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The Basics, Starting Out
Accurizing a Ruger?
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<blockquote data-quote="Fiftydriver" data-source="post: 55938" data-attributes="member: 10"><p>Pat S.</p><p></p><p>Have alot of Ruger M77MkII's come into the shop these days having similar problems.</p><p></p><p>First thing I recommend is a quality bedding job to my customers. Doing this on the Ruger generally helps alot with consistant grouping, certainly better then what you are experiencing.</p><p></p><p>With groups like that I would say you have a mechanical problem somewhere in the rifle.</p><p></p><p>Since you state it shoots tight groups at low end pressures and goes to hell with top level loads, I would be very suspicious of the bolt locking lugs not baring evenly.</p><p></p><p>I have seen this alot with Rugers, especially those of the last 5 years or so.</p><p></p><p>On rifle in particular, an M77VT in 220 Swift was an amazingly accurate rifle when I started load developement for it using virgin brass and lower pressure loads.</p><p></p><p>I was getting groups in the 2's and 3's but only getting 3600 fps with the 50 gr Blitzking from Sierra. Thats pretty weak for a 22-250 let alone a Swift. The customer wanted 3800-3900 fps at least with this bullet and I told him 4000 fps would be easy to get in the Swift but 3900 fps would be easier on the barrel.</p><p></p><p>Well, once the velocity reached anything over 3600 fps, the groups jumped up into the 1.5 moa range and at 3950 fps it was shooting patterns rather then groups.</p><p></p><p>I retested with the fireformed cases leaving them a tight fit in the chamber hoping to improve bullet alignment with the bore.</p><p></p><p>No group with these brass broke the 2 moa mark. </p><p></p><p>Then I took a look at the bolt locking lugs and noticed that only one was baring. The other was totally floating and when I trued the rifle for the customer, I found out it had 0.003" of air between it and the locking recess surface.</p><p></p><p>What happens is that at low pressure, the one lug has enough rigidity to hold the case square to the bore. With the higher pressure loads, the bolt thrust flexes the bolt until the floating lug stops its rearward motion, resulting in very poor alignment with the bore.</p><p></p><p>Once the lugs were trued and the rifle rechambered to the 22-6mm AI since the customer decided he wanted more speed. The rifle is not grouping in the 3's with the 55 gr Blitzking clipping along at 4125 fps with 55.0 gr Rl-22. </p><p></p><p>I have seen this on several other Rugers so pull your bolt out and take a look to see if you have even baring on both lugs. If you do not they need to be recut and lapped.</p><p></p><p>Good Shooting!!!</p><p></p><p>50</p></blockquote><p></p>
[QUOTE="Fiftydriver, post: 55938, member: 10"] Pat S. Have alot of Ruger M77MkII's come into the shop these days having similar problems. First thing I recommend is a quality bedding job to my customers. Doing this on the Ruger generally helps alot with consistant grouping, certainly better then what you are experiencing. With groups like that I would say you have a mechanical problem somewhere in the rifle. Since you state it shoots tight groups at low end pressures and goes to hell with top level loads, I would be very suspicious of the bolt locking lugs not baring evenly. I have seen this alot with Rugers, especially those of the last 5 years or so. On rifle in particular, an M77VT in 220 Swift was an amazingly accurate rifle when I started load developement for it using virgin brass and lower pressure loads. I was getting groups in the 2's and 3's but only getting 3600 fps with the 50 gr Blitzking from Sierra. Thats pretty weak for a 22-250 let alone a Swift. The customer wanted 3800-3900 fps at least with this bullet and I told him 4000 fps would be easy to get in the Swift but 3900 fps would be easier on the barrel. Well, once the velocity reached anything over 3600 fps, the groups jumped up into the 1.5 moa range and at 3950 fps it was shooting patterns rather then groups. I retested with the fireformed cases leaving them a tight fit in the chamber hoping to improve bullet alignment with the bore. No group with these brass broke the 2 moa mark. Then I took a look at the bolt locking lugs and noticed that only one was baring. The other was totally floating and when I trued the rifle for the customer, I found out it had 0.003" of air between it and the locking recess surface. What happens is that at low pressure, the one lug has enough rigidity to hold the case square to the bore. With the higher pressure loads, the bolt thrust flexes the bolt until the floating lug stops its rearward motion, resulting in very poor alignment with the bore. Once the lugs were trued and the rifle rechambered to the 22-6mm AI since the customer decided he wanted more speed. The rifle is not grouping in the 3's with the 55 gr Blitzking clipping along at 4125 fps with 55.0 gr Rl-22. I have seen this on several other Rugers so pull your bolt out and take a look to see if you have even baring on both lugs. If you do not they need to be recut and lapped. Good Shooting!!! 50 [/QUOTE]
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