Loading 223 For Krieger "5.56 Match" Chamber?

Gwhite · March 27, 2009, 08:26 AM

I've got two space guns I built, one for me (blue), and one for my wife (purple). Both have Krieger barrels with their "5.56 match" chamber, which is tighter than a mil spec chamber, but still allows shooting ammo like XM193. We will be shooting the rifles in a local league, which is all 200 yard slow fire, so we will be single loading & don't have to worry about fitting the rounds in a magazine.

I am used to shooting a bolt gun, and spening a lot of time fussing with bullet seating depth to get the ogive close to the lands.

I bought a good supply of 69 gr Sierra MatchKings before the recent craziness set in. I haven't had time to try to measure how far out the throat/lands are in this chambering, so I don't know if I can even come close to the lands with this bullet.

I am planning on starting with the nominal OAL, but was wondering if anyone with this chambering had experimented & found any advantage to loading any longer?

Thanks!

dc.fireman · March 27, 2009, 04:21 PM

G -

I'm currently loading the SMK HPBT 69 gr. myself. I'm loading them for magazine length though - I have done some perusing of the Lymans 49th ed. for the heavier 80 + 90 gr. bullets, which, cannot be loaded to mag. length.

I'm afraid I can't comment on your specific question, but I can give you this personal observation: hand pick those bullets from the box.

If I can find my camera, I'll take a pic and hopefully explain it all a little better, but...after loading about 300 of these, I noticed that they weren't coming out to a uniform length...when I was putting them on the calipers, there was a spread of about .004" between the rounds. After much examining and checking, and tightening, and rechecking, it turns out it wasn't my dies at all, but the tips of the hollow points not being uniform - some of them had a kind of 'ridge' on the tips, that was only visible after close inspection...

I was able to get 'okay'(about a 4-5 " group, at the 100 meter line)accuracy out of them - but it wasn't stellar. I was using them in my 16" AR-15, and here's the breakdown:

Case: Remington Pre-Primed
Powder: Hogdon Varget - 23.5 at first, worked up 24.0 so far. Lymans specifies 26.0 as max.
Bullet: Sierra Match King HPBT 69 gr.
C.O.A.L. : 2.250 - 2.254 - I pulled down anything greater than those variances...

Good luck at the shoot! Love to hear how you made out...

-tc

**Unclenick** · March 27, 2009, 05:48 PM

The difference in length of the bullets is an artifact of how the jackets are formed into the ogive to create the hollow point. You'll see an unevenness in the hollow points of some and not others, with the high sides being a few thousandths bigger on some than on others. All the Sierra MatchKings have that and it doesn't amount to anything measurable on the target unless you are shooting bugholes with with a benchrest gun, IME, and even then is tough to pick out.

Variation in bullet noses is far less significant than is variation in bullet bases. Harold Vaughn did some experiments with filing substantial slants onto bullet noses. The errors they produced on the target were on the order of 1/4 moa, IIRC? The thing is that as long as the bullet is spinning fast enough it remains stable and the deflecting force on the nose gets applied equally in all directions once per revolution. Thus it tends to correct its deflection error on average. The flight path may become slightly helical and ballistic coefficient may be reduced, but the average position of the bullet mass is still along the trajectory line.

It has been pretty well shown in the .223 that 90 grain bullets subtract too much powder space to compete with 80 grain bullets at long range. The latter seem to be about optimal for long shots in that case capacity. If you want to try seating out to touch the lands in a longer chamber, try the 77 grain matchking with its longer bearing surface. You can go plenty far forward with it. But a tight match chamber should be easy to find the throat with using a 69 grain SMK. The freebore is shorter than a military chamber, which has to be long to accommodate some special purpose military ammo. Since military cases are made with the same external dimensions as civilian cases, it has no issues chambering in the tighter civilian chambers as long as the bullet is standard ball.

Gwhite · March 30, 2009, 06:10 PM

I measured the two rifles last night. I've got a Stony Point gauge, but I've generally had better luck making my own "test case" with a slit in the neck to hold the bullet with some tension. You file off the extractor ring, and them push it out from the muzzle with a rod. That way the bullet doesn't get pulled out any if it sticks in the throat. I get much more consistent results in my 308 bolt gun than I ever could with the Stoney Point or the RCBS "freebore" gauge. The concept is similar to the RCBS, but you get to use the actual bullet you will be loading.

The actual rifling is out quite a ways in this chamber. Using the RCBS case micrometer, my rifle measured +87 mils, and my wife's was at +99 mils. By comparison, some Black Hills match ammo with a 68 gr bullet averaged around -12 mils and XM193 ran around +35 mils. The OAL of the cartridge with the 69 gr bullet far enough to reach the lands in my wife's rifle was 2.336", which is 76 mils over the max length spec to work in a magazine.

I also contacted Kreiger, and they said: "The 5.56 Match chamber has a relatively long throat for the 69 grain bullets to touch the lands. I don't think you can seat them out to touch the lands and still have a reasonable amount of bullet in the neck of the case. The good news is, with the tight lead diameter on our chambers (.2254") the bullet cannot 'turn' or yaw in the lead before contacting the throat. It is always best to be able to come close to the lands when loading, but I would be surprised if you have any accuracy issues the way our reamers are designed. I would just load them to a maximum magazine length and see how they shoot."

Even with the 69 gr bullet far enough out to touch the rifling in my wife's rifle, I looks like I still have a good amount of bullet in the neck, so I'm not worried about that.

Given Krieger's comments, I think I will start out with a load that fits the recommended OAL. Some day when I have time to do some careful tests, I will experiment with loading them longer. I don't want to mess with keeping track of different loads for the two rifles, so even if I load close (say 10 mils) in hers, I'll be back 23 mils in mine.

March 27, 2009, 08:26 AM	#1
Gwhite Junior Member Join Date: January 14, 2009 Posts: 10	Loading 223 For Krieger "5.56 Match" Chamber? I've got two space guns I built, one for me (blue), and one for my wife (purple). Both have Krieger barrels with their "5.56 match" chamber, which is tighter than a mil spec chamber, but still allows shooting ammo like XM193. We will be shooting the rifles in a local league, which is all 200 yard slow fire, so we will be single loading & don't have to worry about fitting the rounds in a magazine. I am used to shooting a bolt gun, and spening a lot of time fussing with bullet seating depth to get the ogive close to the lands. I bought a good supply of 69 gr Sierra MatchKings before the recent craziness set in. I haven't had time to try to measure how far out the throat/lands are in this chambering, so I don't know if I can even come close to the lands with this bullet. I am planning on starting with the nominal OAL, but was wondering if anyone with this chambering had experimented & found any advantage to loading any longer? Thanks!

March 27, 2009, 04:21 PM	#2
dc.fireman Junior Member Join Date: December 31, 2008 Location: Manassas, Va. Posts: 8	G - I'm currently loading the SMK HPBT 69 gr. myself. I'm loading them for magazine length though - I have done some perusing of the Lymans 49th ed. for the heavier 80 + 90 gr. bullets, which, cannot be loaded to mag. length. I'm afraid I can't comment on your specific question, but I can give you this personal observation: hand pick those bullets from the box. If I can find my camera, I'll take a pic and hopefully explain it all a little better, but...after loading about 300 of these, I noticed that they weren't coming out to a uniform length...when I was putting them on the calipers, there was a spread of about .004" between the rounds. After much examining and checking, and tightening, and rechecking, it turns out it wasn't my dies at all, but the tips of the hollow points not being uniform - some of them had a kind of 'ridge' on the tips, that was only visible after close inspection... I was able to get 'okay'(about a 4-5 " group, at the 100 meter line)accuracy out of them - but it wasn't stellar. I was using them in my 16" AR-15, and here's the breakdown: Case: Remington Pre-Primed Powder: Hogdon Varget - 23.5 at first, worked up 24.0 so far. Lymans specifies 26.0 as max. Bullet: Sierra Match King HPBT 69 gr. C.O.A.L. : 2.250 - 2.254 - I pulled down anything greater than those variances... Good luck at the shoot! Love to hear how you made out... -tc Last edited by dc.fireman; March 27, 2009 at 04:23 PM. Reason: forgot the powder charge!

March 27, 2009, 05:48 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,061	The difference in length of the bullets is an artifact of how the jackets are formed into the ogive to create the hollow point. You'll see an unevenness in the hollow points of some and not others, with the high sides being a few thousandths bigger on some than on others. All the Sierra MatchKings have that and it doesn't amount to anything measurable on the target unless you are shooting bugholes with with a benchrest gun, IME, and even then is tough to pick out. Variation in bullet noses is far less significant than is variation in bullet bases. Harold Vaughn did some experiments with filing substantial slants onto bullet noses. The errors they produced on the target were on the order of 1/4 moa, IIRC? The thing is that as long as the bullet is spinning fast enough it remains stable and the deflecting force on the nose gets applied equally in all directions once per revolution. Thus it tends to correct its deflection error on average. The flight path may become slightly helical and ballistic coefficient may be reduced, but the average position of the bullet mass is still along the trajectory line. It has been pretty well shown in the .223 that 90 grain bullets subtract too much powder space to compete with 80 grain bullets at long range. The latter seem to be about optimal for long shots in that case capacity. If you want to try seating out to touch the lands in a longer chamber, try the 77 grain matchking with its longer bearing surface. You can go plenty far forward with it. But a tight match chamber should be easy to find the throat with using a 69 grain SMK. The freebore is shorter than a military chamber, which has to be long to accommodate some special purpose military ammo. Since military cases are made with the same external dimensions as civilian cases, it has no issues chambering in the tighter civilian chambers as long as the bullet is standard ball. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 30, 2009, 06:10 PM	#4
Gwhite Junior Member Join Date: January 14, 2009 Posts: 10	I measured the two rifles last night. I've got a Stony Point gauge, but I've generally had better luck making my own "test case" with a slit in the neck to hold the bullet with some tension. You file off the extractor ring, and them push it out from the muzzle with a rod. That way the bullet doesn't get pulled out any if it sticks in the throat. I get much more consistent results in my 308 bolt gun than I ever could with the Stoney Point or the RCBS "freebore" gauge. The concept is similar to the RCBS, but you get to use the actual bullet you will be loading. The actual rifling is out quite a ways in this chamber. Using the RCBS case micrometer, my rifle measured +87 mils, and my wife's was at +99 mils. By comparison, some Black Hills match ammo with a 68 gr bullet averaged around -12 mils and XM193 ran around +35 mils. The OAL of the cartridge with the 69 gr bullet far enough to reach the lands in my wife's rifle was 2.336", which is 76 mils over the max length spec to work in a magazine. I also contacted Kreiger, and they said: "The 5.56 Match chamber has a relatively long throat for the 69 grain bullets to touch the lands. I don't think you can seat them out to touch the lands and still have a reasonable amount of bullet in the neck of the case. The good news is, with the tight lead diameter on our chambers (.2254") the bullet cannot 'turn' or yaw in the lead before contacting the throat. It is always best to be able to come close to the lands when loading, but I would be surprised if you have any accuracy issues the way our reamers are designed. I would just load them to a maximum magazine length and see how they shoot." Even with the 69 gr bullet far enough out to touch the rifling in my wife's rifle, I looks like I still have a good amount of bullet in the neck, so I'm not worried about that. Given Krieger's comments, I think I will start out with a load that fits the recommended OAL. Some day when I have time to do some careful tests, I will experiment with loading them longer. I don't want to mess with keeping track of different loads for the two rifles, so even if I load close (say 10 mils) in hers, I'll be back 23 mils in mine.