120gr Gold Dot Revisited

[Popeye212]

Results from today the temp was between 75 to 80 degrees light or no wind.

20" Ballistic Advantage DMR with Gamma vg65 brake
Aero Precision upper and lower
Athlon Midas BTR 4.5X27
Only one load Chronographed I loaned mine to a guy having trouble with his. Not sure what brand it was so I let him use my Magnetospeed. LOL think I just sold two of em...

Brass pic left to right 27.7,28.0,28.2,28.2

WARNING DO NOT USE ANY OF THESE LOADS AS A STARTING POINT THESE ARE ABOVE MAX PUBLISHED LOADS!!

I am putting these up for discussion. Constructive discussion!

20190726_113548 (2).jpg

120GoldDot820828gr (2).jpg

This group was chronoed and showed POI shift with Magnetospeed attached. Looks I need to revisit this one I think some shooter error is involved as the lateral spread shows. The shakes got me again.

GoldDot120C282P8208. (2).jpg


Synced on: 2019-07-26 09:16:42
Series 120GD2019-07-26_09_16_42 Shots: 5
Notes 28.2 8208xbr
Min 2473 Max 2482
Avg 2476 S-D 3.4
ES 9

Shot Speed
1 2473 ft/s
2 2478 ft/s
3 2482 ft/s
4 2475 ft/s
5 2475 ft/s

Again I started with the Speer Data AND WORKED UP FROM THERE! START WITH THEIR PUBLISHED DATA!!!

[Lemonaid]

Max loads for 120 grain bullets and 8208 xbr

Sierra load data 27.4 max
Speer 25.4 max
Hodgen 28.0 max 50,000 psi
Nosler 27.5 max

Just me, I would heed the 28.0 50,000 psi max.
But some good groups and excellent job on the consistency!

[Popeye212]

Max loads for 120 grain bullets and 8208 xbr

Sierra load data 27.4 max
Speer 25.4 max
Hodgen 28.0 max 50,000 psi
Nosler 27.5 max

Just me, I would heed the 28.0 50,000 psi max.
But some good groups and excellent job on the consistency!

I need to revisit and reshoot that ladder. Brass looks fine, ejection was at 2-3:00. One bent case neck. I think I can do better on those groups the lateral dispersion on the 27.7 and 28.2 were on me and I will chrono the 27.7 for certain. One thing I can't account for is difference in the 120 SMK velocity and the GD. Sierra is 2499@28.0 the GD only gets 2476 with 28.2 where the Sierra is a tad over 2500fps with that charge I think it was about 2515fps. Chalking it up to bullet construction and shape. Thanks for your input.

[Rosecrans1]

Good post. Just a thought...........I would measure the bullet lengths of the 120 SMK and the Gold Dot. If the SMK is a longer projectile than the Gold Dot, it would seat deeper and that would have a pretty profound affect on velocity. Especially at max loads where a longer bullet may be compressing and a shorter bullet may not be. That is if you are keeping the same OAL for both.

[Popeye212]

Good post. Just a thought...........I would measure the bullet lengths of the 120 SMK and the Gold Dot. If the SMK is a longer projectile than the Gold Dot, it would seat deeper and that would have a pretty profound affect on velocity. Especially at max loads where a longer bullet may be compressing and a shorter bullet may not be. That is if you are keeping the same OAL for both.

Good idea I have a fired case I dremeled a slit in the neck I will seat them and compare.

[grayfox]

I need to revisit and reshoot that ladder. Brass looks fine, ejection was at 2-3:00. One bent case neck. I think I can do better on those groups the lateral dispersion on the 27.7 and 28.2 were on me and I will chrono the 27.7 for certain. One thing I can't account for is difference in the 120 SMK velocity and the GD. Sierra is 2499@28.0 the GD only gets 2476 with 28.2 where the Sierra is a tad over 2500fps with that charge I think it was about 2515fps. Chalking it up to bullet construction and shape. Thanks for your input.

Popeye as I recall when I compared the 120 pro hunter, the 120 gold dot, and the 123 class Hornady's in same gun with AR comp (I know diff powder but may still be a point), they all differed somewhat in MV, 2505-ish, 2520, 2540. Bullet specifics, alloy, bearing surface, it all figures in I think.

[Popeye212]

Popeye as I recall when I compared the 120 pro hunter, the 120 gold dot, and the 123 class Hornady's in same gun with AR comp (I know diff powder but may still be a point), they all differed somewhat in MV, 2505-ish, 2520, 2540. Bullet specifics, alloy, bearing surface, it all figures in I think.

I believe you are right. But the data I am getting here is in direct conflict with the Speer reps statement which is a head scratcher also. According to response about the published data being low the rep said the bullet construction lended to higher pressures. Only The Shadow knows the truth... From what I am getting here it's getting about the same as the 120 SMK and the SST. The 123 SST likes 28.2 at 2525fps.

[BobinNC]

Good stuff Popeye and well documented. Thank you.

[Popeye212]

What I didn't show was the loads leading up to these. In my limited experienced I have noticed this about 8208xbr.
1. It does not like low end loads
2. It likes it right at max or just under. Which needs to approached cautiously.
3. Turns out low SD's
YMMV

[grayfox]

I believe you are right. But the data I am getting here is in direct conflict with the Speer reps statement which is a head scratcher also. According to response about the published data being low the rep said the bullet construction lended to higher pressures. Only The Shadow knows the truth... From what I am getting here it's getting about the same as the 120 SMK and the SST. The 123 SST likes 28.2 at 2525fps.

Couple of ideas about the speer rep... 1, they were shooting from their particular barrel so that's all they can speak to.
2, If a bullet has a longer bearing surface or harder alloy, it might mean higher pressure buildup behind it for a given powder charge but it also means more losses to friction and engraving forces... so not always a higher MV. and 3, their lawyers wouldn't let him say much else anyway.
One of the hidden concepts behind MV and pressure is energy losses: how much does bullet speed lose to friction (bullet going going down the pipe), how much is lost to deformation of the bullet (engraving forces of the rifling), and probably a couple other forces at work (twisting torque etc) which siphon off energy out of the gas pressure.... ergo you don't get as much MV out as you thought you would.

[Popeye212]

This pic answers the question for me.
20190726_194923 (2).jpg

[Rosecrans1]

This is why I brought up the length of bullet as a possible cause or contributing cause of the MV difference you observed. The Gold Dots are not as sleek and elongated as other 120 and 123gr bullets I have loaded. My calipers put the 120gr Gold Dot around 1.120".
PS.your observations on 8208xbr are dead on with what I have seen as well!

[Popeye212]

This is why I brought up the length of bullet as a possible cause or contributing cause of the MV difference you observed. The Gold Dots are not as sleek and elongated as other 120 and 123gr bullets I have loaded. My calipers put the 120gr Gold Dot around 1.120".
PS.your observations on 8208xbr are dead on with what I have seen as well!

Another thing that I observed was the boat tail on the Sierra gives more surface area. Similar to the Hemispherical piston theory in a combustion engine giving a larger area for combustion impact... Plus the factors Greyfox brought up all of it together makes sense.

[FLshooter]

I bought 4-50 rd boxes from Midsouth as a consideration for FL hog hunting.I started @ 28g BLC-2.Had it up to 30 g and the velocity was around 2390 out of my Criterion 22” barrel.Accuracy was good.

[plainsman456]

In search of a load that would shoot an inch or better we started with the 110 cc bullets.

Got them doing well then moved on to 120 grain Sierra bullets.

Using Leverevolution powder 31.6 grains i have finally found something that should hammer hogs and shoot good in 3 different rifles.

After reading this work i looked into these bullets and have ordered several boxes.

Did not get the speed yet on the loads of LVR but when we get them i will post.

They shot REAL good.