crimp die differences

j3081

hey guys,,,,can someone tell me the difference between a tapered crimp die and a factory crimp die[FCD].the FCD looks as if there are jaws on it to make the crimp and which one is a better crimp.thank you,,,joe

perry shooter

Hello a taper crimp die is a very very gradual taper and like on a 45ACP you can have cases that vary in lenght by 1/32 inch and they will both work with the same setting of the dies to slightly close the case mouth to say .469 inch this will mean both cases will feed in a 1911 type pistol . a roll crimp is a very abrupt ridge in the die and if you had 2 cases 1/32 inch different in lenght the short one might not crimp at all and the long one might crimp so much it will buckel the case and not feed . Long story short you dont need to trim cases for taper crimp die but you do for roll crimp die .Down side of taper crimp it does not hold the bullet as tight say in a 500 S&W recoil might move the bullet of the loaded rounds in the cylinder "NOT GOOD" "PRAISE THE HARD-BALL GUN"

j3081

hi perry,,,i forgot to mention i am considering these for rifle loads,,,.223,,,.243....257....3030,,,.308,,,.7mm,,,.300 mag,,,to me the FCD actually looks like it goes around the mouth,,,while the tapered goes down and in to form a crimp,,,is that right,,,thanks,joe

perry shooter

Hello you are mostly correct on rifle bullets many of them have a KNURLED band and this is the crimp groove. How ever IMHO a crimp is only needed in a semi auto rifle and if you crimp say a 30-30 and the case is long the case is so soft it wild buldge below the crimp and be impossible to load into the chamber.You must have all cases the same lenght to within .010 inch and not worth the trouble I have been loading 35+ years both rifle "all bolt action or single shot " and never crimped a round. but I have loaded over 250,000 of 45ACP and tapered crimped all of these after trouble the first year or so with roll crimp and no crimp. Your Mileage may vary "PRAISE THE HARD-BALL GUN"

j3081

hi perry,,,,i have a separate case trimmer for every caliber,always set to the minimum,,,so a roll crimp is the same as a FCD crimp,,,i was advised to crimp my loads for more velocity and better accuracy,,,i only use RCBS dies,and now i'm hearing ,,,not from you, that these dies already crimp.is that true or is there another set-up with the dies to do that.thank you,joe

perry shooter

Hello the advice you were given was most likely from a very good loader and the thinking was that the more uniform and harder the bullet pull was the better .As smokeless powder is Progressive burning the more pressure the faster the burn. a crimp will make it harder for the bullet to start to move thus the quicker the pressure build up and maybe slightly more velocity "I would be surprised if you could measure the difference with a Chronograph". My type of shooting /reloading is high volumn (270) rounds of 45ACP per match or practice session 5000 - 7500 per year on a Star Progressive press.so it is not time effective to do much case prep.I also load for hunting with a rifle less then 100 rounds a Year and plinking with rifle maybe 250 rounds a year. I do a lot of ransom rest testing at 50 yards with pistols and taper crimp will out preform roll crimp in my case. but rifle I have never tested. Cheers Karl.

dtknowles

Some Factory Crimps look like a segmented taper crimp. Case mouth squeezed in segments not the whole circumference. I don't know how they do it. You have to very good and very careful to get crimped ammo to shoot tighter groups than uncrimped ammo. I would suggest crimping only when I need to make sure the bullets do not move before you are ready for them to. Semiauto's, heavy recoiling revolvers or bolt guns meant for dangerous game or with heavy bullets. With a given powder charge a heavy crimp will produce higher velocity but at the expense of higher pressures, if you are at maximum charge and you add a crimp you are going over max pressures just like if you added more powder. One other wrinkle with heavy charges of slow, hard to ignite powders the crimp may help get more consistent ignition and in this case the accuracy may improve.

Tim

j3081

hey guys,,,you have all given me positive responses,i value all.my reloaded cartridges takes alot of abuse between my son and i, and i can't argue the accuracy response.i think i am going to add another step in my practice.i knew i would get a resolution on here,,,always have,,,thank you and happy holidays,,,joe