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This is interesting. I’ve always wondered why we couldn’t beat factory loads with 2200. The Hornady 270 Win Custom Lite 120gr SST is listed at 2675fps @24” bbl. admittedly a downloaded cartridge, but your loads are starting to approach 270 Win territory. We should highlight that this is out of not only an ARP barrel, but a 3R which was designed to reduce pressure (engraving force is the term I believe) for heavier gr bullets in 6.8.
I beat most factory loads with AA2200 and Im using a Bison barrel, not ARP. I haven't played around with 120's cause those bastards are expensive to shoot. I got 2450 with Cavity Back 120s and was happy. I can develop my 110/105 load cause S&B FMJ 110s have the same ballistic performance as the 105 MKZ. At this point I'm just playing around with COAL on the rounds. Im happy with 30 grains and its accurate.
 

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Discussion Starter #22
Back to the range for the 10th time. Ran 29.7gr to 30.2gr. Still no pressure signs. Has anyone here actually seen flattened primers? There seems to be no end to how high I can go. Maybe these #450 CCI primers are extra tough?

AA2200 powder, 120gr SST, 18" ARP 3R 1/10 barrel, 73F
29.7gr: 2762fps ave, high 2789
30.2gr: 2776fps, high 2789

Getting close to 2800fps!
 

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Back to the range for the 10th time. Ran 29.7gr to 30.2gr. Still no pressure signs. Has anyone here actually seen flattened primers? There seems to be no end to how high I can go. Maybe these #450 CCI primers are extra tough?

AA2200 powder, 120gr SST, 18" ARP 3R 1/10 barrel, 73F
29.7gr: 2762fps ave, high 2789
30.2gr: 2776fps, high 2789

Getting close to 2800fps!
Flattend a few, blew one out the case.
 

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Back to the range for the 10th time. Ran 29.7gr to 30.2gr. Still no pressure signs. Has anyone here actually seen flattened primers? There seems to be no end to how high I can go. Maybe these #450 CCI primers are extra tough?

AA2200 powder, 120gr SST, 18" ARP 3R 1/10 barrel, 73F
29.7gr: 2762fps ave, high 2789
30.2gr: 2776fps, high 2789

Getting close to 2800fps!
Looks like you have flattened the curve. .5 gr increase didn't give you any more velocity increase. I would be very cautious about increasing much more. Have you found an accuracy node near the top?
 

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Discussion Starter #27
Looks like you have flattened the curve. .5 gr increase didn't give you any more velocity increase. I would be very cautious about increasing much more. Have you found an accuracy node near the top?
Yes, starting to flatten out some. I just started testing accuracy. Tested 29.5, 30.0, and 30.2. All were about the same groupings. Only shot 5 of each and will test more at various loadings.

64804
 

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I get mild flattening with ARP chamber 27.5gr 2200 in SSA (old) case with CCI 41. Sea level, 75-90F. 2398 FPS from 12.5” ARP barrel.
 

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Discussion Starter #29
Broke 2800fps today with the 120gr SST. Still no pressure signs at all. I tested up to 30.7gr now. Ironically, my most accurate load is 30.7gr, the hottest load tested so far. It came in at 0.5 MOA. All other loads tested from 29.5gr and up were 1-2 MOA. I'm not sure if I want to go with the highest load tested, but it is the most accurate. I could try to go up to 31.0gr to see if it's still safe, at least I'll then I have somewhat of a buffer from 30.7gr.

30.5gr: 2781fps ave, high 2801
30.7gr: 2795fps, high 2807


64813
 

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Discussion Starter #32
Well gun deer season starts a week from this Saturday. Looks like I'll be using the 30.7gr load. Took this buck last week with crossbow. Have one bigger yet on camera. The 6.8 will be waiting for him...
64840
 

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Dang nice buck! Congratulations.
 

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Discussion Starter #34
Made it up to 31.0gr today and a max velocity of 2849fps! Still no signs of pressure. The load feels compressed now. Powder is up to the base of the neck of the cartridge. A spike in velocity is seen on the chart too starting at 30.7gr. My most accurate load is 30.7gr. My next accurate load is 30.0gr. I'm not going any higher on the charge. I'm using 30.7gr for opening day of gun deer this weekend, but will probably settle on the 30.0gr load for safety eventually. I'm sighted in at the 30.7gr load now.

30.7gr: 2818fps ave, high 2836
31.0gr: 2840fps ave, high 2849

65145
 

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Once you push those 120 SST's near 2700 fps .. they really start becoming hand grenades. I backed
mine off due to terminal performance. I like frangible bullets for deer hunting but I hunt from blinds with
good rest so depends on what you want to use it for. The terminal performance on ribcage (no bones)
is pretty dramatic. On the other hand, I shot a doe at 50 yards directly in shoulder little over
2700 fps and bullet never made it to vitals. I got her but long track job and needed finishing shot.
In the 2500-2600 range the bullets tend to stay together and penetrate much better.
 

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Once you push those 120 SST's near 2700 fps .. they really start becoming hand grenades. I backed
mine off due to terminal performance. I like frangible bullets for deer hunting but I hunt from blinds with
good rest so depends on what you want to use it for. The terminal performance on ribcage (no bones)
is pretty dramatic. On the other hand, I shot a doe at 50 yards directly in shoulder little over
2700 fps and bullet never made it to vitals. I got her but long track job and needed finishing shot.
In the 2500-2600 range the bullets tend to stay together and penetrate much better.
That does being up a good point about the uncommonly high velocity reached here, especially when hunting at short ranges.
 

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Discussion Starter #38
Yes, not sure how well the 120gr SST holds up over 2800fps. I can tell you the 150gr SST at 3000fps is excellent. I know it's a different bullet and assume it's designed for higher velocities than the 120gr. I shot a 150" 4.5 year old buck last year with the 150gr. It did pass through, totally destoyed the insides, and dropped him in 10 feet. Maybe with my high velocities, I'm better off going with the 110gr Accubond?
 
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