220 gr. and A1680 in a 9" barrel & Suppressed

[Whole Bunches]

My experience has been that as I made the oal longer, I had to use more powder to get the same velocity. So, if you increase the oal with the same powder charge, don't be surprised if the velocity decreases. Keep that in mind as you read my chronograph results from today.

I don't see anything about the accuracy you obtained with your subsonic load; was it accurate enough for your purposes? If NO, then you should try differing powder charges until you get the accuracy you need. For my subsonic shooting, I try differing powder charges (and sometimes differing oal) to get the best accuracy (as long as it is still subsonic). Accuracy first; specific subsonic velocity second for me.

With a suppressor mounted, you can get closer to the chronograph if you want (the suppressor will reduce the muzzle blast). Today I was shooting (suppressed) with the muzzle 3' from the center of the chronograph screens to get a truer picture of muzzle velocity.

I normally use surplus WC680 with 220gr subs in the AR. I've used up 4 of the 8 pounds I had. Since WC680 is no longer on the surplus market, today's testing was getting some subsonic loads with A1680 to try for accuracy tomorrow. 11.7gr WC680 (otherwise the same parameters as below) gives average of 1026fps and nice accuracy. My goal today was 1026fps, hoping for the same point of impact when I shoot for accuracy (I chronograph in my front yard and do accuracy testing at a range), but when I looked at the data, I discovered the low extreme spread of the 11.9gr A1680 load. I therefore loaded up 11.9-12.1gr for accuracy testing tomorrow.

10.3" Delta Co Arms bbl
Gemtech Quicksand suppressor
Formed LC brass
No anneal
No crimp
220gr SMK blems from Midway
A1680 powder
Wolf KVB 223M primers
2.2" oal

11.9gr gave average of 1007fps and extreme spread of 4fps
12.0gr gave average of 1014fps and extreme spread of 35fps
12.1gr gave average of 1026fps and extreme spread of 44fps

Fired for accuracy yesterday. Flawless functioning. Turns out that 12.1gr A1680 gave the best accuracy for my setup, and was even a touch better than my normal WC680 load. I would've thought the 11.9 load would have done superb with its low ES, but while "ok", it didn't beat the 12.1 which coincidently gives the same average fps as my worked up best WC680 load. The 2 loads (WC680 and A1680) hit about a half inch apart though. Now I'm not worried when my WC680 supply runs out. The loads sounded the same to me suppressed, but maybe someone with better hearing would be a better judge of that.

[Legionaire]

WC680 is A1680. Same as 269 is 110. So results should be very close.

[Whole Bunches]

WC680 is A1680. Same as 269 is 110. So results should be very close.

Yep. 11.7gr WC680 (the lot I have) and 12.1gr A1680 both give an average of 1026fps suppressed in my 10.3" upper.

[BretJ]

My experience has been that as I made the oal longer, I had to use more powder to get the same velocity. So, if you increase the oal with the same powder charge, don't be surprised if the velocity decreases. Keep that in mind as you read my chronograph results from today.

I don't see anything about the accuracy you obtained with your subsonic load; was it accurate enough for your purposes? If NO, then you should try differing powder charges until you get the accuracy you need. For my subsonic shooting, I try differing powder charges (and sometimes differing oal) to get the best accuracy (as long as it is still subsonic). Accuracy first; specific subsonic velocity second for me.

With a suppressor mounted, you can get closer to the chronograph if you want (the suppressor will reduce the muzzle blast). Today I was shooting (suppressed) with the muzzle 3' from the center of the chronograph screens to get a truer picture of muzzle velocity.

I normally use surplus WC680 with 220gr subs in the AR. I've used up 4 of the 8 pounds I had. Since WC680 is no longer on the surplus market, today's testing was getting some subsonic loads with A1680 to try for accuracy tomorrow. 11.7gr WC680 (otherwise the same parameters as below) gives average of 1026fps and nice accuracy. My goal today was 1026fps, hoping for the same point of impact when I shoot for accuracy (I chronograph in my front yard and do accuracy testing at a range), but when I looked at the data, I discovered the low extreme spread of the 11.9gr A1680 load. I therefore loaded up 11.9-12.1gr for accuracy testing tomorrow.

10.3" Delta Co Arms bbl
Gemtech Quicksand suppressor
Formed LC brass
No anneal
No crimp
220gr SMK blems from Midway
A1680 powder
Wolf KVB 223M primers
2.2" oal

11.9gr gave average of 1007fps and extreme spread of 4fps
12.0gr gave average of 1014fps and extreme spread of 35fps
12.1gr gave average of 1026fps and extreme spread of 44fps

Please tell me this is not a typo....

[Whole Bunches]

Not a typo. The spread was indeed 4 feet per second. Same headstamp brass, same lot of primers, same box of bullets, powder weighed on digital scale. Hi 1009fps; low 1005fps, others 1007 if I remember correctly. All shots fired registered with the chronograph. The first thing I check if the just fired shot reads the same as before is the number of shots the chronograph has registered in that string. I fired 5 shots to get an average. Muzzle of supressor was 3 feet from middle of the chronograph screens. So the bullets would go into the dirt in the woods in front of my house for safety, the chronograph was in the shade sitting about 2 feet above the ground with the screens tilted and I was standing, aiming downward so all the powder was in the same position. The numbers didn't really dawn on me until I hit the Review button to write them down. I had high hopes for the load once I realized the numbers, but of the 3 loads shot for accuracy the next day (11.9, 12.0, and 12.1), the 11.9 load shot the worst (not bad, just the worst) with the largest ES load shooting the most accurately. I suppose I could revisit the load and fire more groups, but I was happy with the 12.1gr A1680 accuracy results.

[Maryland_Shooter]

Thats true you never know it all. I load more ammo in a day than allot of people do in their life and i still have things go diff than logic or experience say it should.

Wow, how much ammo do you load?

[Legionaire]

I have loaded as much as 40k in a day.

[Maryland_Shooter]

Holy hell - on what?

[Legionaire]

different automated machines.

[hotbrass]

Got any pictures? If there arent any pictures, it never happened.

I'm always looking for automation ideas.