Just got a rifle back from a gunsmith. first round had case-head stretch marks, which I attributed to lubricant left in the chamber walls. Then about 1 in 5 280 Rem factory rounds showed a bit of primer backing.

It appears the head spacing may be a tad long for the factory rounds to seat well?

I tried to load a reloaded fireformed round from another 280 ackley, (different gunsmith, different reamer) and that fireformed round would not chamber without forcefit and sticky bolt removal, even though I did not fire the tight fit round.

So the symptoms are perplexing... solution is to have headspace checked before refiring, and perhaps rechambering the barrel?

I have a message in to gunsmith, but figured I would let all you shadetree mechanics offer insights as well.

Thanks.

THe

It defintely sounds like excess headspace. A lot of gunsmiths don't put the crush fit you need on an improved chamber. You need to feel the bolt resistance increase upon closing in the last 1/3 to 1/2 of travel. I seem to remember that the crush fit should be around .004 to .005.

Jameister

Sam is right. You need to have a serious talk with your gunsmith. To properly cut an Ackley chamber the gunsmith should set the barrel back one thread and re-chamber so there is a crush fit when loading factory ammo. Otherwise you will get exactly what you got, stretched cases and possible head separations. It's possible to accomodate the longer chamber with handloads but the whole idea of an Ackley chamber is the ability to fire factory ammo.

A properly headspaced Ackley might show you the same symptoms you are getting now if the Ammo is a little on the short side. Start by asking your gunsmith if he used Ackley headspace guages. If all is Ok, you might have to pull the bullets out a bit to touch the rifling and that would ashure a proper fireforming.
bigbull

You asked for a custom rifle and you got one. If you were intending to shoot factory loads, then there was no point in doing the conversion, so the loss of the use of factory loads should be little sacrifice.

Take some shiney new .30-06 brass and run it into your Ackley sizer JUST far enough that it will chamber with a tad bit of resistance. Waallah! Your "headspace" problems are solved, and your initial loads can be loaded to improved specs instead of shooting the underloaded factory rounds.

There area number of reasons why you might be experiencing this. It is possible that the chamber is too deep but if you can feel any resistance when you close the bolt on a new cartridge, this is not the case.
Another likely problem is that the factory ammunition is generating insufficient pressure early in the curvve and the brass is actually shortening up. Measuring thelength of the brass before and after firing will help to identify this problem. Keep in mind, it is not uncommon for the brass to shorten up to a certain extent when fireforming.
The stretching at the head of the case is not from lubricant left in the chamber. In fact, it is not uncommon for a shooter to deliberately lubricate his brass to allow it to slide back and move the shoulder forward. Now, before somebody starts freaking out about increasing bolt thrust etc. etc., I should say that I stop short of recommending this to others though have done it myself and quite happily too. There are some potential pitfalls unrelated to increasing bolt thrust ( I actually believe that the amount of bolt thrust increase is, in most cases, miniscule.

Jameister;

Before you do anything drastic, I would like to ask one very important question.

Did you happen to use your "Ackley Improved' sizing die to "iron out" the necks?

If you did it is likely that you "bumped back" the shoulder of the "standard" case.

I made this mistake once when necking up some "06" brass to 8mm to fireform some 8mm-06 A.I. cases, getting results similar to what you discribe. I now shim my die @ least .040" (a little more wouldn't hurt) from the adjusted setting when necking up new brass.

If you did use the "Ackley" sizer die I would suggest that you try some unaltered factory loads and see what happens. As posted, you should feel the "crush" as you close the bolt.

If you did inadvertantly "bump back" the shoulder you will have virtually no shoulder for headspacing. I even had cases that did not want to fire because of this very situation.

Thanks for all the information so far. still waiting for a call back from gunsmith. I am very patient on some things, especially when a skilled machinist with good past work is involved. But heres the scoop so far:

I shot 8 different factory 280 loads. the fed premium was only one with obvious stretched case almost separated. several federal and other brass showed primer pushback.

All of the winchester nickel plated showed no problem...

what I believe now is that there is no pressure on the shoulder, and the firing pin pushed cartridge forward, which then expands into the chamber in a forward position, and the primer then backs out a bit with true brass brass, but with the nickel the nickel is able to slam back and keep the primer from being able to back out.

Now what I dont understand at all: I took some 280 ackley reloads from my other rifle, and they do not chamber in the new chamber at all, matter of fact, when I crushfit them in, I had to use a soft hammer to open bolt back up, even though I never fired them.

So the chamber is too long for the factory 280 rem rounds, but too short for the other 280 ackley? makes me wonder whether I dont have a 280 RCBS improved somewhere?

perplexing, confusing, and not easily explained as of yet...

Jameister

It sounds to me like the chamber WAS cut too long as indeed the other 280 A.I. that you have cases from may be also.

None of this is insumountable as there are several methods that can be employed to make fire froming possible, such as necking up then down to form a false shoulder or seating bullets out into the lands.

It is a shame though as a properly reamed "Ackley Improved" chamber makes fireforming soooooooooo simple.

Harry McGowen did my 8mm-06 A.I. and it is cut with the proper "crush fit".

quote:

Life is more exitin' when yer stickin' suppositories inta a wildcats behind!

it was not until tonight I recognized that your tagline is about wildcat cartriges.. until now I wondered why you would advertise your putting anything in a cats butt.... slow but eventual recognition..

Wildcat Junkie,

You made a good point about not using the AI
dies to load fireforming brass. This would be
an easy thing to overlook and slow up the diagnosis of the problem. Thanks for mentioning it. I shoot a lot of AI'd calibers.
I will remember this.

quote:

Originally posted by Jameister:

quote:

Life is more exitin' when yer stickin' suppositories inta a wildcats behind!

it was not until tonight I recognized that your tagline is about wildcat cartriges.. until now I wondered why you would advertise your putting anything in a cats butt.... slow but eventual recognition..

Years ago all I hunted with were muzzle loaders. I used a .36 flinter for "Squill", (bless you big Mortie)I had both a flinter and a "cap gun".54 for deer and I used a couple of "2 pipe 12 power" muzzleloading shotguns for rabbits etc.

It was then that I picked up the term "suppository gun" (loads through the backside)

quote:

Originally posted by Stonecreek:
You asked for a custom rifle and you got one. If you were intending to shoot factory loads, then there was no point in doing the conversion, so the loss of the use of factory loads should be little sacrifice.

Stonecreek - You missed the whole point of an Improved chamber which is to fireform brass without having to do a lot of reforming work. In a properly done Improved chamber you should be able to make brass either from factory loads or from new brass.

In looking back over this thread I see no mention of the rifle model.
If it is a rifle with a plunger type ejector, the ejector should be removed and the struiker assembly. Then, with a new factory cartridge see if there is any resistance when the bolt is closed on a cartridge. If there is, things are as they should be. If not, the chamber is too long. If you then start putting layers of Scotch tape on the base of the cartridge, you can get a rough idea of how much too long the chamber is. Add tape until you just feel some resistance. Measure the tape then add .004" to this. This figure will be how much too long the chamber is to work well with that brass. Does this mean the guns,ith screwed up? Not necessarily.The standard procedure for an Ackley chamber is to cut the headspace .004" shorter than the standard dimension for the parent cartridge. This is how much shorter the Ackley headspace guage is than the standard. It is entirely possible to have ammunition which is that much shorter than standard and, yet, still within spec. So the poor gunsmith chambers the rifle just as he should only to be foiled by the ammunition. Keep in mind as well that, with the standard cartridge, the headspace is measured to the datum line which is a point on the shoulder of a specific diameter (I think it's .375" in the case of the 280 but don't have a book here to check).With the Ackley chamber the datum line means nothing and it is the distance to the juncture of neck and shoulder which is important. Brass, also, is measured to the datum line and the juncture of neck and shoulder is not a critical measurement (comparatively speaking). These are some of thereasons I started using new brass to use as the basis of my headspace measurements when doing AI chambers rather than using the guage. The truth is, that with many of the Ackley chambers, you can shoot factory loads but it often doesn't work out all that well as a means of forming brass. Pressures may be too low and powders too slow burning to be optimum. Regards, Bill.

Bill: that is some good specific information. now for the news from my gunsmith, a fine gentleman with years of experience. He told me he built the rifle with zero headspace. I take it to mean that it had zero headspace as opposed to .004 crushfit headspace? so the tape trick is on tap after the chores are done tonight. What an amazing amount of board brain here!!! I will add tape layers until the factory load just crushfits and then tight crushfits. Then all I need to do is take a roll of scotch tape into the field with me...

I will report what I find.

Jameister

I have a 280 Ackley with the exact opposite problem. The chamber is shorter than "normal". Factory 280 loads do chamber, but very, very tight. And, my Redding sizer had to be modified to get the shoulder to headspace correctly. But, those were minor problems, and it is up and running wonderfully. Pete from Quality Cartridge really helped me out as well. I sent him fireformed brass, and he made me up a batch of brass to match my gun. He kept one of file, so if I need more, it won't be a problem. He said now his standard policy is to only make the Ackley improved brass to match customers guns. There is no real "standard" and there is quite a bit of vairiance out there from gun to gun.

Wellll.

I put 6 or 7 layers of scotch tape on the primer end of a new cartridge. load and unloading until there was resistnce to bolt closing. at the last layer, the bolt firmed up, and there is the slightest ring around the neck base, where it flares to teh shoulder. so I miked the total length with the tape on, then peeled it off and miked again. the net differnce is 12-13 thousandths.

so is 13 thousandths headspace just right, way off or somewhere in between?

very clever, these board members.

Jameister

So with the tape methods: 6 or 7 layers of scotch tape to the primer end of the brass, and then teh bolt began to feel resistance. there is the faintest ring around the neck collar showing the point of contact. I miked the COL with the tape, then took tape off, and miked again, there is a net difference of 13 thousandths.

Good?
Bad?
IN between?
way bad?

Jameister

I repeat myself.

computer said it dumped.

oh well.

J

Jameister

Yes that sounds right. That much excess would certainly account for the stretched brass. Doesn't sound like "Zero" headspace to me. Sounds more like the reamer was run in too far. But, the situation can be salvaged by forming brass to fit the chamber. I hope you were kidding about taking the scotch tape into the field with you?? Don't mean to insult you by asking that question. What you need to do now is start with fresh brass and expand the necks to 30 or 32 caliber. Then start sizing the necks down a little at a time forming a false shoulder. Keep trying the brass in the rifle until you get that crush fit we have been talking about. Then stop and fire-form. When you get to the crush-fit stage you will see a little remnant of the false shoulder, probably .010 to .020 inches long, at the junction of the neck and shoulder. Also, when chambering one of those cases you should see a bright ring at the beginning of the false shoulder where it made contact with the chamber. Good Luck - Ray

Where are you in AZ. E-mail me at joyray@frontiernet.net. Would like to talk with you off line.

Too much speculation on everyones part. If your gunsmith used Ackley Headspace Guages and did indeed cut the chamber to zero headspace it will indeed be very tight on an Ackley case which has nothing to do with the fit of the factory unfired case. If you have faith in your gunsmith that the job was done as described to you then proceed as follows. Load a bullet long and start seating deeper until the bolt handle closes with a bit of friction, this will assure you that the case is tight against the bolt face and will yield a good fireform. Use a medium load here. A note here: If you get a bright shiny ring at the base of the case after resizing it will have nothing to do with the headspace but rather with the case diameter compared to the chamber.
my .02
bigbull

I was sarcastic regarding scotch tape into the field.

I think that doing a jam-into-lands with bullet seating can take care of problem, but I do not think I am ready to accept an overlong chamber that can not safely take 280 factory..

Otherwise, I would have a wildcat, not an ackley improved.

I think we got there, now to see what my smith offers to do for me. I think that it should be faced off and put forward a half turn or so, whatever 12 thousandths is compared to a thread.

He is making me a pair of these, and I want (need) to have them able chamber the same brass, even if not for benchrest accuracy, for sanity of interchange of rounds in the field.

regarding my other 280 AI brass not fitting into this one. I still am perplexed why the other 280 brass does not chamber in this rifle, but my bet is that is has a larger diameter chamber, and I necksized only, so maybe the brass from that one is built like Hillary Clinton with a fat butt and unlikely to give any headspace at all.

Cheers and apologies to the Billary supporter out there. I could have said it was built like a Bush brass, with empty headspace, but that is rude to a sitting president.

Jameister

jameister

Jamming the bullets can work if you have enough neck tension but is not my preferred method. I think you're right to question the chamber. An Ackley Improved chamber should be able to fire factory ammo. Otherwise, you're right, it's a wildcat not an Improved. What about a subsequent owner of that rifle who assumes it's an Improved and goes happily along forming brass that may result in head separations? Many gunsmiths that chamber for Improves do not use an Ackley headspace gauge, they use a standard gauge and cut the chamber until the bolt will only partially close. That is about .005 short which is what it should be. I have a 280 Ackley myself and that's the way I did mine. I then checked a couple of different brands of new 280 brass to make sure I had the crush fit. Using a full-power 280 load, the brass formed perfectly. Full-power loads is what you use to fireform Ackley brass, by the way, not reduced or mild loads. I'm sure the fired 280 Ackley case you tried wouldn't chamber because it had been fired in another rifle and neck-sized only. JMHO on all this. It's your rifle.

Jameister,
That much clearance is indeed, excessive. In fact, any is excessive in this situation. As I mentioned before, this is not necessarily the fault of the 'smith. Gauges are built to a length as determined by the datum line. Unfortunately, the datum line is meaningless when you are dealing with an AI since headspacing is done on the juncture of neck and shoulder. If the shoulder angle is a bit sharp on the factory brass, headspacing will be long in the chamber. So, a rifle chambered at zero on an Ackley gauge, which should theoretically give .004" crush, could still be too long with a particular lot of brass.
JGS was considering determining a datum measurement then making gauges with the 40 degree shoulder. This might work out but would most likely open a can worms and serve mostly to further confuse the issue.
Anyway, it sounds like your gunsmith has a good handle on things and will, no doubt, be able to fix things up for you. Just have him use a piece of your brass as a gauge and chamber .004 tight on that. When this is done, it is a good idea to gauge the length of the chamber to get a proper "trim to" length for that chamber. Regards, Bill.

I sent the rifle back today to the gunsmith.

I will show and tell when it comes back.

Jameister

Jameister, I would have him cut the excess off the back of the barrel and start over with the process Bill Leeper described. He stated one thing that is overlooked often when dealing with improved cartridges and that is differences in lots /makes of brass. I have shot many Ackley improved designs over the years and you would be amazed at the differences from rifle to rifle.

I have asked the gunsmith to take off at least one thread from the end of the barrel, and then to deepen the remaining chamber until it just crushfits against an unfired factory 280 round.

more later

I have a 243 AI and had 257 AI and 7x57 AI.
all chambered to an Ackley headspace guage,and were all crush fit on virgin brass.

Lyle