Out of 30 rounds of barrel break in and about !280! rounds of load development I could not eliminate the vertical strings my rifle was producing on target. During load development I tried every varible:
Powder types
Powder charges in little jumps
Several different makes &models of Bullets
A WIDE variety of seating depths
Several different match primers
A variety of neck tension
I also tried different scopes, checked and rechecked my bases & rings As well as pulled the rifle out of the stock to check the bedding several times and retourque the action screws.
Still vertical string after string after string. The TresMon was at his handloading end. I had no answers.
This was the consistent result of ANY combination of reloading components and assembly:
Hmm thinks me- "That AMU profile 30" barrel wearing a BIG brake hanging off the nose of a Sav 110 action is asking alot out of an action with a lot of cut outs....
Maybe I need to stabilize the barrel."
So I decide to try a barrel tension screw. I called a friend with a machine shop to see if I could get in and make/install the parts. No answer. 5 times.
So I then new this was going to be a really low precision op in my garage with SIMPLE hand tools. OFF to Lowe's to see what I could see.
I came home with an idea and $3.31 in screw and nuts.
Here's my design. (Sorry but I just have to say) I think this was a pretty ingenious design for such simple parts. Here's what I came up with:
Sorry: Acorn nut & jam nut not drawn jammed together holding pointer and Lock nut absent from drawing.
The winG nut makes a crude V-block to cradle & press on the barrel. I radiused the inside corners to make life good for the barrel. I used an oversize 10-31 wing nut so my stud could freely turn in the wing nut bore. The bore of the wing being oversized allowed the wings to be <span style="text-decoration: underline">self centering</span> on the barrel to compensate for low precision drilling, tapping etc.
I loc-tited a nut on the 8-32 stud. This got greased. Another couple of washers were added with grease on all surfaces to act as bearings so that when the stud was turned to put more pressure on the barrel- the wings would keep their centered & squared position on the barrel.
I drilled and tapped an 8-32 hole up through the forearm near the end.
I threaded the stud down through the forearm and put the bearings and wings in position.
The underside got a loose nut to lock the whole assembly in position. Beneath these were a standard nut and an Acorn nut. Sandwiched between these two final nuts was a feeler gauge I cut to make a pointer, so I could see how far I was advancing the stud & the associated pressure on the barrel.
I hung up four 3/4 moa targets @ 200yds. I already had a lot of targets shot with no tension on the barrel for a baseline with the load so I went to tuning. First I turned in the stud until the wings just barely snugged on the barrel & locked the nut. I fired a 5 shot group. No dice.
I turned the stud on in to a quarter turn in and locked it- and fired another 5. Hmm... getting interesting.
I turned the stud in to the half-turn position, locked it and fired 5. Not much change,
I advanced the stud to 3/4's in and fired 5. HOLY COW!
I advanced the stud to 1 full turn in and gave it a try and it was obviously too much.
All test were done with a load that was in the velocity window I wanted (3060-3160f/s with this one being 3163 { 7mm-300WM, 180 Berger Hybrid}) and with a 10 shot SD average of 5.4 f/s.)
From the target above to this target below NOTHING was changed but the barrel tension:
Not bad for $3.31?????
<span style="font-weight: bold"><span style="font-style: italic"><span style="text-decoration: underline">NOW</span></span></span> I can work up a good load.
Powder types
Powder charges in little jumps
Several different makes &models of Bullets
A WIDE variety of seating depths
Several different match primers
A variety of neck tension
I also tried different scopes, checked and rechecked my bases & rings As well as pulled the rifle out of the stock to check the bedding several times and retourque the action screws.
Still vertical string after string after string. The TresMon was at his handloading end. I had no answers.
This was the consistent result of ANY combination of reloading components and assembly:
Hmm thinks me- "That AMU profile 30" barrel wearing a BIG brake hanging off the nose of a Sav 110 action is asking alot out of an action with a lot of cut outs....
Maybe I need to stabilize the barrel."
So I decide to try a barrel tension screw. I called a friend with a machine shop to see if I could get in and make/install the parts. No answer. 5 times.
So I then new this was going to be a really low precision op in my garage with SIMPLE hand tools. OFF to Lowe's to see what I could see.
I came home with an idea and $3.31 in screw and nuts.
Here's my design. (Sorry but I just have to say) I think this was a pretty ingenious design for such simple parts. Here's what I came up with:
Sorry: Acorn nut & jam nut not drawn jammed together holding pointer and Lock nut absent from drawing.
The winG nut makes a crude V-block to cradle & press on the barrel. I radiused the inside corners to make life good for the barrel. I used an oversize 10-31 wing nut so my stud could freely turn in the wing nut bore. The bore of the wing being oversized allowed the wings to be <span style="text-decoration: underline">self centering</span> on the barrel to compensate for low precision drilling, tapping etc.
I loc-tited a nut on the 8-32 stud. This got greased. Another couple of washers were added with grease on all surfaces to act as bearings so that when the stud was turned to put more pressure on the barrel- the wings would keep their centered & squared position on the barrel.
I drilled and tapped an 8-32 hole up through the forearm near the end.
I threaded the stud down through the forearm and put the bearings and wings in position.
The underside got a loose nut to lock the whole assembly in position. Beneath these were a standard nut and an Acorn nut. Sandwiched between these two final nuts was a feeler gauge I cut to make a pointer, so I could see how far I was advancing the stud & the associated pressure on the barrel.
I hung up four 3/4 moa targets @ 200yds. I already had a lot of targets shot with no tension on the barrel for a baseline with the load so I went to tuning. First I turned in the stud until the wings just barely snugged on the barrel & locked the nut. I fired a 5 shot group. No dice.
I turned the stud on in to a quarter turn in and locked it- and fired another 5. Hmm... getting interesting.
I turned the stud in to the half-turn position, locked it and fired 5. Not much change,
I advanced the stud to 3/4's in and fired 5. HOLY COW!
I advanced the stud to 1 full turn in and gave it a try and it was obviously too much.
All test were done with a load that was in the velocity window I wanted (3060-3160f/s with this one being 3163 { 7mm-300WM, 180 Berger Hybrid}) and with a 10 shot SD average of 5.4 f/s.)
From the target above to this target below NOTHING was changed but the barrel tension:
Not bad for $3.31?????
<span style="font-weight: bold"><span style="font-style: italic"><span style="text-decoration: underline">NOW</span></span></span> I can work up a good load.
