257 Bob AI or 6mm GT???......

[Craig R McMullen]

So I’ve been tossing the idea around of doing another build this year. I’d like to do something that can handle a wide variety of applications. Steel and paper at mid to long distances, coyote and groundhogs, also deer. I want something a little different and have it narrowed down to two cartridges (At least I think I do lol). My options are the 257 Bob AI or the 6mm GT. They both have decent barrel life which is a MUST. The GT is known for long distance shooting and with the 131gr BlackJack .25 caliber bullets, along with Berger adding bullets to their lineup, the quarter bore is no longer lacking in the long heavy for caliber, slippery bullets.

So my question is, has anyone messed with both? I know the 6GT is probably going to have it’s advantages at distance, but, that won’t be my only use. I’ve always had a soft spot for the quarter bore and have never really been a .243” fan. But the GT may change that. We shall see. I’d also like to know exactly how the 257 AI holds up at distance? You don’t hear of many guys going that route for FClass, so there must be a reason.

Thanks in advance.
Craig

 

[Lougler]

So I’ve been tossing the idea around of doing another build this year. I’d like to do something that can handle a wide variety of applications. Steel and paper at mid to long distances, coyote and groundhogs, also deer. I want something a little different and have it narrowed down to two cartridges (At least I think I do lol). My options are the 257 Bob AI or the 6mm GT. They both have decent barrel life which is a MUST. The GT is known for long distance shooting and with the 131gr BlackJack .25 caliber bullets, along with Berger adding bullets to their lineup, the quarter bore is no longer lacking in the long heavy for caliber, slippery bullets.

So my question is, has anyone messed with both? I know the 6GT is probably going to have it’s advantages at distance, but, that won’t be my only use. I’ve always had a soft spot for the quarter bore and have never really been a .243” fan. But the GT may change that. We shall see. I’d also like to know exactly how the 257 AI holds up at distance? You don’t hear of many guys going that route for FClass, so there must be a reason.

Thanks in advance.
Craig

Not sure what action you’re planning to use, but the 257 is a PIA in a short action. Especially with heavy for caliber bullets. If that’s not a concern, put them both in a ballistics program and see what you see.

 

[Craig R McMullen]

It’s a from scratch build. I do know that to get the full potential out of the Bob AI I need to put it in a long action. If I could afford a quality custom Mauser action I’d go that route. Wow I’d love that. But this will likely be an a savage action. I may do some research and see if I can do a Remington but with the Remage option. Shilen makes prefits for the Savage, but not the Remington. My research will be to see if I can use a Remington action, get Shilen to do the barrel but see if the Remage barrel nut will work. I’m going to call Shilen next week and see what my options are.

 

[std7mag]

Or split the difference.

I've been debating the 25GT route.

Still looking for new 25 caliber bullets from anyone.
Looks like it's still the 131gr BlackJack, 115gr Berger VLD, or the 110gr ELDX.

The 115gr VLD is an excellent game bullet!

I've heard of a few using 257 Roberts for F-Class, but that was a little older thread.
I keep getting told to shoot what everyone else is shooting.
But i'm not that guy...

 

[std7mag]

Another option...
250 Savage, or AI.

Stevens 200 with E.R. Shaw 24" sporter contour in 250 Savage. 75gr Sierra HP Varmint. With Alliant Varmint powder.

Adjusted scope after first shot for 200 yard zero. My coyote rifle.
Shot at 100 yards off bench using bipod & rear bag.

Still trying to figure out why it rotated the picture....

 

[ckrifles]

What about the 25-creedmoor. Better brass and will work in a short action.

 

[Walt Krafft]

250 Savage AI. It splits the difference case capacity wise between your two options. Will work in a short action. Feeds well from a magazine. Is easy to make brass. Mine shoots like a dream.

 

[potatojudge]

250 Savage AI is essentially identical to the 25CM. If you go 250AI then form the cases using high quality CM brass or good 22-250.

 

[Craig R McMullen]

Or split the difference.

I've been debating the 25GT route.

Still looking for new 25 caliber bullets from anyone.
Looks like it's still the 131gr BlackJack, 115gr Berger VLD, or the 110gr ELDX.

The 115gr VLD is an excellent game bullet!

I've heard of a few using 257 Roberts for F-Class, but that was a little older thread.
I keep getting told to shoot what everyone else is shooting.
But i'm not that guy...

I’m right there with ya. For me, it’s not all about winning all the time. I want to have fun and shoot what I want to shoot. Not necessarily what everyone else is shooting.

 

[Craig R McMullen]

Another option...
250 Savage, or AI.

Stevens 200 with E.R. Shaw 24" sporter contour in 250 Savage. 75gr Sierra HP Varmint. With Alliant Varmint powder.

Adjusted scope after first shot for 200 yard zero. My coyote rifle.
Shot at 100 yards off bench using bipod & rear bag.

Still trying to figure out why it rotated the picture....

Nice!! Looks like you found a heck of a load!! Good shooting rifle.

 

[Craig R McMullen]

What about the 25-creedmoor. Better brass and will work in a short action.

It has been tossing around in my head. It’s definitely not eliminated that’s for sure. I guess the only downside for me is that name lol. I’m so tired of hearing creedmoor. Hahaha
It’s a great shooting round, heck the whole family shoots great. It’s just that I like to be a little different I suppose.

 

[Ranger188]

25x47L

 

[std7mag]

25x47L

May as well do the Creedmoor, or 25 Souper.

 

[MNbogboy]

My .02,
Having had three 257 Bob Ackleys 40°, the cartridge is great and with 100 gr pills in a 10 twist it was comparable ballistically to several of my 25-06s. Down side is brass, making brass from 30-06/270 brass was a pain but you could always get proper neck length. 257 Roberts brass when available along with 7x57 brass would leave you with less than full necks. Fireforming also required about 2 trys to get sharp shoulders.

My latest wildcat is a slightly shorter (2.005") version of the 6.5 SLR. It is actually a long Creed without the name. The extra. 080 of length equates to about a 2 grain increase over standard CM. Brass can be made from higher quality and even SRP 260 brass in one pass and form the 30° shoulder almost perfect.

A 25 caliber version of this with a faster twist barrel (1:7.5) to shoot the 131 blackjacks to me sounds like a winner. The "SLR" variant would have more capacity than the 25 Creed. 25 Creed reamer and dies should accommodate this wildcat without the need for additional custom dies or reamer.

Just a thought.

 

[SweaterDood]

I’ll support the ole Ackley-Bob. I mean I just built one, so take it as you want, but with a Mauser or XM length action it will launch those Blackjacks at 3100+ out of a 25” 7.5tw tube. I’m just running Winchester brass too, and not seeing pressure until 3200ish. She’s a laser and shooting right at .25-.3moa at 400yds. Still playing with the load but haven’t had much time. Looks like keeping her in the .2s won’t be too difficult.

Regarding F-Class, seems that most everybody shoots 7mm or .30 cal in order to more efficiently buck wind. The lighter bullets, while slippery, get pushed around. Most of the new whiz-bang, high-efficiency cartridges are too slow to offset this. The heavy 7mms are moving just as fast as many of the 6mm and 6.5mm offerings but have more inertia and better BC. The .30s will do the same but at the expense of your shoulder. What if you were to find a node for a highly efficient, lighter bullet at 250fps faster? I’m hoping to find out.

 

[David Milisock]

So I’ve been tossing the idea around of doing another build this year. I’d like to do something that can handle a wide variety of applications. Steel and paper at mid to long distances, coyote and groundhogs, also deer. I want something a little different and have it narrowed down to two cartridges (At least I think I do lol). My options are the 257 Bob AI or the 6mm GT. They both have decent barrel life which is a MUST. The GT is known for long distance shooting and with the 131gr BlackJack .25 caliber bullets, along with Berger adding bullets to their lineup, the quarter bore is no longer lacking in the long heavy for caliber, slippery bullets.

So my question is, has anyone messed with both? I know the 6GT is probably going to have it’s advantages at distance, but, that won’t be my only use. I’ve always had a soft spot for the quarter bore and have never really been a .243” fan. But the GT may change that. We shall see. I’d also like to know exactly how the 257 AI holds up at distance? You don’t hear of many guys going that route for FClass, so there must be a reason.

Thanks in advance.
Craig

What use for the rifle? Target, short or long range? Field rifle? What weight game? What range for hunting?

 

[std7mag]

Sweaterdood,

I tried that with my Stevens 200 in 7mm-08AI.
The 168gr Berger VLD shot great, but velocity was way down. Bullet was further into the case than i liked too.
I ended up shooting the 140gr VLD for my first F-Open match.
173, 173-1X, 173-2X.

Lessons learned.
I need to practice shooting prone more. Was really my first time shooting prone.

I need to read the wind/mirage better.

Light guns suck for long strings of fire! Ohhh the shoulder!!!

Personally, i wouldn't use 30-06, or 270 cases to form 257 Roberts Improved.
I run 7X57 Mauser through full length die. Trim.
Load for 257 Roberts +P (56,000 psi).
Your cases will come out just fine.

 

[JEFFPPC]

It's about barrels and bullets. How's the choice in .257 match bullets???

 

[std7mag]

Sierra makes a 100gr MatchKing.
Berger the 115gr VLD.
Of course the 131gr BlackJack.
For mono's Cutting Edge makes the 100 & 115gr MTH.

And shooters of many other calibers shoot varmint bullets for 400 yards & less.

So there are bullets out there.
And supposedly more are in the works.

 

[SweaterDood]

Personally, i wouldn't use 30-06, or 270 cases to form 257 Roberts Improved. I run 7X57 Mauser through full length die. Trim. Load for 257 Roberts +P (56,000 psi). Your cases will come out just fine.

I honestly didn’t have any issue finding 257 Roberts brass. I picked up enough for the life of the barrel (and probably the next few barrels). I did have to toss a few so far, but that’s why you inspect your brass.

Not sure what the complaint on the neck length is though. .300” of neck is not necessary to hold the bullet, so trim them equally and shoot ‘em. Unless you have a special freebore like mine and want to seat 75gr bullets way too far out, there won’t be an issue. Definitely not worth screwing around with reforming -06 cases.