Home Forums Hunting & Shooting Ask The Gunwriters What's Petzals beef with the 7mm RM?

Quite a concept.....

Hey azzclown, I've been hunting with the .270 for the last decade. Its all I used last year. I already said I owned a 7 mag model 70 but have never hunted it. I sold it to a relative. I get a kick out of guys like you who think internet forums aren't for questions. This has been a damn good thread so wise up.

Never yet met anybody who could read wind perfectly, and the higher the BC and MV, the larger your margin of error in your wind call without missing the target. A 0.125 difference in BC is a big difference, with a very real wind advantage.

Why not 250 yards and 45 mph?

When the wind really gets to whipping, you need to make a decision as to when a shot is appropriate, and when you need to get closer or change position into or away from the wind. If the shot is really borderline, I'm not going to take it, whether I'm shooting a 7 Mag or a 270.

Where are you getting the .125 difference in BC? Comparing Amaxs to hunting bullets? When the 7 Mag's only trump card is one cheaper bullet that isn't currently being manufactured, and has a questionable track record on game.....it's proponents are really grasping at straws.

Just logged on again for the morning visit, and see this is still going, so used Bryan Litz's Point Mass Ballistics Solver to run some numbers. For the 7mm Magnum I used the velocities for the 168 and 180 VLD's quoted by Tanner, 3000 and 2800 fps respectively, and for the 150 Long Range Ballistic Tip used 2950 fps, because that's what I easily get from the 23.6" (60 cm) barrel of my very accurate CZ 550 .270, using H4831.

The wind drift numbers are for Standard Atmosphere conditions:

180 7mm VLD @2800--- 300 yards 4.6"; 500 13.4"; 800 37.4"
168 7mm VLD @3000--- 300 yards 4.4"; 500 13.0"; 800 36.4"
150 .270 ABLR @ 2950-- 300 yards 4.5"; 500 13.3"; 800 37.2"

Well John, you certainly provided a lot of nits for the pickers to grapple with.

Kudos!

D

Agreed, there is a point where a guy has to know not to shoot. But a bullet that cuts the wind better extends that point a little bit.

See 16bore's post above for the 0.125 difference reference.

Interesting data for the 150 ABLR. Do we know how Nosler derived the BC for those, and whether the BC has been field verified?

John,

Is that LRBT even more magical in the wind than the LRAB?

I assume those numbers are for a 10 mph crosswind?

Tanner's 7RM numbers leave the cartridge a fair bit of breathing room...

Jordan, I agree with you about the higher BC extending that range a bit. It's just that for me, there isn't really a range or set of conditions where I draw a line in the sand. That line is constantly changing due to wind speed and fluctuations, as well as what terrain that wind is crossing, time of day for tracking, proximity to nasty cover or cliffs if wounded, stability of my shooting position, how worn out I feel, a gut feeling about the shot, and probably some other things I can't think of right now.

I'd like to think I err on the side of safety if one of those borderline shots presents itself, but it depends. I do know that I've never felt handicapped if I was packing a rifle that fired a reasonable game bullet at reasonable velocity.

Jordan,

Typical Friday morning brain-fart on my part....

I've fooled around with both the VLD's in the 7mm Magnum and while there is some room for more velocity, I wouldn't call it considerable in a typical factory chambered 24" barrel.

There's actually a little room in the .270 velocity as well, since newer powders have also helped it.

I haven't had a chance to verify the Nosler BC info by shooting the .270 ALR's yet, having just gotten started on load development. Have heard info both ways, but suspect Nosler's numbers are fairly close. Will have to see.

Just for what it's worth... I've run 162 A-Maxes at 3150 in a 26" barreled 7 Rem Mag with Retumbo, without an adverse sign of pressure after 6-7 loadings on the brass. I started using 7828 when it showed tighter vertical dispersion at longer ranges, hence my quoting 3,000fps... there is surely untapped velocity there.

I have never loaded 150s anywhere near 2950 in a .270, though (not to cast doubt on JB's numbers, I just haven't used a powder that would do it, yet). I don't know why we're talkin' 300 yards though. Anything with smokeless powder and a piece of lead in front of it will work that close.

I think most subscribers of F&S would probably be suited better with a .270, if they ever shot....

Tanner

Totally agree. Higher BC and MV just edge my confidence a little in making the shot, when all factors are considered, including the "gut feeling". To contrast a bit more, the SHOOT or DON'T SHOOT call would likely be totally different for me if faced with a shot at game 150 yards away across a coulee, with a 20 mph variable cross wind, near last light, depending on whether I was holding a .30-30/170RN or a .243/105 combo. Talking about wind drift only.

The difference there is obviously more polarized than that between the .270/150 and 7RM/162/180, but my point is that any ballistic advantage, however small, gives me a slight edge in those tough situations, and can affect the decision to shoot, and success thereafter. In a no wind condition, any cartridge/bullet that you have drop data on will work fine as long as the bullet arrives with enough speed to expand

Nowadays I almost think one could make an argument for a 'better' cartridge based on the components one could find available. Hopefully that will change soon however the last two pounds of powder I saw on store shelves (at Christmas-time) was a pound of Steel at Sportsmans and a pound of 7828 at an LGS/hardware store.

Could I interest you in a Ruger 338RCM SS/poly stock? That is the first of mine that is leaving. My safe is mostly full of evil black guns, 7 of 'em IIRC.

John,

I was just ribbin' ya a little Nobody is impervious to the odd brain fart. I know I have my share.

I agree with you. IME a .270 will push a 150 to roughly 3000, just like a 7RM will push a 175 to 3000, particularly with short-bearing surface bullets like the LRAB. To compare apples to apples I'd go 3000 on the .270/150LRAB, and 3000 on the 7RM/175LRAB.

Even a difference of a couple inches of wind drift can really help when the target is only 10-12" in diameter. I've personally seen this advantage at ~300 yards while hunting mule deer on a very windy day...

Most F&S readers would be even better served with a .243 or .260, assuming they could find factory ammo...

Tanner,

Oh, I don't doubt it in a 26" barrel--and as I noted in an earlier post here, I just got 3300 with published data usin Norma MRP and 160 Partition from my 26" barreled 7mm Weatherby--though backed it down to 3250 due to very slight pressure signs.

I also once had a 26" .270, and it got over 3200 with 130's and around 3050 wit 150's, using H4831 and the top listed Hodgdon loads--and there is some room there.

The latest 150-grain data for the .270 from 24" barrels shows 2974 fps from Accurate Magpro, and 2999 or 3302 fps with Norma MRP, depending on whether the bullet's the Sierra GK or Nosler Partition.

You guys are making me think that I need to get off my duff and test some of my pointed 6.5mm 140 Berger Hybrids in ballistic wax and see how they behave.

It can really make my 6.5x47L into an overachiever.

Undoubtedly no overlap there..........