Armory Sponsor
Posted: 12/9/2013 5:34:25 PM EDT
OK need some advice on if I should or should not crimp... Loading LC sized to 308. Bullets are PP 175GN BT I purchased from Wideners a few years back. No cannelure on them. Shooting out of a 20rd mag fed LWRCI rifle. Do I put a slight crimp on them or not? Half of what I read says no and the other half says yes because it is a semi. Thoughts
|
| I wouldn't crimp them, assuming you have proper neck tension. I don't reload .308, but I've found in different .223 loadings of mine perceived accuracy improved when I didn't crimp. The only bullets I bother crimping anymore in .223 are 55 gr FMJ in my target loads. |
|
An effective crimp is created by squeezing the brass into a canalure. If you have no canalure there is no place for the brass to go. If you squeeze the brass into the bullet the brass will spring back and the lead core bullet will not. Now you have also weakened your neck tension.
Your bullet is much stronger than the thin wall of brass that it is in. You have a ZERO gap fit. How can you compress a week material around a solid material and expect the week to grip the strong. Think of it as crimping aluminum foil or a paper straw on to a steel rod. |
|
Quoted:
Lets look at this from a different direction for discussion. What are the reasons for crimping? Help secure the bullet and improve accuracy. From Sierra's web site on Loading for Service Rifles. Neck Tension When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it. There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well. Some years ago, we decided to examine this phenomenon more closely. During tests here at Sierra’s range, we chambered a variety of factory Match ammunition in an AR-15 rifle. This ammunition was from one of the most popular brands in use today, loaded with Sierra’s 69 grain MatchKing bullet. To conduct the test, we chambered individual rounds by inserting them into the magazines and manually releasing the bolt. We then repeated the tests by loading two rounds into the magazine, chambering and firing the first, and then extracting and measuring the second round. This eliminated any potential variation caused by the difference between a bolt that had been released from an open position (first round in the magazine) and those subsequent rounds that were chambered by the normal semi-automatic operation of the rifle. Measuring the rounds before chambering and then re-measuring after they were carefully extracted resulted in an average increase of three thousandths (0.003") of forward bullet movement. Some individual rounds showed up to seven thousandths (0.007") movement. Please bear in mind that these results were with factory ammunition, normally having a higher bullet pull than handloaded ammunition. To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension. What are the reasons for not crimping? From Sierra. The first option, crimping, brings up some other issues that can be troublesome. In general, crimping degrades accuracy. Most match bullets are not cannelured (which also seriously damages accuracy potential), a requirement for correct application of most crimps. Still, there are taper crimp dies available from most of the major manufacturers. Lee offers their “Factory Crimp” die as an alternative, which seems to be one of the better options for those bullets without a cannelure. That having been said, crimping is still, at best, an occasionally necessary evil. Avoid it if at all possible. Link. http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm Me, I have found Crimping with the Lee Factory crimp die improves accuracy and I use it on all my semi-auto ammo. Note: since this article from Sierra was written, they have developed a .224 Matchking bullet with cannelure for crimping at the request of the "AR Crowd" . |
|
No cannelure = No roll crimp
The crimp in the bullet seating die is a roll crimp and that requires a cannelure. A crimp usually isn't required with 308. A taper crimp is used on auto pistol cartridge to remove the bell / flare that isn't used in rifle loading. A Lee Factory Crimp is possible but isn't required. Some companies do sell separate taper crimp dies for 308 but other maybe cast bullets there's no reason for a taper crimp. The bullet seating die can be set up to crimp or to not crimp. It's roll crimp is meant for bullets with a crimping cannelure. Revolvers use cannelured bullets and a roll crimp to keep bullets from jamming the action. There are separate roll crimp dies available too but they are also meant for cannelured bullets. |
|
I have nothing in particular against crimping.
The OP specifically stated that the bullets in question have "NO CANALURE". I beg you guys to give this very careful thought. If there is no place for the brass to go, how can you crimp? The Lee FCD uses a collet to evenly squeeze the brass into the canalure. If there is no canalure it squeezes the brass into the bullet itself. Heavily constructed bullets simply resist deformation. Varmint type bullets deform. The problem here is, besides you have deformed your bullet, the brass springs back and the bullet don't. So if you crimped it hard enough it may leave enough brass below the surface of the bullet to prevent it from moving in or out but its still not holding the bullet tight. It's very simple. No canalure no crimp, period. |
Should have gone with a poll to track...
|
Dude. If you don't have a cannelure, you don't crimp. Those bullets are not designed to be crimped.
Use brass in good condition in a good quality FL sizing die, follow proper procedures, listen to the advice you are getting here, all will be well. Most bullets WITH cannelure, I do not crimp, no need for most applications. Makes for very accurate loads. In most rifle reloading applications, crimp is optional. I do crimp some 145 & 150 gr milsurp .308 loads with Lee FCD. That is because I want to and I can. They shoot very well. But still not necessary to crimp. |
Armory Sponsor