max. case length question.

[SwedeNelson]

Checked the max case length of my new toy
over the holiday.

.223 Rem. Kimber.

Speer Reloading Manual #13 list the following.
Max Case Length 1.760
Trim To Length 1.75

Actual chamber length is 1.782

The question would be is .032 excessive?
And how does this affect accuracy?

Probably over thinking this but any input
would be appreciated.

Swede Nelson

[S.R.Custom]

A couple of thoughts:

Did you measure your brass after you sized it? Are you neck sizing, or full length? I recommend neck sizing...

Given the wide variety of .223/5.56 ammo out there, MFRs frequently cut the throats long in the area of the neck. And chamber dimensions themselves vary "Wyldly." I would suggest doing a chamber cast to see what your chamber throat looks like, and for accuracy, I would trim cases .005" shorter than the cast indicates your chamber to be.

[725]

I kind of see it as a balancing act between the actual chamber configuration & cartridge dimension and consistancy in the cartridge construction, all overshawdowed by safety considerations. Tight chambers and throats that fill just so at the point of bullet release work toward accuracy. Consistant cartridge construction that eliminate variations, also work toward accuracy. Necks too long that impinge at the point of the bullet's release create pressure considerations and a danger to you and those around you. (Had a real life experience a few weeks ago when a fella's bolt action let go and gave him hamburger face syndrome, the shooter next to him lost his front teeth, and I was third man in line and only got hit with debris - no injury.) That being said, who knows how your chamber was actually cut and what's the longest case possible that could be shoved in there. For me ------- trim your cases to spec, do a good job of it, and enjoy our safe hobby. The range incident was most assuredly a wrong powder/knuckle head interface but it was a real humdinger of a pressure problem.
725

[1hole]

There are reasons the term is "MAX" OAL, not max plus .035". Trim your brass.

[SwedeNelson]

725

Point well taken.
Safety first!

SuperMag

I used a gauge to check my chamber length.

http://i69.photobucket.com/albums/i80/swedenelson/DSCN0664.jpg

Found a article in Handloader #140
"Know Your Chamber Length"
By Roger Stowers.
That's what got me started on checking.

If I use the standard .010 shorter than
chamber length all the brass I have is .022 short.

Could form .222 Rem Mag brass down and trim to length
but will I gain any thing from it?

May have to just try it and see if it helps any.

1hole

I agree that I need to trim my brass.
But at what point will it affect accuracy? if any.

Thanks for the in put.
Have you gone down this road?

Swede Nelson

[Larry Gibson]

With jacketed bullets accuracy won't be much effected by the shorter cases as long as they are all close to the same. With cast bullets accuracy can suffer with softer alloys at higher pressures. With such loads the bullet can obturate into the space and then is swaged down aqain as it enters the leade. This causes distortions and imbalances that adversely effect the accuracy. I let my .223 cases (and others) stretch a bit before using them for cast loads as long as incipient head seperation does not become a problem. Forming from a longer case and turning the necks is always an option to get case length to equal chamber length. Such full length sized formed cases usually shrink a few thousanths when they are fire formed and it NS'd do not need trimming during the loading operation.

Larry Gibson

[Bob Jones]

I think most of us misunderstood Swede's question, after going back and rereading it he said he checked his actual chamber dimension and it was 1.782 and was wondering if the chamber was cut "too long". Hope I got that right.

Manufacturers cut their chambers all different lengths. I would guess that military style guns are cut both a bit loose and a bit long, this will make them more reliable with dirt and questionable ammo. On the other hand it will hurt accuracy unless you load your ammo to fit your chamber. On the third hand, you'll probably only notice the difference if you're shooting off a rest with a 24x scope, which isn't the normal role for military style weapons.

For my AR's I load them to factory dimensions and they shoot plenty accurate (1.5" @ 100 yds) for the kind of shooting I do with them.

[GrizzLeeBear]

Well what kind of shooting are you doing with this rifle? Worrying about a little room in front of the end of the brass won't amount to beans unless you are shooting benchrest competition (maybe not even then). If your throat (where the bullet comes up to the rifling) and the shoulder (headspace) is correct, the actual space at the front edge of the case won't affect accuracy, especially if you trim all your case to the same length. Shoot the rifle and see how it does. Being a Kimber, I would bet it shoots just dandy. DON'T FIX IT IF IT AIN'T BROKE!
One of the most used, and accurate, calibers for handgun silhouettes is the 7mmTCU. When you neck up .223 brass to form TCU brass, they come out a couple thousandths short when trimmed to square up the necks. I have seen many shooters use the TCU's on the half size targets to shoot 40 out of 40 targets. Again, as long as they seated bullets to fit the throat, there was no problems with accuracy.

[S.R.Custom]

Well what kind of shooting are you doing with this rifle? Worrying about a little room in front of the end of the brass won't amount to beans unless you are shooting benchrest competition (maybe not even then)...

Eh... not entirely true. While those few thousandths of an inch in and of themselves don't mean much, it does have a significant effect when considering bullet seating depth.

The .223 is like most rifles in that the best accuracy comes when you seat the bullet out to or almost to the rifling. If you're using a short bullet, like say, a 40 grainer, you'd want as much neck as possible so that when you seat out to the rifling, you're supporting the bullet optimally. If the case necks are too short, the bloody slug will cock in the free space as it tries to swage into the rifling. Not a real worry in a 38-55 lever gun, but it makes a huge difference in accuracy on a serious varmint rig.


Swede: I wouldn't fool around with .222M brass, unless you're itching to do it for intellectual reasons and like the challenge. The .223 cases will 'grow' soon enough, particularly if you're loading to mil-spec pressures.

But if you're looking to really maximize the potential of the .223, you can do like I did and have your Kimber rechambered to .223 Ackley Improved with a throatless reamer, followed by a separate, custom throat reaming specifically contrived to match your favorite bullet. :twisted:

[SwedeNelson]

Thanks all for the in put.

Think I will just work on
getting a load that works
with .223 brass (Short)
and go from there.

Thanks again!
Swede Nelson