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Thread: 280 Ackley Improved - I NEED some feedback for this !!

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    Default 280 Ackley Improved - I NEED some feedback for this !!

    OK - after I posted the other day I found that buying an 84L Montana in 30.06 is no small task - In the meantime I have been reading what I can find and talking with some old school shooters who tell me I'm crazy not to go for one in 280 AI - I have been reading and reading and ..... and I can't find any "real" applicable differences except for one unanswered question I have come up with - Why is the .284 bore given a 1:9 twist most of the time and there are some 1:7.5 twist rates out there that I hear kill like Thor's hammer yet, at least in my limited experience, I haven't heard of any .30 in faster than 1:10 - my limited understanding is that the faster the bullet is spinning on impact the more energy is transferred to the intended target - I have seen this in application with .22 40 grain varmint bullets in 1:12 vs. 1:14 and it is noticable so here is my question to anyone who "might know" ..... why wouldn't say a 300 WSM with a 1:9 twist rate and 180's be a awesome killer ??

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    Rifle twists are set up for bullet lengths and velocities acheiveable in the caliber in question.
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    Member hodgeman's Avatar
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    I like your choice of an 84L in 280AI very much...so much I plan on picking one up myself.

    Regarding twist rate, I'm not sure the twist has any effect other than stabilizing the bullet. The .300WSM with a 1:10 stabilizes the 180s beautifully and it indeed kills like Thors hammer. The .308 Win is often found with 1:12 and some will have trouble stabilizing the 180 and heavier bullets...but a 1:12, .308 shooting 150 or 165s at appropriate sized game does indeed kill well. I've had two European .30 cal rifles that came with 1:11 barrels- one in .300WSM shot 180s well and one in 30-06 wouldn't stabilize anything heavier than 165s but shot the 125gr Silvertips at blistering velocity into dime sized groups. I killed game with all of them.

    Bottom line is that I haven't noticed a significant difference in terminal ballistics with several .30 cal rifles at a variety of velocities with varying twist rates as long as the bullet I was shooting was stabilized, well constructed and I did my part and stuck it through the boiler room.

    The .223 with 1:14 twist is often barely stable and freqently cause significant damage (a'la early M16s) if the reports are to be believed. I don't know about that as all my .223s had 1:7 or 1:9 barrels but I've not noticed any difference in big game rifles.

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    what I was referring to, and it's not scientific by any means, is that when a prairie dog hit with a 40 at 4000 muz vel from a 1:12 would fly up in the air in pieces violiently and dogs at the same distance hit with a clone rifle but 1:14 twist didn't react nearly so dramatically, not definitive by any means - a friend has killed near a dozen bull elk with a 7x57 w 140 Barnes X and they without exception were DRT (rifle has 1:7.5 twist rate) again not scientific at all have you ever heard of a .30 with a 1:9 twist rate ? - I am trying to figure out why .25's have 1:10, .270's 1:10, .30's 1:10, .32's 1:10, .33's 1:10 and .284 1:9 or faster ....

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    What you're referring to is the standard rifleing for an individual caliber. For instance the 6 mm Rem used a 1-9" twist the 243 used a 1-10" twist these rifles launch 75-100 grain bullets. However 6mm PPC and 6mmBR used for bench rest are 1-12" to 1-14" with the 1-13" being my favorite, These are for the 58-65 grn flat-based bullets. A 1-9" twist would limit the 30 calibers bullet selection by eliminating many of the lighter bullets available.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

    On the road of life..... Pot holes keep things interesting !

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    7mm (and 6.5mm) is one of those calibers that just seems to work very well. I have rifles from 7 TCU up to 7mm Rem Mag and they are all very accurate and kill everything you point them at. I have one of the first Rem Mountain Rifles in .280 (1 in 9") brought into AK by WR Grace in 1985. It made 1 shot kills on everything I shot up to moose with the .280 using 160 gr Nosler Partitions. Leupold 2-7x compact worked perfect and it is a little over 7 lbs loaded.

    I'm a big fan of P. O. Ackley and have done a lot of chamber upgrades to A.I. but the .280 seems to work just fine the way it came from the factory. The AI might add 50 yds the standard .280 but not much more. The .280 is sweet just the way it is.

    Brav01,

    You are correct. My 6BR is 1 in 8" Kreiger and will not shoot less than 75 gr, but it will shoot Berger 105 gr into 3-4" at 600 yds on a good day.

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    Thank you for your comments - what I am pondering is building a 300 WSM with a twist rate of 1:9 meant for 180's and 200's - I like velocity but I like accuracy and lightweight rifles more, I am just brainstorming if I could make a good thing better with a faster twist on those 180/200 bullets - After reading your reaffirmation of the .284 AND agreeing wholeheartedly with those feelings, I am gonna "try" to be patient until I can lay my sticky hands on a Kimber Montana in .280 AI and be a happy hunter (yeah right....)

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    alright ... I just realized I wandered away from the original post (happens all the time to me) I am currently planning on grabbing the first Kimber Montana 280 AI I can get a grip on (unless overpriced of course!) I am looking for any pearls of wisdom on that well respected cartridge ....

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    Best I can say is that the 280 AI has the potential to get near 7mm Rem Mag performance if the particular rifle likes hot loads. Add in the larger magazine and theoretically better barrel life, and even maybe a lighter rifle, and what's not to like?

    I had one for a few years done up by PO himself, and it fell right in between my 284's (22" barrels), my stock 280 (virtually identical ballistics to the 284) on the one end and my 7 mag on the other. PO had originally put a 26" barrel on it, and it came within 100fps of the 24" barreled 7 mag I was chronoing at the same time. I clipped it back to 22", and it was 75-100fps faster than the 284's and 280 with the same barrel length.

    Long and short of it, I'll someday build another one and forget about my 7 mag. It'll have a 22" barrel and weigh a couple of pounds less than my 7 mag while coming within about 100-150fps of the belted case if it likes hot loads. Twist will be 1:8 or 1:9, whichever I can find first. I still love the 7mag, but will welcome the weight loss and extra mag capacity with "comparable" ballistics. At least close enough that I won't care about the vel loss.

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    Why not just get a 7mm mag and be done with it? just my .02

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    Quote Originally Posted by kgpcr View Post
    Why not just get a 7mm mag and be done with it? just my .02
    several reasons off the top of my head. longer/heavier action, less capacity, marginally better ballistics at the cost of more powder. Those are a few of the obvious ones.

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    The twist of a barrel has NOTHING to do with how hard a bullet hits or how it kills. That is pure fallacy. The twist solely affects the stability and therefore the accuracy of a bullet. We all want an accurate bullet. Manufacturers know thru trial and error which caliber/bullet combos prefer what twist rate.
    The 280AI is a cool factor that has been around the 60's when P.O. Ackley blew out the shoulders of a .280Rem. case to 40 degrees.
    Also with the "coolness" will be a much higher brass cost for hand loaders and off the shelf boxes. The 175gr bullet is listed in manuals from 2750 to 2800fps. My 30-06 range session today chronographed 180gr Partitions at 2755fps. While the .284 bullet selection is outstanding, the .280 languished in its 1957 introduction due to marketing screw ups by Remington.
    Consequently the .280 never really competed with the .270 as its head start was too much. The 7mm Rem Mag. in 1962 eclipsed the .280 and people just needed that "magnum" on their rifle. So the AI was overshadowed by the Mag for decades until recently now when Nosler pushed it in their new line of rifles. Kimber is capitalizing on it also. That's fine, but you have to realize marketing takes precedence over "real need". There is absolutely nothing that a well placed quality bullet from a .270Win or a 30-06 will pale in comparison to a 280AI. But variety is the spice of life so to each his own. Good luck.

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    A good lesson on over-twisting a barrel is what happened when Remington introduced the 6.8SPC. They came out with a 1 in 9 twist which in concert with a to-short chamber throat led to the round not achieving the cartridges potential without building to much pressure. These mistakes nearly killed off the cartridge. A few key people stepped up and continued to work on the development and managed to get a lot more performance by lengthening the chamber throat (referred to as a spec II) and slowing the twist to 1-11. These changes still stabilize all common bullet weights but allow much more velocity. Like most things on this earth there are both costs and benefits to different barrel twists.

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    Quote Originally Posted by knikglacier View Post
    The twist of a barrel has NOTHING to do with how hard a bullet hits or how it kills. That is pure fallacy. The twist solely affects the stability and therefore the accuracy of a bullet. We all want an accurate bullet. Manufacturers know thru trial and error which caliber/bullet combos prefer what twist rate. .
    I'm not sure this statement is entirely correct. In P.O. Ackleys book he shot a half-track 3 times with a 30-06 AP round the result was the paint was chipped and a small ding were evident, a 270-130grn merely smeared the paint. A 220 swift 38 grn sp at 4000+ fps blew a hole thru the armor plate. This damage was attributed to the high spin ratio of the bullet, something in excess of 250,000 rpm if I remember correctly . Bullet RPM is a factor seldom taken into consideration, but watch the Barnes videos and you'll see the petals transferring and tearing the gelatin in it's death spiral. Will increaseing the spin increase the terminal damage, YOU BET! However there has to be a happy medium where the gun and bullet work together.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

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    the spin rate of a bullet in flight DOES have an impact, it isn't something we speed entranced shooters think about but it is, in fact, a factor and a faster spinning bullet will cause greater disruption to the target upon impact - PO Ackley and someone else I cannot recall at this moment also did alot of killing and dissecting of burros or donkeys (I think) and their findings concluded the very same things and are published somewhere that I have read in my past - bullet stabilization is also a factor so be aware that I'm not discounting that and I can attest to the fact that pressure does build with a faster twist making velocities easier to push with a slower twist rate all other factors being equal - as for the 7mm rem mag, find me a kevlar stocked SS rifle that tips the scale at 5lb 10oz with a 24" tube for under $1200 in 7mm mag and I'll check it out plenty fast !

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    Quote Originally Posted by back country View Post
    as for the 7mm rem mag, find me a kevlar stocked SS rifle that tips the scale at 5lb 10oz with a 24" tube for under $1200 in 7mm mag and I'll check it out plenty fast !
    The rifle you want is available, Christensen Arms builds one. However the price tag is a little over $1200.
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

    On the road of life..... Pot holes keep things interesting !

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    brav01 - thank you all the same but 700's aren't my cup of tea and neither do I care for the carbon fiber barrels (I've had 5) - I will be patient and have a Kimber Montana soon enough - On another note, I finally dropped off a Kimber Montana in 270 WSM to have altered to a 338 WSM (or whatever moniker you choose) at JES reboring - That will keep me occupied while I wait for that 280 AI

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    A lot of inaccurate statements and fallacies posted here. You guys really think bullets screw themselves into muscle, ballistic gelatin and half tracks? Where did you get those misconceptions? If the spin rate or twist of a barrel were as important as some here think, why aren't ALL barrels made to spin faster? Barrels spin bullets inorder to stabilize their flight. Ballisticians realized that a spinning bullet was more stable and therefore more accurate than a chunk of round lead shot from a smoothbore flintlock. If you spin some bullets too fast, they WILL de-stabilize also. Its all a balance.

    The reference to penetration, videos with petals are the result of bullets designed with different frangibility. That is, they are designed to disrupt, mushroom, open up petals when they strike gelatin, muscle or a rock. On the other had, a full metal jacket bullet cannot deform as it is designed to "pencil through" no matter how fast it is spinning.
    A "cup and core" bullet like corelokts, powerpoints and similar cheaper factory ammo has softer lead and thinner copper jackets inorder to "mushroom" faster. The "cup and core" bullet shot from a .308/30-06 would work great on a deer or caribou. However
    when shot from a 300WM, 300 Weatherby or 300RUM might very well open up too fast and leave a superficial wound on that same deer and caribou. Those "magnum" cartridges need a more premium bullet that a "harder" to open up. A good example here would be a Partition or TSX. You have to consider your animal, your cartridge and the speed it fires a bullet and the distance involved. A "cup & core" bullet shot at a deer from 50 yards is going to expand a lot different than the same bullet shot with the same cartridge at a deer 300 yards away.

    But, people, equating the spinning of a bullet like its some sort of "auger" is absolute fantasy. Slow motion tests also show that once the bullet strikes gelatin, the spinning stops very soon and the bullet begins to mushroom. Shoot it into hide, muscle, bone, sinew and internal organs it stops spinning almost immediately. Hope this helps clarify.

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    I don't believe you or anyone else can shoot a 150 grn or heavier cup and core bullet out of a 300 WM or 300RUM fast enough to have a bullet failure on a whitetail deer or a caribou, providing the bullet is placed in the vitals.
    IF the rifling twist is correct for the bullet weight, length, and rifles velocity you can't over rotate a bullet fast enough to de-stabilize it. You can however accelerate/spin a bullet fast enough that it will vaporize in mid-air.

    Parker Ackley spent more time behind the stock of a rifle than any person I can think of and designed and modified more cartridges than any person I'm aware of, what's your claim to fame ?
    " Americans will never need the 2nd Amendment, until the government tries to take it away."

    On the road of life..... Pot holes keep things interesting !

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    Never realized we had so many ballistic engineers in Alaska and what were the odds all of you are forum members!!! Please don't ask me what my claimto fame is... All I will say butter, and three hot looking girls from south of the border yeehaw!

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