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Need advice - 6 ARC bolt action load data for 103-108 gr bullets
- By Mr. Wolf
- Reloading Depot
- 41 Replies
*** Disclaimer, I am not an expert in reloading, I am rather new to this art and this is my experience. The load information that I have may not work in your system, and may be overpressured which may cause damage to your system, injury or death. Always go 10% below what your find online and work up. Use at your own risk. ***
This has been an interesting journey and I am nearing my goal of 6 ARC bolt load development for PRS style shooting.
Build Goal: 0.5 MOA or better at 100 yards with 103-108gr bullet going 2830-2850 fps using temp insensitive powder.
Some valuable lessons I've learned along the way:
1. Some rifle actions do not play well with small rifle primers. Mass produced actions tend to have larger tolerances. Between different primer hardness/thickness, firing pin hole diameter, and what the shooter is trying to achieve with speed/pressure, some mass produced actions may work fine with SRP, some may blow primers without other pressure signs.
2. A well designed, squared up action will provide consistency and ease of working up a load by showing gradual signs of pressure increase. Think of it as a rheostat where the signs are early, consistent and gradual rather than an on-off switch.
3. My Go gauge vs No-Go gauge had a difference of 0.004". This may be standard in gas guns but I think that the extra tolerance in the headspace was contributing to more primer metal flow and pierced primers. When I set my headspace on the new action, I used the Go gauge and added 2 layers of Scotch tape with the edges trimmed off with a razor blade. This method added 0.0025" to the overall length. What I see now is much less primer metal flow and the brass all are within 0.001" headspace from the mildest load to the 2870+ fps loads. The primer pockets are tight even with Hornady brass after 4 firings. The limited amount of headspace growth should theoretically slow down the progression of the case elongation and insipient case head separation.
4. Download and use Gordon's Reloading Tool for initial ladder development. The key here is finding the case volume of a fired and sized cartridge YOU are using. Don't go by what's listed on the website or what you find on the internet as the case and your chamber will all be different. In Gordon's Reloading Took, once the variables are entered correctly, my true speed was within 10 fps of predicted. This can also be further adjusted (similar to truing your BC in a Kestrel). I've noticed that older powders seemed to be a bit hotter than the new ones. Some speculate that older powders may have lost some of the moisture making it more energy dense per weight or it could be manufacturing tolerances. Whatever the case, the energy factor can be adjusted along with the ambient temperature in the tool to get a very close estimate of pressures and expected speed. Check out Little Crow Gunwork's video on how to use the tool in my previous post.
5. The 6 ARC is an extremely efficient cartridge. The barrel was just getting warm after a 10 shot string. I usually stopped after shooting 2 or 3 five-shot groups. The barrel stopped speeding up after approximately 280 rounds. YMMV as there are too many factors on barrel break-in, but mine is a 26" Criterion button cut stainless barrel, MTU contour, 1:7.5 twist using a Silencer Co ASR brake/suppressor mount. Great chambering, service, and price from Northland.
==============================================================================================
During this load development session:
Fired 58 shots, max string of fire was 10 shots practicing off props.
First chrono info is a mild load with XBR with excellent accuracy and low SD/ES but slow.
The second chrono info was to test max velocity/pressures with CFE 223, tight clusters with 1 outlier but the speed and SD/ES were very good.
The primers for the CFE 223 @ 2877 fps were slightly cratered and mildly flattened, but no ejector swipes, easy bolt lift.
The best 5 shot group today was the last group @ 2753 fps, SD 3, ES 8 and 0.326" center to center group in target #1.
Hopefully the next range session will have my 6 ARC load all sorted out at 2800-2835 fps shooting 0.4" or less.
YMMV, happy shooting
This has been an interesting journey and I am nearing my goal of 6 ARC bolt load development for PRS style shooting.
Build Goal: 0.5 MOA or better at 100 yards with 103-108gr bullet going 2830-2850 fps using temp insensitive powder.
Some valuable lessons I've learned along the way:
1. Some rifle actions do not play well with small rifle primers. Mass produced actions tend to have larger tolerances. Between different primer hardness/thickness, firing pin hole diameter, and what the shooter is trying to achieve with speed/pressure, some mass produced actions may work fine with SRP, some may blow primers without other pressure signs.
2. A well designed, squared up action will provide consistency and ease of working up a load by showing gradual signs of pressure increase. Think of it as a rheostat where the signs are early, consistent and gradual rather than an on-off switch.
3. My Go gauge vs No-Go gauge had a difference of 0.004". This may be standard in gas guns but I think that the extra tolerance in the headspace was contributing to more primer metal flow and pierced primers. When I set my headspace on the new action, I used the Go gauge and added 2 layers of Scotch tape with the edges trimmed off with a razor blade. This method added 0.0025" to the overall length. What I see now is much less primer metal flow and the brass all are within 0.001" headspace from the mildest load to the 2870+ fps loads. The primer pockets are tight even with Hornady brass after 4 firings. The limited amount of headspace growth should theoretically slow down the progression of the case elongation and insipient case head separation.
4. Download and use Gordon's Reloading Tool for initial ladder development. The key here is finding the case volume of a fired and sized cartridge YOU are using. Don't go by what's listed on the website or what you find on the internet as the case and your chamber will all be different. In Gordon's Reloading Took, once the variables are entered correctly, my true speed was within 10 fps of predicted. This can also be further adjusted (similar to truing your BC in a Kestrel). I've noticed that older powders seemed to be a bit hotter than the new ones. Some speculate that older powders may have lost some of the moisture making it more energy dense per weight or it could be manufacturing tolerances. Whatever the case, the energy factor can be adjusted along with the ambient temperature in the tool to get a very close estimate of pressures and expected speed. Check out Little Crow Gunwork's video on how to use the tool in my previous post.
5. The 6 ARC is an extremely efficient cartridge. The barrel was just getting warm after a 10 shot string. I usually stopped after shooting 2 or 3 five-shot groups. The barrel stopped speeding up after approximately 280 rounds. YMMV as there are too many factors on barrel break-in, but mine is a 26" Criterion button cut stainless barrel, MTU contour, 1:7.5 twist using a Silencer Co ASR brake/suppressor mount. Great chambering, service, and price from Northland.
==============================================================================================
During this load development session:
Fired 58 shots, max string of fire was 10 shots practicing off props.
First chrono info is a mild load with XBR with excellent accuracy and low SD/ES but slow.
The second chrono info was to test max velocity/pressures with CFE 223, tight clusters with 1 outlier but the speed and SD/ES were very good.
The primers for the CFE 223 @ 2877 fps were slightly cratered and mildly flattened, but no ejector swipes, easy bolt lift.
The best 5 shot group today was the last group @ 2753 fps, SD 3, ES 8 and 0.326" center to center group in target #1.
Hopefully the next range session will have my 6 ARC load all sorted out at 2800-2835 fps shooting 0.4" or less.
YMMV, happy shooting
Maggie’s Motivational Pic Thread v2.0 - - New Rules - See Post #1
- By fx77
- The Bear Pit
- 299501 Replies
James Elliot “Willie” Williams was just 16 when he convinced a county clerk to change his age on his birth certificate so he could join the Navy. He thought it would be an exciting way to see the world. "I thought there was nothing better than serving my country and getting paid for it,” he said. He went on to become the most decorated enlisted man in the history of the U.S. Navy.
19 years later, Williams was assigned to River Squadron 5 in South Vietnam, where he commanded a patrol boat. His job was to patrol the waterways to prevent the enemy, the Vietcong, from using them to transport troops and supplies. On October 31, he was on a routine patrol, expecting nothing out of the ordinary. "We were on a day patrol, kind of like the 'relax and recreation' patrol — nothing too heavy," he said. But soon, everything changed.
Two enemy speed boats crossed ahead of them, and sure enough, they started firing at Williams’ boat. Williams and his crew chased down one boat and sank it, then turned to the second one. The enemy boat sped down the river and took a sharp turn into a narrow canal. Williams knew it would come out farther up the river, so he raced after it, determined to catch it. But he ended up in a Vietcong staging area, surrounded by enemy boats and troops. "I looked up and didn't see nothing but boats and people and more boats and more people," he said.
Thinking quickly, Williams turned his boat sharply left, causing a wake that rocked the nearest enemy boat and disrupted their fire. Then they sped through the middle of the enemy boats, causing confusion. The enemy fired at Williams, but hit their own boats instead. Williams zigzagged through the enemy boats and managed to escape, but they ended up in an even larger enemy staging area. “There was no way out,” he said. For over three hours, Williams and his crew fought to survive. By the end of the battle, they had sunk 65 enemy boats and killed 1,200 enemy soldiers. Williams and his men all made it out alive. For his bravery, Williams was awarded the Medal of Honor.
His crew, most of whom were in their late teens and twenties, affectionately called the 36-year-old Williams “The Old Man.” Williams always made sure to take care of his team. "You gotta stop and think about your shipmates. That's what makes you a great person and a great leader – taking care of each other," he said.
Williams’ heroics didn’t stop there. He went on to rescue a sailor trapped on a sinking ship and destroyed many more enemy boats. In his last seven months in the Navy, Williams received every sea-service award for heroism. His decorations include:
19 years later, Williams was assigned to River Squadron 5 in South Vietnam, where he commanded a patrol boat. His job was to patrol the waterways to prevent the enemy, the Vietcong, from using them to transport troops and supplies. On October 31, he was on a routine patrol, expecting nothing out of the ordinary. "We were on a day patrol, kind of like the 'relax and recreation' patrol — nothing too heavy," he said. But soon, everything changed.
Two enemy speed boats crossed ahead of them, and sure enough, they started firing at Williams’ boat. Williams and his crew chased down one boat and sank it, then turned to the second one. The enemy boat sped down the river and took a sharp turn into a narrow canal. Williams knew it would come out farther up the river, so he raced after it, determined to catch it. But he ended up in a Vietcong staging area, surrounded by enemy boats and troops. "I looked up and didn't see nothing but boats and people and more boats and more people," he said.
Thinking quickly, Williams turned his boat sharply left, causing a wake that rocked the nearest enemy boat and disrupted their fire. Then they sped through the middle of the enemy boats, causing confusion. The enemy fired at Williams, but hit their own boats instead. Williams zigzagged through the enemy boats and managed to escape, but they ended up in an even larger enemy staging area. “There was no way out,” he said. For over three hours, Williams and his crew fought to survive. By the end of the battle, they had sunk 65 enemy boats and killed 1,200 enemy soldiers. Williams and his men all made it out alive. For his bravery, Williams was awarded the Medal of Honor.
His crew, most of whom were in their late teens and twenties, affectionately called the 36-year-old Williams “The Old Man.” Williams always made sure to take care of his team. "You gotta stop and think about your shipmates. That's what makes you a great person and a great leader – taking care of each other," he said.
Williams’ heroics didn’t stop there. He went on to rescue a sailor trapped on a sinking ship and destroyed many more enemy boats. In his last seven months in the Navy, Williams received every sea-service award for heroism. His decorations include:
- Medal of Honor
- Navy Cross
- Silver Star (with one gold award star)
- Legion of Merit (with “V” device)
- Navy and Marine Corps Medal (with gold award star)
- Bronze Star (with “V” device and two gold award stars)
- Purple Heart (with two gold award stars)
- Navy and Marine Corps Commendation Medal (with “V” device and gold award star)
- Navy and Marine Corps Presidential Unit Citation (with bronze service star)
- Navy Good Conduct Medal (with four bronze service stars)
- Navy Expeditionary Medal
- National Defense Service Medal (with bronze service star)
- Korean Service Medal (with two bronze stars)
- Armed Forces Expeditionary Medal
- Vietnam Service Medal (with two bronze service stars)
- Korean Presidential Unit Citation
- Vietnam Cross of Gallantry (with gold star and palm)
- United Nations Korean Medal
- Republic of Vietnam Campaign Medal
- Korean War Service Medal
