Old gun----new problem....Solution on Page 3

[davidj]

I have had my 20" Shilen AA upper for over a year now. After experiencing all the new 6.5 Grendel problems I finally got it shooting well.The only thing I have ever shot has been the 123 A-Max....Factory and reloads..Hornady and AA brass..IMR8208XBR..CCI450.
The load I settled on was 28.4 gr 8208 and it has been consistently delivering sub MOA .
I always shoot in the early morning when the temperatures are in the 60-70's. Sorry for the lengthy lead-in.
I have started getting pressure signs such a flattened primers and stuck cases. I dropped my powder charge down to 27.4 grains and things seemed to get worse. I have had several
case head separations (on 2nd reload). I have a Wilson case gage and I use it on every single case. The loaded bullets will slide in and out of the chamber but many of the fired cases stick. If I drop the bolt on these I cannot get them loose unless I use a rubber mallet.
Now for the good part: Factory loads work without any problems at all(the primers are a little flat though). Last month I shot a 1000yd qualification course with Hornady 123 A-Max factory loads and it went without a hitch. This leads me to believe my reloads are somehow defective. I have Hornady dies and have used them on both a Rock Chucker and a Dillon 550.I have been weighing ALL powder drops.
I welcome any and all thoughts on the subject.

Dave

[bwaites]

I have had my 20" Shilen AA upper for over a year now. After experiencing all the new 6.5 Grendel problems I finally got it shooting well.The only thing I have ever shot has been the 123 A-Max....Factory and reloads..Hornady and AA brass..IMR8208XBR..CCI450.
The load I settled on was 28.4 gr 8208 and it has been consistently delivering sub MOA .
I always shoot in the early morning when the temperatures are in the 60-70's. Sorry for the lengthy lead-in.
I have started getting pressure signs such a flattened primers and stuck cases. I dropped my powder charge down to 27.4 grains and things seemed to get worse. I have had several
case head separations (on 2nd reload). I have a Wilson case gage and I use it on every single case. The loaded bullets will slide in and out of the chamber but many of the fired cases stick. If I drop the bolt on these I cannot get them loose unless I use a rubber mallet.
Now for the good part: Factory loads work without any problems at all(the primers are a little flat though). Last month I shot a 1000yd qualification course with Hornady 123 A-Max factory loads and it went without a hitch. This leads me to believe my reloads are somehow defective. I have Hornady dies and have used them on both a Rock Chucker and a Dillon 550.I have been weighing ALL powder drops.
I welcome any and all thoughts on the subject.

Dave

You have had several case head seperations without rifle damage?

[davidj]

You have had several case head seperations without rifle damage?

Yes Sir,
maybe they are partial as they did eject in entirety.

[Drifter]

In theory, if a case works in the case gauge, you should be good. In reality, that's not always the case. Your chamber could be tighter, and / or need a case with a slightly shorter shoulder. Your new brass was apparently okay, but perhaps your second loading reveals the need for a die adjustment. Just a thought...

And FWIW, 28.4gr of 8208 in Hornady brass with mag primers would be excessively hot in my barrel. I use 27.7gr in that scenario.

[LR1955]

You have had several case head seperations without rifle damage?

Bill:

Sure. Never had a case head separation with a AR but many times with a M-1A. Some of them only ejected the head, leaving the body of the brass in the chamber. Never any damage to the rifle. The M-1A / M-14 can't take more than three reloads without risking a headspace separation.

LR1955

[LR1955]

Yes Sir,
maybe they are partial as they did eject in entirety.

DJ:

Just to make sure if you by chance have both a 7.62 X 39 bolt face Grendel and a standard Grendel. Make sure you are using the right bolt.

I think you have done this before but get some headspace guages and check the headspace of the rifle itself. If the rifle has the right headspace, my bet is the gas system is causing a problem.

The fired and sized brass sticking in the chamber means a huge amount of pressure is causing the brass to flow. Most likely the head is expanded tremendously and the sizing die won't take it out.

LR1955

[davidj]

DJ:

Just to make sure if you by chance have both a 7.62 X 39 bolt face Grendel and a standard Grendel. Make sure you are using the right bolt.

I think you have done this before but get some headspace guages and check the headspace of the rifle itself. If the rifle has the right headspace, my bet is the gas system is causing a problem.


LR1955

It is a complete upper from AA. I doubt it is a mismatch. I called them and described the problem but they never got back to me.
I will look into getting some headspace guages.

Thanks

[Drifter]

It is a complete upper from AA. I doubt it is a mismatch. I called them and described the problem but they never got back to me.
I will look into getting some headspace guages.

Not sure that it's reasonable to expect AA to fix the issue since you report that factory ammo works fine...

...Hornady 123 A-Max factory loads and it went without a hitch. This leads me to believe my reloads are somehow defective.

I still think you need to adjust your dies (and back off the charge weight a bit).

[davidj]

Not sure that it's reasonable to expect AA to fix the issue since you report that factory ammo works fine...


I still think you need to adjust your dies (and back off the charge weight a bit).

I don't think AA should do anything if it my fault.

I have set the sizing die against the shellholder and I have also moved it up in increments. I have lowered the charge from 28.4 to 27.4. Do you think going lower will change things?
As I originally stated I too feel it is a reloading problem.I was just hoping someone would say"oh, I fixed that same problem by doing..."

[Drifter]

27.4gr of 8208 should be plenty safe with a 123gr A-max in Hornady brass.

Visually inspect your chamber and bore, and closely check your bolt and extractor for cracks (especially if you haven't tried factory ammo since using the potentially hot reloads with 28.4gr of 8208). A bolt doesn't necessarily become completely inoperative all at once.

It might indeed be a mechanical problem and not a reloading issue.

[StoneTower]

Does a reloaded round chamber and eject (without being fired) without problem?

[davidj]

Does a reloaded round chamber and eject (without being fired) without problem?

yes...no problem at all.

[LRRPF52]

Any pics of the separated case heads?

Could be that the larger powder volume is substantial enough to cause the combustion flow to spike through the gas system, and rip the case head off due to too early unlocking and extraction.

This would explain why you're not seeing issues with the factory ammo at tame load volumes.

What buffer weight are you using, and what type of bolt carrier do you have?

If carbine-length stock, look into a heavier buffer, like an H2 or H3.

[davidj]

Any pics of the separated case heads?

Could be that the larger powder volume is substantial enough to cause the combustion flow to spike through the gas system, and rip the case head off due to too early unlocking and extraction.

This would explain why you're not seeing issues with the factory ammo at tame load volumes.

What buffer weight are you using, and what type of bolt carrier do you have?

If carbine-length stock, look into a heavier buffer, like an H2 or H3.

DSCN2715.jpgDSCN2719.jpgDSCN2716.jpg

I believe it is a standard AA bolt(it came as a complete upper)
It has a standard RRA buffer in a RRA tactical car lower receiver.

[StoneTower]

It looks like your bolt is unlocking while the case is still under pressure. That is unless you have a belted Grendel chamber.