress in the bars due to shipping.
I believe that the hummers come from the bars that were in the middle of heat run. Less stress + easier to drill a straight hole and machine.
even after stress relieving most have stress except for a few center bars. I truly believe that's where the hummers come from

 

[Webster]

Maybe the barrel is the final swagging operation in making a bullet. Who knows what a 0.0001" or 0.00001" change in shape will do at 300,00 RPM.

 

[johara1]

I watched this thread progress and still nobody knows why they shoot through the wind mostly unaffected . I will tell you how i test for them and it is simple. Hold the same point of aim above your point of impact so not to ruin the point of aim. Have your wind flags up an when you get a blow from right or left shoot three at the wait for the wind to reverse and shoot three more,if you have a hole you got a hummer the smaller the hole the better it is. If they are strung out a little it maybe above average but if you get a weather report use it to fire forming.
The bullet is asleep when it leaves the muzzle thus it isn't affected by the wind as much as one that isn't as stable. Better minds have pondered over this for long time and can't reach a reason why they do what they do. So i don't worry about the why but how to test for one and know what it is with out wearing it playing with it…….. jim