AI Fire Forming and Short Necks?

[Saskquatch6]

Brought out some older Lapua brass - 4x fired 6.5x55AI - can't remember when it was last used, but likely 5-7 years ago. Its in good shape, primer pockets tight etc - but when I measured case length thinking I may have to trim, I found it all to be around 2.135" with some shorter at 2.127". Specified trim length is 2.155" (max is 2.165"). Checked the Lapua brass I'm currently using (not resized) 3x fired and its length is 2.147" - still short but at least close(er) to min. Checked trimmer pilot and it measured 2.163" (actually a bit long vs trim length). This brass was purchased new and fired only in this rifle. Two questions 1) In your experience is it typical to end up with shorter case necks in this range when FF cases to AI? Would you use these FF cases with necks about .020" shorter than min specified trim length and potential issues/dangers of doing so? PS- my usual case prep procedure would be to trim all new brass to same specified "trim" length then size, load, FF etc.

 

[GLTaylor]

AI cases are almost always a little shorter when formed. One of the chief attributes of AI cases is less case growth when firing. That's the reason I originaly went AI with so many of my cartridges. I hate case trimming!
Shoot them and enjoy!

 

[Saskquatch6]

AI cases are almost always a little shorter when formed. One of the chief attributes of AI cases is less case growth when firing. That's the reason I originaly went AI with so many of my cartridges. I hate case trimming!
Shoot them and enjoy!

Thanks GL - I was comfortable with the cases I'm currently using at only 0.008 short of min - wasn't sure about the older ones at -0.020". I get from what you're saying is there should be no real issues using these going forward then.

 

[L.Sherm]

Stay up on the carbon ring like any other cartridge and you will be fine.

 

[Rardoin]

Yup...shoot 'em. As mentioned make sure you brush out the end of the chamber periodically to keep down carbon formation in the 'bare' area of the neck between the case mouth and the beginning of the bore. I use a short chamber brush and 7mm bronze brush to clean that area on my 6.5's; it just takes a few strokes and twists. Also, remember that when you size the brass it will grow a little in OAL depending upon how far you are bumping shoulders.

 

[Saskquatch6]

Stay up on the carbon ring like any other cartridge and you will be fine.

Yup...shoot 'em. As mentioned make sure you brush out the end of the chamber periodically to keep down carbon formation in the 'bare' area of the neck between the case mouth and the beginning of the bore. I use a short chamber brush and 7mm bronze brush to clean that area on my 6.5's; it just takes a few strokes and twists. Also, remember that when you size the brass it will grow a little in OAL depending upon how far you are bumping shoulders.

Thanks for heads up gents - took a look with Teslong and sure enough black carbon ring just ahead of case mouth to lip - so will take care of that. I've been concerned with throat area leade forward and its clean with no carbon, although noticed lands quite fire cracked. Never paid attention to case mouth area - now I will as part of cleaning routine going forward. Stay safe

 

[Rardoin]

@Saskquatch6 That area I mentioned is less of a concern than a freebore carbon buildup but if you have a hard ring at the end of the neck area of the chamber and switched to brass with a bit longer trim length it could bind on the ring producing a 'crimping' effect. If your trim length never changes it would have to get really thick to cause this issue. Regardless I routinely clean the chamber almost every bore cleaning to keep ahead of any potential issue.