Replacing my .270: 7mm or .300 Win Mag

[davkrat]

For several years I've been wanting to rebarrel my .270. Since getting my .308 I have hardly shot the .270 and running the numbers they are basically identical. Pushing similar size bullets to similar velocities and not much difference in BC. Why so many high BC options in 7mm but not in .277 or the lighter wight .308 I don't know. The 150 grain Etip in the .308 is just about perfect for everything I do here in California.

I can't really see any rounds in the standard '06 case that get me too excited. My brother has a 7mm Rem Mag and a .308 so I was thinking it would be good to convert my .270 in to 7mm Rem Mag. The writing is on the wall here in California and I don't doubt we will go lead free state wide at some point. I have been real happy with the Etips so far and looking at the options there is a 150 gr. 7mm with a BC of .498 but they also offer a 180 gr. .308 with a BC of .523. Running the numbers for the 150 gr 7mm at 3150fps vs. the 180 gr. .308 at 3000fps you get the following at 600 yards:

7mm: -56.2", 2149fps, 1538 ft/lbs. and 21.4" of drift
.308: -61.4", 2076fps, 1715 ft/lbs. and 21.7" of drift

The 7mm has one minute less drop but basically equal in drift with a slight energy nod to the 180 gr. .308. I don't hear much about the .300 Win Mag for long range. I'd think either could easily take Elk sized game at 600 yards. Would the long length of the lead free etips be a problem in a .300 Win Mag? Any other thoughts?

Also I've been looking in to changing the bolt face of my .270 to a magnum size any idea how much that costs? I've seen a few replacement bolts on line but most of them are over $350.

 

[backwoods83]

Well depending on barrel length and what data you may have looked at your figures are a little off. They are both good rounds, easy to load for, and easy to find factory ammo. With both having a 26" barrel around 3220ish is doable with the 7mm/150 combo and around a 3180ish with the 300/180 combo, but my nod goes to the 300wm its very versatile, can be pretty stout or tamed down quite a bit. Assuming you have a remington 700 do a search for competitive edge gunworks for a bolt, they are stainless, snake fluted with a M16 style pinned extractor, very nice piece, accepts factory firing pin assemblies or a tubbs or callahan speedlock setup and I think they go for around 280.

 

[davkrat]

Thanks I was being conservative on the velocities. Picked the upper mid range of velocities per bullet weight out of the Nosler Manual. After the price of barrel, bolt and install I may as well just buy a full custom rifle. Was planning to get a Pac Nor with Rem Nut though so I could save on the install. With a second bolt I could then revert back to .270 if I wanted to I suppose.

 

[backwoods83]

McRee precision does the rem-nut setup (barrel, wrench, recoil lug, and nut for 425) they use Broughton, krieger, or mcgowen barrels and its close to 200 cheaper than pac-nor and you will won't to atleast lap the lugs and fit the new bolt, and as for not having good 27 cal bullets, that's because J4 doesn't make a 27cal jacket.

 

[davkrat]

Berger does make 130, 140 and 150 gr. .277 VLD's but the BC are .452, .487, and .531 in the 7mm the lightest VLD is 140 gr with a BC of .510. The 7mm start at a BC close to where the .277 ends. The Nosler Etip in .277 is 130 gr with a BC of .459 lower than the .469 of the .308 150 gr. I use in my .308.

I wish they would offer a 160-170gr. VLD with a BC up around .600 that would push the .270 quite a bit and I'd think a .270 WSM or Weatherby coulld really take advantage of a long heavy bullet. Unfortunately I don't think there's much market for that style bullet. If Nosler offered a heavy Etip with high BC that would be great too.

Maybe I'll just make it simple and go with a .280 AI that would only require a barrel swap. That way my brother and I could still use similar components (bullets at least) in all our rifles. The 7mm Etip at 150 gr. has a BC of .498 but once again that is very similar to the .308 150gr I use. The 280 AI could certainly get more velocity than the .308 Win but not a huge difference.

 

[backwoods83]

Well they do make a 169.5 and a 179.5grn .277 wildcat using "squeezed" .284 jackets and the only good things I've heard about them is there bc and they should be put through an 8 or 9 twist and most 270 case designs won't push them at respectable speeds. Unless your dead set on keeping your .473" bolt face, personally I think a 280AI is an expensive, inconvenient, joke to try to keep up with a 7mm mag, but its all in what you like. The reason for low bcs on 277 cal is due to very short boat tails!