25.06AI VS 257 Wby

[Forest Walker]

How much diference in performance is there really between the two? I can look in the books and see but I was hoping to hear from someone that has or has had both.

[nomosendero]

 I will tell you this realizing any answer will cause an argument, but here is the least controversial
answer that I know of. Most manuals will show about 200FPS difference between a 25-06 & a
257Wea. Most of the time the manuals use a 25-06 with a 24 or 26" tube & the Wea. most of the time is a 26". I have found this velocity difference to be pretty close but they do of course vary with
slow barrels, fast barrels, etc.
 Now the AckleyAI will give you at least 100FPS, more in some cal. & less in others, in the 25-06, I
would figure on at least 100FPS, mine is a little more, possibly because it is throated where I can seat the bullets out further where I would gain a little more & I know that this particular Sendero has a "fast barrel". So, esp. if you have a 26" tube, I would figure on being within 100FPS. I would
not figure on matching the vel of the Wea. because afterall it still has more cap.
 Before I had this conversion done I researched it a great deal. My gunsmith had worked with & chron. numerous AI's & probably 15 or so 257Wea. He told me what to expect & he was dead on.
The small diff. in the 2 rounds did not justify the belted brass & the Wea. platform which is good,
but not as easy to accurize as the Sendero platform. Fireforming is a little of an issue, but I don't have to trim NEAR as much as in the past, a good tradeoff I think.
 Another benefit I realized is the gunsmith used a very precision reamer, cleaning up the factory chamber & now because of skim bedding, trueing the rec. & other enhancements I now have a precision rifle.
 The main thing with any cartridge is to watch close for pressure signs & DON'T go beyond reasonable pressures, regardless of the chambering.

[Don Fischer]

That answer shouldn't cause an argument, actually it's awfully damn good. But you didn't mention that the Weatherby is also long throated, that's where they get some of their velocity. One question I would ask, how much velocity gain did you get going to the Ackley version? It seems that the 30-06 case is already fairly straight and improving it wouldn't gain a lot with the exception of a sharper shoulder? You are in a good position to tell that as you've used the same barrel for both.

[nomosendero]

I did not mention that the Wea. has a long throat because they do that on all Wea. rounds, I assumed we all know that but some may not, no problem mentioning it.
I was in reference to being able to seat out further, therby giving me a little more cap. , I would
seat out with the heavier bullets the same distance from the rifling either way, therefore pointing out a small gain instead of merely freebore.

I think it is best to stay with the conservative & practical expectation of 100 FPS in this conversion. We must remember that there are NO SAAMI STANDARDS for the AI's & variations do exist. For example, Cartridges Of The World (9th Ed.) state that you gain about 5% but show loads that equal any 257Wea. data that I am aware of, but remember this is not a reloading manual & are not held to as high a standard. I would be cautious of those loads. The Sierra Manual has 25-06AI data & they show the AI to be between the 25-06 (100fps less than Roy) & 257Wea. , but yet they say the 25-06 has 7-8% gain. Yea, the 06 case tapers a little more than most people realize, but not near as much as a 30-30 & some others. If you look at a 308 case, it tapers a little less & is why the 260, 7mm-08, & 308 gain very little in vel. Again the reasonable & safe expectation is 100FPS. Most people who do this conversion do so for more reasons than vel. alone. It gives you a chance to have a better chamber, very good case life if loaded to comparable pressures & a case that rarely needs to be trimmed. But remember, it has to be fireformed, a hassle for some, for me I step outside & shoot those, so weigh what is best for you. The AI is a better overall setup for me, but not for velocity alone.

Don, concerning my rifle, I have seen more than the 100fps, but all rifles are different. As I said before, I also have a long throat & combined with the AI, I may have close to a 10% cap. gain, but also my barrel was running 70FPS or so over other 26" tubes we checked, and also with a chamber that is now totally square with the bore, logically it can be loaded a hair more before pressure signs show, but when it all is lined up you can have pressure sneak up on you, so caution must be exercised as allways. And remember, even re-chambered does not mean that it will be more in line, it was in my case. Again, let's just stay with 100FPS as a gain & start with loads just under 25-06 max. & work up slowly & watch for pressure signs. 

[Forest Walker]

Thank You for the comments. My Father just bought me a MGM 25.06AI barrel for me for my encore. He Uses a 280AI Jerret conversion that is just devestating. He figured that I would like a 25.06 AI a little better since I also reload and wanted a  25 for my encore. Thanks again for your reply

[Don Fischer]

Quite a number of years ago, pre-cronograph, I long throated a 7MM mag to handle 160gr bullets. While now I think ,make that know, I have no idea what really happened i did notice one thing. With the long heavy bullets seated farther out I increased the amount of powder used conciderably. Now I think it was because I had actually increased the chamber size without increasing case capacity. Back then it was reported that that was one thing Weatherby did to get the extra velocity, they free-bored their chamber's, so I was told. I have never messed with a Weatherby cartridge.

Today I think that most, if not all, magnums would be better suited with longer throats to handle heavier bullets with the base of the bullet out of the powder chamber of the case.

[nomosendero]

I agree, but there are action lengths to consider with some magnums, for example you cannot seat a 180 out far on a 300 mag & still use a Ruger77 std action. Another problem is some want to use only the lighter bullets because of flatter mid range trajectories & if throated for long bullets, in some cases the accuracy would suffer, but not to worry, we can get them throated anyway.

[jro45]

I don't know about the 25/06AI but my 257 WBY MAG will shoot the 87gr bullet at 3779 FPS,
the 100 gr bullet at 3530 FPS, and the 117gr bullet at 3323 FPS and the group is within MOA
at 200 yds.

[Catfish]

Let me muddy the water alittle more. I shoot the .257 AI. According to my Serria manual I can push an 87 gn. bullet to 3,500 fps. through a 24 in barrel with 49.6 gn. of H-380. In the .257 WM you can push an 87 gn. bullet through a 26 in. barrel at 3,700 fps., but it takes 66 gns. of H-380 to do it. Max. point blank range, + or - 2 1/2 in, is 305 yrds. with the .257 AI and 320 yrds. with the .257 WM. With the 26 in. barrel on my .257 AI I cronoing abt. 3,600 fps with the 49.6 gns. of H-380 and we are now down to abt 10 yrds. difference for 14.4 gns. of extra pwoder.

[nomosendero]

No doubt, in the 25 bore the bigger cases give a velocity increase in all bullet weights, but much less in the lighter bullets. Where the 25-06AI & the Roy pull away from the 257Roberts AI is with bullets
of 110 gr. & heavier. That works out too because the heavier bullets win at long range anyway, especially in wind drift.

[jro45]

It would seem to me that if you want more FPS you would need more powder. So in the long run it costs more.

[Don Fischer]

It would seem to me that if you want more FPS you would need more powder. So in the long run it costs more.

It does, there are no free rides. But Those that shoot those cartridges aren't concerned with spending a few more grains of powder. That's not what it's about.

[jro45]

It would seem to me that if you want more FPS you would need more powder. So in the long run it costs more.

It does, there are no free rides. But Those that shoot those cartridges aren't concerned with spending a few more grains of powder. That's not what it's about.

That was just an observation.  I shoot alot of large powder consuming cartridges.