What is too hot for a match load?

[broncman]

My load of 24.1 N140 leaves ejector marks but the BR4 primers are flat but not as flat as some of my old federal match primers. No cratering just ejector marks.
This is in an AR15.

This load is holding halfmoa at 300.

So what is your limit?

 

[Beau]

Ejector marks don't necessarily indicate excessive pressure, they are just one sign. Ejector marks may be due to excessive pressure or higher port pressure. The root cause is that the bolt is unlocking relatively early. Burning rate is a factor as well as overall pressure.

From what I understand, ejector marks are part of what you get with N140.

 

[broncman]

That makes sense. The bolt is turning with pressure still on the head. Would explain sooty cases on new brass as well.

I have a carrier weight system. Will throw it in and see.

Thanks!

Ken

 

[amlevin]

That makes sense. The bolt is turning with pressure still on the head. Would explain sooty cases on new brass as well.

I have a carrier weight system. Will throw it in and see.

Thanks!

Ken

Or perhaps an adjustable gas tube?

 

[broncman]

Gas block is loc tited and the barrel assembly is bedded to the reciever as well..it aint coming apart till new barrel time

 

[FroggyOne2]

Question, without the carrier weight in the BCG, where does your ejected brass land?

 

[broncman]

If I am laying on the mat it lands about three feet to the right side and about as far back as my thigh all in a neat pile.

 

[FroggyOne2]

Well then it seems that your carrier is not going to fast, I think that using the weight might indeed help the situation then. When I was shooting service rifle, that is the reason that I put the weight in the BCG, was to slow down the carrier. I was running it pretty hot on the 600 yard load. But that is what the rifle liked and I was getting the brass for free.

 

[broncman]

Went back to the range today and shot in the wind ;D
The carrier weight helped a lot. I had readjusted my scope to a better position.
Ten shots, three to dial in and remaining seven in the 10 ring at three hundred!

Super stoked now. Ready for Butner! Shot everyday for a week and still some to go.
If I can score in the low 190's I will be tickled. My best score was a 192 but that was the only time I got out of the mid 180's...

 

[thefitter]

What bullet, COAL and barrel length?

 

[FroggyOne2]

That is good to hear that you made gounds in improvement.. hope that you do well.

 

[broncman]

24" krieger . 2.25 oal.
77 SMK
Not sure about round count but it is getting up there. It dors seem faster than when I got it. Not sure if speed goes up as a barrel wears but the same load of varget from when I built it was slower.

Hope it just doesnt fall apart at 600!

 

[thefitter]

I ran this through QL. Make sure I got the data right:

5.56×45mm NATO
77gr Sierra HPBT MatchKing
COAL 2.25
N140 - 24.1gr

If that is all correct I'm getting a pressure of 70136 psi which is way up there!

If you give me the case length and bullet length I can fine tune it.

Edit: I changed the load parameter to .223 REM instead of 5.56×45mm NATO and the pressure calculates at 67979. Vihtavuori reloading data shows a range of 21.0gr - 24.7gr, so you are still under book max.