Question about crimp and neck tension

BHuij

Active Member
#1
I’m getting ready to load a bunch of .223 today, both cast and FMJ.

The cast stuff is a little oversized, powder coated/GC, and has a flat base. To get it to seat well I have to flair the mouth of the case a bit. So it makes sense to do a light crimp with my Lee collet style crimp die as a last step, just to remove any leftover flare.

However, the FMJs all have boat tails and I can easily seat the bullet without flaring the case mouth.

I’ve read that crimping is a good way to uniform neck tension, and I’ve also read that neck tension has nothing to do with crimp and everything to do with sizing the brass. The latter makes more sense to me.

Any reason to crimp my FMJ loads? Any reason not to crimp my cast loads?
 

Rick

Moderator
Staff member
#2
If it's a magazine fed firearm the crimp can serve to prevent bullet set back under recoil. Neck tension is the more important one between crimp and neck tension for uniform powder ignition. Lot's of things come into play on that such as bullet weight, age of brass etc.
 

Ian

Well-Known Member
#3
Crimping has nothing to do with tension except bad things if done wrong.

Autoloaders generally need a taper crimp to reduce the lip at the case mouth from catching during feeding and to help secure the bullet from telescoping in the case in the instance of a jam or under recoil in the magazine.

What you need is a cast bullet expanding die. Trying to cram a cast lead bullet into a .223 case which has been resized for jacketed dimensions is an exercise in squishing bullets, egging the necks, and creating wongo ammunition.
 
#4
I’m getting ready to load a bunch of .223 today, both cast and FMJ.

The cast stuff is a little oversized, powder coated/GC, and has a flat base. To get it to seat well I have to flair the mouth of the case a bit. So it makes sense to do a light crimp with my Lee collet style crimp die as a last step, just to remove any leftover flare.

However, the FMJs all have boat tails and I can easily seat the bullet without flaring the case mouth.

I’ve read that crimping is a good way to uniform neck tension, and I’ve also read that neck tension has nothing to do with crimp and everything to do with sizing the brass. The latter makes more sense to me.

Any reason to crimp my FMJ loads? Any reason not to crimp my cast loads?
The best lessons are the ones we learn. I’d try half of each metal composition and compare for yourself. Doesn’t matter unless it does. :)

Report back & educate me.
 

Ian

Well-Known Member
#5
Some will poll the entire internet and average the answers to decide what they are going to do in an effort to safe time/energy. That is all well and good except very little is learned about the whys of the answers and doesn't account for variances of systems/method. Gathering information and becoming educated before attempting something is a good idea, but when it comes to handloading, every individual situation is going to be in some way unique and the only TRUE answer must be discovered by shooting. Bass is right, best lessons are the ones we learn ourselves.
 
#6
Personally, I mostly leave the flare on my cast bullet loads. In my limited experience, it works better in most cases (and less work). In the .223, however, I found an accuracy advantage with a light crimp. I wouldn’t crimp jx loads for bolt gun. Good luck!
 
#7
Personally, I mostly leave the flare on my cast bullet loads. In my limited experience, it works better in most cases (and less work). In the .223, however, I found an accuracy advantage with a light crimp. I wouldn’t crimp jx loads for bolt gun. Good luck!
Rifle dies today are crude for crimp. When reloading, people often take the short cut of NOT trimming or neck turning brass. Longer or thicker neck on one side, & a crimp can push a bullet off center in the case or .... damage the slug. If everything is correct, the crimp should actually work to CENTER the slug & be consistent from round to round. So NOT crimping can actually be better. The faster you wanna run with cast, the better you need to think about / perform your reloading procedures. I recommend reading what Gear wrote under Tips, Tricks & Voodoo for an example of “detailed”. I think it’s #7.
 
#8
I do trim, chamfer, and deburr all of my .223 regardless of what type of projectile is going to be seated. I've never neck turned though.

For now, all of this loading will be for a bolt gun with a short magazine (5+1 I believe).

I think for now I'll skip the crimp on the FMJs. When it's time to get serious about working up a cast load I'll do some testing once I have other factors dialed in (such as powder charge), to see if crimp vs no crimp has a noticeable effect on group sizes.

I think on this forum I often give the impression that I'm trying to become a theoretical expert without actually doing any of the hands-on learning exercises that are necessary to really become knowledgeable about the subjects of casting, reloading, and shooting. In reality, I don't make it to the range as often as I'd like, but tend to find a lot of 10-15 minute windows of free time that I like to fill with as much learning as I can. I find the theory fascinating even if I can't apply it as frequently as I want to right now :D
 
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fiver

Well-Known Member
#9
without information or experience your just poking around in the dark.
I'm not going to be doing any rifle shooting until I can get back out of the range, getting in is no problem it's down hill.
but that doesn't stop me from building brass and reviewing notes and preparing loaded ammo to test.
I have been working on some new cases and refurbishing the old ones in preparation for when I can go shoot.
today I annealed and pin tumbled the 30 cases I neck trimmed yesterday.
later I will set their neck tension and review the oal I want to use.

maybe in another week or so after I build a mold guide for some new Jig molds I just got,, and make up some new jigs for this summers fishing, I will pull out some more cases and build another batch of brass for some more testing I want to do.
in the mean time I will prep a batch of 308 brass and bump the load another .3 or .4 grains
I want to try tightening up a 4064 load I have been having some good luck with.
before I can do that I need to prep the cases, anneal them, clean them, set the neck tension and finally I can load them, 50 rounds will take me a couple of week at the rate I fit things in.
then I need to get some 25-06 ammo made up for one of my hunting rifles and sight in the new upper I started on last summer.

some of these tests have been going on for a couple of years now, some of it is just replenishing the ammo supply for loads worked out years back.
none one of them got to where they are now, nor will move ahead without some planning and preparing well in advance of the shooting.
 
#10
First,you need a rig capable of some pretty fine accuracy and a driver up to the challenge. Solid shooting platform and hopefully windflags.

Next,tension or interference fit is a toughey because if you're using std dies,they're assuming jacketed. Cast frequently can be a cpl thous larger. So now annealing enters the picture because of working the brass so hard..... or not. Different brass,different chambers,different budgets.

Next in line is uniforming case necks..... some do it religiously, some never. You're gonna need some decent tools here. A nice tube mic will work. Before investing in turning tools..... practice your metrology skills by finding some unturned necks that happen to have very close uniformity. Segregate these,load'm up and see if your rig can tell the difference. Like annealing though,neck turning by itself is hit or miss..... it's a building block for other ops.

A crimp is gonna be a hard sell to anyone in the pure accuracy biz for a variety of reasons..... heck,one is..... after you've done all the careful sometimes tedious "sorting" chores above,do you really want to work the brass anymore? If you have anything much over .001" of tension and at least a cal worth of bullet in the neck..... and you are reasonably careful with the loaded ammo(not carrying loose in a pocket).... it will usually suffice for a bolt action. If the load is gonna be subjected to rougher treatment, running up through a magazine.... possibly repeatedly from a hunting standpoint ( some rifles you have to run the rounds up with bolt manipulation to clear).... then add a little tension or "crimp".

So crimp can be looked at as a solution to certain conditions that may not otherwise have a simple fix. But I'd play with other,more foundational aspects before "resorting" to it. Good luck with your project.
 
#11
(For cast only) I hate brass. It's my #2 hate behind LUBE. After all the prep, I weigh it for the bugaboos I wasn't able to correct & the extremes go for copper use where most guns won't care. If you wanna have a …. repeatable, untested by the manufacturer, pressure curve at lower levels than the powder you are using was designed to operate, for a delicate projectile that will deform, ya gotta know your brass is right. (better word is uniform) That's where I am different than a lot of folks for high velocity cast, everything I do for cast is to try to mimic a blow gun and gain the velocity from barrel length. Not like a jacketed projectile substitute. I essence, …. (yea I'lI admit it) I cheat.
 
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waco

Springfield, Oregon
#12
Good uniform brass is definitely a plus. It can get a bit pricey. I have been having pretty good luck with Starline rifle brass in .223 and 6.5cm
Lapua is still tops in my book, and wallet, but you get what you pay for.

There are a couple smaller companies worth mentioning as far as higher end brass goes. Give them a look.
Peterson-https://www.petersoncartridge.com/
Atlas Development Group
https://atlasdg.com/
 
#13
I have a small PM Lathe that I use to turn case necks to make a more uniform neck tension platform. I have been first full length sizing then I turn the necks; trim to a uniform length and load and fire. Next step is to neck size, bump the shoulder if necessary and check case length. I only do this in 10 case increments, it does take quite a bit of time.