Simple question on tension barrels,

Joel, the only reason Jeff and i are a little "fixed" on this wall consistantcy thing is because somewhere along the line we have come to believe that tension, or rather compression, can place an unwanted bend in the setup. Thin side compresses more than the thick side, thus tilting the muzzle off a little that then can be somewhat changed during the barrel heating and heat transfer stage. We don't know for sure if this may or may not happen, but we have a furmula that has brought many more successes than failures, so we stick to it. One day Jeff or i may put in a tube that we have currently that has 30 thou eccentricity, and trial it to see if we are just blowing hot air about this.
When we assemble we have done it as you have, horizontally, relying on the collars and nuts to centralise everything.

Tony Z.
 
I can see your point if the tube has a thinner section the full length. The thin side would definitely compress more. I have seen point of impact shifts with a tube setup before and wondered why since everything was machined very meticulously. Maybe it was the tube itself. That would be a good test though to take a known rejected tube and see what the results are. Thanks
 
Tubes

Hi All, My initial tests before i built the 1st gun proved to me that the wall thickness was important to the muzzle movement when heat was applied (barrelled action set up on the mill bed with X&Y dail indicators)...Also the material that was thicker on one side than the other vibrated in a different way when rung(especially the stuff with a seam).. With this info in hand i have always got the most concentric wall thickness i can find..I just glad the boys at the alloy supply shop put up with me when i go over there with the ultrasonic tester and pull all the stuff out of the rack..JR..Jeff Rogers..ps . i have never found any of the (ET-GTD) Drawn tube to be any good in the walls compared to the (ET-GTE) Extruded stuff..
 
Jeff,

Hmm. My first "big tube" that I got from Charles Bailey was extruded, 3-inch s.s. pipe. It shot OK, but was always a "second place" gun (there could be several reasons for that), with more than one barrel. I though one reason might be because so much metal had to be taken off to true up the outside, it was that bad. Recipe for uneven wall thickness.

My latest big tube is drawn-over-mandril 6061 T-6 aluminum with a .75-inch wall thickness. If I ever get a rifle built on it, we shall see.

I would guess that the most consistent wall thickness is more of an issue with the thin-wall tubing we use in Light Gun. Is that your feeling? Joel & I have been sort of locked into having the tubing shipped & pretty much have to take what comes.

Edit:

with the smaller tubing, I had pretty good success with welded stainless tubing, which would have even walls, but that weld would, you'd think, have an effect.
 
Hi Charles, I think your right about the Big tubes ..The set up we use is nothing more than a slightly larger Light Gun set up , mabye this is where the wall thickness comes into play,but i don't know as i have selected the best tube from the get go.. I am doing a L/G soon it will use 1.500 od with .125 wall 6061t6 extruded , i will fit a Krieger #19 hunter profile in 15 twist 30 cal .. In selecting the tube i'll get a bad piece at the same time ,with as much difference in the wall as i can find ,test the two side by side ..Keep you and joel posted as usual..JR..Jeff Rogers
Charles E said:
Jeff,

Hmm. My first "big tube" that I got from Charles Bailey was extruded, 3-inch s.s. pipe. It shot OK, but was always a "second place" gun (there could be several reasons for that), with more than one barrel. I though one reason might be because so much metal had to be taken off to true up the outside, it was that bad. Recipe for uneven wall thickness.

My latest big tube is drawn-over-mandril 6061 T-6 aluminum with a .75-inch wall thickness. If I ever get a rifle built on it, we shall see.

I would guess that the most consistent wall thickness is more of an issue with the thin-wall tubing we use in Light Gun. Is that your feeling? Joel & I have been sort of locked into having the tubing shipped & pretty much have to take what comes.

Edit:

with the smaller tubing, I had pretty good success with welded stainless tubing, which would have even walls, but that weld would, you'd think, have an effect.
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JR,

What bullets in the 15 twist. Is Randy making you some lighter BIBS?

Thanks,
Joel
 
bullets!

Hi Joel ,RG has OK'd the 15 twist with his 1.150 jacketed 165s..I was hopeing to talk him into making this 160/162 but as yet i have not asked..His estimate was about .480 real world Bc,if i can get these to approx 3150 in the RWS 270w case it will not be ugly in regards to wind ..Then if i ever get my finger out and make my own bullet then the BC should be a little better because of the 11 ogive that we settled on .. That said the BIBs are the benchmark ,for sure ,to judge our efforts on..JR..Jeff Rogers
J. Pendergraft said:
JR,

What bullets in the 15 twist. Is Randy making you some lighter BIBS?

Thanks,
Joel
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