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Jimro · January 23, 2014, 02:15 PM

totaldla,

Whoa dude, why the hostility? Clearly I was totally wrong about the reputation of Marlin microgroove barrels.

Obviously it is totally a myth that people have experienced issues loading up cast bullets for them. I'm so glad you set me straight about that!

Then again, maybe you should look into the source of the "forum myth" that you dismissed.

The inaccuracy myth comes from a rather large number of folks having issues getting Marlin's with microgroove rifling to shoot tight. If you can operate a search engine, you can read their problems.

Those problems are generally solved by 1, figuring out what the actual bore diameter of the rifle is. 2, using a cast bullet harder than 12 brinnel. 3, using that bullet at a moderate velocity (1,900 fps is a common figure), and 4, ensuring that the bullet is .001 to .002 larger than the bore diameter to ensure maximum rifling engagement.

That is it, no "myth" involved. I can't proove that Marlin started advertising "microgroove" rifling as a way to salvage barrels that would have otherwise been scrapped. If you need a 30 cal barrel, the land to land measurement should be 0.300 inches (some British target barrels were intentionally smaller to for fullbore competition). If you end up with a 0.304" bore, instead of turning it into a 0.311 caliber barrel, you just cut the rifling grooves 0.002" and call it "microgrooving" and you can still launch a nominal 0.308 bullet down the bore with acceptable results. But it seems like "microgroove" is a way to salvage barrels and not wear out rifling equipment. Can't prove it though, but what do I know, maybe I should learn something before posting.

On the other hand, Marlins known bore diameter dimensional tolerances have required some 44 mag loaders to use cast bullets up to 0.435" over the nominal bore of 0.429, and some 30-30 loads to use a 0.311 bullet where many 30 cal hand loaders get by very well with a 0.309 bullet. But then again, what do I know?

There are very good reasons for the "myth" you so readily dismissed without any explanation. But we can take it on your say so because you are just that awesome.

Keep being awesome.

Jimro

January 23, 2014, 02:15 PM	#13
Jimro Senior Member Join Date: October 18, 2006 Posts: 7,097	totaldla, Whoa dude, why the hostility? Clearly I was totally wrong about the reputation of Marlin microgroove barrels. Obviously it is totally a myth that people have experienced issues loading up cast bullets for them. I'm so glad you set me straight about that! Then again, maybe you should look into the source of the "forum myth" that you dismissed. The inaccuracy myth comes from a rather large number of folks having issues getting Marlin's with microgroove rifling to shoot tight. If you can operate a search engine, you can read their problems. Those problems are generally solved by 1, figuring out what the actual bore diameter of the rifle is. 2, using a cast bullet harder than 12 brinnel. 3, using that bullet at a moderate velocity (1,900 fps is a common figure), and 4, ensuring that the bullet is .001 to .002 larger than the bore diameter to ensure maximum rifling engagement. That is it, no "myth" involved. I can't proove that Marlin started advertising "microgroove" rifling as a way to salvage barrels that would have otherwise been scrapped. If you need a 30 cal barrel, the land to land measurement should be 0.300 inches (some British target barrels were intentionally smaller to for fullbore competition). If you end up with a 0.304" bore, instead of turning it into a 0.311 caliber barrel, you just cut the rifling grooves 0.002" and call it "microgrooving" and you can still launch a nominal 0.308 bullet down the bore with acceptable results. But it seems like "microgroove" is a way to salvage barrels and not wear out rifling equipment. Can't prove it though, but what do I know, maybe I should learn something before posting. On the other hand, Marlins known bore diameter dimensional tolerances have required some 44 mag loaders to use cast bullets up to 0.435" over the nominal bore of 0.429, and some 30-30 loads to use a 0.311 bullet where many 30 cal hand loaders get by very well with a 0.309 bullet. But then again, what do I know? There are very good reasons for the "myth" you so readily dismissed without any explanation. But we can take it on your say so because you are just that awesome. Keep being awesome. Jimro __________________ Machine guns are awesome until you have to carry one.