9mm inside barrel dimension/tolerances

[villihun]

Hi everybody

I have a 9mm SV Infinity and I'm getting lots of lead fouling in it. The bullets are hard cast lead 124 gr. I'm yet to try the copper jacketed projectiles. At the range someone suggested that the bullets may be a little oversized or the barrel is too tight. I have measured the bullets and they are exactly 9mm. Then I have measured the inside of the barrel at the exit end, and it measures 8.8mm. (.346 in inches). So what are the allowed tolerances with the barrels? Also it was suggested to me to push a bullet through the barrel with a piece of dowel and then measure the projectile to get the true inside dimension of the barrel. Is there any merit to this exercise?

Does anyone have any suggestions as to how to resolve this problem?

Thanks in advance

villihun

It takes one good man to do nothing, for evil to prevail.

[superdude]

"slugging" your barrel (pushing a bullet through the barrel with a wooden dowel) is a classic method for measuring bore diameter. start with a soft (swaged, cast, plated; NOT Jacketed) oversize bullet - .357 or .358. lube the bore plenty to make the job a little easier.

slugging is a vary useful method and will give you the best measure of your specific barrel bore. the classic byline to this technique is to select a bullet diameter that is equal to, or just slightly larger (0.001 inch) than the bore diameter. this ensures a good gas seal between the barrel and bore.

tolerances vary. i've seen some 9mm bores measure as large as .357, and a .357 magnum barrel slug at .355.

[TonyT]

Slugging the barrel will tell you the groove diameted of the barrel.

Your leading problem may be due to pushing the lead bullets too fast. For lead bullets in 9mm I prefer the 147 gr. at about 900 fps.

Hi everybody

I have a 9mm SV Infinity and I'm getting lots of lead fouling in it. The bullets are hard cast lead 124 gr. I'm yet to try the copper jacketed projectiles. At the range someone suggested that the bullets may be a little oversized or the barrel is too tight. I have measured the bullets and they are exactly 9mm. Then I have measured the inside of the barrel at the exit end, and it measures 8.8mm. (.346 in inches). So what are the allowed tolerances with the barrels? Also it was suggested to me to push a bullet through the barrel with a piece of dowel and then measure the projectile to get the true inside dimension of the barrel. Is there any merit to this exercise?

Does anyone have any suggestions as to how to resolve this problem?

Thanks in advance

villihun

It takes one good man to do nothing, for evil to prevail.