Raised Ring at Base of .223 case?
- Thread starter WindSurgeon
- Start date
- Status
BoydAllen
Gold $$ Contributor
I prefer to compare actual case dimensions. You mentioned spec. dimension. I think that at this point you know what the problem is. I was mostly making a point for others that are reading the thread. It would be interesting to see what the velocities of the load was in the Lapua, and LC cases. Perhaps the difference in pressure showed up in that way as well. At this point I think that we are reviewing how to get a handle on pressure signs for rifles of this type.
effendude
Gold $$ Contributor
Occasionally I see posts like this. While I am not an AR expert, I have shot them enough in my early years of F-Class to realize that you cannot load AR's like bolt rifles. Some of the suggestions members post are meant to be helpful, but often lose the perspective needed for a gas operated rifle. Quick Load, S**t Load. Again, loading for AR's in completely different from bolt rifles. We don't know the gas port location, length of the gas tube, or what the actual pressures in the chamber are. Mil spec chambers are generally very generous (they are designed to chamber and fire ammo in dirty real world life or death situations). The actions are also usually over-gassed from opening too soon. The miltary doesn't reload its brass. They want functioning rifles, not long brass life. There are some simple solutions for these problems to make the rifle less sensitive to load issues but these solutions won't solve everything.
Load recipe changes that may be of little significance in bolt rifles will often cause huge issues in an AR. The symptons may not be immediately visible, but they show up eventually. Bolt lug wear, brass expansion issues, overworked brass all are eventual issues. Drop your charge, install a carrier weight system, use tougher brass and don't expect it to last anywhere near as long as a bolt rifle's brass.
Scott
Load recipe changes that may be of little significance in bolt rifles will often cause huge issues in an AR. The symptons may not be immediately visible, but they show up eventually. Bolt lug wear, brass expansion issues, overworked brass all are eventual issues. Drop your charge, install a carrier weight system, use tougher brass and don't expect it to last anywhere near as long as a bolt rifle's brass.
Scott
bigedp51
BoydAllen said:
We have a BINGO!
Lake City cases are made to higher standards and are harder in the base than commercial brass. Do you see the same ring on your Lake City cases with the same load?
The Lapua brass your using is not as hard in the base as Lake City cases and the AR15 chamber is .002 larger in base diameter.
If your Lapua brass was a woman your brass would ask you if her butt looks bigger when shes wearing her AR15 chamber.
Sorry for the delay. A lot of great info.
I measured the post fired cases from the starting load of 23.6 up to the maximum listed for Varget in the loading manual. Base average measurements are as follows:
23.6: .3775
23.8: .3775
23.9: .3776 (smallest group)
24.0: .3860 (max load)
The brass did not exhibit a ring at 24, but was significantly larger at the base.
To answer a couple of questions:
1) These are longer than mag length, but unfired rounds extract easily and they eject to the 4-5 o'clock position consistently.
2) Primer pockets are not loose. Very snug.
3) LC brass I used to use does not exhibit this condition
Based on all of this, I wonder if my chamber is not fully supporting the brass all the way from the neck to the base.
My plan now:
1) Have my smith check the chamber length and bolt lock up and fix if there is a problem.
2) Velocity is clearly important to shoot the 80 grain Berger bullets. 23.9 grains was the node. That load chrono'd at an average of 2815 fps with a standard deviation of 11.48.
3) If no chamber issue try a couple of other things: Go back to LC brass and bag the Lapua . Or, find another powder that can give me the velocity without the pressure
If the chamber is not out of spec then I will have an unopened box of lapua for sale or trade for LC match brass.
I measured the post fired cases from the starting load of 23.6 up to the maximum listed for Varget in the loading manual. Base average measurements are as follows:
23.6: .3775
23.8: .3775
23.9: .3776 (smallest group)
24.0: .3860 (max load)
The brass did not exhibit a ring at 24, but was significantly larger at the base.
To answer a couple of questions:
1) These are longer than mag length, but unfired rounds extract easily and they eject to the 4-5 o'clock position consistently.
2) Primer pockets are not loose. Very snug.
3) LC brass I used to use does not exhibit this condition
Based on all of this, I wonder if my chamber is not fully supporting the brass all the way from the neck to the base.
My plan now:
1) Have my smith check the chamber length and bolt lock up and fix if there is a problem.
2) Velocity is clearly important to shoot the 80 grain Berger bullets. 23.9 grains was the node. That load chrono'd at an average of 2815 fps with a standard deviation of 11.48.
3) If no chamber issue try a couple of other things: Go back to LC brass and bag the Lapua . Or, find another powder that can give me the velocity without the pressure
If the chamber is not out of spec then I will have an unopened box of lapua for sale or trade for LC match brass.
Rewinder said:
This will also get checked by the smith. Beyond my technical capability.
As mentioned before, the ring is likely caused by the resizing so you are not going to see a ring after firing unless you resize your round. The fact that you see a progressive increase in the head dimensions would say that you are over pressured at 24.0.
When you say longer than mag length, you really mean 0.001†off the lands as per your OP, and as more than one person here have said – you are likely jamming. Jamming is known to cause significant over pressure.
When you say primer pockets are not loose and very snug, are you describing the 24 grain cases which is your max load?
When you say LC brass does not exhibit this, did you go up to the same charge with the same bullet and the same distance from the lands? Even if so, others have already mentioned that Lapua brass is heavier- in my hands ~95 grains compared to 90 grains and so it has less volume. Putting the same charge in a case with smaller volume will get you higher pressure.
It could be your chamber but the fact is before you start blaming your chamber, you already have at least a couple of things mentioned above which could be responsible for what you see.
When you say longer than mag length, you really mean 0.001†off the lands as per your OP, and as more than one person here have said – you are likely jamming. Jamming is known to cause significant over pressure.
When you say primer pockets are not loose and very snug, are you describing the 24 grain cases which is your max load?
When you say LC brass does not exhibit this, did you go up to the same charge with the same bullet and the same distance from the lands? Even if so, others have already mentioned that Lapua brass is heavier- in my hands ~95 grains compared to 90 grains and so it has less volume. Putting the same charge in a case with smaller volume will get you higher pressure.
It could be your chamber but the fact is before you start blaming your chamber, you already have at least a couple of things mentioned above which could be responsible for what you see.
In terms of my seating depth, I used a stony point guage to get the right depth, then made dummy rounds with my Redding micrometer seating die to find the lands at that length, then backed off until the round extracted easily by hand. This ended up two increments (Each is supposedly .001" according to Redding) from the measurement of the SP tool. I use a comparator tool each loading in order to keep the case length to the Ogive the same from the original. I have not changed anything for the last two years since doing that.
The OAL is shorter than the OAL indicated in the loading manual. 2.46 vs. 2.55 so it gives me some confidence that I am at least off the lands as another data point.
I have been reloading since the 1980's and believe I am very methodical about my technique and not way off the reservation in terms of pushing limits.
I agree that the bases are expanding too much and the die is creating the ring. I re-sized the 24 grain rounds this morning and got two of the five with the ring after re-sizing. These were the ones over .3800". Now I need to find root cause, which is the interesting journey. Chamber, premature bolt extraction (gas block?), powder charge, OAL.
The OAL is shorter than the OAL indicated in the loading manual. 2.46 vs. 2.55 so it gives me some confidence that I am at least off the lands as another data point.
I have been reloading since the 1980's and believe I am very methodical about my technique and not way off the reservation in terms of pushing limits.
I agree that the bases are expanding too much and the die is creating the ring. I re-sized the 24 grain rounds this morning and got two of the five with the ring after re-sizing. These were the ones over .3800". Now I need to find root cause, which is the interesting journey. Chamber, premature bolt extraction (gas block?), powder charge, OAL.
stool
chambers do not support from the neck to the base.....go drop a sized case in your chamber...
i do not have the exact numbers but aprox 0.2 of the 223 case sticks out of the chamber, the bolt encircles this but is not support.
so where the expansion takes place is important.
material out side the chamber or inside the chamber.
if it is out side the chamber its just too hot as this is about the thickest part of the brass.
if it is occurring inside the chamber..then the chamber is most likely to big.....
i do not have the exact numbers but aprox 0.2 of the 223 case sticks out of the chamber, the bolt encircles this but is not support.
so where the expansion takes place is important.
material out side the chamber or inside the chamber.
if it is out side the chamber its just too hot as this is about the thickest part of the brass.
if it is occurring inside the chamber..then the chamber is most likely to big.....
Yes, I am aware of that and so is my gunsmith.
stool
this is why i posted what i did....
WindSurgeon said:
bigedp51
WindSurgeon said:
You have a military type chamber that is .002 larger in diameter than SAAMI standards.
You are not shooting milspec Lake City brass that is designed to shoot in fatter and longer military chambers and is harder in the base.
Bottom line, Lupua brass is not milspec and is made to European civilian CIP standards.
Your Lake City cases do not have the problem but the Lupua brass does.
I can tell you from years of experience collecting milsurp rifles with fat long chambers and using commercial brass..............you need to lower your load, your Lapua brass doesn't like your fat military chamber and the pressures you are loading to.
The head stamp on the brass actually means something. (.223-5.56)
Below milspec 5.56 brass on the right and left and commercial .223 brass in the center. If you want your commercial brass to last longer when shooting from a AR15 type rifle you need to keep the chamber pressure below 52,000 psi.
If you want to go faster you can't use Lupua unleaded gas when you need Lake City Nitromethane.
Ed – are you sure about this? Lapua 223 brass is significantly heavier than LC brass (with the NATO Cross) and in fact have the expected smaller internal volume than the LC brass. That increase weight and smaller internal volume is cause by thicker walls. What you show may be true from some commercial brass but not Lapua. If you are talking about 308 then that is another matter.
bigedp51
jlow said:
His Lapua brass has a ring around the base and his Lake City cases do not, this isn't rocket science, and there is a reason why they have milspec brass for the M16/AR15 rifle. (how many pictures and charts do I have to show you to get the point across?)
It also doesn't matter if Lupua brass is thicker, the real question is "how hard is the brass in the base. It does matter if he worked up his load with Lake City brass and then switched to Lapua,
Bottom line, how many AR15 shooters use Lupua .223 brass in their AR15 rifles when auto loaders are so hard on brass?
One more time, the military didn't make the 5.56 cases thicker, they made them of harder brass and this dates back to the initial jamming problems when the M16 rifle first came out.
All the information in the world is written in books and all you have to do is read.
And "WHY" would someone use Lapua brass in a rifle that throws perfectly good brass away and makes you go look for it?
effendude
Gold $$ Contributor
Go back to my post above. You reference a reloading manual. Which one and does it give loads specifically for the AR-15 or just for the .223 Rem? If you are using .223 data not designed for the AR, then all bets are off. Many of us are giving you the answers you need and you are not listening.
You are treating a mil-spec chamber like a match chamber. You are running overpressure loads to hit some mythical node you have found. At the least, get yourself a carrier weight system, some new brass and start over carefully with your load development using data designed for the AR-15 platform.
Scott
You are treating a mil-spec chamber like a match chamber. You are running overpressure loads to hit some mythical node you have found. At the least, get yourself a carrier weight system, some new brass and start over carefully with your load development using data designed for the AR-15 platform.
Scott
- Status
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.