Crimp precision loads??

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1shot

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I've been reloading for about a year now but now have a question for the experienced- hoping someone can answer..

Tikka M55, .223 Win Brass/SR primer, Hornady 50gr, 26gr of 4895, Lee dies.

I usually seat the bullet to "just" touch the lands and get .75 MOA reliably with the old girl.
From a reloading manual I read that factory crimped bullets can have similar accuracy and got thinking.. What if I were to seat in the lands AND give a medium to heavy crimp? So I did- and what a difference..

Went from .75 MOA to .4 with crimp! I shot three groups like that last night but cannot understand where the difference comes from- was I "trying harder" to group, or does the powder wind up for a further millisecond? :confused: I'm lost on this one, but in a good way.. Does anyone else crimp for the range?
 
Hi

I've chronied Crimped and non crimped of the same rifle loads, the crimp does give more consistant velocity then non crimped.

The most accurate factory match ammo I ever fired in my 700P was winchester ranger, and older lot with the sierra MK bullet (they use noslers now), and they where crimped.
 
Unless you have a tight match chamber, crimping usually adds to accuracy.

Careful when crimping AND seating into the lands - this will increase pressures (possibly dramatically - read kB!. Or maybe not, but always re-work up wour loads if you decide to try this).

Crimping also adds huge accuracy when your not able to seat to the lands, due to magazine length restrictions, or whatnot.

Big fan of the lee factory crimp dies - no fuss at all
 
prosper said:
Unless you have a tight match chamber, crimping usually adds to accuracy.

Careful when crimping AND seating into the lands - this will increase pressures (possibly dramatically - read kB!. Or maybe not, but always re-work up wour loads if you decide to try this).

Crimping also adds huge accuracy when your not able to seat to the lands, due to magazine length restrictions, or whatnot.

Big fan of the lee factory crimp dies - no fuss at all
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I have been wondering this for a long time. Thanks for the info!

I will be loading for an AR15 soon and I will be crimping.
 
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