Having chambered my pre-64 Win in .270 Weatherby with a 27" Lilja barrel I chronographed the 150 Grain factoryload here the other day I got a shock . The chrono showed 3320(Not 3220)Ft/sec!. . I am much aware that that the 7mmRUM can throw the 175 grain bullet faster than the .270Weathetby, but in the 140-150 grain department the weatherby can compete feet by feet with the RUM.

My sole question is, have I missed(overlooked) something with the RUM?

That is fast for the .270 Wby, faster than the numbers you normally see. On the other hand, you have a 27" barrel - that should might give you an extra 20-30 fps or so. I have seen velocity claims for the .270 Wby just below 3300 with 150 grs bullets, so make that 3310-3320 with a 27" barrel, and all of a sudden your numbers don't look impossible. Norma does stoke its Weatherby loads, to the point where I have often seen flattened primers in factory loads. In general, it is not easy to best Weatherby factory loads as far as velocity is concerned.

Can't really comment on the 7mm RUM.

- mike

I don't find that unusual at all. I had no trouble at all getting to 3350FPS with the 140 grain Barnes XBT. IMR 7828 is THE powder of choice for the 270 Wby IMO.

I have a 270 wby that is a great shooter. But the 270 wby certainly has nothing over a good 7mm rem magnum. Even though I don't own a 7mm I have to admit that bullet choice is much better than .270 caliber. In all honesty, with only .007" difference in bullet diameter there isn't enough to "talk about" for performance difference between the two in my book. I would think the 7mm rum would add another 100 fps to the comparison.....but at the expense of all the powder, recoil, etc I would have a hard time getting excited about calling that a "move up".

Not really. The 7 Rum can throw 150 gr. bullets 3500 fps with a 26 in bbl. Faster if you give it a longer tube. Case capacity wins. The 7 rum has more case capacity than the 270 weatherby. The 270 weath. is a great round but it can't run with the rum when it comes to velocity.

The simplest expanation is that factory weatherby loads are very hot and if you are using a custom barrel with a tighter chamber or less freebore ,you may be developing even more pressure(perhaps well above design pressure) which would provide added velocity.
On the other hand the 7mmRUM factory loads are pathetically mild and handloading can add close to 200fps.

I suspect most Weatherby factory loads are built with freebore in mind. If your custom tube has no or minimal freebore, that could explain your higher velocity.

-Lou

On the other hand the 7mmRUM factory loads are pathetically mild and handloading can add close to 200fps.[/QUOTE]
Hi.... I am loading 105 gr wc872 & 140tsx..chronagraphs 3490fps in my rem 700 26"
Do you have any better loads?

There are diminishing returns w/ really overbore carts. like the 7RUM. While case cap. may win, you'll use alot more powder to get little vel. gains. My 7mmDakota will easily do 3200fps+ w/ a 160grNP from it's 26" bbl. The 7RUM doesn't beat that by much & uses 30gr more powder to get there.

quote:

Originally posted by fredj338:
There are diminishing returns w/ really overbore carts. like the 7RUM. While case cap. may win, you'll use alot more powder to get little vel. gains. My 7mmDakota will easily do 3200fps+ w/ a 160grNP from it's 26" bbl. The 7RUM doesn't beat that by much & uses 30gr more powder to get there.

That is true, The same thing can also be said about the 7mm STW. It does everything the 7mmRUM can do with less powder which in turn means slightly less recoil.

My STW does 3300 with 160 TSXs with 78 grs. of powder. My last 270 WBY did 3200+ with 150s and 66 grs of powder. 3450 with 130s and 68 grs.

I get 3610 fps out of the 160 grain bullets ....

Oh crap, wrong data, that's for 106 grains of H4350... Guess the 338-378 doesn't count in this case ....

Ken....