Erik,
Please point out the word popularity or a Derivative from this post. I'll help you out, and "bold" every word even starting with P in it. You can't find that word of inference to it. Plain and simple.. "misreprenting" it would, in all honesty, be to say it means popularity, when the word doesn't occur in context or fact.

Then please review this post for context, which is twist, stability, and penetration. Then please review the post Dan is "correcting" me upon, where I stated the 577 nitro is the king of penetration.

While I do have a gold metal in stirring the pot, misunderstanding this post, isn't a case of that.

quote:

Originally posted by 500grains:

quote:

Originally posted by jeffeosso:

Dan,
you are welcome to your opinion, of course, but I must also state that too fast a twist is worthless at best, and determental to a rounds performance at worst. TOO much pressure is that, too MUCH.. and there's no point.

I am not talking about too much twist - just enough to keep the bullet well stabilized both in air and in a heavy boned animal. I am talking 1:10 instead of 1:18.

If the rounds are loaded so hot that a change in twist to 1:10 makes them dangerous, then the problem is in the loads, not the twist.

May I remind folks about 1:7 and 1:8 AR-15 barrels? What happened with the 1:14 barrels? The bullets were stable to 100 yards, but tumbled down range, or tumbled in flesh. It is the same principle here.

quote:

What twist was that 470 NE you did penetration tests with?

I have not performed penetration tests with the 470 NE. Keep in mind that with the old 1:20 twist the 470 NE had only an ok reputation. It is only lately, with Federal making ammo, that the 470 NE became king of the hill.

Dave,
you are right.. what does it matter past a couple FEET of depth?

quote:

Originally posted by 470 Mbogo:
You know all this twist rate may be a moot point as all my rifles from 1:14 to 1:10 keep tipping things over. Penetration has never really been a problem. Bullets have been the bigger problem but with the high quality of bullets a person has to choose from it isn't much of a problem either. Solids have improved tremendously so that's no longer a real problem. Lets just shoot and have a good time and quite picking fly shit out of pepper.
Take good care,
Dave

Thanks Dave,
you are right.. but I wait with baited breath for Rip's results... will be interesting to see if there's any measurable difference...

Nose shape and speed certainly seem to have more effect than twist, once the bullet is stable.

jeffe

Jeff,

This is as bad as the thread where you kept criticizing the photos of a lady with a fantastic leopard.

Jeffe,

Since you have mentioned the 1-14 twist .223 (M193 5.56mm)several times, I should point out that when the M16 still had a prong type flash supressor and was adopted by the air force for use in guarding air bases in the early 60's it did in fact have a 1-14 inch twist.

I knew the late Gene Stoner quite well as the small arms correspondant for Janes Defense weeklies monthly magazine, International Defense Review for 17 years, and since he enjoyed the royalties from all M16 sales for the next 40 plus years, he told me little details like this. (He flew a Gulf Stream personal jet). Quite a guy.

Anyway, the 1-14 was stable in air with M193 out to 500 yards or more. The problem w stability was when it was tested in Alaska, in very cold weather, and that is why the twist was changed to 1-12 when it became type qualified as M16A1.

This just goes to show you that testing a rifle in expected conditions is a good idea, and that is why so many of us prefer a slightly faster than normal twist. We have tested them. And the benefit is measurable both in artifical test mediums and on game.

Andy

quote:

Nose shape and speed certainly seem to have more effect than twist, once the bullet is stable.

In my tests the 458 winchester averaged 58 1/2 boards with the 500 grain Hornady FMJ-RN using the long barreled BRNO 602 and two diffeent kinds of ammo including the very hot Federal.

Changing from a 1-14 to 1-10 twist increased penetration to 62 boards with no increase in velocity or recoil!

That is one more board penetration than a standard 375 H and H with Hornady FMJ-RN.

So you can take the marginaly respected 458 and move it up into the well repsected 375 for penetration just by using a faster twist!

(My PH Myles McCallum believes the 375 to have more penetration than just about any other rifle with FMJs, and hes seen alot of elephants killed at close range).

So this probably is a significant achievement.

Andy

Andy,
I didn't bring up the 223 issue, or the associated changes in ammo that predicated the rapid twist change, sorry. That is, when changed to 1x7 for the heavier nato ball. I wasn't aware of an intermediate twist change to 1x12... though, to be fair, blackguns aren't my area of interest.

Neat results on the 458... Can't wait to see rip's results on the .50s.. My results, (remember, i built some rifles a decade ago to test pressure) on the pressure end of things, point that the slower the twist, at a given velocity, the lower the pressure.

Since africa is generally the target environment where penetration past 2 feet would matter, I think the lowest pressure possible to achieve X velocity is the best path, within reason... of course a smooth bore would go faster (chuckle) but stabilitiy would tend to fall off...

Would be interesting to see the the penetration comparison from a 4581x10 at 2130 vs a 458 lott at 2300 1x14 ... wanna bet the lott at 14 still out penetrates the 458 at 10, given spec velocity?

jeffe

Andy- Nice posts and I appreciate your results and sharing them with us. I would like to humbly suggest though that you take some of your bullets, run them through a bullet spinner i.e "Junke Machine". Developed by Vern Junke for the rest of the "EXPERTS" here to identify bullets with non- obvious concentricty issues and repeat your penetration tests with two groups of bullets. One with low Deveiation and one group with high deveiation. I think you will be surprised at the difference in penetration in wood, ballistic gelatin or anything else.. Oh yes, use any twist barrel you want. Any caliber Too. Of particular interest to me is the comparison of bonded core solids to monometal bullets( gee I'll be the experts here think these all all concentric too( surprise). Since I'm not impressed by Art Alpin and his devotees, I may just have to conduct this experiment myself. To be clear my hypothesis is that the depth of Penetration of DGR bullets from a 500a2 in wood at point blank range is more highly correlated to bullet concentricity than twist rates from 1:10- 1:15. -Rob

Jeffe said:

". . . wanna bet the lott at 14 still out penetrates the 458 at 10, given spec velocity?"

Of course it does. Twist does not increase velocity (or pressure)!

The 465 grain A-Square which was stable with a 1-12 due to relatively high velocity and short bullet length, perforated 13 more boards with a 200 fps increase in velocity. The progression is fairly logical with all the 1-12 and faster bullets except those that deform like the Kodiak in which case it is predictably inverse.

But remember, with increased velocity you are simultaneously increasing rotational velocity and stability.

The most significant two conclusions of my test were:

1. 458 win mag. Moving from 58 to 62 boards just by increasing twist from 1-14 to 1-10.

2. 450 Ackley was still not consistently stable with 1-14 at 2,400 fps. So your Loott surely wont be at 2,300 fps.

It will probably penetrate more about 1/3 of the time, but it will veer off course about 2/3 of the time.

This instability may actually improve its performance on small game.

Velocity certainly helps but in this case, its just not fast enough to be a consistant performer.

Andy

Andy,
sure wish you were down here to shoto with... and chop up a ton of plywood!

though you need less twist at lower spped, right?

jeffe

So if it is possible to have a bullet understabilized with a slower twist then is overstabilization also a probability with the faster twist, and at what point does it occur?

Rob,

Jeff was recommending 1X18 or 1X20 for .474 dia. 500 grain bullets. It would be interesting to see how that would stack up against 1X10. I would expect that the faster twist will do even better at high velocities such as the 470 AR is intended to achieve.

The test you propose would be interesting as well. It would be best to do it both in wood panels (such as in www.470mbogo.com) and in the plastic water buckets per the test designed by Andy. However, such testing will be time consuming and expensive. That is why my bullet testing is limited to shooting up big animals that are already down on the ground. However, if I could find a 500 A2 switchbarrel to borrow, I would be willing to perform the test on animals.

i've got an enfield mule, with a flat bolt face, that you can "swap" the barrels on.. stocked, and setup for a 1.25" threaded blank barrel.

.........

and a 470 AR reamer........


jeffe

Hi Andy
http://img.photobucket.com/albums/v645/atillman/Bullets/Teststandlowres.jpg

http://img.photobucket.com/albums/v645/atillman/Bullets/450AckleyFMJ.jpg

I have a couple of comments on your testing that you can take as you see fit.

1/ In this first picture you can see how the bullet paths are not unique and that there is an overlap of bullet paths which would lead to possible increases in bullet travel.

2/ In the second picture you said
"A 1-14 twist .458 may be stable in air but it sure is not in a La Grange stop box. Pictured one of just three 1-14's that kept point forward, and even this one is tipped downward about 30 degrees." I would think that this bullet had no choice but to be pointed down. There is only material on the top half of the bullet. I don't know what created this huge void below your bullet but this is also what I was refering to about unique bullet paths. Without unique bullet paths the results really are not accurate of what you are trying to prove. This is one practice that I really made sure I adhered to during my testing. I never ended up with any hole that looked like the void you have pictured on picture number 2.
My other thought is how can an unstabilized bullet penetrate 58 boards and one that is stabilized only penetrate one more board. I would think both bullets were stabilized very well.
I'm not trying to be critical of your efforts, just pointing out some observasions I think you should be aware of if your preparing an article for a magazine.
Take good care,
Dave

Hi, gumboot here. I had the first 500 A Square in Alaska .Got it in 1986 . It had a 21 " barrel and was a Hannible that I sent back to Art and had him put a 4x leupold pistol scope on it .along with the express sights. It was a great rifle. I should have sent it to KDF and had a brake put on it. I got injured and couldn,t shoot it for sevral years. I don,t know what everyone is argueing about. Call McGowan,s ,ask Harry what twist the factory barrels were. As they were McGowan barrels. And order one in stainless. Mine stabilized every thing from 300 gr. barnes 50/110 jacketed bullets to 707gr monolithic solids. The 450 gr Barnes flat nose bullet would go roarin out the barrel @ 2600 plus . I didn,t go faster as my neck couldn,t take it .Should have put a corn cob and an MPI fiberglass stock on it . That would have put the fun back in it. I,m haveing one built on a CZ 550 saf. mag. action this winter and it will have a 20 " barrel with a 12 " twist and a Holland Quick Discharge brake.I,ll shoot Hawk .050.jacket 500gr bullets@2650. It will be my brown bear finalizer. I need the 12" twist so I can shoot 600 gr solids in case a bear gets on the back side of a log or rootwad like they sometimes do..The 416,s are GREAT and the 458 win mag IS possibly my favorite . But the power of the 500 A- Square. is just WOW .10" twist would probably do fine as well. But not slower than 12.

quote:

Originally posted by Glen Urquhart:
H Call McGowan,s ,ask Harry what twist the factory barrels were. As they were McGowan barrels.

They were 1:10" twist.

quote:

Originally posted by Glen Urquhart:
Hi, gumboot here. I had the first 500 A Square in Alaska .Got it in 1986 . It had a 21 " barrel and was a Hannible that I sent back to Art and had him put a 4x leupold pistol scope on it .along with the express sights. It was a great rifle. I should have sent it to KDF and had a brake put on it. I got injured and couldn,t shoot it for sevral years. I don,t know what everyone is argueing about. Call McGowan,s ,ask Harry what twist the factory barrels were. As they were McGowan barrels. And order one in stainless. Mine stabilized every thing from 300 gr. barnes 50/110 jacketed bullets to 707gr monolithic solids. The 450 gr Barnes flat nose bullet would go roarin out the barrel @ 2600 plus . I didn,t go faster as my neck couldn,t take it .Should have put a corn cob and an MPI fiberglass stock on it . That would have put the fun back in it. I,m haveing one built on a CZ 550 saf. mag. action this winter and it will have a 20 " barrel with a 12 " twist and a Holland Quick Discharge brake.I,ll shoot Hawk .050.jacket 500gr bullets@2650. It will be my brown bear finalizer. I need the 12" twist so I can shoot 600 gr solids in case a bear gets on the back side of a log or rootwad like they sometimes do..The 416,s are GREAT and the 458 win mag IS possibly my favorite . But the power of the 500 A- Square. is just WOW .10" twist would probably do fine as well. But not slower than 12.

Glen,
You were advanced to the 500 A-Square stage when I was living in Anchorage and just getting started with Willis Fowler over on the Hillside of Turnagin Arm, having him chamber my first .375 Weatherby. 1986. I am impressed Old Timer!

Those great results you got were indeed with a 1:10" twist McGowen barrel if it was an A-Square Hannibal.

I have 3 stainless 1:10" twist McGowen barrels, and would not have any different twist than that in a .510 caliber sporting rifle.

Thanks for the recommendation for McGowen 10" twist on a 500 A-Square.

I found this to be a very interesting read.

http://www.riflebarrels.com/articles/bullets_ballastics..._imbalance_twist.htm

The only thing that leaves me still wondering is what increase in MV will compensate for a slow twist on a fired projectile. I believe that a min. of 300fps is required but I can't find the article that referenced this.

mix3006- Well ol Dan lilja sure KNOWS a THING or two about guns doesn't he? That article should be a must read for all the "EXPERTS" on this site! Dan actually competes and knows what he's talking about. I was just weighing a box of Woodleigh .50 cal solids for ha ha's. Now I don't think I need to use my Junke machine to know why they veer off course in wood and maybe fail to follow a straight line. I just can't seem to understand why a twist rate that is in the 100,000-200,000 RPM RANGE!( 1:10 to 1:18) HAS ANYYTHING TO DO WITH penetration. I think I can run the gyroscopic stability calculations and convince myself of that fact. The bullets are all adequately stabilized! Now I do believe that the more inherently stable a bullet is in any media, that the further it will penetrate and that if it yaws or precesses, that it will shed velocity very rapidly. is it too much of a stretch in imagination to consider this? Maybe this is just too much for the Art Alpin fans. By the way woodleighs are not benchrest quality bullets from a weight consistency standpoint. I also believe I know why barnes solids penetrate less in any given media than lead bullets of the same weight. Density! -Rob

Rip, I am JUST funnin with you here...

remember, you are shooting a 500A2, right?
aint that off the weatherby case?
The SEVERLY rebated weatherby case?
So severly that only the 500 jeffe has more?

quote:

Originally posted by RIP:
ONLY THE WANTONLY RECKLESS USE REBATED CARTRIDGES IN ANY RIFLE!!!

quote:

Originally posted by RIP:
I have 3 stainless 1:10" twist McGowen barrels, and would not have any different twist than that in a .510 caliber sporting rifle.

Just for arguement's sake... Should someone offer you a screaming deal on a 500 NE doublerifle Merkel, for say, $2500, would you pass on basis of it not having a 1x10 twist?

jeffe

Rob,

If penetration is all about bullet density then Woodleighs would out-penetrate GS Custom and Bridger. But they don't.

__

Jeff,

Thanks for the offer, but I really don't want to build rifles and go on a hunt for the purpose of proving or disproving the various viewpoints posted here. If, however, I could get a loan of a switchbarrel rifle in 470 AR, 458 Lott or 500 A2, with a first barrel being 1X18 and the second being 1x10, I will fire 20 rounds of solids from the fast twist into a first elephant and 20 rounds of solids from the slow twist into a 2nd elephant and report on the results.

When you going?
jeffe

Dan- Penetration is not just about density, but also the bullets ability to resist deformation forces that cause it to lose velocity and ultimately gyroscopic stability in any media. However, if you had two bullets of equal hardness but differing in density, then the denser bullet will penetrate more. Obviously as the density of the media the bullet moves through increases ( air vs meat for example, the deformation forces increase, velocity decreases and because of the loss of the axis of symetry from non symetric deformation, you lose gyroscopic stability quickly. ( 200,000 RPM vs 100,00 rpm -doubt that makes much of a difference assuming the bullets stabilize at 100K or lower). Once the gyroscopic stability is lost, the bullet then yaws,veers off axis and stops quickly. Woodleigh solids seem to deform and stop surprisingly quickly in my tests in hard OAK and in game and are invariably distorted. Although its obvious that denser metals will penetrate better. Tungsten vs lead for example( 19600 vs 11340 kg/cu.m.)! Assuming you could make a pure tungsten bullet of the same shape and size as the Bridger brass 360 half-hard, and fired from the same twist barrel at the same velocity, I would tend to believe you'd see a significant increase in penetration! Wanna bet that difference would be way more than the difference seen between two rifles varying in twist by 1:20- 1:10? Why because in addition to increased density, tungsten resists the deformation forces better than lead. Interestingly, Pure Gold has about the same density as tungsten but deforms just about as easily as lead. This thinking has led to the use of depleted Uranium in armour piercing military ammunition. I've also seen some experiemnts done with it in long range target shooting where maintaining bullet stability ( i.e Dan Lilja's article is quite accurate. It works too!
I've also had great results from Bridgers in DG. They are CNC turned on equipment that maximizes bullet concentricity and are made of a homogeneous alloy. They have very low std deviation on my Junke machine and seem to be extremely stable in hard media. I have recovered them after stooting through 64 inches of oak in my .600Ok and other than the rifling grooves, you could shoot them again! Now if they were only made of tungsten! I maintain shoot the slowest twist possible that will gyroscopically stabilize a given bullet made of the hardest material possible, having the most concentricity possible and the highest density will result in maximal penetration. 1:10 vs 1:20 making the big difference. Rubbish!-Rob

Rob, twist rate is important for maximizing penetration in game animals because of bullet yaw. All bullets have a tendency to yaw, and higher velocity means more yaw. Lack of concentricity in the bullet aggravates the problem. The more a bullet yaws, the shallower it will penetrate because it will experience greater lateral forces and have a tendency toward early tumbling. A faster twist reduces bullet yaw and therefore increases penetration depth by reducing or compensating for the factors that reduce penetration.

I have seen the deepst penetration from Bridgers, although they are brass and not so dense. But the noses will deform to an extent.

I have seen the second deepest penetration from GS Custom (copper), although the noses deform, in some cases badly.

I have seen third deepest penetration from Woodleighs (lead core), even though they are more dense than Bridger or GS Custom. Deformation of Woodleighs has been minimal in my experience. Only one had a slightly dented nose. Many of them had a bit of lead sticking out of the butt, but much less deformation than a GS Custom, and about on par with a Bridger.

TCCI round nose solids, which are denser than Bridger but are also lathe-made, penetrate far less than Bridger.

So I think there is more going on than just density and concentricity. It's also about controlling yaw, and nose shape.

Jeff,

Currently scheduled for April '07.

Barrel 1: 1x10 twist
10 rounds Woodleigh solids
10 rounds GS Custom solids

Barrel 2: 1x18 twist
10 rounds Woodleigh solids
10 rounds GS Custom solids

Protocol:

A. Shoot all 20 rounds from barrel 1 into elephant 1. Attempt to avoid hitting bones on the way in. Shoot from the hind end toward the front. Hopefully the bullets can be recovered in the chest rather than in the intestines (which is why the shots will be from rear to front rather than front to rear).

B. Repeat procedure with elephant 2 and barrel 2.


Total 40 rounds fired, testing 2 bullets from 2 twist rates. Anything more complicated will be extremely difficult to carry out. If anyone knows where I can get a wand metal detector, it will help with bullet recovery. I have found that bullet recovery on ele runs 50-65% at best.

The rifle should be suitable for DG hunting, such as an Enfield that feeds properly and has iron sights. Due to baggage limits, the rifle will end up being backup for a double, which will be the primary hunting rifle. A tracker would carry the Enfield, and will cherish the experience (as long as the rifle does not weigh more than 11 pounds).

Dan- I honestly don not believe twist does anything except agravate bullet yaw. I also believe that round nose bullets penetrate less than bullets with flat or pointed shapes as its much more difficult to produce a blunt nopse bullet with a truly symertrical nose. Moreover, even a slight off- axis change in this shape should aggravate the yaw problem.-Rob

quote:

Originally posted by mix3006:
I found this to be a very interesting read.

http://www.riflebarrels.com/articles/bullets_ballastics..._imbalance_twist.htm

So, going from a 15" twist to a 10" twist in a DGR will increase your group size by roughly 0.072" at 100 yards?

What is that? Minute-of-Gnat-Nuts?
NUTS!

But if the temperature or barometric pressure should change so as to make the air denser, then the paper punchers at 1000 yards scurry to a faster twist barrel.

Heaven forbid the bullet should encounter something denser than air!

Fast twist is about being prepared to get a marginal gain on penetration when the chips are down, and being able to try the greatest variety of bullets before settling on the one that works best in that rifle.

So we might increase our group size by less than 1/10".

So we might increase our pressure for a given load by less than 1%, or lower our velocity by less than 1%.

Big frickin' deal?

With all the potential gain in versatility of the rifle and terminal performance, it is well worth it.

I do like Lilja barrels and have a No.6 stainless fluted 26" long 1:12" twist Lilja on the .375 Simba.

500 Grains
Can't wait to see the pictures..
AK

ONLY THE WANTONLY RECKLESS USE REBATED CARTRIDGES IN ANY RIFLE!!!

Jeffe, that is why there is the 500 Mbogo.



Just for arguement's sake... Should someone offer you a screaming deal on a 500 NE doublerifle Merkel, for say, $2500, would you pass on basis of it not having a 1x10 twist?


Jeffe, no sir, I would buy it and then sell it to someone for more than I paid for it. Then I would have Butch Searcy build my 500 NE with 10" twist barrels.

glad to know the 500 mbogo and its slightly smaller brother the 500 ar will be making its daybeau soon and we wont have to deal with belts anymore...

or hey, file the belts off the a2 loaded ammo, grind the belt off the reamer and viola! no belt a2...call it the a3!

grains...i think yer offer to test the theory is very generous of you.

lets have some kind of bet as to the penetration...

cigars, scotch and crow!

Rip- Read my posts carefully! 1:10 just isn't the magic penetration genie you think it is. It may not be a bad choice if you like high pressures and lower velocities but I'd sure not be pimping it.-Rob

RIP, et al,

please note: Dan Lilja is referring specifically to the 6mm PPC cartridge and 62-65gr bullets at 3200-3300fps.



Rich

quote:

Originally posted by Robgunbuilder:
Rip- Read my posts carefully! 1:10 just isn't the magic penetration genie you think it is. It may not be a bad choice if you like high pressures and lower velocities but I'd sure not be pimping it.-Rob

Higher pressures and lower velocities by less than 1% . Bigger groups by less than 0.1" ... There is more variation than that between ANY two 15" twist barrels you can find to compare.

Just not important Rob. You need to read my post more carefully and try to understand. Maybe form the words silently with your lips as you read. That might help.

You will need that faster twist in case the weather changes.

RIP
one of us

Posted 04 March 2006 05:29 Hide Post
I wish I had some elephant shooting experience with North Fork Flat Point Solids.

I did shoot the "Iron Buffalo" (plywood and water alternating), some may recall. Before dismissing it as an "un-elephant-skull-like" penetration medium, consider that it is a medium that is more like a Texas Heart Shot on a big bovine or even an elephant. It may be an apple when you want an orange. However it is a test medium for penetration when comparing one variable to another, such as twist rate or bullet velocity, with other parameters fixed.

Fixed: North Fork .474/500gr Flat Point Solid of monometal copper. Nowadays they may be .475 and have different band structure, but the older ones shot well in all my rifles.

Vary impact velocity for same twist:

Data points below have so far been all the same for penetration: they bounce off the eleventh "1/2 inch thick" plywood board having traversed 11 compartments of water about 8" thick between boards. A four layer thickness of truck innertube is the entry to the first compartment, then water and board alternating. Water is in 2 mil plastic trash compactor bags with a wire tie. They are all key-holing through the tenth board and stopped by the eleventh. Laser straight until the tenth compartment water is entered.

.470 NE 18" twist at 2100 fps.
.470 Capstick 10" twist at 2100 fps
.470 Capstick 10" twist at 2300 fps
.470 Mbogo 16" twist at 2100 fps
.470 Mbogo 16" twist at 2500 fps

Not enough difference in twist or impact velocity to make any difference. They all penetrate the same.

The higher velocity bullets expend their energy by flinging water and board fragments into the air in a bigger splash in the first three compartments, then they all settle down to penetrate the same.

A .375/300 grain GSC FN solid at 2500 fps and at 2700 fps penetrates the same, both with 12" twist.

A .375/270 grain GSC FN solid at 2900 fps (12" twist) penetrates reliaby less than any of the loads above, .375 or .470.

A sectional density of .300 or greater and a flat nose monometal work best in the "Iron Buffalo."

Speed can't make up for lack of bullet weight, with a solid/nondeforming bullet.

Monometal bullets much over .300 SD are just too long to be practical for various reasons, but they are "enough bullet."

It ain't elephant skulls, but it is something repeatable, reliably, this Iron Buffalo stuff.

The Iron Buffalo is out to pasture now. It taught me a few things.

Letter Rip :
L to R (RIPoff Line)
308 Lapua (Chui)
338 Lapua (for reference)
375 Lapua (Simba)
423 Lapua (Kifaru)
458 Lapua (Tembo)
500 Mbogo (Mbogo)

Outer Circle Jeffery Knight
Posts: 7756 | Location: USA posts from: KY, AK, CT, SD, NE, TN, KS | Registered: 09 December 2001


You seem to have forgotten what you learned.

quote:

Originally posted by boom stick:

lets have some kind of bet as to the penetration...

No, no bets. Not even crow. Accurate data is the most sacred of all pursuits and I do not wish to cast any shadow over it whatsoever. I provide the elephants, Jeff provides the rifle (and 2 barrels).

I contacted Geoff McDonald to get his take.

"I subscribe to the theory that a fast twist is beneficial to the stability of a bullet once it penetrates an animal.
This may also add to its lethality due to centrifugal force and cutting effect of expanding soft nose bullets".
Regards,
Geoff McDonald.
WOODLEIGH BULLETS
PO Box 15, Murrabit, VIC, 3579, Australia
Ph. 61 3 5457 2226
Fax. 61 3 5457 2339
zedfield@iinet.net.au
www.woodleighbullets.com.au

I believe RIP's Iron Buffalo test results for another brand of projectiles disproves this theory.
I also asked Geoff if his projectiles were tested and developed using a certain twist rate.He didn't address this question unfortunately.

A big thank you to Mr. McDonald for his input.

Jeff,

I will broaden my proposal:

Rifle: Functional CRF DGR in 458 Lott, 470 AR, 470 Captick, 500 A-Square or 550 Express. 2 barrels, 1:10 twist and 1:18 twist (or 1:20 twist if you prefer). Functional iron sights. I will load the ammo if I can borrow some dies. Rifle to be returned at the conclusion of the hunt.

mix3006,
Thanks for digging that up.

The Iron Buffalo formula has since been changed to a tougher mix of 1" plywood to 7" water thickness, because that more closely matches the elephant results of Andy and 500 grains in total inches of penetration. But it makes it even more insensitive to resolving differences in penetration.

Anyway, it is consistent, with fresh plywood and water bags for each shot, and any hidden variations in the boards are averaged out and uniformed over the multiple compartments (glue filled knotholes in the internal layer laminations,etc.).

At least this shows that having extra twist does not hurt!

Regading Penetration: Bullet nose shape and bullet weight are always more important than velocity and twist, within the normal velocity and twist ranges!

Faster velocity kills better and penetrates no less with the right solid.

Faster twist is an extra safety margin on stabilization with slower velocities and heavier/longer bullets, especially good to have with monometals.

Twist is a marginal performer in penetration for sure. Faster than the "ideal" target twist is always desirable in a hunting rifle.

It is a certainty that some rifle and bullet combinations are marginal stabilizers, whether due to twist too slow or mismatch of barrel and bullet bearing surface contact areas (diameters and widths of lands and grooves, and diameters and linear run of bearing surface engraved).

Of course all the rifles of mine tested in the above quoted post, were good with even the .474/500-grain NF FN, known to keyhole on paper in some .475 caliber rifles.

We can't all be so lucky, all the time. Specifying a faster twist can only make the hunting rifle better, when the chips are down.

There is absolutely no meaningful detractor to using a faster-than-paper-puncher-ideal twist.

Anyone with any brains will choose a faster twist than 15" for a 500 A-Square.

Just don't go any faster than 1:7" and things can only be better than 1:15" could ever be.

1:10" twist for the 500 A-Square cannot be beat.

/

G'day Alf

I think that you may have missed the rest of my post where I said I disagreed with Geoff. I'm with you and your take on the mechanics (physics) in regard to this.
I believe that a barrel can be most certainly too slow or too fast in respect to twist.Appropriate twist is the key here.After 4 pages I am still wondering if the Greenhill formula is the best indicator or if it is even still applicable with regard to modern firearms and components.
So far the Iron Buffalo formula is the only one I'm sure of.