1 3/4" on my Wasp Jackhammers and 1 1/2" on my Rocket Sidewinders. Shot alot of deer with Thunderheads at 1 3/16" and they've worked well. The big cut mecanicals have dramatically bigger blood trails. ( and therefore shorter also). They're great if you have a big KE.
1 1/8" 4 way cut on both Phantoms and slick tricks
1 1/2" cut on sidewinders if I'm in the mood (usually evening hunts near dark) for the reason listed above.
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Disclaimer- I am not now, nor ever have been a paid bow technician, any advice given is just my opinion.
The broadhead I will be shooting this year are Rocket Hammerhead 4L. It's a 4 blade mec. with a 2 inch cut. I have been wanting to try them for a while just havn't had the KE or momentum to use them before. But before I do I will make sure I have enough of each before a screw one of those bad boys on. Talk about a blood trail. I will be shooting them out of a Bowtech Allegiance set at 70lbs with a 29" draw with easton 3/60 ACCs. I think I will have penty of juice for them broadheads.