rebarreling the 30-06

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rebarreling the 30-06

Post by mtngun » Thu Feb 14, 2008 6:17 pm

finally found time to make an action wrench and barrel wrench for the M700, and screwed on a factory take-off barrel that I picked up on ebay. The barrel had some light rust but otherwise looked fine. Headspace was tighter than the old barrel. I haven't gotten around to buying a reamer, so I ground a few thou off a shellholder until the case shoulder was set back enough in the sizing die to chamber in the new barrel. The bore and throat seem to be a little tighter than the old barrel, too, because I had to seat the bullets deeper.

An Omega gage was mounted using Loctite 4211. The 4211 is a viscous superglue that takes several minutes to set up, so you have time to wiggle the gage around and iron out the air bubbles. I like it better than the Loctite 401 that RSI recommends.

Here's the jacketed validation load. Pressures seemed a little high, so I subtracted 2000 psi from the traces. All the traces shown here have the minus 2000 psi offset. By comparion, this load averaged about 54 ksi on the old barrel, so the traces may be a little high even yet. Velocity was 2734, about the same as the old barrel. The best 3 shot group was 1.2". The old barrel was consistantly sub MOA.

Owing to the tight throat, I decided to give my 180 gr. bore rider another try. The nose engraves nicely in this tighter barrel. The load was 47.2 gr. WW748. Five shots spanned 12" at 100 yards, and I gave up after that. Note that WW748 was low-spike in the old barrel, but gave significant spikes today.

Here's the usual 180 gr. Loverin and 56.0 gr. WW760. The average group was 2.16", not bad considering the velocity. By the way, the bullet had to be seated well into the powder space, which according to some people, is guaranteed to produce poor accuracy and possibly blow up the gun.

Spikes This barrel has bigger spikes than the old barrel, with all loads tested. Perhaps it is just the gage, so next time I will mount a second gage. WW760 looks to be the most spike-resistant powder.

Velocities Were the same as the old barrel, despite the tighter dimensions.

Primary Pressures were a little higher with all loads. Considering the normal velocities, the higher pressures may be due to the gage calibration.

Accuracy was not as good with most loads, however, 2" at 2760 fps is nothing to complain about with cast bullets. The WW760 / loverin load is worth tweaking. Next time I'll try backing off the velocity slightly, to bring the pressure down to a safe level. I was used 0.314" bullets, which the old barrel preferred, but this tighter throat may do better with 0.312" or even smaller.