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Web Bulge Question When Fireforming

I am at a loss.

I recently built a 22-250 AI and while fireforming I noticed that the web was expanding somewhat. After the 3rd reload the bolt what significantly harder to close than the first 2 times.

I tried full length sizing, to no avail.

Could my fireforming loads have been to hot causing the web to expand to the point of no return??

Sloppy chamber??

The gun shot very well while fireforming and it also shot well after the second reload.

The third reload shot like junk.......Any thoughts?

I have had several wildcats and ackleys, but this is the first time that I have experienced this.

My fireforming load was 36 grains of H4350 pushing a 75 amax.

The gun wears a 8 twist Shilen built on a Remington 700 action.

Please give me your thoughts
 
There is really no way to get 'lost' here.
How is everything measuring?
You tell us, is it a headspace issue, or web expansion?
 
There is a slight crush fit when chamberinh new, unformed brass. Do you think it could be a headspace issue? Too long or too short?
 
I hope this is not what's happening, but if your chamber is eccentric, or wallowed out, or both, from an off-center chambering job, the web will grow too much, even if the headspace is good. Try something with a few once fired cases. Push a fired case into the chamber by hand, with the headstamp indexed up. Then close the bolt. If the round chambers smoothly, extract it and rotate the headstamp 90 deg and do it again. Repeat until you have chambered the round at 000 deg, 90 deg, 180 deg, and 270 deg. If the chamber is eccentric, the fired hull won't want to chamber in all 4 orientations. If it's just wallowed out, it probably will.

Some factory ammo and new brass is pretty small. Check an unfired round against SAAMI chamber specs and see if it's well below the dimensions listed. It looks like mikecr posted a good drawing to use as a std. If your fired cases are only a couple of mils larger than the SAAMI dimension and they pass the rotation test, you may just need to find larger brass, or resize with a small-base die.

Good luck, Tom
 
Ok. My brass passed the rotation test. The new winchester brass is quite a bit smaller than saami specs. At the web the new brass measures .4590

After is fireformed it measures .4660

Once fireformed all others measurement are at spec with the diagram expect oal. My brass arent quite 1.8920

The only measurement that is not the same is just above the bottom of the case where the diagram says .4700

Mine measure .4630

Like I said they chamber fine after the 1st and 2nd reload. The third is tight and accuracy falls way off. Full length sizing does nothing to make the chambering either.

Any ideas?
 
The only thing I can think of is to put a new hull in the shellholder, run the ram up to the top, then screw the F/L resizer down until the locknut contacts the top of the press, or the die contacts the hull (unlikely). If the die body makes up on the press frame without contacting the new hull, loosen the lockring and screw the die body down until it contacts the hull. You may not have to leave it there, but may be able to set it somewhere in between where it is now and where it makes contact with the new hull. Returning a fired hull to original length works the brass a lot, and is usually not necessary. Just bumping the shoulder back enough to chamber smoothly is ideal. When you think you've got it, check a fired, unresized hull's diameter at the body/shoulder corner, then resize it and check the diameter again. It should not be larger. If it is, resizing is buckling the shoulder, and may cause hard chambering, and will cause some loss of accuracy.

One last thing. Be sure to clean the brass, particularly inside the neck, and use a tiny amount of sizing lubricant in it. If you don't, pulling the neck back out over the expander plug may pull the shoulder/neck junction forward enough to make chambering hard, and affect accuracy. Some use dry mica for inside neck lube, but I use a bore mop with just a little bit of sizing lube rubbed into it, and then wash and dry every hull individually, particularly inside the necks. It's time consuming, I know, but do it if you can. When I was match shooting, I loaded too much ammo to do all this, but I did cycle every round of loaded ammo through the rifle, (with no firing pin) including alibi ammo.

Looks like your chamber is good, judging from the fired case dimensions compared to SAAMI. Try measuring some Remington, Federal, Hornady, Norma etc, brass or ammo. The Winchester that I have runs small too.

Standard resizing dies are not designed to return fired brass to original size. The "small base" dies I referred to are. You should be able to use standard dies and just bump the shoulder back .001" or so. The .22-.250 cartridge headspaces on the shoulder. Chances are that's what is making the 2nd or 3rd reload hard to chamber, and maybe inaccurate. I'm not sure. Mikecr is right. Without having the rifle and brass in hand, it's guesswork. Maybe we'll guess right.



Didn't intend to write a novel, but maybe something will help.

Tom
 
tunacan said:
At the web the new brass measures .4590
11thou under.. HOLY CRAP!

tunacan said:
After is fireformed it measures .4660
tunacan said:
Mine measure .4630
Ok, which is it?

tunacan said:
Like I said they chamber fine after the 1st and 2nd reload. The third is tight and accuracy falls way off. Full length sizing does nothing to make the chambering either.
Can you tell us specifically what the web measures after each firing, and at what point the case becomes a misfit?
Do you have a tool for measuring headspace? Readings along the way here would be very useful.
I suspect your die will never size those webs, as they haven't reached a point where it's needed.
With a case that far under chamber, it can't grab the sides under pressure to prevent stretching toward the boltface. This would cause a headspace issue in short order.
You might not see this with mere case OAL checks because the shoulder improvement pulls the neck backward on forming.
Accuracy would fall off because your case capacity is ever varying by a huge amount.
Does that brass measure ~.473 at the case heads?
 
Mike,

Mine measures .4630 in the same location where the diagram measures .4700.

Just above that in the web area mine measures .4660

I tried fireforming some brass with an off the shelf box of Remington 55grain bullets also. The bulge is not quite as prominant, but the measurements are the same.

When I chamber a new, unfired round there is a slight mark at the neck/shoulder junction.

Could my headspace be a tad long? Would loading the bullets into the lands a bit negate this?
 
The dimensions on the web are as follows;

New unfired brass .4590
Once fired .4655- Chambers nice after this
Twice Fired .4660 - Still chambers smooth
Third Firing .4665-.4670 - Requires fair amount of forced to close bolt
 
Mike, I checked my math. Using tunacans last data, on 1st firing it comes out .0065" growth over new brass.

2nd firing is .007" over new.

3rd firing is .0075" to .008" over new.

If he's measuring it where the drawing shows, that's a lot of growth in the solid brass web. As you say, the small brass may be letting the round ride forward in the chamber and driving the case head backward when fired.

tunacan, you said in your 2nd post that new brass was a slight crush fit. That's tight. I did a bad thing and assumed that you had checked headspace with gages, even though you never said so. As Mike said, you need to gage it. If it will close on a no-go, the chamber is obviously too long. On the other hand, if it is tight on new brass, it may not even close on a go gage, let alone a no-go. That, of course is tight, but not necessarily bad. It may just give you trouble sizing back far enough to get multiple firings. If the shoulder is the problem, it'll be easy to bump back, but if the web is the problem, it'll be much harder to swage it back down. Good brass has to be hard in the case head area, and will harden even more if it is getting worked, possibly explaining why it's not coming back small enough after the 3rd firing. Too much cold spring? Questions, questions.

Tom
 
Thanks for the measurements tunacan.
I still think it's not a web issue, but negative headspace.

On extraction, does the bolt handle easily turn into a 'click' at the top as though the case is popping loose from the chamber? Or is it a tuff turn all the way?
 
I suspect that the issue is with your loading die. Any time i cut a minimum length chamber i run into this problem. I think that your die is probably to long to bump the shoulder back on the case when sizing. If you don't have the equipment to do it yourself you will probably have to get someone to trim your die.

A surface grinder works great, trim the die .001" at a time until it bumps the shoulder back just enough that the bolt will close without interference.

Everyone likes to cut chambers to a tight fit, but it can cause difficulties also.

Thanks Gary
 
The die is too short. I lit a match and got some black soot on the shoulder of the case. I chambered the round in my rifle and the shoulder came out shiney.

I then put more soot on the case and adjusted my FL Redding die down as far as it would go. The soot was untouched, therefore the die is too long.

I will go to my buddies tomorrow and trim a little off the die with his lathe tomorrow.

Why the unsightly bulge and the base of the case?? Its a little disconcerning
 
The bulge at the base occurs because of the taper in the 22-250 case. The standard case has a large amount of taper and the Ackley version has very little. There is some taper in the solid section of the case at the web area that cannot be blown out when you fireform the case, so the fireforming starts about 3/16 of an inch above the rim. This gives the case a litttle bit of a bulge just above the solid section. It isn't a problem, just a result of fireforming a case which has a lot of taper into one that has very little taper and you can't fireform the solid section.
 

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