Seating depth vs Cannelure (223 / 5.56)

[cowtownup]

Quick question on bullet seating depth on 223...

55 Grain FMJ-BT with cannelure
mixed headstamp brass
25 grains of H335

My brass measures out at 1.75" after trimming.. Lyman manual says 1.76"

When I seat these bullets to an OAL length of 2.260" then cannelure never reaches the case mouth.. The neck tension is solid... Should I leave it where its at or seat it until it touches the cannelure?

Thanks in advance...

 

[heavydluxe]

Ummm... all my manuals have the trim to length listed as 1.75" and the COAL as 2.250".

That said, I wound up seating the bullet at a level where the cannelure was touched by the case mouth. Mine were shorter than 2.25 COAL by 1/10th of an inch. I did that to match the factory ammo I had on hand since these were my first loads.

 

[witchhunter]

If you are crimping, you might want to adjust your die so the crimp falls on the cannelure. If you are not crimping and it fits your chamber and magazine, you are good to go. The cannelure is for crimping.

 

[cfullgraf]

Nomenclature for case length can get confusing.

Generally, 1.76" is the max length for 223 Remington and it should be trimmed when at or longer than that figure.

It is generally accepted that the "trim to" length is 0.010" less than the maximum length which in 223 Remington's case would be 1.75"

Sometimes, manuals call the max length "trim length" which means the length at which should the case should be trimmed.

When searching for the information, I like to find information that gives both numbers regardless what they call them. Then I know the maximum and minimum.

If you want to crimp, seat the bullet deep enough so that the case mouth is nominally in the middle of the cannelure. At this depth, the cartridge should fit in the magazine with no problems.

If you do not want to crimp, no problems, do not crimp. This will allow you to vary the seating depth a little within magazine length, unless you want to single load.

The cannelure will end up where it ends up. The cartridge may look a little strange with the cannelure not exactly at the mouth of the brass.

Hope this helps.

 

[gahunter12]

Mine are trimmed to 1.750" per the Lee Case Gage trimmer, and my OAL is 2.227" +/- .001". This OAL has worked for me in all of my AR rifles, and usually gets me in the canelure for a very very light crimp with the Lee FCD. I have always had good neck tension, but I like the extra insurance of a light crimp. 98% of my rounds are used for tactical rifle matches, or SD classes where I run the rifles hard, and sometimes drop mags.

 

[32_d3gr33s]

my trimmer trims to 1.60, and i use an oal of 2.225

 

[Rule3]

The only way to match things up exactly is to use the trim to length and the exact bullet used in the manual. Even then it it is off a bit.

Example using Hornady brass and Hornady bullets with their trim length the cannelure should fit in the case mouth. Even then it it is sometimes a bit off, I usually do as with revolvers and lead bullets and seat to the cannelure.

 

[rg1]

Looks like a Hornady 55 FMJ and Hornady recommends 2.200" oal. I seat Hornady's from 2.210"-2.230" which puts the cannelure in position to crimp if you crimp. Hornady's 55 FMJ has a blunt rounded shape tip which makes the overall length shorter. Military and some other 55 FMJ bullets have a longer sharply pointed tip and their overall length is longer and normal seating is at 2.250". At 2.260" which is maximum magazine length for AR magazines the 55 FMJ's would be seated too far out but still would work if you have adequate bullet tension. You won't gain in my experience any accuracy by trying to seat 55 FMJ bullets longer. Plus if you have a bolt action rifle, at least in mine, they would not chamber and would jam the bullet into the rifling. I'd seat the bullets in your pic to at least mid cannelure. Your trim length is correct. Recommended trim length is 1.750" and they are ok as long as 1.760" but should be trimmed if longer than 1.760"

 

[Walkalong]

55 Gr FMJs are not match bullets by any stretch of the imagination. Load them so the case mouth is in the middle of the cannelure and they will work just fine. Loaded long may (Or may not.) cause issues with fitting the mag or feeding.

 

[steve4102]

Seat to whatever works for you. The OALs in the manuals are NOT written in stone and are a simple guideline, not a requirement. Some manuals don't even list the OAL they tested it is that unimportant.

This is from Accurate and Ramshot Powders.

SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must be seen as a
guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of the barrel, 3)
ogive or profile of the projectile and 4) position of cannelure or crimp groove.

 

[Fatelvis]

If you can't push the bullet deeper into the case by pushing against a wood workbench or such, don't bother crimping anyhow. The neck tension is enough, and crimping doesn't help accuracy. Ask people who shoot ARs competitively if you don't believe me.

 

[steve4102]

The neck tension is enough, and crimping doesn't help accuracy.

This may or may not be true. IME, neck tension is often times not enough and crimping with the Lee Factory Crimp die increases accuracy.

Here is what Sierra says about "Neck Tension" in a Service Rifle.

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.

Link.
http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm

Here is just one of many accuracy tests using the Lee Factory Crimp Die. Note, that in all three rifles and all three cartridges, accuracy was Improved by crimping. YMMV

http://www.accuratereloading.com/crimping.html

 

[GrandpaBear]

There is a lot of good information here and I'm sure we all appreciate every word. cowtownup, what are you loading for (gun)? If its an AR then you are approaching the area where you can experience jamming caused by over length.

That said, the bottom line is simple, the cannelure is designed for the crimp, so use it. Overall length (OAL) is a Maximum length for the round to work in all firearms. If you are using an AR I suggest that you keep within the recommended OAL of 2.250". If you are using a bolt action or single shot then you might be able to safely exceed that length depending on the finished chamber in your rifle. To determine that you need to measure it. Otherwise, stick to what the books show.

Finally, there is a difference in .223 and 5.56 NATO chamber measurements; the former being SAMMI (read http://www.thegunzone.com/556v223.html) and the latter being neither SAMMI nor identical to the .223. This means that while one chamber may take your longer round without any problems the .223 SAMMI chamber might experience overpressure and other potentially dangerous problems.

 

[hentown]

Unless you're roll-crimping into a cannelure, you're not going to mitigate bullet movement during cycling.

I crimped my .223s for years, using the FCD, until I wised up and stopped crimping, tens of thousands of rounds ago.

Taper crimping will have no effect on bullet movement during cycling.