# 22-250 Ackley Improved Bullet Depth Question



## SaberX01 (Sep 25, 2009)

I've started a new build 22-250 AI and have been doing a fair bit of research regarding fire forming cases. Most seems pretty straight forward, however, in the Nosler - 6 reloading manual ( and maybe this is a quesiton for them, not sure ) it stated a recommended fire forming process, same process for all the AI's listed in the manual. One point in the process ( the one in quesiton ) is:

"Seat the bullet well out into the rifling so it makes good contact with the lands when the cartridge is chambered. This holds the case head against the bolt face and eliminates case stretching in the web area, a cause of case head seperation. We recommend using 50-55gr bullets. Lighter bullets are generally too short to reach the lands".

I've always started a minimum of .005 to .010 off the lands when working up a load ( or at least since I've had the ability to measure head space and seating depths). I also understand there is about 0.004 headspace delta between the normal chamber and that of AI, thus the reason for a shorter seating depth. I dont think I have a load that is less than .005 off the lands. Question is, is it safe to bring the bullet into physical contact with the lands and does this not dramatically increase chamber pressure? I know moderate pressure is required to re-form the shoulder to 40 deg and even out case taper but I have no way to physically "measure" pressure, other than to look for the standaed pressure signs.

"Good Contact With The Lands" - That seems ambiguous, how much is "Good", 0.000 off the lands, positive pressure against the lands ( how one measures that I have no idea )? I know I can measure this distance rather accurately, and set the seating die accordingly, or use a modified case to allow for movement of the bullet backward into the case when chambering, then measure the OAL ( Case-Head to Ojive ) but is there a better known method?

Additionally, would I not have to repeat this process if I changed bullet type / Ojive, realizing of course, that only those cases fired from this rifle could be used to load AI rounds for it?

Comments much appreciated.


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## southdakbearfan (Oct 11, 2004)

When fire forming for my 257 ackley improved I use the Nosler Process listed in the manual.

My bullets are well into the lands ( 0.010 to 0.015), the reason being, if you don't seat the bullet into the lands the case will move forward in the chamber as the firing pin impacts the primer since there is no case shoulder to hold the case back, then as ignition occurs, you get excessive stretching in the case web as the case is no longer seated against the bolt face due to the firing pin impact. With seating the bullets into the lands, all the case stretch should occur in the shoulder area, which is where you want it.

I start with a very mild, bottom load listing for a relatively fast powder for the bullet weight in the standard caliber loading data, so 257 roberts for me, 22-250 for you. Any pressure signs will show fast with a backed out primer or case shoulder failure. I would also recommend a not so sleak bullet as some of the sleaker bullet designs (ballistic tips or v-max's and others) you really have to seat out a long ways to get good contact with the rifling. I actually prefer speer boattails for this process. They are a little fatter further up the bullet, for lack of a better description. I would only load a couple and try them, to see if you have enough powder behind them to actually fire form. Also temperature will play an issue. My standard load will fire form perfectly at 60 degrees and above, but at 40 degrees will hardly move the shoulder out at all.

I use to use the corn meal method or buy factory ammo to fire form, but after 3-4 full powder ackley reloads I was seeing head separations because of the case movement in the chamber during firing pin strike.

Now, after changing methods of fire forming, I have gone well over 15 loads in a case with no signs of failure with the same exact loads I was having issue with before, after fire forming using the process in the nosler manual. Also, with the ackleys, I can go 7-8 reloads, full power, and not see case stretching issues (no need to trim) as the taper is virtually removed from the case and the stretch is taken out during the fire forming process.

When you load after fire forming, for your ackley improved case, you will want to be off the lands as you described, how far, depends on the bullet and load.


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## Csquared (Sep 5, 2006)

Hey guys, the above shows why we will always be asking questions. Nosler says the bullet in the lands will keep the case from stretching from the web area?

Really?

How will it prevent that, and where then will the stretched brass be taken from if not from the head area? Brass will flow forward until all voids in the chamber are filled, and I can think of no way to "hold" the brass static at the head while allowing the brass from the middle of the case to flow. I don't think the bullet has any contact with the case while the bulk of the stretching is going on anyway. Nosler's explanation makes no sense to me, but they're not the first to say it.

I think the only thing a bullet into the lands does for fireforming is guarantee a good primer strike. And I could be wrong, but doesn't both the .22/250 AI and the .257 Roberts AI both retain the same measurement to the neck/shoulder junction (headspace)in both forms? That makes the bullet in the lands a moot point. I believe AI chambered rifles by design should be able to shoot SAAMI rounds and AI rounds interchangeably.

You're a smart guy, bearfan, so please help explain what it is Nosler knows about selective case stretch that I can't comprehend.


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## SaberX01 (Sep 25, 2009)

southdakbearfan,

TNX for the input. My main concern was / is the "seating into the lands" portion of the whole process. It makes sense to me, that with the AI chamber being honed out, there's a need to make up the diffrent in headspace ( .003 to .005 or so ) somehow when fireforming standard 22-25 cases. Keeping the case-head in solid contact with the bolt face while firing to keep the "case stretch" for lack of a better word, more toward the shoulder/neck section is very important in preventing case-head/web seperation.

I dont think I will have trouble with long enough bullets to achieve this need, as the design goal targets a 1:10 or 1:12 twist barrel, most likely 1:10 or 1:9 (still discussing this with my gunsmith) to allow for using heavier bullets, 70gr to 80gr weight range
but the point is well taken about using sleek bullets.

It's understood this will impact on lighter weight selections of 50gr to 60gr weights but I have a standard 22-250 to cover those weight ranges. If the current project works out well, I may convert the 1:14 twist 22-250 to an AI also. If for no other reason than to extend case life and improve brun effeciency.

[EDIT]
Here's an Article on a 22-250 AI build. Pretty good reading: http://www.varminter.com/particles/aifront.htm

More comments always welcome.


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## southdakbearfan (Oct 11, 2004)

Well, as I said above I use to use various methods of fire forming. Firing factory ammo, cornmeal method among others and I got head separations after 3-4 reloads. The rifle chamber's were cast and checked for headspace issues, finding none.

After switching to the method listed in the nosler manual, I have run as many as 15 reloads through a case, the same exact load, bullet, and OAL in the same exact rifles without a case failure and all cases are specific to each different rifle and kept separate as most of the time they are neck sized only for varmint/target shooting and only full length for big game.

Hence it would seem that the nosler manual is absolutely correct. I stated this before, and I can figure no other reason to doubt it to be true.

When using virgin brass or factory ammo it is resized to below chamber specs, just like full length resizing, so it will move, however slight of a movement that is, on the firing pin impact as the shoulder/neck junction will not be exactly where it is on the spec sheet or in the chamber. This is exactly why full length resized brass will see failures in the case web (head separations) faster than just neck sized brass, especially under maximum loads.

Previously fired brass, only neck sized may be tight enough to do what you are saying but I never fire form on old brass and you may have chambering issues as every chamber is different and this would be from two different rifles in this case, although I would doubt it would be much of an issue with the jump from the standard to AI.

That being said movement right prior to ignition definately is enough to cause additional stretching in the case web in my experience, actually in both my AI's and in my father's AI. Once ignition is started the brass should expand fast enough to grab the chamber walls. The rear of the case is closer to the chamber wall that the front shoulder section by an extremely long ways when fire forming in an AI, so most of the stretch should be out of the front shoulder and not the case web or at least minimize it, if you are keeping the case as tight against the bolt as possible, which loading out into the lands sure seems to do, as stated above.

Are there some chambers out there that may be tight enough that this wouldn't be an issue, sure. But I have two and my father has one, all with different barrels and different smiths doing the build, that act the same way.

So, please explain why what I have said above is not true, and have some proof besides a theory to back it up.


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## Csquared (Sep 5, 2006)

Bearfan, first let me aplogize for appearing to question you. Not my intent. I'm questioning the science behind Nosler's explanation. Your history here has shown you're pretty well versed in physics so I was hoping you could explain _why _you think the location of brass stretching is being controlled. It's a fairly common opinion, but there are MANY different theories on why and how the brass is controlled at the head. Some, like me, believe it is not.

Some believe the brass "sticks" to the chamber wall, preventing forward movement. I don't, but the main problem I have with those theories is if brass gets bigger anywhere, it's getting smaller somewhere else, and I don't believe there's any physical way to keep it from ultimately coming from the case head.

But the bright side is if the sizing die is adjusted correctly that amount of stretch should only happen once, so I don't see how subsequent firings should have any detrimental effect on case life, relative to how the brass was originally formed. Although I'm sure my mach4 and whisper brass stetches quite a bit when fireformed from .223 brass, they are among the ones that stretch the least after they fit the chamber, and I've never had any case head issues with them. Once again, I'm not doubting your results, just asking why.

But as to the original question, and whether it's necesary to push a bullet into the lands to fireform, my Nosler book lists the 257 Ackley Imp being .006" _shorter _than SAAMI specs for the factory round (to the neck/shoulder junction) so the chamber should be supporting the case better during fireforming than one could expect from any of the standard chamberings.

Again, I wasnt being critical of you. I just ALWAYS ask when something doesn't make sense.


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## southdakbearfan (Oct 11, 2004)

no problem


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## Seven1 (Mar 30, 2010)

On correctly headspaced AI chamber the the parent cartridge should should fit very tightly into the chamber and "crush fit". The bolt will close with a little force. Fireformed brass is shorter than the parent, the shoulder is moved back and the case walls are blown out.

The only reason you would want seat a bullet into the lands is to make sure the pressure is high enough to fireform the brass properly the first time.

On my 22-250 AI I have never seated any bullets into the lands and I get perfectly fireformed brass, it's not neccessary. I've used factory ammo for lots of my fireforming, I've even used 40 grain bullets for fireforming, the key is to keep the pressure up to get a properly fireformed case. I use 4064 and 4320 for fireforming my Norma brass and factory wolf gold ammo has nice brass and long life as 22-250AI loads, seems to be high quality brass.

Ackley's main advantages are no case stretching, and reduced or zero bolt thrust. The straight walled Ackley case grips the walls of the chamber reducing bolt thrust. The more taper the case has the more bolt thrust you will have.

My 22-250 Ackley has a 1-14, 25 inch barrel and I get 4080 fps from 40.0 grains of IMR 4895 and a 50 grain vmax and half minute accuracy. Seating the bullet into the lands has nothing to do with case stretching, if you're seeing problems with case head stretching or separation with only a few reloads you should take a look at your reloading practices not the fireforming technique.


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## spitfire_er (Jan 23, 2010)

in general they want you to seat that bullet out to keep the case head held firmly agaist the bolt face to allow for undersized cases to form properly. Keeping in mind that your chamber specs are the outside case specs AFTER you fire your case. The only cases I have found to have case head seperation are cases that were fired in an out of specs chamber, or cases that have been FL sized every firing for several firings which moves the case back and forth from chamber specs and work to brass to the point to where what becomes the weakest point (above the case web) will fail.

When a primer goes off, if not long enough, the case can be pushed forward in a loose chamber, then there are two forces the inital backwards push, then a forward push, although it is not very substantial it's there. All these somehow tend to reak havok on that case head and along with the FL sizing or bad chamber that will wreck a case quick.

I know that with my reolads that I ether neck size or partial FL size only, they will last as long as the primer pockets stay tight. I have over 20 firings on quite a few of my .220 swift cases with no case failure other than the primer pocket. Just a neck/ Partial FL size clean the case, maybe trim, reload and shoot.

anyways, hope that helps a little, I was rambling there for a bit.


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## Csquared (Sep 5, 2006)

> When a primer goes off, if not long enough, the case can be pushed forward in a loose chamber, then there are two forces the inital backwards push, then a forward push, although it is not very substantial it's there


Huh? Discounting the miniscule force of the actual primer strike, there's one force, and the resulting "push" is in ALL directions..... equally. Pressure knows no direction. Where the case is relative to the boltface when the powder ignites does nothing to create direction, and I would expect it could be shown that the very first movement of the case would be back to the boltface anyway as taking up that slack would require less pressure, therefore happen sooner, than actually expanding the case, but that is strictly my opinion.

The question that needs to be answered is how does a bullet keep 60,000 psi and 6000 degrees from putting that brass wherever it wants it to go?

I fell into that trap about neck sizing years ago but long ago realized that with hunting rifles _properly_ full length sized ammo need not give up anything to neck sized....accuracy or case life.


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## spitfire_er (Jan 23, 2010)

Hey, I must have forgotten to eat my wheaties the other day.

I guess I was thinking more in terms of the rifle itself and was overlooking the actual question.

seating the bullet out spikes the pressure more than if it was seated off the lands allowing a proper form of the case.

As for the neck/ FL debate. I like neck sizing if I have a die in my hunting rifles, and if not I'll partial FL size, ether way they have about the same case life. I quit doing complete FL sizing a few years back.


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## southdakbearfan (Oct 11, 2004)

I am no physicist, by my rifles are headspaced correctly, chambers have been cast to check and they were cut correctly and when I fireformed in the past without seating the bullets out to the rifling I got head separations within 3 or 4 reloads.

Once I used the method in the nosler book, 8-10 reloads without problem.

The only explanation is that the case was moving forward, however minute an amount it was, then stretching back to the bolt head with the resulting force that pushes rearward after ignition.


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## Csquared (Sep 5, 2006)

We had this discussion above, and Seven1 did the same thing as you but without the head separation. My question with your point above is why did it take 3 or 4 firings for the damage done by the intitial firing to manifest itself? It is a rare situation when a new case doesn't stretch rather drastically the first time it's fired, but a properly sized case (assuming fired in the same chamber) will never be allowed the opportunity to stretch much because the chamber itself limits it's movement. And I would submit that the distance between the case shoulder and the shoulder portion of the chamber of a factory rifle when firing factory ammo is at least as much (probably more) than a custom Ackley chambered rifle fireforming brass, and for several reasons. Closer tolerances with the custom rifle. Cut by the gunsmith himself, in most cases, etc., etc. Remember that the appeal of Ackley's concept is that both factory ammo AND improved ammo can be fired in the same rifle, and both cases share a datum line virtually the same distance from the boltface, so I disagree with the necessity of trying to account for space in the chamber...but perhaps that explains why making the bullet engage the lands appears to help...because it isn't necessary . And assuming the custom Ackley chamber is cut to tighter tolerances than I believe the vast majority of factory chambers are cut, thus leaving more excess headspace in the factory chamber, why aren't we told that if we don't pull all the bullets out of our factory ammo to contact the lands before we fire them the first time in our factory rifle we won't be able to reload the brass?

I don't expect for us to agree on if the location of the bullet truly was the reason for case life differences...just doesn't make sense to me. I have a factory .280 that did to me exactly the same thing your rilfe above did, bearfan. Was having case head failure by the 3rd firing. But it turned out the sizing die, when adjusted as directed, was pushing the shoulder back much too far (don't remember the actual measurement) and as soon as I adjusted the die properly, using the fired case to tell me what was right instead of the die directions, the brass lasted until the primers fell out.

What we're learning here is why centerfire rifle shooting will never get boring, cause we simply will never know it all. :beer:


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