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Discussion Starter #1
Finally had some time to test my loads and work them up. I seem to be getting very good velocities compared to others on this forum. Also, I mentioned in a post a few months back, that I was getting heavy swipes on my brass with factory S&B 110gr ammo with the first shots through my new build. Some of you mentioned to polish the chamber. I did a light polish and no more swipes now.

18" 3R 1/10 twist, stainless ARP barrel
Temperature 53F
120gr SST bullet, AA2200 Powder, 2.295" COL
Tested 4 rounds at each weight

27.5gr
Ave Velocity (fps): 2516
High: 2534
Low: 2478

28.0gr
Ave Velocity (fps): 2630
High: 2650
Low: 2604

28.1gr
Ave Velocity (fps): 2645
High: 2682
Low: 2624

28.3gr
Ave Velocity (fps): 2652
High: 2677
Low: 2635

Zero pressure signs, even at 28.3gr. I know published max is 27.2gr. Primers look identical for all loads, no swipe marks. Do you think I could go higher yet and try to hit 2700fps? I did not gain too much by going from 28.1 to 28.3 though, so might be getting maxed out. Did not test accuracy yet, but all were hitting a 6" steel plate at 100 yards free hand.

I also ran a few of the factory 110gr S&B through the chrono. Keep in mind, it's 110gr, not 120gr as above.
Ave Velocity (fps): 2690
High: 2710
Low: 2666
 

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Finally had some time to test my loads and work them up. I seem to be getting very good velocities compared to others on this forum. Also, I mentioned in a post a few months back, that I was getting heavy swipes on my brass with factory S&B 110gr ammo with the first shots through my new build. Some of you mentioned to polish the chamber. I did a light polish and no more swipes now.

18" 3R 1/10 twist, stainless ARP barrel
Temperature 53F
120gr SST bullet, AA2200 Powder, 2.295" COL
Tested 4 rounds at each weight

27.5gr
Ave Velocity (fps): 2516
High: 2534
Low: 2478

28.0gr
Ave Velocity (fps): 2630
High: 2650
Low: 2604

28.1gr
Ave Velocity (fps): 2645
High: 2682
Low: 2624

28.3gr
Ave Velocity (fps): 2652
High: 2677
Low: 2635

Zero pressure signs, even at 28.3gr. I know published max is 27.2gr. Primers look identical for all loads, no swipe marks. Do you think I could go higher yet and try to hit 2700fps? I did not gain too much by going from 28.1 to 28.3 though, so might be getting maxed out. Did not test accuracy yet, but all were hitting a 6" steel plate at 100 yards free hand.

I also ran a few of the factory 110gr S&B through the chrono. Keep in mind, it's 110gr, not 120gr as above.
Ave Velocity (fps): 2690
High: 2710
Low: 2666
Careful when you start geting close. I run 30gr for 110 ammo, but started getting pressure signs at 30.7
 

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There is a point of diminishing returns and when you hit it why go on up ? 50 fps up or down will make an almost immeasurable difference in ballistics . You should be looking for an accuaracy node with a little room on both sides to accommodate for velosisity change due to temperature . Speaking of temperature , 2200 is known to be a little sensitive so be careful at higher temperature as you worked up at 53° ( cool ) and 98° may cause excessive pressure .

Sent from my moto g(7) play using Tapatalk
 

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What’s your elevation?
Those are pushed pretty hard and definitely stout loads. Even with the 3R, not many With ARP barrels are getting to run that much powder. I understand all barrels are different, but to see that velocity and no pressure seems abnormal.


Ther other tell tale sign of reaching max pressure is flattening of the velocity curve. Maybe chart your powder charge vs velocity and if it is flattening like it appears, you’re reaching max even without brass/primer signs.

When you do shoot for accuracy and it is where you want it, I’d stop and/or back down slightly

Proceed with caution.
 

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Discussion Starter #5
There is a point of diminishing returns and when you hit it why go on up ? 50 fps up or down will make an almost immeasurable difference in ballistics . You should be looking for an accuaracy node with a little room on both sides to accommodate for velosisity change due to temperature . Speaking of temperature , 2200 is known to be a little sensitive so be careful at higher temperature as you worked up at 53° ( cool ) and 98° may cause excessive pressure .

Sent from my moto g(7) play using Tapatalk
I got a huge gain going over 27.5. I don't know the point of dimishing returns yet. The curve appears to be flattening out some though. I will test for accuracy once I know what my max is.
 

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Discussion Starter #6
Speaking of temperature , 2200 is known to be a little sensitive so be careful at higher temperature as you worked up at 53° ( cool ) and 98° may cause excessive pressure.
Thanks for the temperature info. I plan to use these loads for hunting. I'm in WI, so deer season is cold, 20-30F.
 

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Discussion Starter #7
What’s your elevation?
Those are pushed pretty hard and definitely stout loads. Even with the 3R, not many With ARP barrels are getting to run that much powder. I understand all barrels are different, but to see that velocity and no pressure seems abnormal.
I'm at 860 feet. I'm looking at primers and swipe marks. Primers show no signs of flattening, look identical to the 27.5gr load. No swipe marks. Brass lands at 4 o'clock. One thing to note, I have an adjustable gas block and had it set to the factory S&B ammo to lock the bolt back on an empty mag. I had to open it up 3 more clicks to get the 28.3gr load to lock back. That leads me to believe the factory loads are higher pressure than the 28.3 AA2200 loads. It's possible too that my scale is off. I have a 1980's Hornady scale. They are very accurate, but I never checked it with a test weight. But still, I'm getting 2650fps, so 28+ grains sounds about right.
 
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