[William Iorg]

I would be interested in hearing from anyone who has chronographed loads with two rifles of the same caliber, one having a micro groove barrel and the other conventional rifling.
We have been working with a Winchester M-94AE and a Marlin 336, both in .30-30AI. The Micro groove barrel seems to be faster, but has higher extreme spreads. There does not appear to be a difference in accuracy between the two barrels.
Two barrels do not make a rule so I would like to hear of other experiances.

 

[Ed Harris]

When I was at NRA I did numerous tests in .30-30, .357 and .44 Magnum with Microgroove and conventionally rifled barrels chambered with the same reamer, and the velocity differences were statistically insignificant, being well less than the velocity standard deviation of the 20-round samples fired.

 

[William Iorg]

Thats interesting. A large sampling (over ten shots) of any given load will sometimes give a surprising result, as will shooting the same load on several different days. While the differences in performance we were seeing is consiten, with only one barrel of each type of rifling available we could only guess at what the differences we were seeing between them meant.
I have your article: Cast bullets in Micro groove barrels, it is very interesting and informative. Was it you that wrote about a fellow named Ellis Lea and his Remington 788 in .32 S&W Long? This was a very interesting article of high performance .32's.

 

[gmushial]

Slim -

This might be a difficult comparison to make, ie, we've seen cases where two "identical" marlin mg barrels, both slugging within a couple (one or two) ten-thou of each other with fullhouse 30-30 loads (same loads shot back to back - first shot barrel a, 2nd b, 3rd a, 4th b etc, same temp, same chrono), but clocked with almost 150fps difference. Trying to find the signal in the data is going to be difficult (or worse). [we ran into this in trying to quantify the improvement in going from a 3030 win to AI.]
do shoot straight,
greg
www.gmdr.com