I finally got my rifle finished, and did a small amount of shooting yesterday.
About 5-6 years ago, I bought a CZ 527 American in 6.5 Grendel. It failed to impress me accuracy wise, despite bedding it, and all else appearing normal. It sat unloved for most of the time since I purchased it, when the .22 ARC caught my eye. The 6 ARC didn't excite me, I've got a couple of 6BR's. I needed something that fit the .445 bolt face and the .22 ARC was it!
I had International Barrels make me up a .985" straight barrel, 1-7 twist with an intent of a 26" finish length, I like to get the most out of the powder. I wrote a program to thread and counter bore the breech face, and had master chamber artist, Larry B (F class guys will know him) ream the chamber and set the headspace. I got the barrel back on Friday afternoon, saturday morning I threaded the muzzle 5/8"-24 and did my standard lapped crown. I torqued it on, threw it in the 4th axis on the mill and engraved it. I had an extra Bell and Carlson stock for it, but I needed to open up the barrel channel for the fat pipe. DONE!!! I raced home, but ended up with a visitor for a couple of hours, with the sun getting low, low, low.
I had a box of factory Hornady 88 gr, and used one round at 50 for zeroing, then fired 5 shots at 100. The velocity on the box was 2820, I got 2860, the group was 3/4 moa or so.
The night before, I had experimented with necking down Hornady 6.5 Grendel brass, I used a 6BR body die, raised a bit to not crush the shoulder, followed by a trip through a Hornady .22 ARC full length. The neck above the shoulder looked like it wouldn't fit the chamber, but they did without any undue pressure on the bolt. Playing around with QuickLoad, I had decided on VV N550 with the 80 gr Sierra. I use CCI 450's in my other Grendels, so went with that in this case. Since I was short of time, and lacking a case gauge to measure the throat, I went with magazine length as my start point. I picked a starting charge of 27 gr, and went up a singe shot of .3 grain increments. I walk from my loading room to a shack I have at 100 yards, and started firing strings.
I used a Garmin chronograph mounted outside of the shack for velocities and ended up with the following. I missed one when I forgot to turn the chrono on.
The target is as follows. Centre diamond is the factory ammo, low and right of that was the solo shot at 50. Top right diamond was 27.0, 27.3, 27.6 and 27.9. I wasn't logging individual shots for position. Bottom right 28.2-29.4. Bottom left 29.7-30.5. Top left was a 5 shot group of 29.8gr.
By now, the sun was very low, and mindful of my neighbors, I don't like shooting too late. Based on the strings fired, and got decent speed out of a barrel that has to speed up yet. I thought that 3100 fps was a nice round number, and picked 29.8gr as the one to try. I sized 5 of the previously fireformed cases, dropped powder, and went back out. This gave me 3106 fps with an SD of 11.6. and the following five shot group at 100.
Some numbers
Manson 'Go' gauge with the Hornady 'B' .350 comparator body 1.212"
Hornady factory ammo measures 1.209"-1.210"
Hornady factory 88 gr CBTO 1.687"
Hornady factory 88 gr OAL 2.255"
Hornady .22 ARC
unprimed case weight 110.5-111.5gr
fired water capacity 35.2gr
AMP AZTEK setting 126
Hornady 6.5 Grendel necked down to .22 ARC
unprimed case weight 111.3-113.74gr
water capacity 34.98-35.34gr
AMP AZTEK setting 128
About 5-6 years ago, I bought a CZ 527 American in 6.5 Grendel. It failed to impress me accuracy wise, despite bedding it, and all else appearing normal. It sat unloved for most of the time since I purchased it, when the .22 ARC caught my eye. The 6 ARC didn't excite me, I've got a couple of 6BR's. I needed something that fit the .445 bolt face and the .22 ARC was it!
I had International Barrels make me up a .985" straight barrel, 1-7 twist with an intent of a 26" finish length, I like to get the most out of the powder. I wrote a program to thread and counter bore the breech face, and had master chamber artist, Larry B (F class guys will know him) ream the chamber and set the headspace. I got the barrel back on Friday afternoon, saturday morning I threaded the muzzle 5/8"-24 and did my standard lapped crown. I torqued it on, threw it in the 4th axis on the mill and engraved it. I had an extra Bell and Carlson stock for it, but I needed to open up the barrel channel for the fat pipe. DONE!!! I raced home, but ended up with a visitor for a couple of hours, with the sun getting low, low, low.
I had a box of factory Hornady 88 gr, and used one round at 50 for zeroing, then fired 5 shots at 100. The velocity on the box was 2820, I got 2860, the group was 3/4 moa or so.
The night before, I had experimented with necking down Hornady 6.5 Grendel brass, I used a 6BR body die, raised a bit to not crush the shoulder, followed by a trip through a Hornady .22 ARC full length. The neck above the shoulder looked like it wouldn't fit the chamber, but they did without any undue pressure on the bolt. Playing around with QuickLoad, I had decided on VV N550 with the 80 gr Sierra. I use CCI 450's in my other Grendels, so went with that in this case. Since I was short of time, and lacking a case gauge to measure the throat, I went with magazine length as my start point. I picked a starting charge of 27 gr, and went up a singe shot of .3 grain increments. I walk from my loading room to a shack I have at 100 yards, and started firing strings.
I used a Garmin chronograph mounted outside of the shack for velocities and ended up with the following. I missed one when I forgot to turn the chrono on.
The target is as follows. Centre diamond is the factory ammo, low and right of that was the solo shot at 50. Top right diamond was 27.0, 27.3, 27.6 and 27.9. I wasn't logging individual shots for position. Bottom right 28.2-29.4. Bottom left 29.7-30.5. Top left was a 5 shot group of 29.8gr.
By now, the sun was very low, and mindful of my neighbors, I don't like shooting too late. Based on the strings fired, and got decent speed out of a barrel that has to speed up yet. I thought that 3100 fps was a nice round number, and picked 29.8gr as the one to try. I sized 5 of the previously fireformed cases, dropped powder, and went back out. This gave me 3106 fps with an SD of 11.6. and the following five shot group at 100.
Some numbers
Manson 'Go' gauge with the Hornady 'B' .350 comparator body 1.212"
Hornady factory ammo measures 1.209"-1.210"
Hornady factory 88 gr CBTO 1.687"
Hornady factory 88 gr OAL 2.255"
Hornady .22 ARC
unprimed case weight 110.5-111.5gr
fired water capacity 35.2gr
AMP AZTEK setting 126
Hornady 6.5 Grendel necked down to .22 ARC
unprimed case weight 111.3-113.74gr
water capacity 34.98-35.34gr
AMP AZTEK setting 128
