I am not into precision Bolt Guns so I am some what ignorant to their precision needs, however Semi loads are handled far differently then bolts. You don't crimp and the bullet depths change from auto action cycling.
I find that a 2" modeling chop saw and jig to suffice for quick and accurate trimming of cases. Once trimmed a deburring tool is all that is required to complete the process, easy peasy.
I don't crimp my AR ammo. Didn't crimp my M305 ammo either. But I make sure that the ammo is feeding properly so they are not jamming into the feed ramp.
IF, and this is a big if, a semi rifle is functioning and feeding properly, the bullet shouldn't hit the feed ramp. That is what the case shoulder is for and why the angle is what it is
But since some rifles do not feed properly, ammo makers have gone to crimp the ammo just to make sure of no kabooms or other jams. Full auto also tends to change this discussion but since I have none of these toys, nor likely to get to play with any, I will leave that argument to those that do.
Personally, if I was going to crimp for an AR, I would use a taper crimp... just like a pistol. That way you can put a squeeze on the bearing surface vs squishing a waist into the bullet somewhere. A roll crimp into a canneluere would be a no brainer but the bullets I prefer to use do not have a cann.
I have a taper crimp for the 223 (also have a lee FCH). Still haven't used either as my sized brass holds the bullets just fine and function testing shows, no bullet set back no matter how vigorous I cycle my Norc.
Accuracy has been very positive so I think things are going in the right direction.
I know from discussing this with customers, they crimp because that is the SOP. I have not talked to any that actually tested to see if a crimp was needed. After suggesting doing a simple test, I haven't heard back from any of these shooters so assume all went to plan....or they just got the crimp from someone else
Jerry
