75 grain Speer Gold Dot gas drive

[Disciple]

I havent shot 64gr Gold Dots for a long time but the 75gr's have a weird pressure curve, it ejected more like 5.56 than .223 even with an A5 system.

The 75gr Gold Dot is the most violently cycling round I have ever fired, including:

IMI 77gr
Hornady T2
70gr Browntip (clocked 2900fps from my 16" gun)
M855A1 (averaged around 3040ish from my 16" gun)
M855
All the other Gold Dots
77gr TMK

75gr Gold Dot kicked harder, and cycled the action more briskly than any of the others. If your gun will only run ONE round because it's so undergassed or you keep turning the gas-block adjustment down, it's likely to be the 75gr GDSP, lol!

How does this work? If an unusually slow burning powder is used why isn't there more difference in velocity between 16" and 20" barrels? What else would increase peak pressure or duration at the gas port compared to other 70+ grain loads?


https://www.youtube.com/watch?v=QswX2r6PcxM

16" barrel average: 2,587 fps

20" barrel average: 2,633 fps

[opngrnd]

This has intrigued me as well. Hopefully someone chimes in.

[fz1boxer]

where is the original thread that vicious and WS6 were replying to?

[Disciple]

where is the original thread that vicious and WS6 were replying to?

See the little blue >> arrow icon () next to the names? Click one of those and it will take you to the original post in context.

[gaijin]

The 10.5” reading seemed abnormally slow. Both of my 11.5” guns run 2400+- FPS with 75 gr. G. D.
Looks as though Speer was attempting to dial in powder/load to optimize in a 14.5”- 16” barrel in view of what looked to be just 20 FPS per inch velocity gain with the 20”/additional 4” of barrel.
My assumption would indicate a fairly fast powder.

Might look at this:
https://youtu.be/2lkI36eUoy4

[fz1boxer]

Thanks I need to get some Speer and hornady black 75 grain,shoot both and see if I can tell any difference.

[vicious_cb]

The 10.5” reading seemed abnormally slow. Both of my 11.5” guns run 2400+- FPS with 75 gr. G. D.
Looks as though Speer was attempting to dial in powder/load to optimize in a 14.5”- 16” barrel in view of what looked to be just 20 FPS per inch velocity gain with the 20”/additional 4” of barrel.
My assumption would indicate a fairly fast powder.

Might look at this:
https://youtu.be/2lkI36eUoy4

Both Speer and Hornady are running some kind of "SBR" optimized powder.

[fz1boxer]

Molon's chart tells me hornady and speer need to get on the same page on what they are labeling 5.56.

[gaijin]

Both Speer and Hornady are running some kind of "SBR" optimized powder.

Good info, I imagined something like this in view of performance.

[ggammell]

Both Speer and Hornady are running some kind of "SBR" optimized powder.

That’s not going happen. Speer is in the business of selling to LE agencies and has to stay at .223 pressure because of all of the agency issues .223 rifles out there. They had a 5.56 round once and discontinued it. Too many people doing the buying don’t understand the difference. Hornady is gonna Hornady.