Fire formed brass by using a light load from regular Robts info and IMR 4895 powder as stated in the Nosler #4 book. My first loading after fireforming was 41 Gr. of IMR 4895-Rem. 100 Gr corelokt sp-RP brass and col of 2.765, well off the riflings. This loading backed out the primers about the thickness of a fingernail, with abour 4 to 5 thousandths expansion at the expansion ring, it shot into 5/8th of an inch at 100 yds. Changing the powder to 45 gr. of IMR 4350 gave decent accuracy but had slightly flattened primers. I know it is hard to tell over the net but does anybody see anything wrong so far?
It is the 40' version.
Steve E......

[ 10-20-2003, 04:47: Message edited by: Steve E. ]

Steve,
Are you getting a good form or are you getting a radius instead of sharp corners? Was this a re-chamber or a new barrel? It sounds like a re-chamber that was not set back a couple of threads and you have a slight head space problem. Jim

That doesn't sound too unusual to me. The case is too short after the first fireform and the pressure is not high enough to set the head back onto the bolt face on the second.

You could help yourself by seating the bullet into the lands from the start. That will hold the case back firmly against the bolt head and give you a better forming with less case stretching. If you have a plunger type ejector (like a M700) the case will be pushed away from the bolt face by the plunger, and seating the bullet firmly into the lands will counteract this.

Have fun, it's a great round.

Fireforming loads (100 gr. Core lokt?)were loaded with the bullets firmly engaged with the riflings and it is a small ring Mexican Mauser, the barrel started life as a 250 savage but that didn't work out. Brass seemed to have good sharp shoulders after fireforming. Didn't have any of these problems with my 280 Imp. I swabbed out the chamber to remove all oils before shooting.

Steve E.......

Steve,
If you are not getting a good crush fit when you close the bolt thats where your problem lies. I don't mean to the point where you have to beat the bolt handle down with a 2X4 but you need to feel it close on the case and "crush" thereby holding the case firmly against the bolt face. If you can't feel it close on a .257 Roberts, It ain't right. Jim

Steve E.,
Just a couple of questions, neighbor. First, when you chamber the cartridge to fireform, do you feel a slight resistance as you close the bolt? A properly cut Ackley chamber is about .004 short of the standard chamber and you should feel slight resistance as you close the bolt.
Second, here is how I set up a fireform load for the rifle using brand NEW brass! I find the load in one of the handloading books (I use Speer)and use a load that is 1 grain UNDER the max load listed for that powder and bullet. This has worked well for my 257 AI, 6.5/08 AI, 8x57 MAI and my 338x57 MAI (Mauser Ackley Improved). On the 338x57 MAI, I used the MAX load for the 8x57 Mauser since this is no data for the 338x57 MAI. This system has worked for me. Hope this helps.

Ol' John

You do not have an improved chamber.
You have a wildcat. With an improved chamber
you will have a crush fit on a factory case
There will be no problem with fireforming.
They will all fit.
Yuman

low pressure... bad seat...

you can do a couple things...
1: resize formed brass and see how it does...

2: expand case neck to 7mm or 308 (got 30-06 dies) and then reform to .257.. this should give you a tad more shoulder to fit.

jeffe

I used a 257 Robets case as a chamber gauge when I chambered my 257 Roberts Ackley Improved [mistake].

Now my chamber is .004" too for the shoulder of the unformed brass to stand up to the sharp ring where it touches the chamber with the force of the firing pin pushing.

What I do is ~~10 gr of Unique and fill the rest with Cream of Wheat, with no bullet. [less for Bullseye, more for 2400, etc.] This make a 90% formed shoulder. I then load the case with a 257 RAI load and get accuracy as good as it gets. After shooting that accurate load, the shoulder is 100% formed.

I have a mountain of experiments I have tried to get perfect fire forms in one step. I can't do it without overstressing the brass and getting primer pocket expansion.

So I do it in two steps.
Oh well.

Jim White is correct. If you look in Sierra #5 the dimension for the standard 257 from the base to the neck-shoulder junction is 1.912" and so called improved version is 1.906"

Since the rifle shoots such good groups I would not have it rechambered unless the webs weaken too much with factory loads. Is there web thining when you feel inside of the case?

Don,
It's not "so called improved" it's VERY IMPROVED!
If 3607fps.with a 100gr.bullet on 57gr.of MRP isn't improved then I stand corrected.
And out of curiosity how do you feel the inside of the case? I can't get my fingers into mine.
Stepchild

Stepchild,

I would be curious as to the specifics of the load. Which bullet, OAL, and barrel length.

Stepchild,

You can make a feeler wire from a piece of coathanger. Just bend a tiny hook about 90 degrees on one end and file it some but not too sharp an edge. Feel inside the case down near the expansion ring and if you feel a groove in there the case may be damaged. Feel around as the ring starts on one side. A small, shallow ring is usually ok but that's up to you.

Check your velocity on that load. My internal program shows 57.3 grs of MRP with a 100 gr out of a 24" 257 AI at 3330 fps. A 257 Weatherby with freebore can hardly reach the velocity you posted.

Have a safe day.

Ramrod340,
The rifle is a 700 Remington LA with a Shilen barrel(27.5")polygon rifled. The bullet that achieved the highest velocity was the 100gr. Speer spitzers. I lost about 50fps with Sierras for whatever reason.Winchester cases.
The velocity was recorded over an Oehler 33.
In the initial tests I loaded as much as 63gr.of MRP(drop tube) and got velocities up to 3,763 and yes this was a gross overload and the cases and primers came out seperately.Only did a couple of those. With 57gr.this rifle shoots dime sized groups and kills deer as though they were electrocuted. Also does a nice job on Elk,ask Jim White about that one.

Savage99,
I don't know about your ballistic program, just reporting what I experienced. I never had any strange readings from this chronograph. It never missed with my .17 Remington either and velocities were always in line with the load being used.
I was just having a little fun about feeling the inside of the cases.
Stepchild

Savage99,
Just an after thought. My Speer #8 manual shows their test rifle with a 22"barrel at 3,410 with 57gr.of Norma 205,100gr spitzer, which is what started the wheels turning. I wondered what it might do with a longer barrel and was very pleased with the results.
Stepchild
Anyone reading this data is warned to start with a lower powder charge.

stepchild,

Your posts have given me a new #1 reason why so called improved cartridges are not good.

Savage9.9,
If you live to be 200 you still wont be any smarter than you are today! You badmouth ACKLEY improved cartridges at every opportunity you get.
You read your Nosler manual, shooters bible, your ballistic program and accept every word as gospel.You don't own a chronograph do you?
I don't have any axe to grind here. Surely Ackley made some that weren't all that "IMPROVED" but give credit where credit is due. You place them all under a blanket and label them as no good.And don't do it or you'll lose value on your gun.HOGWASH.
You have badmouthed the .257 Roberts, when you made that statement I knew you didn't have any hands on experience with that cartridge or you wouldn't have made such an ignorant statement!
And yes I went out of the envelope when I was developing loads for my .257 ACKLEY'S But I didn't stay out there.
I could go on with this but it wouldn't do you any good, would it?
Stepchild

Most of the Ackley Improved have their place, and Mr. Ackley was the first to admit that some were not an improvement over the factory. I have been following this thread with some interest, as I have a neighbor who built his 257AI over thirty years ago on an old Mexican Mauser action.It has had at least two barrels, maybe more, on it in those years. He called me up three years ago, after he learned I had just bought a chrony, and wanted to meet me at my range. He wanted to double check his chrony. We did this, and he averaged just under 4100fps for three rounds. One ragged hole at a hundred for the first two, with the third a half inch out due to extreme barrel heat.He just wanted to see how fast he could push it. He has five grand-daughters, and all have taken whitetail deer with this rifle, the latest (nine years old) in 2002.I am not sure that the Ackley Improved is needed in any caliber in this day and age, but it was when the old master was doing his thing.And I will say this. It is hard to sell one to the general public.

I just looked at my manual again to be sure before I stuck my foot in my mouth and it states(Nosler #4) on page 198 under the 257 Robts. Ackley Improved using IMR 4895 starting load at 40.5 and max load at 44.5 so my load of 41 gr. was well below max. It scared me for a minute when you posted that cause I thought I might have misread my data when loading. Using the same bullet IMR 4350 is 46.0 to 50.0 max, so that loading for 4350 would be low for the Imp version.
After that first firing everything seems fine.
Steve E......

[ 11-08-2003, 05:28: Message edited by: Steve E. ]