.223 Chamber Lengths?

[dc.fireman]

Howdy High Roaders!

So... I've been using my LnL OAL Length Gauge a lot as of late - I'm looking for some data from other users concerning their OAL readings using this tool. I was greatly surprised at the measurements I was getting - considering magazine length ( I can squeeze 2.262" out of my AR-15 magazines, I haven't tested the Steyr yet...)

I measured three of my rifles, using three bullets I load, and took each measurement three times. The rifles measured are:

Rock River Arms Elite CAR-A4 (16" Wilson barrel 1/8, .223 Wylde chamber)
LaRue Tactical LT-1011 (18" barrel unk. mfg., 1/8, .223 Wylde chamber)
Steyr Jeff Cooper Tac. Scout (19" barrel 1/9, .223 Rem. chamber)

Sierra Match King 69 gr. HPBT:

RRA - 2.364"

LT1011 - 2.353"

Steyr - 2.381"

Hornady 68 gr. BTHP:

RRA - 2.352"

LT1011 - 2.332"

Steyr - 2.366"

SMK 52 gr. HPBT:

RRA - 2.328"

LT1011 - 2.307"

Steyr - 2.344"

I'm not sure what can be inferred from this info, other than I'll obviously loading to magazine lengths for all three rifles, and simply dealing with what seems to be huge jumps to the rifling.

For the record, I have kept records of the round counts for the three rifles, if someone happens to have the same types / round counts for comparison:

RRA - 8700 rounds, mixed 5.56 (WCC, LC, RORG, Speer)
LT1011 - 30 rounds (my reloads)
Steyr -85 rounds (40 Remington .223, 45 my reloads)

Anyhow, if you have any data from your .223's, reposit it here - I'm kind of curious as to how close/far apart some of the numbers really are...

-tc

 

[JimKirk]

Unless you going to shoot single shot ... what choice do you have?

Have you measured the point where the bullet ogive touches the rifling and compared that?

The tip of the bullet touches nothing in the chamber... so the OAL really has no bearing except for the ability to fit the magazine.

The point of the ogive touching the rifling ... that is another matter. I seen some guns that like very little free jump to the rifling, others that prefer some distance between. Even bullets themselves can have their own prefered depth... like the Barnes all copper, they like some jump to the rifling.

Forgive me for not being a Big AR person ... but I've been doing the same thing with my AR for the last few week.

Jimmy K

 

[dc.fireman]

Jim-

I don't have a bullet comparator- I couldn't think of any other way to measure the spot where it touches the ogive. I was hoping that the bullet ogives were fairly consistent from box to box within the same manufacturer, which would give me the reference point to the rifling -

I used the modified case from Hornady, put the bullet in it, made sure it would slide freely, chambered it, and then pushed it all the way in until the ogive hit the rifling. I then used a coated cleaning rod to 'help' the bullet back out from the chamber.

I fully realize that bullets vary from box to box, but I was really hoping that the ogives are pretty consistent - the Sierra bullets always seem to measure dead on at either 69 gr. or 52 gr., depending on what I'm using that week.

I don't hadn't planned on using the single shot method...

 

[rcmodel]

If you are that worried about jump to the rifling, you probably should get rid of the AR-15's.

SAAMI Max length for the .223/5.56 is 2.260", and that is what I would load them at for your three rifles.

I doubt you will gain anything but problems trying to seat to the rifling unless you go single shot for long range competation.

rc

 

[243winxb]

dealing with what seems to be huge jumps to the rifling.

Very common in some factory rifles. The only reason to jam a bullet into the leade/rifling is to center the round in the chamber. IMO. Unless a chamber is custom cut to fit your loaded cartridge AOL, your not going to benefit by seating into the leade/rifling. When possible, the bullets base, when seated, should be at the neck/shoulder junction of the case. There are other ways to center the cartridge in the chamber.1. Controling your shoulder bump, if done carefully for an auto. 2. Using bushing dies and only sizing part of the neck area. If you were using a bolt action a Lee collet neck sizing die would work also, when only sizing part of the neck area.

 

[JimKirk]

DC

I hope that you did not misunderstand ... that I meant to seat live ammo to touch the rifling...I meant only to find the rifling like that using the marked bullet with a fired case... I would never suggest loading live rounds to touch the rifling

I only have 1 AR and have very little experience loading for it other than plinking ammo, I haven't got really serious about accuracy with it.

You really don't need(or have to have) a bullet comparator to find the OAL of a cartridge.
A fired cased, with a neck sized just enough to hold a bullet, some folks use a split neck case... seat the bullet longer than the expected OAL. Mark the bullet with a magic marker or smut it with a candle. Chamber the cartridge and note where the rifling marks the bullet. Back off .005 - .030 from the rifling marks ... depending on what the gun likes.

For the AR
Unless you're shooting single shot... You really don't have much choice but to load OAL for the magazine AS RC said close to 2.260" depending on your magazine

Jim K