|
|
|
Discussion Forums
Forum Index
> Rifles general discussion
> ackley improved
ackley improved
@ 12:58 am (GMT) |
jason brownwho wants to explain Ackley improved to me....I hear it all the time, I understand that the case shoulder ends up flatter. how do you get one, is it just new barrels by request, I couldn't imagine a rifle with a standard chamber being able to be re-reamed. it seems you can still fire standard chamber rounds then becoming fire formed, do you also buy a Ackley improved die or once there fire formed you have to neck size only? and so you get a case with a flatter shoulder. im not 100% why this is so good, are there any other benefits or negatives? |
Replies
@ 03:14 am (GMT) |
Guy MainlandRe: ackley improvedHi Jason, check this out, interesting reading.http://en.wikipedia.org/wiki/P.O._Ackley |
|
@ 03:24 pm (GMT) |
Nathan FosterRe: ackley improvedHi Jason, Ackley managed to achieve two main factors with his improvements- increased power and decreased case growth (great way to cut down on trimming operations). That said, any increase in power was largely dependent on how much body taper the original case displayed. Inother words, cases with heavy body taper stood to gain the most.If you have a look at the .30-30 photos in the Wikipedia article, you will see that he not only blew the case out to maximum body dimensions, but he also shifted the shoulder forwards a touch. The result was a significant increase in velocity. In the KB, you will see that I have made notes on some of the AI cartridges towards the bottom of the cartridge section. The reason I have not gone into great detail is because sometimes, shooters set far too high expectations of the improvements. Even the person who submitted the Wikipedia article set such expectations we he wrote that the .280 AI "duplicated the 7mm Rem Mag with 30% less powder". Ackley's goalwas to increase powder capacity, not pull rabbits from his arse. We cannot then say that increasing powder capacity by 30% is non productive. We could say such if a cartridge is overbore but the 7mm rem Mag is not overbore. The trouble is, folk read these Wikipedia type comments and then hot load their AI cartridges to brass killing pressures with less than optimal accuracy. If I was to guess, I would say that there are possibly more .280 AI rifles in circulation than standard .280 Rem rifles. This is certainly the case in NZ. The .280 AI certainly has the potential to beat the parent cartridge in velocity- but this does not always happen, so we need to set realistic expectations as to potential gains. The gains I see include: Reduced case growth The potential to use slow burning powders with heavy bullets where otherwise the slow burning powder would have been too bulky to fit in the case and also non responsive. Of course, a long barrel is required to gain such benefits and even then, some rifles will display sluggish behavior with slow powders and so forth. I like to see clients and readers set an expectation of about 50fps increased velocity unless the case improvement is radical. At the same time, I caution people with the reminder that the barrel has the final say. One barrel may have a sweet spot at high velocity while another may show best accuracy 100 to 125fps slower. If we are lucky, it all comes together. Hope for the best but plan for standard velocities. |
|
@ 08:15 pm (GMT) |
jason brownRe: ackley improvedthanks guys.Nathan, what does over bore mean? I looked at a local internet store and through hornady I only see one Ackley imp die, the 280. im guessing you can get others and there full length and you arnt restricted to fire forming and neck sizing? I see there could be some improvement but not all calibres. its not like an after market option for any chambering. I feel I understand better now, or at least enough to know whether or not I want to go down that road. |
@ 09:53 pm (GMT) |
Les MulloyRe: ackley improvedG,day JasonHere is my 2 cents worth - probably worth s.f.a. I have owned 3 rifles in my life chambered in 30-06 Ackley Imp One had a 22 inch barrel and gave me only more fire and brimstone. The second was a custom made long range Target Rifle with a 28 inch barrel which shot half inch groups was very easy on brass and did not burn the barrel out in less than 1000 rounds - this rifle was very easy to shoot well, as the recoil was quite manageable and you did not have that " is the scope gunna cut my eye? " feeling each time you fired it - I may have been lucky with the barrel but that rifle was a ball tearer - only sold it because of an offer I could'nt refuse. I have recently had a custom hunting rifle made with a 26 inch barrel - purposely tailored to shoot high ballistic coefficient 180 and 200 gr bullets. Nathan was right in that this calibre won't pull bunnies out of bums - but the calibre has all the attributes ( to me ) to be able to shoot it well and get good results - especially when recoil levels are compared to a 300 wsm or a 300 win mag and even a 7mm mag in a hunting weight outfit.( mine is 8 lb scoped ) Reloading dies for most Ackley calibres are category C and cost around $200.00 au. for a 3die set. I have RCBS So there's my story !!! My choice to continue using a 30-06 Ackley is based on fond memories - not a desire to blow elephants in half. Regards - Les |
|
@ 10:15 pm (GMT) |
jason brownRe: ackley improvedthanks les.initially I didn't even realise they made a bit more power than there standard brother. I thought it was more about case shoulders. if I wanted more power id probably just get the next size cartridge up, unless there was something I was really stuck on but wanted a bit more. even the case thing, im not too bothered by some trimming. at this stage I doubt its something I will take further. |
|
@ 11:10 pm (GMT) |
Nathan FosterRe: ackley improvedHi Jason, Overbore (my take) is the point where the bore simply cannot handle any more energy. If you look at the 7mmPractical for example, it is near maximum regarding the amount of energy that can be channeled through a 7mm oriface. The STW is absolute max and either the same or only a little faster than the Practical. The 7mm RUM is overbore. No maytter how much more powder is put in the case, the bore cannot generate more velocity. A small measure of velocity is gained by extending the freebore forwards (bullet basically space walking for a bit until it eventually hits rifling). But without this freebore, the RUM cannot outperform the much smaller Practical.This is all explained in the second book (must be your homework tonight huh). As to your second question, RCBS have always been supporters of the Ackley cartridges. Hornady can also make anything you can imagine and will already have die reamers for all of the Ackleys. Les has a point and has employed the .30-06 AI in a good way. He is going for maximum potential velocity but with realistic expectations. He does not want the full power / recoil / barrel life etc of a magnum. He wants something just in between which is quite common. Les is able to experiment to his hearts content. If the rifle does not yield higher velocities than standard- no problem due to the already good power levels. He may still nevertheless be able to have a bit of fun with 200-220 grain bullets and slow powder which again is all a part of the joys of experimentation. If the rifle yields higher velocities all round, then that is a double bonus. I have already mentioned that some case designs stand to gain more than others. I should mention Jason, one of the most responsive cases is the .303 Brit. Ackley never tried this, a man called Epps did it instead. I have correspondents who have been supplying data to me, being doubly careful (two chronies, multiple rifles etc) to make sure that if I relayed their info, it would be of the same standard as my own research and not isolated results- extremely kind of them. The Epps yields the same velocities as the standard .30-06. 180gr bullet goes around 2750fps. |
|
@ 11:42 pm (GMT) |
jason brownRe: ackley improvedthanks Nathan. I do remember the term over bore, but wasn't sure where I last seen it. which as you pointed out must of been the second book. (I get excited when a new book comes out, I must read it too fast and theres just too much to sink in.)but I do now understand thanks. that's very interesting that theres a cut off point and you cant neck down a tank shell to 7mm and get a huge velocity. you would just be burning powder for the sake of it or blow your head off. |
@ 03:20 am (GMT) |
Shawn BevinsRe: ackley improvedI know that this a few weeks old but PO Ackley has a two volume set in print that is a good read and reference. One of the added benefits of an Ackley cartridge in my understanding is less bolt thrust. As someone who shoots Encores, this is a big plus. Case life should be extended in this case also. |
|
@ 03:20 am (GMT) |
Shawn BevinsRe: ackley improvedI know that this a few weeks old but PO Ackley has a two volume set in print that is a good read and reference. One of the added benefits of an Ackley cartridge in my understanding is less bolt thrust. As someone who shoots Encores, this is a big plus. Case life should be extended in this case also. |
@ 01:10 pm (GMT) |
sam smithRe: ackley improvedI have a few "improved" rifle in my gun case. I have to 6.5x55 improved and a 22-250 improved.The 22-250 is worth doing just for the improved case life. I was always trimming my brass with a standard 22-250 and after I made the change to a A.I version I have little need to ever trim my 22-250 A.I. cases. I would also note that if you wish to make a 22-250 A.I. I would use a faster twist as I did. I built the rifle with a 1-8 twist so I can make use of heavier bullets. I shoot 80 gr bullets at 3300 fps and with the higher B.C. of these heavier bullets it makes for a good deer rifle for my wife. It carries over a 1000fp of energy out to over 400 yards. If you don't run a faster twist with a 22-250 A.I. there is very little gain in performance with 50 and 55 grain bullets. I have been shooting my 6.5x55 improved in f class shooting and find it does very well and keeps up with the 6.5x284 with about double the barrel life. I was able to take 140 VLDs and JLKs up to 3000FPS with a 29" barrel. I then built a hunting rifle with one of my old F class barrels by setting the barrel back 8" and was was still able to get a respectable 2850 fps with the 140 grain bullet. Using a 140 grain 6.5 bullet at 2850fps this gun is over a standard 270 like a tent. Most 270s have trouble taking 1500 ft/lb out to 400 yards and my 6.5 easily takes 1500ft/lb out past 450 yards. |
@ 02:53 pm (GMT) |
GREGG FOSSERe: ackley improvedThis is an excellent discussion with a lot of very good information from Nathan and others. Since reloading becomes more attractive every day (due to the high cost of factory ammo), the reduction in case trimming is a real benefit of the AI cartridges - and they retain ability to fire factory (non AI) ammo in a pinch. For a single shot the rimmed 30-30 AI or the rimmed .303 AI offer a useful improvement in performance over factory loads with the simple headspacing and extraction that a rimmed case delivers - and of course a single shot makes the use of a long barrel much more comfortable. I am happy to have had access to this discussion since it reinforces the impressions I have had about the ackley improved cartridges, and comes from folks who have really used 'em. Thanks. |
Please wait
ABOUT USWe are a small, family run business, based out of Taranaki, New Zealand, who specialize in cartridge research and testing, and rifle accurizing.
|
KNOWLEDGEBASE |
KNOWLEDGEBASE |