Well, if we’re talking about comparing loads in two specific rifles, then we should clarify the barrel length and twist rate of those barrels. Not an idealized, normalized comparison, but an actual comparison of the ballistics provided by various loads on your rifles. The .270’s 22” barrelled velocity is real world. What twist rate does it have? That makes a difference. If a factory R700 and 10” twist, then Bryan Litz’ testing says the true G1 BC of the LRAB exiting your barrel is around 0.550.
He tested the 7mm 150 LRAB at 0.576 G1 BC using a common 9” twist. Assuming a 7RM of the same weight as your .270, a minimum charge of H4350 or H100v would generate about 18.3 ft-lbs of recoil and about 2830 fps. Likewise, the 162 ELD-X at 2755 fps using a min load of IMR 4451 generates 18.7 ft-lbs. The recoil would be less in a rifle heavier than your .270. Both of those loads drift less in the wind at 600 than the .270/150 LRAB, and the recoil is comparable.
As an aside,
the 143 ELD-X from the 6.5 Creedmoor at 2750 fps also drifts less in the wind at 600 than the .270 load, and would recoil even less for her.
Jordan -
First, thank you for your thoughtful and civil response.
Daughter's .270 is a lefty factory M700 with whatever the standard twist was back in 1970. I have not measured it but assume 1-10. My 7mm RM, a Ruger M77 made in 1982, is also factory stock and assumed to be 1-9.5, which is the current Ruger twist.
My original thought was to buy a rifle for the action, then rebarrel to 6.5PRC, 6.5-06 or 6.5-06AI. If the .270 I purchased hadn't been accurate, I would be looking at rebarreling to one of the latter two. (I reload for the 6.5-06AI and her husband reloads as well.) At this point it is moot as the .270 does everything needed with superb accuracy. Daughter is very happy with it (a BDL model in good shape) and that is what matters most to me. I've taken time to glass bed it and check and adjust the trigger. Her hubby will probably replace the trigger with a Timney.
If Bryan Litz is correct about the .270/150g LRAB, the difference between 6.5/143 ELD-X @ 2750fps and the .270/150 LRAB @ 2910fps is pretty thin. Nosler reduced the B.C. values for many of their LRAB bullets based on testing by EMRTC in New Mexico, which provided the .591 value for the .270/150 LRAB. In any case, we will shoot her .270 out to 600 to verify what the B.C value is for her rifle. Whether .550 or .591, the difference in drift is only 1.3" at 600.
Thanks again.
CH
