Michelle e mailed me from HART barrels and my .257 Roberts AI is on it's way from upstate NY out to Montana.



Any words of wisdom? RP cases just as good as WW?? Whats a good load to fireform?



FN in MT

I always used Winchester cases when I had one. I used to use Herco powder, backed by cornmeal and blocked with soap to fire form. It worked okay.

Bob257

the fireforming advice that I've always followed is to use a relatively heavy (117 or 120) bullet over a medium charge of relative fast burning powder (4064, Varget, etc). And be sure to seat the bullet out to where they contact the lands so as to provide solid headspacing...have fun!

Frank:
To fireform my .257 AI, I follow the instructions in the Nosler, fifth edition manual. However I use a 100 gr. Hornaday bullet because they are inexpensive. To fireform, I use either 33 gr. of IMR-4895 or about 36.5 grs. of IMR-4064 and seat the bullet to give a length of 2.470" TO THE OGIVE. You want to be sure to solidly engage the lands. I don't use any fillers and my cases are Win. .257 Rob.
Hope this helps some. You're gonna love this cartridge. Bear in Fairbanks

Frank, the only real disagreement I have with the previous posts on this subject is the need to seat bullets into the lands for fireform loads. If the chamber is properly headspaced, there is no need to jam the bullets into the lands. A 257 case will give a crush fit in the chamber, establishing proper headspace. This is one of the primary benefits to an Ackley improved cartridge, it can use standard ammunition without worry. I think that the habit of using the bullet instead of the shoulder for establishing headspace came from the outdated practice of reaming the AI chamber without setting the barrel back when rechambering existing barrels. This created excessive headspace when firing standard ammunition, hence the need to seat the bullet out.

These comments aren't meant to disparage Olarmy, Bear in Fairbanks or anyone else those does it that way. If you're comfortable with the practice and it works well, I'm not critisizing it. I'm just saying that it isn't necessary.

My fireform load has been 87 grain bullets with either Varget or 4895. Mainly because I had a lot of 87 grain bullets that I had no other need for. I'm planning to change that to a 100 or 117 grain load so that I can use my fireform loads for a game load.

I agree with Pursell but caution that not all 'smiths will cut a chamber like this without specific instruction. Either specify the crush fit or cast your chamber before loading for an unknown rifle. I'm not a big fan of the Cereal Approach to fireforming, otherwise see no problem with the previous advice in regards to loads.

When properly cut per Ackley's philosophy, the easiest path is to load ammo as if shooting a regular Bob and then go about your business. Properly executed, you can expect about .004" crush.

I think the key is to make sure that the base is held solidly against the bolt face. If you are confident that the 'smith has cut the new chamber correctly, there is no problem...

Olarmy, I agree that your method is safest if you don't know how the chamber is cut. Since Frank's stated his barrel is coming from Hart, I assumed that they would have cut it correctly. I know that the ones I do are cut correctly. I forget that not everyone does things my way. (Mighty inconsiderate of them.)

I do cringe when I read, either in print or on the net, comments about making AI chambers being as easy as running a reamer into the existing chamber.

You can check the chamber with headspace gauges. When chambering to the Ackley version the standard caliber "go" gauge should not go. In this case the the bolt should close on a 257/7x57 Ackley improved "go" gauge but should not close on the standard 257/7x57 "go" gauge. As far as fireforming I try to pick up the cheapest bullets I can find at a gun show and load them with powders on the fast-medium burn rate listed in the reloading manuals for the standard caliber. I also use new brass for this, but not Remington anymore (really got crappy lately). This is also the time for you to start "breaking in" the new barrel. Follow the maker's recommendations. I feel this is very critical to accuracy. I also wouldn't use moly coated bullets for this either.

Well if all this good advice doesnt work you can donate the rifle to me. Been doin the AI thing for a while with various calibers. Been lucky to have a smith with a good head on his shoulders. When I started delving into the AI loads, I didnt know about the "crush fit" or anything else for that matter. Just knew my buddy had an AI and it was one bad dude. And I had to have one. When I had my first AI made from a factory barrel, my smith told me he had set the barrel back just a tad. Then he went on to explain in depth about the fireforming bit. Good thing he takes pride in his work. I too use my fireforming loads for dual purpose. At least in my 7-08AI. 100grn sierra hp over a charge of blc-2 perfectly forms the cases and gives the crows hell. This was a throw together load and surprisingly it shoots some serious groups. So good luck with your new 257. And remember, have fun while fireforming. That way there is always a good excuse to go warm that barrel.

My suggestion would be to load up the initial loads to be fireformed as if they were going to be your hunting loads and then treat them as such. Ive been able to get some very impressive accuracy AND velocities while fireforming!!

What's more, I have also tried fireforming with inexpensive 87 grain varmint bullets, but found that they only fully form the case about 75% of the time, the other 25% end up getting fired again just to accomplish a uniform case. Use at least a 100 grain bullet and a good peppy load to fireform. I get a crush fit and dont worry about seating into the lands.

I recently called Hornady requesting a 115-120 grain Interbond for this chambering and if they made one Im sure it would be my go to bullet. Preferably about 117 grns. If anyone else would like to see this please give them a call and request it. 800-338-3220

I have tried 100 ways of doing it.





Now I put 10 gr Unique [many pistol powders will do] and top off with Cream of Wheat.

The case is coated with Imperial sizing wax.

I point the barrel straight up.

If there is a range master to deal with, I poke the mouth in a soap bar so I can shoot horizonally.



That forms 90% of the case into the 40 degree shoulder without shooting bullets.

Barrel wear costs more money than the bullets.

The next shot has full load and full accuracy.



With 75 gr Vmax moly coated, Win +P brass, WLR primer:

1) 49.4 gr. of IMR4895 at 3.4" with Sinclair bullet comparitor gives 3942 fps and the extractor cut grows .0035"



2) 48.3 gr. gives 3757 fps and the extractor groove grows .0005"



3) 47.2 gr. gives 3736 fps and no extractor groove growth



4) 45 gr. gives 3674, 3621, 3630, 3614, and 3630 fps and a .9" group at 100m



5) 45 gr. with OAL 3.5" w/ Sinclair nut gives 3674, 3621, 3630, 3614, 3630 fps and a .46" group at 100m.

Got the rifle a few days ago and have REDDING AI dies as well as RP .257 Rob cases on the way. I did have a half a dozen RP .257 cases so decided to fireform a few just to see that Sexy AI case. I used 36.0 of H4895 and 100 gr bullets.
Popped the case out perfectly. I mounted a new 6x42 Leupold so all I need nowis some more brass.

Sweet looking little case!

FN in MT

Frank:


But if ya think that's neat, wait'll you see the groups you get. Good luck.
Bear in Fairbanks

I guess I'll be the outlaw on this one.First I want to say that in all my years of fire forming I have never had a problem.

In a 25-06 IMP that I had Ijust used factory ammo to fire form until I acquired enough cases.If the head space is right on your .257IMP or you have even a little crush there should not be a problem and you should get near complete form.If you have cases you want to load use 95% of max. loads of 3031,4895,4064,4320 or4350. If fireing factory loads is safe this should be too.
The idea of spacing using a bullet jammed into the rifling is not a bad idea some times it is absolutly necessary by design or accident. In 1966 Fred Barnes and I made up a 6mmx.270 IMP.The shoulder was .055" farther out than the standard .270 shoulder and I screwed up by bringing the new shoulder to close to the standard shoulder. Because of a deep throat we had to seat some of Freds 115gr. bullets way out to meet the lands.A case load of 4831 and full form. I really don't want to sound cavalier but I really think that this one is rather straight forward. roger

Frank,

The first thing for you to find out is if the chamber has been cut to the proper length for an Ackley round.

I cut all of my ackley chambers for a 0.004-0.005" crush fit. What this means is that when you chamber a round, the neck/shoulder juction of the chamber will contact the neck/shoulder juction of the case 0.004" shot of the bolt locking down.

When you fully lock the bolt, the case neck/shoulder juction is compressed that 0.004-0.005" and provides a very positive gas seal.

Other things it does for you is hold the case firmly back against the bolt face and stops any forward motion of the case when it is struck by the firing pin. THis eliminates the problem of case stretching on the fireforming load.

Also, the reason a properly chambered AI rifle is generally so accurate with virgin loads is that this crush fit helps to position the bullet on axis with the bore.

If you can close the bolt on a fireforming load and feel no resistance, then your chamber is not fitted correctly. THe folks at Hart should do a very good job for you but this is something to pay attention to. There should be just a bit of resistance when you close the bolt.

Because of this there is no need to seat the bullets into the rifling and I strongly advise against this practice as it can cause some variations in chamber pressure even with the low pressure loads.

Most of the modern load data books have the 257 AI in them. Use at least a 100 gr pill with a near top charge of moderate burning powder for this round and you will get sharp shoulder cases.

One thing to remember about the 257 AI. Most will tell you it is the equal to the 25-06. Loaded to very high pressures it will come very close to equalling the much larger 25-06. When loaded to the same pressure in the same barrel length, the 25-06 will have a 125-150 fps edge.

Point being, the 257 AI is a great little round for what it is. If you want to drive a 100 gr bullet at 3400 fps get a 25-06. If your happy with 3200-3250 fps, the 257 AI is a very useful and fun round to load for.

Many will tell you they are getting near 3400 fps with their 257 AI with 100 gr pills. IF they are shooting the round in a 24" barrel and getting these velocities, they are running the little round extremely hard.

Do not get pulled into this way of thinking. If you want more performance than the 257 AI can provide, let me know. I have a very accurate 25-06 AI reamer here that would give you 3600 fps with a 100 gr pill very comfortably.

Good Shooting!!

50

Got my dies and brass. Fireformed a few cases and HART knows what they are doing as the cases ARE a slight crush fit in the chamber. NEVER had any thoughs to the contrary about their knowledge or expertise.

Now all I need is some time to get the chrono set up and work up some loads. Same goes for the CZ 550 9.3x62 I bought LAST YEAR. Too much work not enough play time.

FIFTYDRIVER........ I didn't do the AI hoping to set velocity records. I like seeing 3000+ with a 100 grain but have NO illusions of seeing thirty TWO hundred. I'm not a big velocity guy anyway other than in varmint guns. And thanks for all the info too.


FN in MT

I wouldn't be surprised if you got 3200 w/100s. I get 3150 w/ 100s out of my 23" barreled .250 AI.

John

Frank,

If your only looking for 3000 fps why didn't you go with either the 250 Savage AI or the standard 257 Roberts.

Both will easily get 3000 fps with 100 gr pills.

I'm not saying at all to hot rod the 257 AI. 3200 fps loads with a 100 gr B.Tip is certainly not pushing the envelope, in fact it should be relatively comfortable to get those speeds.

Its common knowledge that top accuracy is seldom found at top chamber pressures and velocities.

It is a lesser known fact that to low a pressure can also degrade accuracy just as much. YOu have to deal with velocity variation, poor powder burn which leads to excessive bore fouling which will lead to increased copper fouling.

Every round has an efficency window that it should be running in, 3000 fps with a 100 gr bullet in a 257 AI is certainly at the very bottom of any productive window for that round. It will perform much better with a little more pressure, especially when it comes to a clean powder burn.

Good Shooting!!!

50