Ram ringers

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jask
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Re: Ram ringers

Post by jask » Wed Feb 04, 2015 11:54 pm

Snake, that is a good point on the angle of impact but the splotches I've seen are pretty much round. Also higher velocity bullets would have less drop. One consideration might be jacket damage with the higher muzzle velocity. Jacket damage would give a lower BC and less energy at 500 m and more ringers. Would annealing the jackets make them more or less prone to damage? Does fast twist damage the jacket more?

Would this help with jacket damage?

http://www.bartleinbarrels.com/Trifling.htm

jask
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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 12:57 am


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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 10:43 am

[quote="with the 162 at 2600 lose rate was ~20% (shot alot at St Louis back then) after dropping velocity I logged 136 hits with 162s....rang 7. The Cauterucios? The man never made a bad bullet in my opinion...these were no different[/quote]

That is an interesting statement. A drop in velocity gets less ringers? Barrel stayed the same. Bullet stayed the same. Doesn't make sense unless you assume the extra velocity was damaging the bullet in some way that affected the impact velocity/force.

I find progressive twist rate intriguing to say the least. That would be the best way to have the least damage to a bullet jacket. When shooters are having custom 6.5's made, what twist are they using?

Does anyone know the twist rate for the factory 260? 9:1 or 10:1 or did they use both?

I see comments about using 1:8 twist. Just a thought but I think that twist would damage jackets.

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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 11:02 am

I had a Rem XP 100 chambered in 7 TCU 1:9 twist for my wife. I loaded the rams with Sierra 168 moly coated. It had about 2400 fps and didn't ring many rams. It stretched a few primer pockets on hot days so I kept the rounds in a cooler. I wonder if moly prevents some jacket damage? It had really mild recoil with lighter bullets and loads for the closer animals. I let her fire my original 308 at rams once and it almost knocked her over. That was the first and last time she fired my 308.

Hi Chad, nice to see you on here and the fact that you are still attending the nationals. And yes, I was really pleased that Charles won that scope. I attended two of the IMSSU matches, Finland and Australia. I would never again go to Australia for a match. Great country but horrible gun laws. They would not even let us check the rifles out of the armory unless the line was hot and the range conflicted with other ranges so it was always closed. Essentially zero practice and absolutely no time for dry fire. My wife just left and went to Cannes.

I retired 10 years ago and got some equipment for machining. If you need something made, let me know.

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Re: Ram ringers

Post by Snake » Thu Feb 05, 2015 12:01 pm

Jask---a) the shape of the splotch doesn't indicate much. there is no doubt that a bullet approaches a target at 500 m at a steeper incline than at 200m.
b) twist rate generally is commensurate with projectile length relative to diameter and form. You cannot over stabilize a bullet but you can increase centrifugal forces that stress jackets. c) jackets are extruded and certainly have integrity errors which vary in each production run....annealing should help but I'm wondering about the effects of 700 degrees on my bullets core d) a lower impact velocity sometimes means the bullet spends a split second longer pushing as its disintegrating and opposed to literally exploding and dissipating its energy across the target surface as opposed to against it. e) too much twist impedes velocity. The most accurate twists are those that 'just' stabilize...so the bench heads tell me

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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 1:09 pm

." The most accurate twists are those that 'just' stabilize...so the bench heads tell me"

Bench heads are just interested in holes in paper, not energy on a target. I think they know well how to make holes but not everything.

If a bullet is stabilized in roll, it would not be aligned to the relative wind. It is still pointed directly at the target but impacts at a downward rate that gravity imparts. If it is not stabilized, then we do not know how it impacts.

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Re: Ram ringers

Post by yankee » Thu Feb 05, 2015 2:04 pm

The old 6.5x55 mausers were 7.5 twist. Most of my 6.5's are 8 twist which will stabilize the 142 sierra. Remingtons early venture into the 260 was a 9 twist which was marginal on the 142 but usually worked with the 140 sierra mk. Steyer 8 twist, savage 8 twist, tikka 8 twist, sako 8 twist.
An interesting thought that follows your question on angle of impact. If the scope is a level line of sight to the target- the bullet is launched at a slightly upward pointing angle- does this angle continue to the target or does it break over to level then end up in a slightly downward angle as it reaches the target? Does it make any difference? Again, the old thoughts with the 308 was that the bullet point was hitting at a downward angle the point rolling over and pulling the bullet with it thus hitting not square on.
Gain twist barrels-- Just reviewing some thoughts the past couple days. As the bullet slams into the rifling of an 8 twist does it skid or slide a ways before it starts to rotate? Is that rough start disrupting the jacket to lead core bond? Or is it better to start out slow like 14 twist and take it to 8 near the end of the barrel? As the bullet travels down a gain twist barrel imagine the angle of the grove the rifling makes changing on the bullet jacket and disrupting the jacket to core bond or does the bullet change to what ever it is pressed into and it doesn't make a difference.
Kind of cool here this morning at 0. Maybe I should get out and quit thinking.

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Re: Ram ringers

Post by Snake » Thu Feb 05, 2015 2:15 pm

Bullets lacking stabilization do not travel true...generally witnessed by key-holing (if it gets that far)....the ubiquitous sign of the unstable projectile. The influence of wind is generally unaffected by the spin of a projectile...a yaw or divergence between center of moment and center of gravity cannot be 'stabilized' by twist or spin. Hence stable projectiles that have 'centers' coincident will make one hole...in theory and have a consistent and predictable reaction to winds. I'm all for one holer silhouette guns....and I have no idea what you suggest by 'not aligned to the relative wind' :-\
Last edited by Snake on Thu Feb 05, 2015 2:22 pm, edited 1 time in total.

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Re: Ram ringers

Post by Snake » Thu Feb 05, 2015 2:20 pm

Yankee----the 6.5 carcano that famously assassinated JKF is a gain twist. That concept rears its ugly head every so often. I think its pretty tough to have a bullet skid in that its swaged through a barrel.....now a cannon with driving bands..maybe :D

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Re: Ram ringers

Post by DennisC » Thu Feb 05, 2015 3:47 pm

Old article from Lilja on gain twist, down under pic of button couple of paragraphs:

http://www.riflebarrels.com/articles/ba ... curacy.htm

I can see their thinking with the service rifles, that's gotta be some awful stress on a jacket with a 1x7 twist and that long a bearing surface. I did read somewhere (Tubbs, Zedicker?) that recovered moly coated bullets showed less jacket distortion from the engraving of lands. I started coating bullets last year, primarily in hopes of getting a few more seasons out of my old barrels, didn't help scores any.

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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 9:48 pm

Dennis, I was shooting my hunter in both classes at matches with moly coated and I did not have cleaning problems. I found that to be the biggest advantage since the barrel did not get to the point of losing accuracy even after firing a hundred rounds or so.

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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 10:34 pm

Snake, from reading your post, I think you are saying that a bullet is continuously pointed in the direction of the arc it is traveling. That is what I am talking about when I said "relative wind". BTW, I flew airplanes for 50 years so I know a few things about aerodynamics. The bullets we use always remain above the transonic region of 1 to 1.2 mach so we never get into conventional aero. If a supersonic bullet is adequately stabilized, it continues to point down the line of sight of the barrel. It would not be pointed downward when impacting a target at 500 meters and the downward velocity component is so small as to the forward component that it can almost be ignored.

There would be some effects of spiral divergence if the bullet is not consistent in its manufacture but well made bullets should not have much spiral divergence.

As for bullets "skidding" upon entry into the rifling, there would be some degree of resistance to rotation but it would definitely cause stress on the jacket and between the jacket and the lead core. The faster it begins to rotate, the more stress on the jacket. Logic would tell us that an advantage would be in favor of gain twist barrels. Probably the biggest advantage would be the ability to increase the powder charge and have more energy on the ram.

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Re: Ram ringers

Post by jask » Thu Feb 05, 2015 10:44 pm

Dennis, I would agree that gain twist barrel would not gain much if any accuracy. That's why the paper shooters don't use them. Bench rest experts don't have a lock on the holy grail of all shooting disciplines.

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Re: Ram ringers

Post by Snake » Fri Feb 06, 2015 8:12 pm

Jask---I don't think I suggested what you seem to think I did. Bullet impact at 500 is at a steeper approach angle than the bullet impact at 200....no matter if supersonic or subsonic. Certainly the longer time of flight the greater the influence of wind. I suggest that a poorly aligned bullet to bore produces a divergence of center of moment and center of gravity. In a sense all bullets are skidding ...they are being swaged through the bore and that transition is fraught with friction, hence its skidding. Amy lateral skidding can only occur if there is some space between bullet and bore. Centrifugal forces will explode bullets if you push them fast enough and twist them rapidly.....do it all the time with my 17 cal....when I get a little too carried away :ymdevil:

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Re: Ram ringers

Post by dustinflint » Fri Feb 06, 2015 8:42 pm

I love it when we get all scientific! :-B

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