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Fireforming difficulty

 
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  #1  
Old 03-26-2006, 04:07 PM
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Fireforming difficulty

Having some trouble getting my 22-243AI to fireform well on the first attempt. Sometimes it seems to blow out nicely with sharp shoulders and other times it doesn't.

I fired 10 new Lapua cases with IMR 4064 and a 55gr Ballistic Tip which was loaded long for a crush fit. The charge weight was heavy enough to flatten the primers (probably too heavy) but only 5 cases formed corectly. The other 5 cases have very round shoulders and look just like that new 5/35 SMc case.

Any suggestions?
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  #2  
Old 03-26-2006, 08:18 PM
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Re: Fireforming difficulty

Leave a false shoulder on the neck where the case is a crush fit on closing. ie do not size the neck all the way to the shoulder, just enough that the bolt will close but tight.

go to www.6mmbr.com and look at the fireforming article.


BH
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  #3  
Old 03-26-2006, 09:07 PM
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Re: Fireforming difficulty

I dont know if this will help but for what its worth when Kirby told me how to fireform my 270AM cases I would size the factory 7mmRUM cases down to .277 all but for the last 1/4 of the neck. this is the crush fit people talk about

From what I understand this allows the case to be held more firmly for fireforming.

I am just going off of what I remeber and this was my first and only experince with fireforming for a case where a drastact change takes place.

good luck
steve
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  #4  
Old 03-27-2006, 06:40 AM
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Re: Fireforming difficulty

V.H.

I have forme many AI cases, and never seated the bullets out to touch, only the case necks as was referred to by the others. Try slipping the case into the chamber before seating the bullet. You want to size the neck back so that you can just feel things touch when closing the bolt.

Your not looking to to neck size in the chamber so just go slow and careful. If you start with about half the neck sized and move your seater down in like 1/16 turns you will find the proper depth. You want to feel it make contact, right as the bolt handle drops with a slight resistance. Once you got the die set right, then load them as you normaly would.
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  #5  
Old 03-27-2006, 09:23 AM
 
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Re: Fireforming difficulty

A method I have used for a .243Ackly is empty primed case put in 23-25 gr of fast shotgun powder NO BULLET!!!! point rifle up at about 45deg. to set powder at back of case and fire it .The cases come out 98% formed. Saves ware & tear on the throat and waste of good bullets.However cleaning can be a bitch.I have used near top loads for the standard ctg and used them for varmit loads and fireform at the same time.
Old Bear
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  #6  
Old 03-27-2006, 05:09 PM
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Re: Fireforming difficulty

The AI chamber was cut tight and the bolt will close on the empty 243 Lapua case with slight resistance, thus keeping the case head against the bolt face when the firing pin strikes. I loaded the bullets into the rifling as a precaution just because that is normally recommended when forming cases in a chamber that may have been cut a tad too deep for forming.

What I can't understand is how the primer could flatten and the shoulder fail to fully form. I think I'll try a heavier bullet to see if that works any better.

By the way, this is a tight-neck chamber and all the cases must be turned in advance of forming.

Thank for the input.
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  #7  
Old 03-27-2006, 07:16 PM
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Re: Fireforming difficulty

The primers may flatten if you have a bit of extra head space. Primers alone are a poor indicator of pressure. Extractor marks and bolt lift drag are much better indicators. I fireform all my improved cases with full house loads if they will fit. Accuracy is good and they always come out perfect. How much powder were you using?
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