629 Classic Fouling

[jjrobo]

I have guns that shoot better dirty, and some that shoot better clean. But my 629 has me baffled. It is a 6.5" S&W 629 Classic with a 2x Nikon.

I can shoot 2.5" groups at 50 yds for the first 20 rounds, then things get weird.

Remington 240 gr. softpoints move up and left, and keep going in that direction the longer I shoot. All the while my groups get smaller.  

Hornady 200gr. XTP's go straight  down and my groups get bigger.

Hornady 240 gr XTP's just go every where and I can't hardly keep them on the 2' x 2' box.

I am just wondering if any one else has ever had a gun like this? I've seen groups get bigger, but never had the point of impact shift as the bore gets dirty. I am leting the barrel completly cool off between groups, so that's not it.

It just bothers me, because I shot a few good rounds and then it goes to pot and ruins my self confidence by the time I'm done. I suppose I just need to start taking my cleaning stuff with me when I shoot.

Jeff

[Iowegan]

Try the same tests with open sights. I suspect the internal tube in your scope is drifting.

[jjrobo]

It did the same thing with open sights before I put the scope on it.

I went out tonight and shot it until it started fouling. Then I cleaned it and it shot right where it was supposed to.

Jeff

[Mikey]

jjrobo:  I would do a couple of things.  First, I would check the alignment of each chamber in the cylinder with the barrel.  The second thing I would do is firelap the bore.  If your bore is getting that dirty with jacketed bullets after only 20 rounds she needs to have the snot shot out of her or firelapped to impart controlled wear for enhanced accuracy, smooth out any rough spots in the bore and enable you the effective use of cast bullets.  

I would also have the forcing cone opened up to about 11 degrees.  Don't forget to check the end of the barrel for dings or marks that might effect accuracy.  HTH.  Mikey.

[jjrobo]

How would I go about checking the alignment of each chamber?

What is firelapping?

I have shot about 400 rounds so far. I wish I had the time to shoot it more.


Thanks,

Jeff

[Hcliff]

Firelapping is rolling bullet in a medium that has grit.  When this is shot down the barrel it minorly cuts and polished the bore.  You can get these kits from Midway and other suppliers.  This polishing will give the bore even smoothness.  It will also help to reduce bore leading.  Does the barrel get very dirty?  

Hcliff

[Mikey]

jjrobo - you can check the allignment of each chamber as it indexes to the barrel by cocking the hammer back to full cock and then seeing if there is any rotation of the cylinder after the hammer is locked back - that might be one indication.  Another method is to use a light to shine through the firing pin hole as you rotate the cyclinder - you might see if there is any misalignment.  Also, having the forcing cone opened to about 11 degrees would help redcue bullet offset as the bullet enters the barrel.  

Firelapping is a process of imparting controlled wear to the bore - it removes minute obstacles and sharp edges that would cause fouling and poor accuracy.  You can either go to Veral Smith's Forum down the line here for info on firelapping or go to the Beartooth Bullets website for thier information and materials.  

You have beenusing jacketed bullets and if yo have a rough bore you can get a lot of copper fouling that will ruin your accuracy within just a few shots.  

400 rounds from a M29 is not even breaking it in.  Firelapping will impart the controlled wear of a coouple of thousand rounds and just really improve your barrel and accuracy.  HTH.  Mikey.

[Snowman366]

No disrespect intended...but after 20 rounds of .44 magnum ammo, I wouldn't in the least be surprized if my groups started opening up or drifting one direction or another. Could good-old-fashioned muscle fatigue be a factor, too?

[Ahab]

The advice for fire lapping is good. Had a similar problem with a Ruger Bisley. After fire lapping groups shrank and way less copper fouling. You may want to wait with the 11 degree forcing cone mod as that is usually done if your using lead bullets only.

[jjrobo]

Thanks for all the suggestions, I appreciate it.

I'm going to look into fire lapping.

My very first inclination was what Snowman336 suggested, muscle fatigue. But I've ruled that out by shooting multiple days, having other people shoot it,  as well as cleaning in the same session.

Thanks again,

Jeff