Range Report G1 vs G7 for 308 SMK 168 grain BTHP

[Gmac]

Just started some long range shooting with my Savage 11 in 308. Long range for me is currently 200-600 yards until I get better. I'm shooting SMK 168 grain exclusively. Rifle seems to like it. My understanding is that G7 ballistics should fit this bullet shape better than G1 but my range data shows otherwise. MV is about 2550 fps. Published BC is 0.462. Groups are tight. I'm shooting < 1 MOA out to 400 yds as long as I do my part. BUT...... G1 calculations fit my drop data MUCH better than G7. Can anyone help me understand why G1 ballistics fit better?
Thanx, Mac

 

[tnichols]

At that distance, both the G1 and G7 will mimic each other, or very close. It’s once you get beyond 700 or so (I picked a random distance) that they will start to separate, and all other factors being equal, the G7 “should” more closely replicate what your seeing on target. The G1 doesn’t recognize the the efficiency of the more modern shape of BTHP projectile. Just my opinion, I’m wrong a lot.

 

[tnichols]

I reread your post, and after thinking about it, I want to add that make sure your input data into the calc is correct when comparing both drag scales. Poor or incorrect data entered can lead to erroneous information.

 

[Gmac]

I reread your post, and after thinking about it, I want to add that make sure your input data into the calc is correct when comparing both drag scales. Poor or incorrect data entered can lead to erroneous information.

I reread your post, and after thinking about it, I want to add that make sure your input data into the calc is correct when comparing both drag scales. Poor or incorrect data entered can lead to erroneous information.

Understand and completely agree. I’m getting repeatable drop data out to 400. Using Nikon’s SpotOn ballistic app. Their G1 and G7 data are significantly different. Using G1 I’m at least hitting paper at 500 and occasionally at 600. Their G7 data show less come ups by 3 and 4 MOA respectively so I don’t even hit paper. Maybe it’s a crappy ballistics calculator??? Haven’t tried others yet. Once I get to 600 I need to look for another range. That’s all the distance they have.

 

[ballison]

Just to be clear, the G1 and G7 values are not interchangeable. If you select G1 in your app, you need to enter the Sierra G1 number. If you select G7, that is a completely different value (prob around .220?). Plugging a G1 number into a G7 calculator will give you bad output

 

[Kobyashi72]

Applied ballistics has this listed as:

.434 G1

.222 G7

Sierra has it listed as:

.447 between 2600 fps - 2100 fps

Which converts to .229 G7

 

[Gmac]

Just to be clear, the G1 and G7 values are not interchangeable. If you select G1 in your app, you need to enter the Sierra G1 number. If you select G7, that is a completely different value (prob around .220?). Plugging a G1 number into a G7 calculator will give you bad output

THANK YOU!! That's new info for me. Didn't know they were different. Had another reply with similar info. Apparently my Nikon SpotOn ballistic app only listed G1 BCs for SMKs and did not label it as such. That's why my drops out to 400 fit better with G1. Coulda saved 50-60 rounds if I'd researched this better. Appreciate the info. I guess it's time to upgrade my ballistics app.

 

[jLorenzo]

THANK YOU!! That's new info for me. Didn't know they were different. Had another reply with similar info. Apparently my Nikon SpotOn ballistic app only listed G1 BCs for SMKs and did not label it as such. That's why my drops out to 400 fit better with G1. Coulda saved 50-60 rounds if I'd researched this better. Appreciate the info. I guess it's time to upgrade my ballistics app.

For what your doing try the free version or Strelok, works very well. Also Shooter is a good one for 10$

 

[jLorenzo]

THANK YOU!! That's new info for me. Didn't know they were different. Had another reply with similar info. Apparently my Nikon SpotOn ballistic app only listed G1 BCs for SMKs and did not label it as such. That's why my drops out to 400 fit better with G1. Coulda saved 50-60 rounds if I'd researched this better. Appreciate the info. I guess it's time to upgrade my ballistics app.

For what your doing try the free version or Strelok, works very well. Also Shooter is a good one for 10$

 

[Deleted member 113831]

THANK YOU!! That's new info for me. Didn't know they were different. Had another reply with similar info. Apparently my Nikon SpotOn ballistic app only listed G1 BCs for SMKs and did not label it as such. That's why my drops out to 400 fit better with G1. Coulda saved 50-60 rounds if I'd researched this better. Appreciate the info. I guess it's time to upgrade my ballistics app.

Strelok Pro is my favorite. $11 I think for iOS. Very easy to navigate, all info is either visible or accessible from the home screen. It also has features like the multi-BC option as well as a huge list of reticles to use when using the scope view to visualize hold over.

 

[Jimgal62]

I find Strelok Pro to be more user friendly.

 

[07jkjeeper]

Applied ballistics has this listed as:

.434 G1

.222 G7

Sierra has it listed as:

.447 between 2600 fps - 2100 fps

Which converts to .229 G7

I've found applied ballistics to be more accurate in some cases. In the 142 LR Nosler Accubond the published info seemed to be way off. Not sure about your particular situation but I would try to track down the most tested BC and then verify.

 

[proftwo]

anybody try the new tipped 168 Sierra? They claim it to be supersonic at 1000 yds.

 

[b6graham]

anybody try the new tipped 168 Sierra? They claim it to be supersonic at 1000 yds.

that's entirely dependent on MV

 

[proftwo]

i am referring to the velocities of ammunition that traditionally use 168 gr,SMK like FGMM. I have no doubt that if it i fired at 3500FPS it will stay supersonic at 1000 yds

 

[isofahunter]

I have just started running 168 tmk in my 308 at 2686 fps: per 4DOF at 1000 it is running 1310fps. I have shot this load to 865 yards so far and the data is true so far IRL. The 168 mk load starting at 2695fps is 1150fps at 1000 and was falling apart, 900 was good but the transition to subsonic was hard on it.

 

[b6graham]

I have just started running 168 tmk in my 308 at 2686 fps: per 4DOF at 1000 it is running 1310fps. I have shot this load to 865 yards so far and the data is true so far IRL. The 168 mk load starting at 2695fps is 1150fps at 1000 and was falling apart, 900 was good but the transition to subsonic was hard on it.

so the added BC does help for you and most people as well. a super low DA may start to mess with it at 1100ish maybe a little sooner

pretty big BC jump over the SMK (168 and 175) and damn close to the 175 TMK somehow

 

[Deleted member 10043]

The 168 SMK is an oddball and was originally designed for 300 yard competition. It is a hot rod but out to 800 it will start crapping out depending on twist and speed. Banded G1 values published by Sierra is what I have used. I have seen a few rifles take it out to 1000. But G1 is your huckleberry for this bullet.

 

[rhsc]

anybody try the new tipped 168 Sierra? They claim it to be supersonic at 1000 yds.

If you don't roll your own, Spark Munitions has a (claimed) fairly hot .308 load topped with the 168gr TMK. Link to their listing here.