Sierra 120 Tipped Gameking

[Bobke]

Grayfox-Your points of impact on the 30.3/30.6/30.9 were all awfully close, suggesting a node. Have you thought about playing with seating depth to see where you optimum accuracy lies. I have four sets of six rounds using CFE, Lever, PPV and AR Comp set at 2.280 OAL to start my testing. Look forward to more of the collective test results.

[grayfox]

Grayfox-Your points of impact on the 30.3/30.6/30.9 were all awfully close, suggesting a node. Have you thought about playing with seating depth to see where you optimum accuracy lies. I have four sets of six rounds using CFE, Lever, PPV and AR Comp set at 2.280 OAL to start my testing. Look forward to more of the collective test results.

Looks like that, but there's 2 reasons why I don't typically trust that:
1. These shots were with a magnetospeed, which does alter the point of impact, although in theory it should do all shots the same way -- sometimes it doesn't.
2. I don't trust my own steadiness enough to rely strictly upon impact points on paper, and these were only 3 shots each anyway. I'm not as rock-solid as some guys on here.

My method uses a different approach, based on Chris Long's OBT theories (appeals to the eng-geek in me).
1. I shoot a few over a spread of charges to establish a chrono-MV ladder vs charge, graphically. If the result is relatively linear then it tells me the powder/combo could be a useable one. (sometimes I have gotten pretty zig-zaggy graphical results from a powder on this step, so I usually move to another powder). I define a "well-behaved" powder as one that shows "pretty much linear" increases in MV for linear increases of powder charge, over a reasonable charge-volume case combo. That's what powder should do anyway!
2. I will shoot a narrower charge spread, with 4-5 per charge, looking for a node close to a mechanical one predicted by Long's theory (longitudinal pressure wave-travel). For a 22" barrel and 120 class bullet in Grendel, this usually means 1 is close to 2520 fps give or take.
3. I pick one from this narrower spread, close to the node, which usually has the lowest or close-to-lowest MV spread in SD. Then shoot these while changing OAL length to find the best group.
4. Then I can zero that group-charge for 100 yds.

[zholley]

The listed BC on the Sierra website remains .466 and they are currently showing in stock if anyone is interested.

I've got some loaded up over TAC and CFE223 and I'm hoping to get them shot this weekend. I'd have to look at my notes, but I did run out of room working to the max load for CFE223. I was definitely compressing powder and then began to have trouble reaching my seating depth. Obviously, I will shoot with caution working through those and I'm worried I may end up pulling some bullets rather than shooting them.

I feel fairly confident in getting good results with TAC either way. If so, I'll load up 50 and hunt with those the next few hunts.

[Popeye212]

Got my 300 today

[grayfox]

Comparing the 123 MK from JBM bullet length values to this new 120, seems the 120 tgk is about 0.012" longer, 1.295 and 1.307 (my measurement on the tgk). So, not considering if the boat tail dimensions throw us off or not, if you load the tgk a bit longer, say +0.012 (ie, 2.272 cp to Sierra's listed 2.260), you should be able to reference the Sierra load listings for that 123 as a guide. I'd expect the actual MVs to be 20-30 fps faster than the 123, but need to factor in any delta's from your barrel to the sierra test barrel.
Also haven't looked lately but I'll bet there is some load data for the 123 smk in the Grendel handbooks too.
So couple of resources there to consider.

[Popeye212]

I read in the Sierra book and recall from elsewhere to use the 123gr data which I have been using for the ProHunter and the match 120.

[koden]

I loaded up 3 more powders for testing this weekend. All of these were loaded to 2.280 and powder was settled in case before seating bullets. Hornady 3x fired brass.

Leverrevolution from 28 to 31.2 (same as CFE) Compressed at max but not bad.

H4895 from 25 to 27.4. slight compression started around 26.6 with 27.4 being pretty compressed but not hard to seat and COAL has not grown since seating. No deformed ring around the nose from seating.

8208 from 25 to 27.4. This powder actually fit well. Its slightly smaller than 4895 and arcomp. 27.4 was the max listed for the 120smk. It was just slightly compressed at max load.

[Bobke]

[Jake TN]

[Timitus]

I made a quick load up for deer season that started for me today. 27.5g of imr 4064 gave me a 5/8 group with an average 2450 fps. While I didn't get a deer today I did bring home some game.20231111_181419.jpg
35 yard shot. DRT. The 120g TGK was a complete pass through after taking out it's neck. Lol
I hope for something bigger tomorrow.

[VASCAR2]

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[Jake TN]

Photos

[koden]

Went to the range today and shot a bunch or powders.

18" John Benjamin barrel with .264lbc chamber
Magnetospeed chronograph

Factory Hornady 123 eldm ammo measured 2391 average of 5 shots which I thought was pretty low velocity even for my 18" barrel and the SD was up around 20. Im wondering if my magnetospeed was having issues today. I may have set it too far away from the bore. Some of the velocities below seem pretty low for the powder.

LVR: 28gr 2278 up to a charge of 31.2gr 2532
CFE223: 28gr 2231 up to a charge of 31.2gr 2441
ARComp: 26gr 2310 up to a charge of 27.1gr 2418
PPV 27gr 2308 up to a charge of 29.6gr 2436 Light ejector swipe on the max charge.
H4895: 25gr 2216 up to a charge of 27.4gr 2441
8208: 25gr 2175 up to a charge of 27.3gr 2401

Other than the max load of PPV there were no pressure signs. I was only shooting for speeds so no accuracy but LVR rounds all went into a pretty good area even though all rounds were different charges.

[zholley]

Timitus, I'm not sure I'd call that a pass through! Little hard to tell from the picture considering the head is just about gone, but I would say that it certainly expanded!

[Timitus]

I harvested a doe yesterday. Here is a break down of how the Sierra 120g TGK performed. The load was 27.5g of IMR 4064, COAL of 2.280 at 2450 fps average from my 22" barrel Ruger American. The doe was shot at 30-40 yards. It was facing the right of me slightly quartering away. Shot entered just behind the right leg. It ran 10-15 yards and piled up. The bullet was a pass through with no bones destroyed. Passed between ribs on both sides of the doe. I found the right front shoulder broken but could see no visible reason. When she was running away after bullet impact I didn't notice her leg not working correctly. The bullet did fragment on impact as I found a couple of 1/8th or smaller pieces. It is possible that I will find more in the broken shoulder later. There was no lung damage that I could find.
bullet entry closeup.jpg Bullet entry.
bullet exit.jpgBullet exited the chest and passed through the off side elbow.
heart bullet path.jpgBullet path through the heart.
heart that shows bullet fragment damage.jpgBullet fragment damage to heart.