223/556 OAL question. with 77gr boattail hp

[rparker1866]

hello.
im confused about OAL with the 77gr hp boattail with cannelure.
i have trimed the cases to 17.40. its also even with the dillion case guage.
my OAL is 2236. the min legneth in the manual is 2260.
the bullet is right at the start of the cannelure .
have i trimmed the cases to short?
do I need to seat the bullet to the cannelure?
how important is OAL?
Any advise
thanks

 

[Walkalong]

I haven't used those, but trimming to 1.740 instead of 1.750 won't hurt.

Those are heavy and long for .223, so they may not fit the mag, a lot of the "heavies" won't. Is that what you're trying to do?

 

[rparker1866]

im just worried about spec. they fit in the mag fine.
they are alot shorter than the manul says.
thanks for the reply

 

[Walkalong]

Ok, but you can quit worrying about the case length.

 

[Laphroaig]

do I need to seat the bullet to the cannelure?

No you don't, unless you are crimping which I have never seen a need for. If they are Sierra MK's or Nosler CC's, they were designed for mag length. 2.260" is generally considered mag length. You are a little short but like @Walkalong said its not a big deal.

 

[dfish1247]

2.260” is max magazine length.

You’ve trimmed a hair to short, no real big deal, I have trimmed to 1.745” before, I just used 223 data till the cases lengthened back to 1.750”, then back to normal.

 

[DMW1116]

Exactly which bullets are you using? I use the Hornady 75 grain BTHP and the Sierra 77-grain Match King. Hornady, and possibly others, have bullets in that weight range that cannot be seated to magazine length of 2.26" without too much of the bullet in the case, causing high pressures. Consult the bullet manufacturer's load data for COAL measurements. For their 75-grain Amax and ELD Match bullets, Hornady lists a COAL of 2.390 inches. The 75-grain BTHP and Sierra 77-grain Match King seat to 2.25" to 2.26". The 77-grain SMK used in Black Hills Mk262 ammo seated to the cannelure is about 2.245"-ish, based on length measurements taken on Johnny's Reloading Bench of Black Hills factory ammo. Check the designated COAL listed by the bullet manufacturer. Did I say that already? Because I'll say it again.

 

[rparker1866]

thanks for the replys.
i am new at this. so bare with me.
i have Sierra 77-grain Match King. my OAL IS 2236. yours are seated to 2250 or 2260
im like 25 thousands shorter.and just barly touching the cannelure.
"i watched a video on youtube were the guy said thats were you should seat these"
so dont worry about were the cannelure is and seat them to were you are at 2250.

so were im confused. is why would they tell you OAL is 2260.. with no min or max legnth.
"layman manual and hodgdon website"

as i look at differant bullet weights. in the lyman manual they have differant OAL SPECS.
2260 is the longest if legnth doesnt matter. shouldnt there be range
so to short is not a problem. but to long is were you blow up guns.
color me confused

i have the tendency to be OCD about stuff like this

thanks again for the help

 

[rparker1866]

2.260” is max magazine length.

You’ve trimmed a hair to short, no real big deal, I have trimmed to 1.745” before, I just used 223 data till the cases lengthened back to 1.750”, then back to normal.

i just seen this.
so 2.260” is max magazine length not the required OAL of the cartage. but differant bullet weights have a differant spec for OAL.
So the OAL spec must mean something. if your to short does it affect accuracy or make the round kick harder. increase pressure?
thanks

 

[cfullgraf]

Most if not all reloading data for 77-80 grain 22 caliber bullets are for Service Rifle completion where the course of fire is slow fire and ammunition is loaded one round at a time and does not need to be loaded to fit the magazine. Range is 600 yards if I remember correctly.

The bullets are not designed to be loaded to magazine lengths. If loaded to magazine length, the diameter of the bullet at the case mouth is greater than the maximum diameter of the bullet at that point.

When I was shooting Service Rifle, it was mostly at a 100 yard range with targets designed to simulate the longer ranges with a normal course of fire. 55 grain FMJ worked fine at that range but I generally used 69 grain Sierra Match kings. These could be loaded to magazine length.

 

[DMW1116]

Shorter overall length means the powder charge fits into a smaller volume. That means higher pressure. Too long an overall length and the cartridge won’t fit in the magazine and may not chamber at all.

You have some leeway in adjusting overall length. For these bullets I use 2.260” down to 2.255”. The Black Hills ammo uses a shorter length because they are after higher pressure for higher velocity. The cannelure is set for their shorter length. What does Sierra say about the overall length?

 

[dfish1247]

Yup, shorter oal means higher pressure. It also means a larger jump distance to the start of the rifling, which will affect accuracy, usually negatively.

I’m guessing we are talking an AR platform, correct?

I’ve loaded the 77gr match king from 2.24” to 2.26” oal. Granted, this was with 5.56 data and brass at least 1.75”. As I said, I’ll load some 55 or 62gr 223 loads until my brass stretches back out, then onto 5.56 77gr loads. And this is using range pickups, nothing special. My stiffest load is about 85% power in the load books, if I was pushing velocity and pressure, I’d be more strict on brass (brand, length, case capacity, load work up,etc.)

I don’t seat to the cannelure, I’ve been lucky in having tight enough neck tension to not have to crimp.

What twist rate barrel do you have? What powders do you have to work with? What powder and how much have the rounds in question been loaded with?

 

[wanderinwalker]

OK, wading in here.

1) Read @Walkalong again. Don't worry about the case length. They're a little short, but that's irrelevant to your final OAL measurement. And it also is irrelevant to whether or not you use ".223 Remington" or "5.56 NATO" data. The little bit of missing case length is in the neck, it does absolutely NOTHING for your case powder capacity.

2) The 77 grain Sierra Matchking is designed, intended and supposed to be loaded to magazine-length in an AR-15 type rifle. The maximum working length to fit, feed and function in an AR-15 magazine is about 2.26". Some magazines might even require you do drop to 2.25" OAL. It's OK, these bullets and the load data associated with them are meant for this.

3) In fitting with point 2: Matchkings are very, very tolerant of how far they jump to the rifling. I actually have no idea how far any of my 69, 75 or 77 grain have to go to the rifling when loaded to 2.25". As long as they aren't jammed in the rifling, it doesn't matter. They'll shoot just fine.

4) OAL and case pressure. Again, the difference between 2.25" and 2.26" in a .223 case, being fired in a "normal" AR-15 chamber, doesn't matter. Rifle cartridges behave differently than pistol cartridges in this regard, so long as the bullets aren't severely set back into the case. Very important to keep this in mind. What you absolutely need to avoid when loading rifle cartridges is inadvertently jamming bullets into the rifling! (See point 3.) That will cause you a very bad day pressure-wise. But seating your bullets .010" short of the ideal OAL isn't likely to result in ballistic disassembly.

5) Ignore the cannelure location!

Edited: corrected misplaced decimal point in point 4.

 

[Nature Boy]

My 77gn SMKs don’t have a cannelure so I’m a bit confused

 

[Yankee1986]

My 77gn SMKs don’t have a cannelure so I’m a bit confused

They come with or without.

 

[Nature Boy]

A match bullet with a cannelure seems anachronistic to me. Why would Sierra do that?

 

[DMW1116]

The military wanted a cannelure for the Mk262 round made by Black Hills, so Sierra added one.

 

[Laphroaig]

IMI offers some excellent 69 and 77 SMK ammo with cannelure also.

I think that mag length .223 match ammo is intended mainly for service rifle competition. The events you'd use it for, standing and the 2 rapid fire strings, have forgiving 10 rings and the ranges, 200 and 300 yds., are moderate. Success is due more to hard holding than benchrest rifle accuracy.

 

[Bfh_auto]

A match bullet with a cannelure seems anachronistic to me. Why would Sierra do that?

The with cannelure 77SMK had much better terminal effects in my experience. So I shoot WC on coyotes and use the W/O fire target shooting. Since I could find them more easily.
I don't crimp either. Just seat to 2.25 and shoot.