Zen Archery
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- Dec 27, 2012
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I wasn't planning on shooting a coyote at 530,000 RPM's but now inquiring mines wants to know
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Super Fast Twist Barrels for Hammer Bullets
- Thread starter nksmfamjp
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You will notice the difference!I wasn't planning on shooting a coyote at 530,000 RPM's but now inquiring mines wants to know
The best School there is. The guy who pushes a button and watches a multi axis machine center... is a bit limited. His input is limited. You obviously are not limited. Even if you don't have pages of measurements, measured trends, failure modes will start to paint a picture (ugly) but will help lead to a clear measurable picture. What I note is your shooters seem to be pretty successful... No big issues. Your continued success while "maybe" not a measured statistic is certainly a trend measurable if it were plotted. Hard to ignore that trend.
We were recently told our barrels don't work by a very respected facility. They have never shot one or ever will. They note that barrel harmonics don't effect accuracy. That our successful shooters ( "I am sure they are good shooters but..") don't have data to counter theirs. Where the term "anecdotal" arose. Harmonics is "old school thinking, vibration of a barrel won't have 1fps effect on speed (variable geometry cutters ?? I guess are a fluke too), group size, group placement"
... but I have faith in our shooters/clients and the anecdotal evidence is very very high. I at this moment don't care what the experts are saying I am watching the trends...
It seems the implication is that other than twist rate, assuming good inner dimensions, a barrel has nothing to do with accuracy. (A bit of stirring the pot- )
If I may ask- grooving of the bullet - material has a high impact on the consistency of the groove event and its repeatability. You must work to a specific source and material grade. Toot your horn.
Of course you might come back and say "material" has nothing to do with bullet performance...
We were recently told our barrels don't work by a very respected facility. They have never shot one or ever will. They note that barrel harmonics don't effect accuracy. That our successful shooters ( "I am sure they are good shooters but..") don't have data to counter theirs. Where the term "anecdotal" arose. Harmonics is "old school thinking, vibration of a barrel won't have 1fps effect on speed (variable geometry cutters ?? I guess are a fluke too), group size, group placement"
... but I have faith in our shooters/clients and the anecdotal evidence is very very high. I at this moment don't care what the experts are saying I am watching the trends...
It seems the implication is that other than twist rate, assuming good inner dimensions, a barrel has nothing to do with accuracy. (A bit of stirring the pot- )
If I may ask- grooving of the bullet - material has a high impact on the consistency of the groove event and its repeatability. You must work to a specific source and material grade. Toot your horn.
Of course you might come back and say "material" has nothing to do with bullet performance...
HARPERC
Well-Known Member
Im certain he won't say that , but I'll let him answer
As I said earlier and I know it sounds crazy but I could feel the twist fighting the bullet the harder I pushed, I was severely disappointed in my mistake and I know for a fact that the material that is sourced by Hammers has a ton to do with it
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RockyMtnMT
Official LRH Sponsor
We do have very specific raw material that we work with. It is very essential to terminal performance. Ballistically the material is not so consequential, terminal performance is very much influenced by material.
Following
Minor counters- no arguments:
I would agree ballistically a shape is a shape.
The question for me is to get the solid down the barrel 40-50 times without significant accuracy degradation (F1, PRS, Mil).
Lead is basically 1/2 the hardness of brass or copper. At room temp. At 500deg I would say it might be 1/8 as hard.
I would say that a copper jacketed lead conforms to the barrel.
Brass seems to act a bit like a button. It does not seem to conform but "wipes" to the nearest relief (observed in retrieved bullets) or off onto the boat tail. Edges to the grooving are like a hoe pulled thru soil- high edges are formed. Either to remain or wipe into the barrel. Barrels accuracy appears to reduce at a dramatically faster rate than copper jackets. They also appear to be harder to clean from the barrel.
Don't get me wrong... I believe in solids... and your success is outstanding. Outside of a precise shot- a fast kill should be a primary goal. Pencil holes aren't it. If your rounds are ever expected to go beyond 40shots- its godzilla.
My thought is a 5kfps round will not be a copper jacket bullet-- 200gr or more category. Solids have to be researched.
Perhaps it is time to run a small caliber test first- 6mm or 6.5- 50 rounds of copper jacket, retrieve the rounds and weigh them. 50 rounds of a solid- and repeat. We have retrieved a bunch of solids - at final velocities of <600fps in sand things stay pretty intact. Rather do water.
I believe the barrel interaction with the solid has several impacts on its success- including BC down range, maybe a bit further than a typical hunt LOL. However I think 55kpsi will "skid" a bunch of things.
We did a recent 300BO test: testing 4bullets, 4mfgs, and four different bullet weights starting at 16". Cut one inch, bevel the bore and shoot 4rounds each over a LabRadar. The fps dropped much slower than expected. Powder burn became the big issue/failure. We tested down to 7". Point being a huge amount of work is being done in the first 7-10 inches (this example). A potential is during the initial engagement of the lands, if the round is crooked - it remains crooked. Of course if it is crooked its area of contact is now greater than the base diameter of the bullet- where is the extra material going... deforming or in the barrel as a "wiped" component.
As a note on the 300BO - the heavier rounds are much more dependable than light grain rounds (gas gun). The heavy round seems to "force/effect" the burn rates during its initial acceleration event. Light rounds failed as the test progressed- which would, I believe, have an effect in cold weather.
RockyMtnMT
Official LRH Sponsor
Between our design with the PDR radius drive bands and the copper that we use, we see less copper fouling than jacketed bullets. We rarely see any copper fouling, even in new factory barrels.
Less copper fouling- music to my eyes and ears.
Then its time to make an order. We demo five main platforms: 6xc, 6.5CM, .260Rem, .300Norma and 33xc.
What is a target bore diameter for the cartridges listed?
We will have barrels built to that with a minimum of 4T of gain.
6mm -- 10.5t to 7.0t in one barrel length-- gas gun specific.
6.5 -- 11.7 to 7.5t in one barrel length -- gas gun and or bolt gun. I have a standard gas running copper leads with a standard 7.5t. This could go either 6.5PRC or another gas gun for direct comparison.
308cak -- 12-8 in one barrel length-- we already have this barrel on a 300WM-- bolt guns. A 300Norma or PRC.
338 cal 13-9 in one barrel length-- being chambered. -- bolt guns.
Please tweak and provide recommendations.
What barrel combo would you like to see?
Do you see twist rate directly linear to speed? (2500m and less)
Thanks
RockyMtnMT
Official LRH Sponsor
We cut our bullets 5 ten thou over caliber. We are able to to this without causing pressure issues in tight bore barrels because of the PDR radius bands. Run a standard bore diameter. Other than @ButterBean not being able to get the 5k fps he wanted in his fast twist I can't say that we have seen any significant decline in velocity from faster twist. Maybe 20-30 fps for 2" faster. This is low enough to be the difference from one barrel to another regardless of twist. We have never worked with a barrel that has the kind of gain you are using or gas guns.
I agree, I was pushing really hard
Devils in the detail- and same language of communication.
.308 cal: you produce .3085.
Land diameter .300
Tolerance or running mean value?
Would you rather have an error towards the plus side or minus side of the .308 target?
The velocity question: slower twist values have the potential of faster speeds as less work is being performed. To your point maybe inconsequential.
