Why are there grooves in boollets if the smooth-sided design is effective? I load 9mm and 38 Special. Sometimes getting the roll crimp in just the right groove is a pain. I would think that smooth-sided would allow the crimp to make its own groove. I see many mold makers make boollets with many grooves while others do not. Why? Is it just marketing or is there a functional reason (under what conditions will each type perform better?). Is there a reason why one style is better than the other?
Crimp grooves were common in revolver cartridges, pistol cartridges tended to just have lube grooves. Then we started powder coating and pistol cartridges no longer need any grooves. I still prefer a crimp groove for revolver cartridges because they get a roll crimp which works best with a crimp groove.
Go shoot some of those grooved boolits naked and get back to us. PC didn't come around until recently. Ya either use lube or PC a lead boolit.Quote:
Originally Posted by bbogue1
and... 9mm should be taper crimp.. not roll crimp.
As mentioned.. for bullets that don't headspace on the case mouth.. I like roll crimp and a cannelure. otherwise all other grooves to me are lube grooves.
It gets sorta complicated ... but first you have to remember there are two basic designs :
Revolver boolits and Semi-Auto pistol boolits ... both are different for different reasons ,
A revolver boolit will have a crimp groove (usually one but sometimes two) it is designed to take a roll crimp . It will also have a Lube groove (one large one or two smaller lube grooves ,
A semi-auto boolit has no crimp groove , the case headspaces on the case mouth so it get a taper crimp , not a roll crimp , therefore no crimp groove needed .
If you try to put a roll crimp on a smooth sided semi-auto boolit ... the brass case has nowhere to go ...the case will bulge out or crumple and the round won't chamber .
Besides that I now see some that now have NO lube grooves and are designed for Powder Coating not conventional lubricating , These may or may not have crimp grooves depending on if designed for revolvers or semi-auto's .
Once you get some experience you will see there are ways to load some, but not all , revolver boolits in semi-auto cases and ways to load some , but not all , semi-auto boolits in revolver cases ... you have to get tricky with your crimp dies ... but it's not rocket science.
When buying boolits or moulds it's best to buy one that is designed for the cartridge you are loading .
If loading for a 45 acp buy boolit / mould designed for 45 acp ...not one for 45 Colt . The 45 Colt boolit is just going to make your reloading life difficult .
I hope this helps you ...it can get confusing
Gary
Thanks, I did some research and learned more about revolver headspace. That brought up another part of the issue. Some bullet designs have a groove that is sharp-edged and then tapered along with an additional groove or more that are not tapered. Is my assumption that the tapered groove is the crimp groove? Does it matter if the roll crimp is in a non-tapered or tapered groove as long as the OAL is less than SAAMI specs?
Your assumption is correct. A crimp groove will look somewhat like a number "7" when viewed from the left side. The taper is to allow the lip of the case to fold in without bulging when crimped, the square edge at the top serves as a stop when loaded in lever action rifles and carbines. Back in the day, what we now call lube grooves were more commonly called "grease grooves." Many older manuals refer to "water pump grease" as a lubricant, as well as various combinations of tallow, bees wax, Japan Wax and others that were apparently pretty goopy, as they were smeared into the "grease grooves" with fingers.Quote:
Originally Posted by bbogue1
Nowadays, many prefer groove-less designs and apply a plastic powder that serves to keep leading to a minimum when heated and melted onto the boolit.
And yes.. Some bullets you can play with length and crimp in a grease groove if case space neck tension and oal are safe.
A slight variation on a smooth-sided boollet is the boolets with mini grooves designed for PC lube. Usually, there is no cannelure or crimp groove. Once PC'd they have bumps. Then would there be preferable for a taper crimp? I am thinking so, correct?
Or factory crimp by collet