Fixing vertical stringing

[azshooter]

I picked up a Ruger M77 MKI that in 7 shots had a vertical string about 3.5 inches top to bottom but side to side measures just over .5 inch.  Any suggestions on what to look at first to fix this stringing problem?  It is currently topped with a Redfield 3 X 9 scope and is in overall good shape.

[nipprdog]

how quickly did you shoot those 7 shots?

what caliber?

possibly due only to barrel warming.

[azshooter]

I shot two waited about 5 min, shot two more, waited 5 shot 2 waited then then 1 last shot.  25-06 is the caliber.  The tiny horizontal spread has me thinking it is either bedding or possibly the scope.  I don't have another quality scope that I can just slap on  so looking for advice.

[Catfish]

Vartical stringing is usually due to velosity variation most often caused by bad primers. If it is due to bad ignation 1 shot might go high and the next low or what ever. If it is a heating problem they will eather start at the top and go down or visversa. Vert. stringing is usually not a scope problem, but check your mounts just to make sure they are tight.

[Big Paulie]

My first fix is always to take the action out of the stock, and look at the barrel channel.  My wife bought a new Ruger bolt two years ago, and when I did this, the channel was very very roughly finished, with actual chunks of wood chips in it!

    I simply cleaned all of the woodchips out, and then took medium sandpaper and sanded the channel until the barrel was totally smooth and free floated (barrel would not touch the channel in the stock at any point).  You can test this by reassembling the rifle, and taking and index card and shoving it between the barrel and the stock.  It should slide very freely all of the way from the tip of the forestock, up until about one inch in front of the action.

     After this, I test fired, and there were no verticle string problems.  So, I then used fine, and then extra fine, sandpaper, to sand the channel very smooth.  I then took regular liquid polyurythane (the kind for finishing wood), dipped my finger in it, and gently rubbed two coats on the sanded channel.  This sealed it completely.

    Never had any other problems with the rifle stringing.

    Also, two other problems that very often cause verticle stringing.

    1.  Make sure that the front guard screwed, holding your action in the stock, is not tightened too tight.  If it is, then verticle stringing will occur.  Simply screw it down until it meets firmly, and then give it an extra half turn.

     2.   If is very very common when sighting in a new rifle at the bench, for a person to shoot 2 or 3 shots, and then very slightly adjust or change how he is sitting behind the rifle (for comfort.)  Perhaps you shrug a little lower behind it to reduce recoil, or to get a better view through the scope.  Perhaps you put an extra pad under the forestock to lift  the rifle up slightly higher, so that it is more lined up with your shoulders etc.    
       Believe it our not, these slight adjustments in the way you sit behind your rifle can cause verticle stringing of 2 inches or more!   This is especially true if you wear glasses.   I had this happen to me with a new rifle, and I would never have figured it out unless I had gotten this tip on the Boards!    Set the rifle up so that it is totally absolutely comfortable.  Sit behind the rifle exactly the same each time.    Wait 5 minutes between shots.

   Check out these simple fixes before you do anything radical.

Hope this helps.

Big Paulie


  Hope this helps.

[KYsquirrelsniper]

Big Paulie gave some very good advice.

About the only things I can add are...

When I start getting vertical strings at 100-200yds, it's usually due to the stock making contact with the barrel. This will be fairly apparent though, as the rounds will seem to "walk" higher the hotter the barrel gets. Cold shots will print low and hot shots will print high.

If the shots are going high, then low with no apparent relationship to the barrel temp, then I'd investigate the torque on the action screws and then the bedding.

The scope may have parallax, and if your eye isn't in the same spot each time, you'll get a shift in POI. However, if it were a prallax problem, I would expect to have seen more horizontal shift considering there's 3.5" of vertical.
 
Also, try to be consistent with the placement on the rest and the amount of tension you're holding the rifle with, as it will make a difference.

[Coyote Hunter]

Chances are your barrel touches the stock at the tip of the forearm.  While this helps some rifles shoot better, as the wood heats up it pushed the barrel causing stringing.

I don't even take a new Ruger to the range any more without first floating the barrel.  The proces is simple, requireds a minimum of tools, and takes about 15 minutes.

The tools required include:
Sandpaper
Round cylinder (I use Magic Markers)
Screwdriver
Polyurethane
Rag
Dollar bill

The procedure:

[list=1]

•  Check to see if the barrel touches the forestock by trying to slip the $ bill between them.    If its touching, continue.
•  Remove the stock from the action and barrel.
•  Loop the sandpaper around the Magic Marker and sand out the barrel channel.
•  Replace the stock and try to slip the $ bill between the stock and the barrel.  If it doesn't slide easily all the way to the receiver remove the stock and continue sanding until it does.
•  When satisfied with the barrel channel, dip a rag in polyurethane and coat the freshly sanded wood.
•  Allow the polyurethane to dry, reassemble and recheck with a dollar bill.
[/list:o]

[azshooter]

Thanks all for the advice. I will fill you all in on where I am now.  It has been a busy week - I tried the free floating which took care of the vertical stringing but opened up the groups larger than I liked.  My next step was to pull out the dremmel and fiberglass resin.  I bedded the action from the recoil lug to about 1 inch from the tip of the stock.  I took 5 different loads out today and the best ones are now shooting about 1/2 inch center to center for 3 shot groups if I wait between shots.  Strange thing is the boat tails consistantly shoot almost exactly 2 inches to the left of the flat base bullets regardless of the charge.  Does anyone know why boat tails do this?

[Big Paulie]

Dear Friend,

Just some thoughts.

1.  Once you fix the verticle string problem (which you have) the absolute fastest way to tighten your groups on the Ruger is to yank out that horrible factory trigger, and replace it with a Timney or other custom trigger.  You will be amazed at how much this helps.

2.  My only thought on the boat-tails:

      a.  The effect of a cross wind on these bullets when you were shooting them?

      b.   Are these loads hotter, making your barrel heat up quicker?   If so, check now to see if the barrel is touching anywhere on the side of the  barrel channel?     (P.S.-Are these rounds so hot that they are making you flinch when you shoot them?  If so, you will consistently get a group right or left of your normal group.)

Big Paulie

[azshooter]

Dear Friend,

Just some thoughts.

1.  Once you fix the verticle string problem (which you have) the absolute fastest way to tighten your groups on the Ruger is to yank out that horrible factory trigger, and replace it with a Timney or other custom trigger.  You will be amazed at how much this helps.

2.  My only thought on the boat-tails:

      a.  The effect of a cross wind on these bullets when you were shooting them?

      b.   Are these loads hotter, making your barrel heat up quicker?   If so, check now to see if the barrel is touching anywhere on the side of the  barrel channel?     (P.S.-Are these rounds so hot that they are making you flinch when you shoot them?  If so, you will consistently get a group right or left of your normal group.)

Big Paulie

Actually it is a M77 MKI which has a very nice adjustable trigger from the factory.  I wish Ruger still made them.  There was no wind and I tried different loads with the boattails with the same result.  I don't think I was flinching.  I shoot a 300 Mag pretty regular and this had a lot less recoil.

[safetysheriff]

Are there any sling swivels or studs catching on anything when the rifle recoils?    Are you shooting on a leather or suede rest, which has a lot of friction that interferes with free movement of a recoiling rifle?    If so, cover it with something slipperier like denim and the rifle will shoot more consistently.    

Good luck,

SS'