FIRE LAPPING EXPERIMENT

We ran the following fire lapping experiment, trying to see if there is any improvement from this procedure. We ran the test on three different rifles of different calibers.

Following are the results of the tests.

  1. 223 REMINGTON
  2. RIFLE: Sako S491 # 893377, 22-inch factory barrel

    SCOPE: Burris Signature 8-32X in Leupold mounts

    BRASS: Federal Gold Medal, match prepped.

    PRIMERS: Federal 205M

    This is a brand new rifle out of the box. I removed the factory sights so that I can install a large scope on it. I cleaned the barrel and then fired 7 shots to get the scope sighted in, then the following loads were fired through it. No cleaning was done in between groups at all. The velocity difference before and after lapping was very small smaller than the difference between two shots in the same group, so I included only one velocity reading. Five 5-shot groups were fired with each powder charge.

    The barrel was then completely cleaned and 15 shots were fired using 800-grit, then the barrel was cleaned again and 15 shots were fired using 1200-grit. The load we used was 6 grains of GREEN DOT. This load gave us a velocity of 1576. I ran a patch with Hoppes # 9 and then a clean one after every five shots fired.

    Then the same loads as we used before fire lapping were fired for both groups and velocity.

    POWDER

    BULLET

    VELOCITY

    GROUPS BEFORE LAPPING

    AVERAGE

    GROUPS AFTER LAPPING

    AVERAGE

    29.4 BL-C2

    NOSLER 50 B. TIP

    3281

    0.839

     

    0.850

     
         

    0.411

     

    0.678

     
         

    0.502

     

    0.798

     
         

    0.675

     

    0.881

     
         

    0.666

    0.618

    0.690

    0.779

    24.2 VVN 133

    BERGER 52

    3171

    0.534

     

     

    0.677

     
         

    0.808

     

    1.072

     
         

    0.717

     

    0.810

     
         

    1.101

     

    0.600

     
         

    1.318

    0.895

    1.302

    0.892

                 

    27.7 H 335

    NOSLER 40 B. TIP

    3454

    1.182

     

    0.764

     
         

    0.567

     

    0.677

     
         

    1.256

     

    0.496

     
         

    0.903

     

    0.500

     
         

    1.017

    0.985

    0.314

    0.550

                 

    26.0 H 4895

    BERGER 52

    3220

    1.056

     

    0.448

     
         

    0.844

     

    0.704

     
         

    0.723

     

    0.489

     
         

    0.721

     

    1.371

     
         

    0.477

    0.764

    0.596

    0.721

                 

    22.5 H 4198

    NOSLER 55 B. TIP

    3257

    0.893

     

    0.921

     
         

    1.691

     

    0.942

     
         

    1.614

     

    0.981

     
         

    0.415

     

    1.214

     
         

    1.207

    1.164

    0.659

    0.948

                 
                 

     

  3. 243 WINCHESTER
  4. RIFLE: RUGER M 77 # 74-75302, 22 INCH FATORY BARREL

    SCOPE: LEUPOLD 6.5 20X IN RUGER MOUNTS

    BRASS: WINCHESTER, MATCH PREPPED

    PRIMERS: RWS LARGE RIFLE

    This rifle was owned by at least three previous owners. I have no idea how many rounds were fired through it. Externally it looked in very good condition, and I checked the bore with a bore scope and that looked in very good condition too. There was no sign of any throat erosion at all, so I would presume that this rifle has not been fired very much.

    No attempt was made to accurize the rifle at all, I just cleaned the barrel and put the scope on it.

    We followed a different procedure with this rifle. I used the Nosler 95-grain Ballistic Tip bullet with 12 different loads before fire lapping. Then I picked the best load and fired five 5-shot groups with it. I used this same load after fire lapping.

    POWDER

    VELOCITY

    GROUP

    BULLET

    40.0 H 4350

    2503

    1.406

    NOSLER 95 BALLISTIC TIP

    41.0

    2566

    1.526

     

    42.0

    2670

    1.492

     

    43.0

    2774

    1.094

     

    44.0

    2854

    1.658

     

    41.0 W 760

    2772

    2.926

     

    42.0

    2839

    1.988

     

    43.0

    2901

    1.311

     

    44.0

    2923

    1.589

     

    42.0 RELOADER 19

    2573

    1.912

     

    43.0

    2634

    1.420

     

    44.0

    2695

    1.085

     
           

    Five, 5-shot groups with 44 grains of Reloader 19 were fired. I then cleaned the barrel and then fired 10 shots with 800-grit and 10 shots with 1200-grit. The barrel was cleaned and then five 5-shot groups of the same load were fired. These are the results.

    GROUPS BEFORE LAPPING

    AVERAGE

    GROUPS AFTER LAPPING

    AVERAGE

    1.085

     

    1.025

     

    1.782

     

    1.240

     

    1.294

     

    0.662

     

    1.674

     

    1.482

     

    3.032

    1.773

    1.393

    1.160

           

     

  5. 308 WINCHESTER

RIFLE: A copy of the Mauser 98 of unknown manufacturer made in Germany was all we could find about it! 24 inch barrel.

SCOPE: Burris Signature 6-24X in EAW mounts

BULLET: Sierra 168 Match King

BRASS: RWS, match prepped

PRIMERS: RWS large rifle

POWDER: 43.0 VVN 140

This rifle was also brand new. I glass bedded the action and free floated the barrel. I picked a load that has given us exceptional accuracy in several 308 Winchester rifles.

Ten groups of 5-shot each were fired, then the barrel was cleaned and fire lapped using 20 rounds each of 800-grit and 1200-grit. The it was cleaned again, and ten 5-shot groups were fired again. Here are the results.

GROUPS BEFORE LAPPING

AVERAGE

GROUPS AFTER LAPPING

AVERAGE

2.625

 

0.858

 

1.947

 

1.179

 

2.159

 

1.399

 

1.886

 

2.642

 

2.884

 

1.373

 

1.479

 

1.708

 

1.381

 

0.863

 

1.928

 

1.204

 

0.972

 

0.602

 

1.230

1.849

1.271

1.309

       
       

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Last updated 3 January 1999