Home Forums Hunting & Shooting Ask The Gunwriters 7mm-08 - 120gr. vs. 140gr. re-visited

First, I want to say this is not to argue that the 120 is not effective, it is, but it's an exercise of 'ballistic gack' - Doberism

My impetus for this exercise, is b/c so many 7/08 users rave on the 120 (not a bad choice mind you, but I don't see the 'benefit' in common std. chambers). Do note I have shot my share of 7/08 rifles, from 100-160gr bullets. I do like the round.

Below is comparing typical speeds in 7/08 std. chamber using 120/140 BTs and a comparison w/Dogzappers rifle: 7/08 AI using 120s.

Here is how the numbers crunch:

7/08 Std. chamber - 140 Ballistic tip at 2950:

Muzzle -1.5 2950 2705
100 1.5 -6 2758 2364
200 0.0 0 2574 2059
300 -6.8 9 2398 1787
400 -19.7 19 2230 1545
500 -39.5 30 2067 1329

7/08 AI - 120 gr Ballistic tip at 3255mv:

Muzzle -1.5 3255 2823
100 1.2 -4 3017 2425
200 0.0 0 2791 2075
300 -5.6 7 2576 1768
400 -16.5 16 2372 1499
500 -33.6 26 2178 1264

10mph Wind deflection at 400 yds:

11.3" for 120/3255
10.9" for 140/2950

Let's compare a 7/08 standard chamber - 120/3050 mv

Muzzle -1.5 3050 2479
100 1.4 -5 2822 2122
200 0.0 0 2606 1809
300 -6.6 8 2400 1535
400 -19.2 18 2205 1296
500 -39.0 30 2018 1085

Wind 10mph at 400 yds: 12.3"

Therefore in a std. chamber, I'd rather use a 140 vs. 120 b/c:

Using a 140/2950 vs. a 120/3050 will cost you 1/2" of drop ONLY at 400 yds, and GAIN 250 lbs energy, and drift is 2.4" LESS by using the 140gr.

I hope that clears up some thoughts on 120 vs. 140 in the 7/08 - assuming standard chambers.

Ballistically speaking, I just don't see the advantage of 120s myself.

This however does not mean to negate the deadliness of the 120 Btip and TSX/TTSX at typical speed and ranges, as they do kill just fine.

The outcome will be the same as Dogzapper says, 'Dead is Dead' and that is true.

Now if using an AI, the increase in speed over a std. chamber, I believe is greater using a 120 vs. a 140 due to their modest capacity (as a say 280 or 7RM would be more efficient - in a sense, w/heavier bullets, due to more powder). SO, the compelling reason for a 120 in a 7/08 - assuming at AI speed - is created - IMHO.

No doubt, as always when crunching numbers, one can play w/#'s a little either way, but suffice to say before flames begin, the small differences of input/ouput in a ballistics calculator are not going to drastically change the analysis, IMO.

Now that's settled, I need to get my new custom 6.5s done as soon as McM ships my stocks so I can spit some 130 ABs downrange! LOL.

What a lot of 120 users like is its thicker jacket.

Yep

I get it that the jacket is 'thick' for a light bullet and it penetrates well, but is that 120 jacket 'THICKER' than the 140 version? NO doubt it's a performer, I just like the extra energy and wind drift advantage at a 1/2" price in trajectory at 400 yds using a 200 yd sight in.

Personally I'd pick a std. 139 or better yet, 140 Accubond, expecting better penetration w/the 140 AB, not necessarily needed w/o hitting heavy bone. But one step up, I think the 120 TSX and TTSX 'offer' more penetration potential than any of the above bullets, assuming normal ranges/speeds.

Yes. Ballistic Tip 120 Design was altered for Silly-Whette shooters (Long story, Dogzapper has related several times).

AND it kills stuff every effectively.

BMT

BTW, IF the 120 was developed after the original 140 BT, OR re-designed, it may well have a thicker jacket than the original 140. No doubt Noz changed things in their BT line up as the .277 130 BT was said to be 'soft' upon intro from what I am told, though I never had any issues w/150s - my rifles just preferred the heavier BTs in accuracy.

Maybe somebody KNOWS the latest facts on jacket thickness in 7mm BTs, the 120 vs. 140. My guess is today's production - they are the same. I could be wrong.

That said, the 120 BT is the ONLY cup/core 120gr 7mm I'd fire at deer or larger game. Yet, when I want a 140 bullet, the BT is not going to be my choice, I'd rather an Accubond over the BT and I guess a case can be made for tougher bullets yet if one wants to take really large game with one.

Again, not to say there are many flies on the proven 120 BT, but the 'math' just does not compel me.

BMT, no doubt, I recognize they work, and why it was changed.

I guess what would be interesting enough, would be a penetration and wound channel comparison of say:

120 BT
140 BT
120 TSX/TTSX
140 AB
140 TSX

Do you guys that like and use the 120 BTs feel 100% confident if you had a 'bad angling' shot or hind end shot on a large deer or elk? Curious.

Myself, I'd rather either the TSX/TTSX or a good 140 for 'insurance' if I must drive really deep or thru heavy bone.

That's more a reason to me than 250 lbs or a dope advantage.

I don't hunt elk, and I would (and have) passed on ass end shots on deer. But that's my preference no matter the cartridge/bullet I'm using.

If I absolutely had to shoot one from the back end, then I'd first concern myself with busting up the "rear axle" to immobilize.

While you can yap about numbers all you want, it's all just conjecture while looking in the book for results.

My 22" runs 140's at 2950, but runs 120 BT's at 3175 and shoots little knots out to 500. So the "superior" advantage of the 140's is flushed right down the [bleep].......

A very wise choice of shot location with any bullet

WOW, what powder are you using? Your speeds are well above what I have seen and obtained.

Can you 'quantify' in more specific terms how 'inferior' a 7mm 140gr at 2950 is then a 7mm 120 at 3175?

Running #s -

I see the 140 load needs 30 clicks vs. 27 clicks of come up w/a 200 yd zero, at 500 yds.

The 140 load needs 13 clicks windage for 10mph, the 120 needs 14.

The 140 has fps/lbs 2067 1329.

The 120 has fps/lbs 2116 1192.

SO Aalf, it looks like you get 3 clicks advantage of elevation using a 120 gr, 1 click disadvantage on windage, and a REDUCTION of 137 lbs of energy.

I don't use the 120 cause I think it's "better"....nor does the study make me think it's much worse either. I tried the 120's and work good so I've kept shooting them.

At 500 yards I'm my biggest disadvantage......grin.

Thought it was just me.

Googles your friend. Stole from another site, but pretty sure it's been posted here as well.



FWIW, I remember some time back, a poster from TX was switching from using the 120s to the 140s because the 120s didn't open as fast out of his 7mm Rem Mag...

Kaleb, no doubt it's close enough to call awash, no big +/- either way - so I too see them as ballistic twins.

Thanks for the pic, googled this one up to:

http://www.flickr.com/photos/40165144N04/3701055916/

<a href="http://www.flickr.com/photos/40165144N04/3701055916/" title="cross sections by baldhunter, on Flickr"><img src="http://farm3.static.flickr.com/2664/3701055916_058f4ae6f4.jpg" width="500" height="375" alt="cross sections"></a>

The 140 AB looks a little sturdier yet. Nice someone did the sectioning. Re-inforces my pick of the 140 AB. Thanks for the 'google images' reminder

And yet another pic..

http://media.photobucket.com/image/...n/Shooting/120bt150bt140ab168bt180bt.jpg

Yep, looks like the 120 is thicker esp. in the nose to 'control initial expansion' which far better than using say a Vmax...no doubt each having a different intended use. As I said, its no doubt the best pick for say deer in a 120 Cup/core, assuming you are choosing a 120.

Thanks for the viewpoints to all.

Our own experiences are the best teacher. However, it's good to know others get similar results. Dogzapper has posted very good results and I'm a Tim fan, so I'm good to go.

I shoot the 120x....not tsx or ttsx....As with only +/-100 critters, from 265# wt to a 5# nutria, have yet to find a bullet....When I run outta 120x's then I've got 1500-2000 Tsx's to shoot....for my needs the 120's do great....One wt deer took 2 shots to do him in, but that was cuz he was running wide open in front of some dogs and a poor shot was made on the first one...YMMV.....


George

Cliff, my main turn off with the 140NBT is its explosive characteristics when it strikes heavy bone. The 120NBT has proven itself to NOT demonstrate this. Quicker opening than the accubond, yes. But it do penetrate. Double shoulder shot at 225 and it was on its way out. Tad more meat damage than the accubond, but very serviceable. In the 7-08, I have not seen a bullet take a WT off its feet faster than the 120NBT. Now if I'm driving the good ol 280AI, the 140AB is the only bullet I'd consider. And if I were to twist another 7-08AI, I dont know if I'd go 140NAB or 120NBT. My fav in that particular caliber is no longer made. My old 7-08AI had a thing for the 140XLC. 26" tube produced 3185fps with that bullet. No pressure signs but I would not hesitate to agree with anyone that said I got a fast barrel. Was a Douglas on that rifle. But anyway, thats my take on things.

Ramshot Big Game will get you in the 3200 fps. neighborhood with the 120 BT, been discussed at length in the reloading section.