This spring I picked up a Ruger Guide Gun in .30-06. While doing the initial cleaning before the first firing I noticed the barrel had 5 narrow, shallow lands, the Ruger web site spec sheet shows 6 grooves. i searched around this forum 5R but didn't find anything so I went off on my own, Let me clarify that I'm not a competitive shooter, most of my shooting is pretty casual. I have shot a fair number of cast bullets in a variety of rifles so I'm a little familiar with the world of infinite variables we all deal with. I should state that my typical alloy is WW and depending on the mold I add lino or solder to get the diameter I want. I use a lot of Lee molds.
Some loads I had luck with in other '06 rifles such as 24/IMR 4198 and a Lee 160 GC sized .309 or .310 want to run around 3" +at 100 yds. This load most always shoots under 2" in every other rifle I've tried it in. I went to the other end of the spectrum and tried some Lee 113's without checks. LLA, pushed through a Lee .309 sizer with 7/700X, delighted with cloverleaf groups at 50 yds I moved the target to 100 and got more 3" groups. Along the way I continued trying a wide spectrum of bullet weights, alloys, diameters and powders with a lot of similar results. About this point I bought a Garmin chronograph and started learning a lot and got a little smarter. Further experiments eventually gave better results. For now, after trying about 30 different loads, my best load is a Lee 150 without a check, light coat of diluted LLA sized .309 over 8/700X. Chrono at 1275fps. Most days I can keep 5 shot groups close to 2" at 100 and I'm beginning to think that this is about all I can expect from this rifle with cast bullets.
I should state that I did fire a few jacketed bullets while doing a break in procedure and it looks like 5 shot 1" groups at 100 shouldn't be a problem. No load development, just trying something that always works. in a .30-06.
I live about 2 miles from the Newport plant so finding factory people to ask questions of is no problem. The general consensus is that they are eventually changing all their rifles to 5R, one engineer was explaining all the wonderful benefits of 5R barrels but was surprised to hear they have been common for 20 years and 5 grooves were used in 1917 Enfield's, When I asked about the use of cast bullets all I got was a blank look. Apparently that isn't something the engineers are concerned with.
I wrote all this to lead up to a couple questions. Has anyone else run experiments in a gun with 5R rifling? Is this type of bore similar to Micro-groove in that bullet hardness and velocity range are critical? Am I making a big deal out of nothing and just have to accept that I bought a rifle that's not very accurate? Wouldn't be the first time. In the meantime I'll keep looking for a better load.
