Seat to mid-cannelure?

[tcoz]

I'm currently loading 55gr X-Treme FMJBT over 24.2gr of H335 for my AR. My question involves seating depth. Cases are trimmed to 1.750 and I've been seating to a COL of 2.250. Accuracy is very good (for me) and the gun functions flawlessly, but the bullets are only seated to the very bottom of the cannelure, barely touching it, at 2.250. Changing seating depth to 2.20 would bring it more into line with the mid-cannelure rule of thumb but I hate to mess with anything at this point. Is there any reason I should do this or should I just leave well enough alone? Since bullets come both as cannelured and non, I'm hoping it's just there as a guide. BTW, I use mixed brass and CCI41 MilSpec primers.

[goodoleboy]

I wouldn't seat deeper, because that will raise your chamber pressure, which could be bad if you are using a hot load. If the loads group well, as is, the issue is purely aesthetic and I would leave it alone.

[tcoz]

Exactly what I was hoping, goodoleboy. My load isn't hot, but I see no reason to change things if it isn't necessary. I just didn't know whether the cannelure performed any function other than acting as a guide to bullet seating depth. Thanks.

[Clemonsds]

The cannelure is there to hold the bullet in place under semi auto fire the way i understand it and your're using it in an AR, that doesn't mean you can't run non-cannelure. If you use projectiles with cannelure don't worry about C.O.L since yours is falling under that spec. It really just there for loading round that still fit into a magazine, if yours fall under that measurement you're okay. I would concern myself with over pressure at your charge weight for that projectile, below are two .223 load data and one 5.56 load data.

I'm not sure what data your're using but looking at my book(Hodgdon 2014 annual manual reloading) for a 55 grain(BAR TSX FB) it says shows a C.O.L. of 2.180" and a max charge of 22.7 for H335 3,110 FPS @ 51,500 PSI.

Another book i have (hornady) says a C.O.L. of 2.200" for their 55 grain FMJ-BT with a max charge of 23.2 H335 @3100 FPS.
You will notice that C.O.L. will vary slightly depending on who makes the projectile.

I hope your barrel is chambered in 5.56? The burn rate of H335 is slightly higher than IMR8208xbr, and my load data book for 5.56 chamber shows 24.5 grains of 8208xbr for a 55 grain hornady GMX C.O.L. 2.200"

I say all this just as precaution to watch for pressure signs on your cases for the charge weight you're using. :fie: :confused:

Use it if you got it, otherwise don't buy cannelure projectiles.

I hope this helps.

[tcoz]

The cannelure is there to hold the bullet in place under semi auto fire the way i understand it and your're using it in an AR, that doesn't mean you can't run non-cannelure. If you use projectiles with cannelure don't worry about C.O.L since yours is falling under that spec. It really just there for loading round that still fit into a magazine, if yours fall under that measurement you're okay. I would concern myself with over pressure at your charge weight for that projectile, below are two .223 load data and one 5.56 load data.

I'm not sure what data your're using but looking at my book for a 55 grain(BAR TSX FB) it says shows a C.O.L. of 2.180" and a max charge of 22.7 for H335
3,110 FPS @ 51,500 PSI.

Another book i have (hornady) says a C.O.L. of 2.200" for their 55 grain FMJ-BT with a max charge of 23.2 H335 @3100 FPS.
You will notice that C.O.L. will vary slightly depending on who makes the projectile.

I hope your barrel is chambered in 5.56? The burn rate of H335 is slightly higher than IMR8208xbr, and my load data book for 5.56 chamber shows 24.5 grains of 8208xbr for a 55 grain hornady GMX C.O.L. 2.200"

I say all this just as precaution to watch for pressure signs on your cases for the charge weight you're using. :fie: :confused:

Use it if you got it, otherwise don't buy cannelure projectiles.

I hope this helps.

Thanks for your input. I had accumulated 23 different loads from various sources including Hodgdon, Nosler, Sierra, some well respected Internet sources and of course, some Internet forum posts (which are way down on my load prioritzation). For 55gr FMJ, they were almost all in the 23.5-25.5 range. I laddered from 23.5 up to 24.9 and 24.1 to 24.2 functioned and shot the best, so I'm pretty confident in my load. For my type of bullet, Hodgdon lists 23.0-25.2. Also, I don't have any over-pressure signs and most loads I considered were at COL shorter than 2.250.

All this being said, I do appreciate your comments and will continue to watch.

[Clemonsds]

well i hope my info wasn't chatter on what you have already done, but it may have been.

[tcoz]

No problem. It's always welcome. Thanks.

[markm]

I'd turn the seating die down to mid cannalure and shoot a few groups. Chamber pressure change will be completely negligible. Factory ammo regularly comes short of "Spec" Over all length.

And this bullet, as far as I know is tangent ogive and thus not depth sensitive. If you're putting a crimp on it, might as well have it in the cannalure just right. But again. Load 10 or 20 and shoot to see if there's any change... good or bad.

[bigedp51]

tcoz

I'm loading 25 grains of H335 in my ARs with mixed brass and after scouting the net and looking at other mix brass loads and my work up load I settled on 25 grains.

Below are two 5.56 cases, the top Quickload chart is with Lake City brass with 30.6 grains of H2O case capacity and 25 grains of H335 at approximately 43,000 psi

http://i122.photobucket.com/albums/o254/bigedp51/308_zpsf81bb4cc.jpg

The bottom chart is Israeli IMI 5.56 case with 28.8 grains of H2O capacity and approximately 50,000 psi with the same load.

http://i122.photobucket.com/albums/o254/bigedp51/288_zps26698a67.jpg

You have 6,000 psi difference between the max and min case capacity's and 5,000 psi below max rated pressure of 55,000 psi. (and your load will be a lower pressure yet)
And the charts above represent the highest variations in case capacity you will find between .223/5.56 cases.

http://i122.photobucket.com/albums/o254/bigedp51/casecap_zps3f8bb2c9.jpg

http://i122.photobucket.com/albums/o254/bigedp51/223-556weight_zps3566d29a.jpg

With mixed brass your not going to get benchrest accuracy but it is more than good enough for 100 yards or less practice shooting.

I have the RCBS AR series .223/5.56 dies that taper crimp the cases and I crimp all my practice loads at the cannelure.

Just remember when looking at .223/5.56 loading data that you remember to take into account the throat variations between the .223 and 5.56 load data.
NOTE: Quickload has the loading variations for the short and longer throats and does show pressure variations between them, meaning .223 and 5.56 throats.

And as a side note my Savage .223 has a 1 in 9 twist and a longer throat then either of my AR15 do.

[AverajeJo]

I think the counter-lure is there so you can crimp the case. I think

[bigedp51]

I think the counter-lure is there so you can crimp the case. I think

Yes, and the RCBS AR series dies use a taper crimp.

And Hornady only uses a cannelure on their 55 grain bullets for shooting Zombies.;) (V-Max and Z-Max)

http://i122.photobucket.com/albums/o254/bigedp51/VZ_zps4391ae19.jpg

[AverajeJo]

zombies??? Why would anyone train for anything else :0)


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[HambelA&A]

At this point this is probably preaching to the choir and I realize some have already touched on this, anyways here is my 2cents(for what it's worth). The cannelure helps the bullet maintain it's COL dimension. It works best when the mouth of the case is covering a min of 50% of the cannelure. The idea is that once crimped the rim of the case will be pressed into this recess of the bullet creating resistance against bullet shift during recoil in the magazine and during feeding. I have always seated Hornady 55gr FMJ at 2.200" with great results, this leaves very little cannelure visible. Do not feel obligated to change your recipe if it works for you, just remember, if you change your overall length you have to adjust your powder charge +/- accordingly to attain the target velocity or pressure you are looking for. Happy Hand loading!

[Tzed250]

The cannelure exists so that the mouth may be crimped without damaging the bullet jacket. If no crimp is used then the seating depth doesn't matter. I crimp all of my 55FMJBT loads so I'm seating to a 2.21 COAL.