OAL and trimming questions

[esheato]

Gents,

I solicit your help.

I'm loading for a .223 AI and I recently went to a lighter weight bullet and it doesn't have enough length to seat to the lands. Even .020" from the lands the bullet is barely in the case and I can still remove it with my fingers. A friend suggested that I should have at least half of the bullet diameter in the case neck. I seated the bullet .110" into the neck and everything looks right, but there has to be a better way to determine the length. I'm open to suggestions.

Also, I'm having some trim issues. Using the AI system, cases tend not to grow in length. I have a trim gauge and it measured 1.771" to the lands so I was trimming to 1.765" which leaves .006" clearance for brass stretch under firing. The cases never even get close to that length! I end up with cases from 1.737 to 1.752". This is not conducive to accuracy but how do I fix it?

The way I figure it there are two ways: cull by length from the beginning or find the shortest case and trim to that length. I did the latter and my cases are now at 1.740" but now my OAL case doesn't match my trimmed cases. :banghead: I'm leery to trim my OAL case and I'm confusing myself.

Somebody help me, LOL.

Ed

 

[brickeyee]

It sounds like the AI chamber (and leade) have been cut for a longer bullet.
AI brass shortens when formed, adn does not appreciably stretch after that (one of the advantages of the AI shoulder angle).
You can try a longer bullet (heavier), or have the barrel set back one turn and the chamber/leade cut for shorter bullets.

 

[esheato]

It might have been cut for a longer bullet, but why does the bbl sport a 1:14" twist rate which demands the lighter weight bullets?

I understand that the brass doesn't stretch, that's one of the reasons that I bought into the AI cartridge.

I guess I'll just start with my half-diameter seated bullets and see what happens. I can always adjust seat depth at that point.

I know they're difficult questions, but thanks for helping.

Ed

 

[brickeyee]

" It might have been cut for a longer bullet, but why does the bbl sport a 1:14" twist rate which demands the lighter weight bullets?
"

Probably because that is the reamer they had. Reamers with changeable leade cutting are rather pricey.

 

[Rockstar]

Maybe I'm just reading your post wrong, and if I am, please clairify. You seem to be relating trim length to a measurement regarding the lands. You sure you mean that? Trim length has very little, if anything, to do with o.a.l. and seating a bullet relative to the lands, unless, of course, you are using a bullet so short that the trimmed case further exacerbates your ability to seat "just off" the lands.

 

[esheato]

Well, I went and shot my messed up ammo today.

I guess I'm doing everything right after all. I shot 12 groups and this was my best, but not by much. The average of the rest of the groups is: .525" with several in the threes. Things could be a whole lot worse.

The mirage is damn difficult to focus in. One minute the scope is crystal clear, the next minute the target is waving at you.

You seem to be relating trim length to a measurement regarding the lands. You sure you mean that? Trim length has very little, if anything, to do with o.a.l. and seating a bullet relative to the lands, unless, of course, you are using a bullet so short that the trimmed case further exacerbates your ability to seat "just off" the lands.

The problem that I was having was that the trimmed cases (trimmed to match the shortest case in the lot) were shortened so much that the light for caliber bullet is too short to stay in the case and touch the lands. If the bullet is touching the lands it's not touching the case...Sooo, my OAL is short and my bullets are at least .100" from the lands....but after shooting it today, I think that's the least of my worries.

Thanks for all the help.

Ed

 

[Rockstar]

There are a lot of shooters who'd love to have a "bad" day like that! Looks like you got a shooter.

 

[The Bushmaster]

And at what range did you have the target from the muzzle, esheato?? No disrespect here unless you were 10 feet away . Mostly curious....

 

[esheato]

Exactly 100 yards using my Leica rangefinder. Believe it or not, but the wind was blowing pretty good too...

I guess I have no excuses for asking questions about loading for accuracy now..

Ed