Crimping .223 for AR

[Lilswede1]

Have read huge amounts of pro and cons on crimping .223.
This is my first semi-auto (MSR) and I have decided I will apply a light crimp.
My question is: what is a "light' crimp.
What is the best method for measuring amount of crimp.
Don't need a debate on whether crimp is necessary or not.

[dallasb]

Originally Posted by Lilswede1

Have read huge amounts of pro and cons on crimping .223.

This is my first semi-auto (MSR) and I have decided I will apply a light crimp.

My question is: what is a "light' crimp.

What is the best method for measuring amount of crimp.

Don't need a debate on whether crimp is necessary or not.

Measure the diameter of the case mouth before and after crimp. You will want the calipers as far up as you can to get the best measurement. Do your bullets have a cannelure?


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[Lilswede1]

Yes, am using Hornady 55gr. V-Max w/cannelure.
Seating bullets so that 75% of cannelure is seated.
Before crimp station get a reading of .0244"; after crimp station .0241"/0242" measuring as close to top of neck as I can.

[Reloadron]

My question is: what is a "light' crimp.
What is the best method for measuring amount of crimp.

Call it crimp, bullet hold or neck tension, whatever you wish. Typically it is measured doing as dallasb mentions, measuring the neck diameter before and after. As to crimp or not? Your call for your loads. Personally I do not go beyond what my seating die does simply because I never needed to. I do have several Lee FCD (Factory Crimp Dies) but never had a need.

One thing you will find is necks can vary in thickness from brand of brass and even within a brand lot to lot. Load a round and seat a bullet. Using a hand push the bullet against a hard surface. Does it move? Deriving a number by subtracting a before and after neck diameter really doesn't say much as all you have is a number and no clue how tight the bullet really is in the case neck. Other variables are not considered.

This thread...
This thread
and likely several more threads cover crimping pretty well.

The reason I don't care for just doing a simple subtraction and getting a number is because it omits too many important variables like:

Bullet grip is affected by many things, such as:
1. Neck-wall thickness.
2. Amount of bearing surface (shank) in the neck.
3. Surface condition inside of neck (residual carbon can act as a lubricant; ultrasonic cleaning makes necks “grabby”).
4. Length of neck (e.g. 6BR neck vs. 6BRX).
5. Whether or not the bullets have an anti-friction coating.
6. The springiness of the brass (which is related to degree of work-hardening; number of firings etc.)
7. The bullet jacket material.
8. The outside diameter of the bullet and whether it has a pressure ridge.
9. The time duration between bullet seating and actual firing (necks can stiffen with time).
10. How often the brass is annealed
— and there are others…

The above quote was taken from here and the link is a real good read on the subject.

Ron

[Stats Shooter]

I reload for the following semi-auto rifles.

An AR-10 Ruger SR 762
An AR-15 Stag model 2 carbean
An AR-15 Ruger SR 556 Varmint
A Saiga .308
And A VEPR 7.62x39

I do not crimp for ANY of those rifles....If you have a bullet puller, seat a bullet and try to pull it and you will see why. Because neck tension is enough.

But the other issues with crimping are these.
1: you have to trim every single case to the exact same length. If you are making bulk plinking ammo, that's an extra time consuming step.
2: if you are not making plinking ammo, and you are making the most accurate stuff you can, then crimping will likely lead to inconsistent velocity compared to no crimp.
3: if you attempt to roll crimp, you run the risk of pushing the shoulder out and having out of battery ignition if the shoulder is pushed out....Or at least a stuck unfired case.
4. You can deform the bullet
5: you probably shouldn't use mixed headstamp brass because of different neck thickness or hardness potentially making the crimps inconsistent.

I tried crimping when I first started reloading for my gasser guns, I dealt with all the above issues, and found that it was not worth it.

Some folks on this forum crimp, they have crimping dies in a turret press, and they are very knowledgeable reloaders and may disagree with me. But I suggest you try NOT crimping first.

You can load a magazine, shoot a few reloaded rounds, and eject a loaded round that was fed into the chamber and see if the OAL changed in your gun.....Do this a few times to convince yourself they are not moving. Then forget crimping.

As a side note. Crimping is a good idea in tubular magazine, heavy recoil guns. This is because there are springs and other cartridges pushing directly on the bullet. The .45-70 government lever action is a cartridge I would probably crimp, probably even a 30-30.

But detachable magazine guns do not press back hard on the bullet, even when they are chambered.

You can obviously do as you wish, and if you do a good job, crimping is totally fine. But I don't think it is necessary for what you are doing.

I know you didn't ask for a debate....I just wanted to state the above issues so that you can avoid them and not wind up pulling a bunch of bullets like I had to once.

Good luck and most importantly, Have fun!!!

[disseminator]

The reason I crimp all loads for semi auto firearms is not because they will move in the magazine, but because the bullet takes a direct hit when being chambered and that is, IMO, the reason to crimp semi auto loads.

And of course all magnum revolver rounds should be heavily crimped as recommended in virtually all of the manuals.

AR's are hard on bullets. Ever load up a batch of soft points and run them through? (Sierra SBT for one.)

It is apparent the bullet takes a good hit on the way into the chamber.

[chris in va]

if you are not making plinking ammo, and you are making the most accurate stuff you can, then crimping will likely lead to inconsistent velocity compared to no crimp.

A fellow member decided to test this theory and came up with the opposite result. His extreme spread got cut in half with using a Lee FCD. I don't know what effect the seating crimp would do.

[rodfac]

A fellow member decided to test this theory and came up with the opposite result. His extreme spread got cut in half with using a Lee FCD. I don't know what effect the seating crimp would do.

That's for that individual rifle and not indicative of the vast majority of AR's in my opinion. Check out the firing line at Camp Perry. There, accuracy is measured in group size out to 600 yds. I can't ever recall a competitor using a crimp, it's a practice shunned by the various service rifle teams. However, YMMV, Rob

[JeepHammer]

Rodfac,
A die maker bought heavily into advertising in a 'Gun Magazine' and ran a series of articles about crimping making rounds more accurate.
The articles were reported to be from the die manufacturer & 'indipendant' testing, but were all part of the same advertisement campaign.

Suddenly 70 years or more of tried, true, bench rifle & fixture testing were out the window...

In over 40 years of building rifles & ammo, I have NEVER seen one single rifle/ammo combination shoot more accurately with a crimp.
Only a handful of rifles shoot as accurately (and I mean like 4 or 5) in over 40 years with a crimp.
These were all, without exception, crimped at a cannlure...

I agree with you about Camp Perry, and all other national shoots.
Crimps are avoided like the plague.

Crimps are the quickest way to kill accuracy by killing consistancy.
Virtually no one pays attention to the way a crimp die works, the cas preparation it takes to get a crimp die to work consistantly, or tests for consistancy crimping in their reloads.

If anyone wants to crimp, it's their prerogative, totally their choice.

When they start talking about crimping adding consistancy, then I want to see the test fixture testing to back up their claims...

[Average Joe]

I do, I have the FCD, so why not, its cold outside, and I have nothing better to do.

[Metal god]

If the bullet has a cannelure a light crimp will just barely bend into the cannelure A light crimp on a match bullet will barely leave a mark on the bullet if you were to pull it and look . Only crimp rifle bullets that have the cannelure if you want best accuracy . Crimping a bullet that does not have the cannelure "can" cause the jacket to deform and even crush the lead core inside . If the jacket is thick it could have some spring back and the lead core will not . This could cause core stripping when the bullet engages the lands which is the core detaching from the jacket resulting in your bullet flying like a Eli Manning pass Now that's not something you see every day but even crushing the lead core a little can cause the bullet to lose some stability in flight .

[Stats Shooter]

If the bullet has a cannelure a light crimp will just barely bend into the cannelure A light crimp on a match bullet will barely leave a mark on the bullet if you were to pull it and look . Only crimp rifle bullets that have the cannelure if you want best accuracy . Crimping a bullet that does not have the cannelure "can" cause the jacket to deform and even crush the lead core inside .

Yup, its pretty simple when you think about it. If the bullet has a cannelure, a light crimp will not likely deform the bullet. But, if there is not space (like the cannelure) for the rim to fold into, then something must give in order to get the crimp....and what gives is usually the bullet, either the core or the jacket. And there is absolutely no feasible way that this does NOT hurt accuracy, especially at longer ranges. Deformed bullets do not usually fly as true as non-deformed bullets.

But, I say again, what convinced me I didn't need to crimp is when I have had to pull non-crimped bullets. It takes ALOT of effort to pull them, even though I lube them when seating. I figure if it takes that much effort to pull them, then there is no way in hell they are moving in the mag or when they are chambered.

I also checked this by filling a 10 round mag, firing 1 round, then ejecting the next unfired round...doing repeatedly, and checking the base-ogive measurement.

Again, im sure in heavy recoiling guns that have a TUBE magazine where a spring and other cartridges are pushing on the bullet might warrant an crimp, but otherwise, I think it is not only pointless, but counter productive.