BC of the Sierra .277 175gr TGK?

[TRexF16]

Has anyone (Mr. Litz, perhaps?) tested the BC of this bullet? Sierra's published best case G1 of .560 in a 1:8 twist just looks a little conservative for such an extremely long bullet. And they didn't list a G7, which I would figure is the more accurate BC to use if available.
I shot these for the first time today in my 1:8, 24" .270 WSM and it looks promising, but if the BC is really that much worse than the 165 ABLR I don't know how deep into the load work I'll go. 2850+ looks like it's going to be very comfortably achievable, so that's the speed range I'm interested in.

Any help?

Thanks,
Rex

 

[TRexF16]

I guess I'll take that as a "no."

Anyone?

Thanks,
Rex

 

[FEENIX]

Has anyone (Mr. Litz, perhaps?) tested the BC of this bullet? Sierra's published best case G1 of .560 in a 1:8 twist just looks a little conservative for such an extremely long bullet. And they didn't list a G7, which I would figure is the more accurate BC to use if available.
I shot these for the first time today in my 1:8, 24" .270 WSM and it looks promising, but if the BC is really that much worse than the 165 ABLR I don't know how deep into the load work I'll go. 2850+ looks like it's going to be very comfortably achievable, so that's the speed range I'm interested in.

Any help?

Thanks,
Rex

FYSA ...

https://www.longrangehunting.com/threads/277-175-game-changer-tgk.275970/

 

[TRexF16]

Thanks much Feenix. I had read that and everything else I could find online but did not see any reference to any independent testing of Sierra's published BC, nor a reference to a G7 BC.
I'd hoped someone here might have some data on that.
Thanks again,
Rex

 

[TRexF16]

Revisiting this issue since the release of the new Nosler 170 grain .277 BT. Its published G1 BC is .560, exactly the same as the published BC of the 175 Sierra TGK.
I know it's not scientific, but looking at the 170 BT, a .560 G1 looks about right to me. Just as, looking at the 175 TGK, a .560 G1 looks like a VERY conservative number. Now that I have them both in hand I feel even stronger about this.
Look at the pictures fellas - these are the 175 TGK, the 170 BT, and the 165 ABLR. Does anyone think the BC on the TGK and the BT should be the same? BT has a smaller boattail and a blunter ogive (at least to my eye), and of course much shorter OAL.

Is it possible these have the same BC? (I know the answer is to test it myself with drops but I have not yet had that opportunity. My regular range only goes to 200 yards.)

BTW, the TGKs are shooting about 0.5 MOA in my 8" 270 WSM and pressures are quite low at 2850 FPS (65/Magpro, GM215M, 3.00 COAL).

Cheers,
Rex

 

[Lou270]

I suspect it is because the low velocity they tested (around 2k). If you look at the new 140 6.5 it is same. For rounds where they have higher velocity you see a jump above 2600 fps is published bc. FWIW Browning lists .617 for this same bullets and their ammo is at 2835 fps

 

[TRexF16]

I suspect it is because the low velocity they tested (around 2k). If you look at the new 140 6.5 it is same. For rounds where they have higher velocity you see a jump above 2600 fps is published bc. FWIW Browning lists .617 for this same bullets and their ammo is at 2835 fps

Thanks Lou.
Am I reading you right that the "they" in your post is Sierra? If so where did you find the information about testing at 2000 FPS? Was it the following from Sierra's site where they list out the BC and velocity ranges?
.560 @ 1900 fps and above
.530 between 1570 and 1900 fps
.485 @ 1570 fps and below

I'd say Browning's .617 number looks a little closer to what my eyeball suggests, just comparing the 175 TGK to other bullets. I'm shooting these a little over 2850 FPS in my 8" twist 270 WSM, which is pretty mild but accurate.

Thanks again,
Rex

 

[Lou270]

Rex,

Yes, that is where I found it. Anyway that is why I suspect BC are published differently for same bullet.

Lou

 

[TRexF16]

Down there in the fine print, lower left side of the dope table...

 

[257Tony]

Their 7mm 165 TGK is showing as .610 G1, I'm sure the .277 175 would be higher than that.

.284 Cal / 7mm 165 Gr. TGK - Sierra Bullets

Optimal jacket wall thickness controls expansion and retains weight Open pocket under the polymer tip expands lead core instantly on impact Tuned ogive for industry-leading BC Boat tail design for stable flight and accuracy Introducing the Sierra GameChanger hunting bullet: the perfect...

www.sierrabullets.com