I just finished reloading my first batch of 100 5.56 rounds and I have a question about bullet seating.
I purchased 69 gr HPBT MK for my 1/9 16" M4. These bullets do not have cannelures. I seated them last night without any issues. My only question is if cannelures are a preference or a necessity? I noticed that without them, the bullet could be pushed past max seating depth.
Any thoughts? Do any of you prefer cannelures over not?
If your neck tension is adequate, then you neednt be concerned. I have shot many uncrimped reloaded rounds with no problem, never had any setback.
A lee factory crimp die is a worthy investment IMO, however. I use it for plinking rounds with just a very light crimp into the cannelure.
Thanks Captain. Neck tension felt good but then again, this was my first batch of reloaded rounds. So I am not sure where it should be. Is there a way to check? All rounds seated with same snug resistance.
Load up a dummy round(no powder or primer) seat the bullet like normal. Push the nose of the bullet down on the reloading table and put some weight into it. Shouldn’t really move when you push. I think you will find it to be more than adequate 
Bullets with cannelures should be your first consideration in an autoloading rifle. Bullets without a cannelure are for bolt guns. Bullet setback is not the potential problem. The bullet moving forward and coming into contact with the rifling during chambering is the problem to consider.
Isnt the cunnalure to get more consistancy across mag to mag, case to case?
sent from mah gun,using my sights
I disagree unless you are loading for a heavy magnum. I’ve done it both ways and find that a crimp adds little to nothing when setback is concerned, although a deep cannelure might help “a little”.
Neck tension is almost everything, although a rifle/feed-ramp/magazine combination that feeds smoothly is also a factor.
I seat my 150gr Hornady FMJ (7.62x51) for FAL and SCAR with the cannelure well above the top of the case neck - and don’t crimp. I’ve tested numerous dummy rounds multiple times by hard chambering (along with pushing the bullet tip against the bench) with no setback.
Similar results with 5.56 loads in rifles with M4 feed ramps.
Having said all that, I have one AR with A2 feed ramps (/w 2 different barrel) - that will severely setback 68-77 grain loads with or w/o a cannelure and firm crimp (if you count the quasi cannelure on the 77 gr SMK /w Cann, as one.
The best way to check your loads is to load a half doz or so dummyies and hard chamber (full force from a magazine) a few times in your rifle as a test. The COL should not change more than a few thou (in either direction). Mine tend to stay the same or get longer by .001-.002".
Canellure is there to give the case mouth a place to go when you crimp. When you crimp with no Canellure it tapers the mouth into the bullet. With a Canellure the displaced case mouth can taper into the Canellure.
Crimp can help with consistency, but the Canellure does not really have anything to do with it other than it may help with the consistency of the crimp.
Really? I thought that it had something to do with sealing the barrel.
I load lead semi-wadcutters for my .40, and the bullets have a fat cannelure, but it winds up nowhere near the top edge of the case mouth.
Some lead bullets I’ve seen 3-4 cannelures, like these:
http://courses.path.utah.edu/classes/webpath/tutorial/guns/gunterm.htm
Or are we talking about something different?
Grease grooves?
The cannelure was originally used for black powder cartridges to keep the bullet from being pushed out, due to the compression of the powder. Later it was used in lever action rifles, when smokless powder came out, to keep the round from being pushed into the case from the recoil. It has since been used to prevent most bullet movement, in or out, in most loadings to increase durability of the cartridge, in favor for some loss in accuracy. The groves shown in the link are not crimp grooves but lube groves. The crimp grove is usually at the top most of the groves and has a tapered profile in lead bullets to match the shape of the case when crimped. Some bullets, such as full wadcutters, crimp over the very end of the bullet making them flush with the end of the case.
You should be able to generate enough neck tension so that you don’t need to crimp. If for some reason you don’t have enough neck tension, fix the problem. Don’t use a crimp to cover it up. That said, I do crimp when loading 55gr FMJ’s. Why? Because it’s there and it doesn’t hurt.
+1 The Lee FCD for bottle necked rifle cartridges is way better than a typical roll crimp. In order to get consistent roll crimps, all the cases have to be trimmed to the same length. The Lee FCD is much more forgiving when it comes to case length. It also produces a crimp that, as the name implies, is more like a “factory” crimp. BTW, the Lee FCD for straight walled pistol cartridges is a completely different animal. I don’t personally recommend it, but that’s for reasons not relevant to this conversation.
For military ammo the crimp is a failsafe. I have 7.92x57 ammo produced during WWII that has no neck tension at all and the bullet is only held on by the crimp. The ammo is still perfectly reliable and produces around 2MOA groups reguardless.
The crimp is what helps the bullet to be held in place. The Canellure give the brass an area to taper/roll into. If you look at a lead bullets crimp groove. You will see it is merely an indentation that gives the case mouth some where to go. After cramping the mouth is now slightly smaller diameter. Which helps with set back, and in some type of firearms it helps keep the oal from growing.
Canellure has nothing to do with sealing the barrel. The Canellure is a slight indentation. For it to seal the barrel it would have to be slightly larger than the diameter of the bullet.
This is full of problems. Roll crimp is not used in many rifle cartridges. Taper crimp is generally used for rifle cartridges, and semi auto pistol. There are exceptions of course. Roll crimp are generally used in revolvers, and some tube fed rifles. Even in tube fed rifle like 30-30 the taper crimp is still the most common type. Tube fed rifles that shoot rounds like 44/357 mag use roll crimps.
The fcd is great for rifle, and pistol. The pistol fcd’s apply the proper crimp. It applies taper for semi, and roll for revolver.
There’s a lot of mis-information in this thread.
In an autoloader like an AR-15, a taper crimp is unnecessary if you have good neck tension. It does nothing to “seal the chamber” does little to prevent setback and can destroy accuracy if applied to non-cannelured bullets if you compromise the lead core.
Sierra (bullet mfg.) tested un-crimped factory rounds, chambering them three times each in an AR. The cumulative average of all three chamberings combined was of the OAL increasing by .007". Not enough to matter. While factory rounds usually have more neck tension than reloaded rounds, you can test this for yourself by repeating the experiment to see your own results. I have. As a result, I’ve fired tens of thousands of uncrimped rounds through ARs.
However, a properly applied taper crimp can improve accuracy at times. Due to work hardening and varying levels of carbon build up in the neck of brass that’s been reloaded, particularly if you don’t sort by number of X fired and headstamp and brush out your case necks, you’ll have different amounts of neck tension leading to an inconsistent bullet release. You can feel this at times when seating a bullet, some will seat easier or harder than others. A good taper crimp can create a more uniform bullet release by smoothing out the impact of these inconsistencies. The only way to know if this helps your ammo is to test it on target and over the chrono.
If you’re talking factory ammo, then what you’re saying is correct. However, most reloading dies that come with a crimp in the seating die are setup to roll crimp. That what I was talking about. I agree that this is not what you’d want to use for most rifle chartridges, hence my recommendation of the Lee FCD.
As for calling the factory crimps that are applied to most factory loaded bottle necked rifle ammo that have bullets with cannelures “taper” crimps, this is incorrect in my opinion. A taper crimp is simply removing the remaining flare from the belling step when loading straight walled cartridges. It is not pressed in to a cannelure and is not designed to help hold the cartridge. Because of this, the term “taper crimp” is really a misnomer. It should really be called “debelling” or something like that. As for what to call the crimps that you find applied to most factory bottle necked rifle cartridges (that are not roll crimped), I don’t know. I call it a “factory” crimp because the Lee FCD die for straight walled rifle cartridges replicates it. Some people call them “taper” crimps, but to me this is incorrect because they are in no way the same as the taper crimps that are applied to straight walled pistol cartridges.
The fcd is great for rifle, and pistol. The pistol fcd’s apply the proper crimp. It applies taper for semi, and roll for revolver.
The problem with the Lee FCD’s for straight walled pistol cartridges is in how they’re used. If one is simply applying a taper crimp to remove the flare from the belling step, then they’re working fine like any other taper crimp die. However, some reloaders use the Lee FCD’s to postsize the entire cartridge in an effort to ensure that it will fit in their pistols chamber. If one has to postsize a cartridge to get it to fit in a firearm chamber, then they’re doing something wrong. The case should be sized down properly with the sizing die. Fix the problem, don’t cover it up.
Mizer’s post is absolutely dead on.
Bret i agree with most of what you say. I do disagree with a couple things, but there is no real reason to point them out. Unless i just want to start an argument. One thing i will say is the taper crimp is very much a crimp, and does not just remove the bell. The taper crimp is as much a crimp as the roll crimp is. A roll crimp requires a Canellure. A taper crimp can be used with or without. The amount of crimp that should be applied with out a Canellure is another story.
One thing about cramping everyone should know is. Crimping is not a safe substitute for lack of neck tension. I know there are a lot on here that know that, but from some of the responses it will be news to some. Over Crimping can actually cause set back. If your bullets are not being held with neck tension alone you need to figure out why, and fix the neck tension before you move on to the crimp.
Yep… I’d sub Lee Factory Crimp die over Taper crimp… but other than that… My experience echoes his.
100% disagree, but as long as we’re both producing good quality safe ammo, it doesn’t matter.
One thing about cramping everyone should know is. Crimping is not a safe substitute for lack of neck tension. I know there are a lot on here that know that, but from some of the responses it will be news to some. Over Crimping can actually cause set back. If your bullets are not being held with neck tension alone you need to figure out why, and fix the neck tension before you move on to the crimp.
100% agree and couldn’t have said it better myself.