greyling22
Member
I've got a 257Ai. it's great. I don't know how it actually compares to a roberts, but on paper it's supposed to net another 200fps and be one of the better ackley conversions.
Thoughts on Ackley Improved cartrages
- Thread starter Kachok
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Is essentially a proof load...
SAAMI pressure for the .223 is currently expressed in CUP but roughly translates to ~63kpsi. 75kpsi is a 20% overpressure load and 10kpsi over the max that SAAMI considers safe for ANY load.
I think that I understand your basic premise though. Many of the claims for significant velocity increases come from the fact that that loads are well outside safe pressure levels, not because of an, often very modest, increase in case capacity. The basic danger of wildcatting is the lack of pressure tested load data. You're often on your own.
Chedderbob
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Seeing as how I am constantly buying, selling, and trading firearms (looked down upon on this particular board, but hey, the truth is the truth!), I avoid AI cartridges like my ex-wife.
There is a fella on a local gun trading board I frequent that has been hawking a savage .270 AI for months with no takers (price ain't to terrible either.) If you like marginal gains over common cartridges, forming your own brass, and being stuck with a gun for your entire life, the. AI is for you.
I generally find that there is nothing an AI cartridge can do that a commercially available cartridge can't do. Again, to each his own.
There is a fella on a local gun trading board I frequent that has been hawking a savage .270 AI for months with no takers (price ain't to terrible either.) If you like marginal gains over common cartridges, forming your own brass, and being stuck with a gun for your entire life, the. AI is for you.
I generally find that there is nothing an AI cartridge can do that a commercially available cartridge can't do. Again, to each his own.
MachIVshooter
Member
This.
I wouldn't bother imrpoving a case that already has a fairly sharp shoulder and little body taper (.308 based cartridges, .222/.223/.222 RM). But those based on the 250 Savage, the Mauser cases (6mm rem, .257 Bob, etc.) and the '06 family seem to benefit noticeably.
I'll probably improve my .25-06 at some point. My 6mm-06 build is going to be AI. I would love to have a Kimber 84L Classic Select in .280 AI.
That's the thing with AI, though......your brass is formed by shooting the standard factory load in your rifle. The only expense is AI dies. It's not really a wildcat; You can still shoot ANY factory ammo in your AI chamber.
Resale? If the prospective buyer is a handloader, he'll probably appreciate it. If he is not, well, he'll just be throwing his brass away, so it doesn't matter if it's fireformed to the AI chamber. The non-handloader will still have a perfectly good rifle, he'll just never realize the benefits of the AI.
http://www.riflemagazine.com/magazine/article.cfm?magid=7&tocid=38
I'm just about set on the 257 AI for my first build from the action up. I went to my LGS and talked with one of the fellas there about it. He said the most improved round was to the 30-30, that is until the lever revolution ammo came out. He also agreed that the 257 AI was one of his better successes. Read the article I linked and you'll see that not everything Ackley tried was a success. He admitted to that.
However, I still haven't shot one, so take my word with a grain of salt.
Zor
I'm just about set on the 257 AI for my first build from the action up. I went to my LGS and talked with one of the fellas there about it. He said the most improved round was to the 30-30, that is until the lever revolution ammo came out. He also agreed that the 257 AI was one of his better successes. Read the article I linked and you'll see that not everything Ackley tried was a success. He admitted to that.
However, I still haven't shot one, so take my word with a grain of salt.
Zor
MachIVshooter
Member
.257 AI is a great round, but IMO, doesn't make a lot of sense if you don't already have the .257 rifle. The cartridge is too long to fit in a short action, and the AI version of the .257 bob still won't match the performance of unimproved .25-06. Might as well just buy a .25-06.
Kachok
Member
As much as I like the 257 I already have the perfect close-medium range deer rifle (6.5x55) I would be looking for extended range and performance.
I'm going with the improved bob for a list of reasons. It fits in the intermediate action Mausers (6.5 swede and 7x57), it's an oddball (which I like), and for the sake of curiosity. Sierra has loads listed for it and claims that it outperforms the 25-06 right in their manual. I have a rifle that chucks bigger bullets at fast velocities for big game, this rifle is for smaller stuff like antelope, javelina and whitetail. Also, I'm building the rifle so the cost is going to be pretty much the same no matter what the chamber is.
MachIVshooter
Member
If you're building on a small ring Mauser action, that's a little different story. I just hadn't assumed so, since very few people do. I like the small rings, though already having a .25-06, I'd just stick with the 7x57 (maybe improve it).
But for the record, the improved bob cannot match the standard .25-06.
5th edition Sierra's top load for the .257 Roberts AI is 2,900 FPS with 117/120 gr. pills. The unimproved .25-06 is listed for 3,100 FPS with those weights, and I've driven them a full 100 FPS faster than that in my 24" Remington 700 BDL with no overpressure signs. Both test guns in the Sierra manual were Savage 12VSS with 26" barrels, so there's no discrepancy there.
The "far more efficient" wording in the book is also self-contradictory; With the 117/120 gr. bullets, There are two common powders listed for both calibers at the 2,900 FPS mark. IMR4831 Charge in the Bob AI for 2,900 is 46.4 grs; To get 2,900 in the .25-06 unimproved with IMR 4831, they show a charge of 44.9 grs. With IMR 4350, the charges are exactly the same. Oops.
I'm not saying there's anything wrong with the Roberts. It's a good round. But the .25-06's equal it is not, improved or otherwise.
35 Whelen
Member
Not contradictory in the least. In fact you unknowingly contradicted yourself. All things equal, a particular cartridge case cannot obtain more velocity with less powder than a smaller case of the same caliber. It's simple physics. Think about it: the 25-06 case has more internal capacity than the 257 AI, that is a given. Therefore, it will require more of the same powder to propel a given bullet a velocity the same as that obtained by the 257 AI with the same powder and bullet.
Your quoted load from the Sierra manual was either misread or is a gross misprint. I'd bet the farm that the 25-06 load should read 49.4. Consult the Hodgdon on-line manual and I think you'll see what I'm talking about.
All I have handy is an old 80's vintage Speer #9 manual, but it has both cartridges and generally speaking, the 25-06 has about a 100 fps advantage over the 257 AI.
So in the real world: From a velocity/energy standpoint, that gives the 25-06 less than a 50 yd. advantage and from a trajectory standpoint, less than 1/2" at 400 yds.
Pick your cartridge, no animal's going to know the difference.
35W
RevGeo
Member
I have two AIs. The rifle barrel on my drilling is .22 Sav HiPower AI. It shoots a 70gr .228 bullet at about 3400 fps using H380. Powerful antelope and whitetail medicine, but kind of messy.
The other is a sporterized Original Haenel Lorenz Wehmanns Gewehr single-shot 98 Mauser chambered for 30-40 AI but requires a .315 bullet because it was originally chambered for 8.15x46R which is about like a 32-40, power wise. I have a bullet forming die to squeeze .323 (8mm) bullets down to .315.To form cases I shove regular 30-40 cases over the expander ball in the sizing die and seat a .315 bullet over a standard Krag load. That gives me 'factory ammo'. Never had a problem fire forming cases in either gun,BTW.
Parker Ackley (who did the rechambering on both of these rifles for my late father) claims .300 H&H velocities from this cartridge but his loads of 4350 look pretty hot to me. I load it to 30-06 levels using H380 with no problems.
Some of the loads in Ackley's book would have the lawyers sharpening their pencils these days, I'm thinkin', but apparently he had no problems with them.
For anyone unfamiliar with Ackley's books his Handbook For Shooters And Reloaders has a fascinating chapter on his attempts to blow up various military surplus actions with rediculous loads. The results are rather surprising.
The other is a sporterized Original Haenel Lorenz Wehmanns Gewehr single-shot 98 Mauser chambered for 30-40 AI but requires a .315 bullet because it was originally chambered for 8.15x46R which is about like a 32-40, power wise. I have a bullet forming die to squeeze .323 (8mm) bullets down to .315.To form cases I shove regular 30-40 cases over the expander ball in the sizing die and seat a .315 bullet over a standard Krag load. That gives me 'factory ammo'. Never had a problem fire forming cases in either gun,BTW.
Parker Ackley (who did the rechambering on both of these rifles for my late father) claims .300 H&H velocities from this cartridge but his loads of 4350 look pretty hot to me. I load it to 30-06 levels using H380 with no problems.
Some of the loads in Ackley's book would have the lawyers sharpening their pencils these days, I'm thinkin', but apparently he had no problems with them.
For anyone unfamiliar with Ackley's books his Handbook For Shooters And Reloaders has a fascinating chapter on his attempts to blow up various military surplus actions with rediculous loads. The results are rather surprising.
pcf
Member
I've had one AI, it was a superb Cooper 52 in .280 AI, that I foolishly let it go for a 7mm STW in a misguided quest for more velocity.
Speaking in very general terms, with a 150gr bullet, I was using 3-4 grains more powder in the 280 AI over the 280 Rem and gaining 150-200 fps. I was using 21-24 grains more powder in the 7mm STW over the .280 AI and picking up another 200-250fps.
IMO the .280 AI nears peak efficiency in a 7mm. There are cartridges that can beat it's performance, but it comes with disproportionate increases in powder and recoil.
Speaking in very general terms, with a 150gr bullet, I was using 3-4 grains more powder in the 280 AI over the 280 Rem and gaining 150-200 fps. I was using 21-24 grains more powder in the 7mm STW over the .280 AI and picking up another 200-250fps.
IMO the .280 AI nears peak efficiency in a 7mm. There are cartridges that can beat it's performance, but it comes with disproportionate increases in powder and recoil.
Kachok
Member
Yeah i like speed and all but I would never trade a 280 Ackey for a massivly overbore 7mm STW. The 06AI case seems to be just right for 6.5-7mm bore, nobody fussing about rapid barrel burn, no excessive recoil, but they are nipping at the heals of hot belted magnums.
Kachok
Member
Nosler #6 has load data for the 280AI and 30-06AI but no pressures given.
Hodgdons site has pressure data with their load info.
They do not have the 6.5-06AI, just the stanadard. Top velocity with 140s is in the high 28s pressure running about 63K.
.280 AI shows about 2850ish with 160/62s at 60-62k, bout 3k with 140s.
06AI they dont list....odd that, of all the AIs i thought they would have...
They do not have the 6.5-06AI, just the stanadard. Top velocity with 140s is in the high 28s pressure running about 63K.
.280 AI shows about 2850ish with 160/62s at 60-62k, bout 3k with 140s.
06AI they dont list....odd that, of all the AIs i thought they would have...
pcf
Member
Hodgdon data center http://data.hodgdon.com/main_menu.asp has some info on the 280 AI with pressure.
MachIVshooter
Member
Not hardly. He cited the Sierra manual, I referenced it.
They list 50.9 for 3,100 FPS, and I have real world data to back the numbers up. My go-to load is 54.0 Grs. 4831 with 117 Sierra Gamekings, and it averages 3,195 FPS over my Chrony Gamma Master at 15', with a high of 3,227 FPS and a low of 3,166 FPS. And remember, my 700 BDL is a 24", not the 26" Sierra used for both the .257 AI and .25-06.
Speer #13 also shows 45.0 Grs. IMR4831 to get 2,793 FPS from the unimproved Roberts (Speer doesn't have AI data) from a 24" Ruger M77, and 46.0 Grs. 4831 in the .25-06 (700 BDL 24") to get 2,769 FPS. With IMR4350, Speer shows the Roberts at 43.0 Grs. for 2,758 FPS and the .25-06 at 44.5 for 2,773 FPS. Again, both 24" barrels, and this is the unimproved Roberts case, so it should have slightly better efficiency than the improved.
I'm in agreement with you that, as a rule, smaller cases are more efficient with a given charge weight. But there is also a phenomenon that can occur when some cartridges are at the top end of their capacity where efficiency actually decreases. I can't explain it, but I've witnessed in with handgun cartridges using certain powders and loading over max published data. Kinda like a Bullet's BC rating usually increases with velocity, but sometimes it falls off.
The Roberts does maintain higher efficiency with lighter bullet weights, and when you load below it's maximum. Not by a lot (3-6 grains for the most part), but it is.
I'm in agreement there. I'm not disputing that the .257 AI is a perfectly capable cartridge. Just pointing out that it ranges from slightly more efficient to no more efficient than the .25-06, and cannot match the ballistics.
Think of it like this; Chevy small block V8 - You have a 350 (roberts) and a 400 (.25-06). You can turn that 350 into a 383 stroker and it'll make more power than it did at 350 CI, but it's still not a 400. And at best, there'll be a hair's breadth difference in fuel economy. In fact, larger, more powerful engines are often more efficient in heavy vehicles or when towing, Just as sometimes the larger cartridge case is more efficient with the heaviest loads.
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c.latrans
Member
They are fun to tinker with. 20 years ago I thought the AI concept was brilliant, and still believe it has its advantages in certain areas. I have built several AI guns over the years, but probably wont bother with another. I still have a .25-06 AI that will honestly run on the heels of a .257 Wby. Age has changed my attitude about many things, including this issue. If I need more than, say, a standard .30-06 offers I will simply step up to a .300 mag of some version. Trying to get more out of a cartridge than it was designed to provide seems to me, at this point in my life, to be a really good way to bring grief I dont need.
I have never had a blow up with an AI, but I have seen pressure issues such as significant bolt face extrusion and primer pockets that opened up WAY faster than normal, so it seems intuitive that the pressures can get up there.
I have never had a blow up with an AI, but I have seen pressure issues such as significant bolt face extrusion and primer pockets that opened up WAY faster than normal, so it seems intuitive that the pressures can get up there.
Clark
Member
The 257 Roberts, 257 Roberts Ackley Improved, and 25-06, all use the 1889 Mauser 7.65x53mm case head built with large Boxer primer pocket.
That case head is good for 67kpsi and long brass life for an individual rifle in all three rifles.
For those who do not use load books, that makes all three very similar.
I built a few 257 Roberts Ackley Improved rifles on VZ24 actions 10 years ago.
The first one I headspaced like a 257 Roberts.
That is a mistake.
It should be .004" tighter, so that when the firing pin pushes the case forward, it is already crushed into the sharp chamber shoulder. Otherwise, it crushes .004" into the sharp edge, expands, grabs the walls, and then stretches back. That long stretch can crack the brass. In that rifle, 10 years later, I still fire form with Cream of Wheat to get some shoulder for the the firing pin to work against.
Look at the good groups at 100 meters!
That case head is good for 67kpsi and long brass life for an individual rifle in all three rifles.
For those who do not use load books, that makes all three very similar.
I built a few 257 Roberts Ackley Improved rifles on VZ24 actions 10 years ago.
The first one I headspaced like a 257 Roberts.
That is a mistake.
It should be .004" tighter, so that when the firing pin pushes the case forward, it is already crushed into the sharp chamber shoulder. Otherwise, it crushes .004" into the sharp edge, expands, grabs the walls, and then stretches back. That long stretch can crack the brass. In that rifle, 10 years later, I still fire form with Cream of Wheat to get some shoulder for the the firing pin to work against.
Look at the good groups at 100 meters!
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RevGeo
Member
I have Ackley's Handbook For Shooters And Reloaders and he doesn't list pressures with his loading data.
35 Whelen
Member
True, the 25-06 is slightly more efficient with IMR-4350, IMR-4831 and other relatively slow burning powders in that particular manual. My old Speer manual used exactly the same powder in both the 257AI and the 25-06. Even counting the IMR4350 and 4831 the 257AI is uses quite a bit less powder than the 25-06, but this is especially true with powders with a faster burning rate than 4350 and 4831.
I almost bought what you showed in the picture of the Sierra manual, but there's one small detail that causes me to question Sierra's data (and nothing against Sierra..I have two of their manuals).
Under the 25-06 data, if you'll look close at the charges for IMR-4350 and IMR-4831 you'll notice that Sierra show almost identical charges of each of these powders for the same velocity (2800-2900 fps range)with the same bullet.
35W
MachIVshooter
Member
Yeah. Why does that make you skeptical? 4350 and 4831 are both medium-slow powders.
#137 & #146:
http://www.reloadbench.com/burn.html
Those are two of my most-used powders from 6mm Rem to .375 Ultra Mag, and they do tend to require very similar charge weights in a given cartridge.
35 Whelen
Member
It makes me skeptical because they're similar only in that they're relatively slow burning powders, but not even remotely the same as the Sierra data would imply.
If you still don't understand this, work up a 120 gr. load in your 25-06 using identical charges and see which one begins to show pressure first, it'll be the 4350, I assure you. Then stop and continue on with the other, which will be the 4831, and make a note of how much more 4831 can be loaded before pressure signs appear.
If you're serious and you really don't understand this, you might want to get some different manuals and do some studying.
I've used both of these powders for around 20 years in the same 280 Rem. In fact I use identical charges (55.5 grs.) with both powders. The difference is I use 4350 with a 140 gr. bullet and and 4831 with a 160 gr. bullet. Were I to assume they were very similar powders and us said charge of 4350 under a 160 gr. bullet, I'd be pounding the bolt of my rifle open with a rubber mallet because it'd be a good 1.5 - 2.0 grs. over maximum.
See what I mean?
35W
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