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6mm-22-250 Ackley Improved Project Rifle

I have had Brett Evans of N.W. Armswerkes build a custom rifle around a Remington 700 CrMo action. Here are a few of the goodies that are part of this project rifle:

•    Chambered for 6mm-2-250 AI

•    Action trued and blueprinted, threads re-cut

•    Bolt faced, trued, and rear bumps welded on

•    Speedlock Systems firing pin installed

•    Recoil lug surface ground

•    Kreiger SS 27” barrel, 1:8 twist, #17 profile

•    Removable muzzle break (made by N.W. Armswerkes) with optional cap

•    Action bedded into a HS Precision thumbhole stock

•    Jewell trigger, set at 4 oz.

•    Leupold 8.5-25X50 LRT scope or Weaver T36 target scope, both with QRW rings for switch scope capability

•    N.W. Armswerkes custom 20 MOA scope mount rail

I settled in on the 6mm-22-250 AI over the .243 Win. after doing some studies with QuickLoad. I found that the 6-250AI delivers nearly identical ballistics with the heavier bullets that I plan to use as the .243 Win., but with less powder. This is very attractive as I have become convinced that achieving high ballistic efficiency is critical to both barrel life as well as accuracy. My 220 Swift is very accurate, but it is very picky to load for, and not easy to find an accurate load. Conversely, the .223AI is also very accurate, and is very easy to load to its accuracy potential. All the available data indicated that the 6-250 is an excellent long range and varmint cartridge, and delivers very good accuracy. I chose the AI variant only to deliver that little bit more oomph for the 107 and 105 grain VLDs with the slower powders.

Here is a comparison between some loads for the .243 Win and the 6-250AI. Notice that the ballistics are nearly identical, with the 6-250 using 18% less powder than the .243.

As this rifle becomes a reality, I will post the range test results here.

UPDATE:   3/26/04

I received the rifle last night from Brett. Here are some pictures of the completed rifle:

The bore and throat looked perfect through the bore scope:

I will be breaking it in tomorrow and plan on using 36.8 gr VVN550 in a unfired 6-250 case with a BR-2 primer, and under a 107 grain Sierra MatchKing bullet as the fireforming load. I will be working up to this during the break in, but expect this to be very close to the OBT/OCW load (at least with fireformed cases).

UPDATE:   3/27/04

The barrel was broken in today, and the accuracy was excellent. Here is a group from the fireforming/break-in series with a light load of VVN550:

Keep in mind that these were unfired Norma 22-250 cases necked up to 6mm. There was no real attempt to tune the load other than find the sweet velocity. The OAL was set such that the bullet was hard into the lands. The COL will be shortened a bit on the next few runs to see if that will tighten up the groups. Almost every charge weight tried yielded less than 0.5” groups.

UPDATE:   4/4/04

Tuned the fireforming load a bit today, and got this performance at 200 yards:

 The five shot group size was 0.287”, at a mean velocity of 3049 FPS, with a standard deviation and extreme spread of 7 FPS and 18 FPS respectively. The barrel measures almost exactly 27.5” from bolt face to crown (does not include muzzle brake), and the OBT calculations predict the best groups at 1.257 mS barrel time. Quickload gave an estimate of 1.258 mS for a muzzle velocity of 3047 FPS, at 37.5 grains VVN550. This nearly a perfect match to the barrel time and muzzle velocity as predicted by Quickload and the OBT calculation process. The best COL was found to be when the bullet was seated hard into the lands.

Tests with fireformed cases will be done next.

Kudos to Brett at N.W. Armswerkes!

UPDATE:   6/21/04 – LWR Prairie Dog Hunt

Used the rifle during a recent Prairie Dog hunt in South Dakota. It performed beyond my expectations. I was able to make two hits at 1150 yards, even in fairly windy conditions. The 107 grain Sierra MatchKings at about 3050 FPS really bucked the wind. Here are some pictures from the trip. This is the second time I have stayed at the LWR Ranch for a guided PD hunt. You cannot find better hosts than Jon and Sherry!