Speer Gold Dot Duty Rifle 75gr load?

[ffhounddog]

Doc and Chuck,

Is loading to 5.56 vice .223 really necessary for this round? I know I like speed and a 10.3 inch gun is less barrel but sometimes I have had better accuracy with .223 ammo than I did 5.56 ammo loaded with the same bullet.

[2alpha-down0]

Why do they bother starting with .223 for serious ammo? That never made much sense to me, given that all of the serious AR manufacturers (and even most of the hobbyist guys) do their chambers in 5.56.

They used to load 5.56 Gold Dots; I've got a few mags worth of 55gr for my carbine at the house. The reason they discontinued the 5.56, as I understand it, is because too many people couldn't wrap their heads around the concept that .223 compatibility with 5.56 chambers is a one-way street, and the .223-spec loads perform fine anyway.

[Rich]

Doc in all of your testing of BB 5.56mm and 223rem which load penetrated the most Bare Gel and Auto Glass.

I think I remember seeing a old gel test of the Nosler Partition 62gr in 223rem
BG P= 18 inches
AG P=18
Not bad for a 60year old bullet design

[Sixgun_Symphony]

Doc in all of your testing of BB 5.56mm and 223rem which load penetrated the most Bare Gel and Auto Glass.

I think I remember seeing a old gel test of the Nosler Partition 62gr in 223rem
BG P= 18 inches
AG P=18
Not bad for a 60year old bullet design

I believe the 70gr TSX pens deeper than that.

[BWT]

Doc and Chuck,

Is loading to 5.56 vice .223 really necessary for this round? I know I like speed and a 10.3 inch gun is less barrel but sometimes I have had better accuracy with .223 ammo than I did 5.56 ammo loaded with the same bullet.

I'm not Doc or Chuck (So whoooooa nelly before you take my advice too seriously),

However, in observing this thread over on M4C by Mike Pannone.

I'll give a direct quote,

The addition of 1.5" from the military configuration (14.5"bbl>7.5"tube) over-gassed an already over-gassed design. The 14.5 over gassing was by design for reliability under adverse combat conditions.

http://www.m4carbine.net/showthread....ems-and-the-M4

I believe we're in the same school of thought with 5.56mm versus .223 Rem. The military asked for a higher pressure loading going from 55k PSI of .223 to 62k PSI of 5.56 chamber pressures to promote reliability.

That's it. Accuracy is one of the goals but not before reliability. That's why BH Mk 262 Mod 1 introduced a cannelure into the bullet so it could be crimped in the cartridge. As a side note, I'd be interested to see if that feature came over to the BH 77 gr TMK. They cannelured and crimped the MK 262 Mod 1 not to improve accuracy, but to ensure there wasn't any set back or other issues with the MK 262 Mod 1 not being crimped. Sierra, IIRC, wasn't excited about potentially damaging the accuracy potential of their rounds by introducing a cannelure in the bullet and crimping it in the cartridge.

But, push came to shove and the cartridge was designed with auto-loading weapons in mind and that needed to be done.

http://www.militaryphotos.net/forums...7-grain-5-56mm

That's also why primers are crimped in most 5.56mm loading to more permanently attach the primer, and usually have some kind of sealant to prevent moisture into the cartridge.

We see things like this in military/L.E. Systems.

Now my concern with this 75 gr loading is being a Soft Point, do you still run into leading issues on the M4 Feed ramps.

I'm no SME though.

[Unobtanium]

I'm not Doc or Chuck (So whoooooa nelly before you take my advice too seriously),

However, in observing this thread over on M4C by Mike Pannone.

I'll give a direct quote,



http://www.m4carbine.net/showthread....ems-and-the-M4

I believe we're in the same school of thought with 5.56mm versus .223 Rem. The military asked for a higher pressure loading going from 55k PSI of .223 to 62k PSI of 5.56 chamber pressures to promote reliability.
It was actually to maintain X velocity out to X distance. The same can be seen with the push to drive M855A1 beyond reasonable pressure, which has led to many interesting URG's.

That's it. Accuracy is one of the goals but not before reliability. That's why BH Mk 262 Mod 1 introduced a cannelure into the bullet so it could be crimped in the cartridge. As a side note, I'd be interested to see if that feature came over to the BH 77 gr TMK. They cannelured and crimped the MK 262 Mod 1 not to improve accuracy, but to ensure there wasn't any set back or other issues with the MK 262 Mod 1 not being crimped. Sierra, IIRC, wasn't excited about potentially damaging the accuracy potential of their rounds by introducing a cannelure in the bullet and crimping it in the cartridge.
TMK is crimped.

But, push came to shove and the cartridge was designed with auto-loading weapons in mind and that needed to be done.

http://www.militaryphotos.net/forums...7-grain-5-56mm

That's also why primers are crimped in most 5.56mm loading to more permanently attach the primer, and usually have some kind of sealant to prevent moisture into the cartridge.

We see things like this in military/L.E. Systems.

Now my concern with this 75 gr loading is being a Soft Point, do you still run into leading issues on the M4 Feed ramps.

I'm no SME though.

Allegedly, the Gold dots don't have the leading issue secondary to how little lead is exposed. According to Dr. Roberts, most of the leading came from non-bonded rounds.

[BWT]

Allegedly, the Gold dots don't have the leading issue secondary to how little lead is exposed. According to Dr. Roberts, most of the leading came from non-bonded rounds.

Are you sure about the chamber pressure. What a brief Google search on XM193 chamber pressure indicated was its maximum chamber pressure of tested XM 193 was around 63,000k PSI. Whereas tested .223 was around 50k.

http://www.ar15.com/archive/topic.ht...&f=16&t=244375

I think they switched powder types in early 5.56mm partially to reach that goal, IIRC.

ETA: I may be incorrect, but I didn't think I was.

[Unobtanium]

Are you sure about the chamber pressure. What a brief Google search on XM193 chamber pressure indicated was its maximum chamber pressure of tested XM 193 was around 63,000k PSI. Whereas tested .223 was around 50k.

http://www.ar15.com/archive/topic.ht...&f=16&t=244375

I think they switched powder types in early 5.56mm partially to reach that goal, IIRC.

ETA: I may be incorrect, but I didn't think I was.

Velocity isn't free. Chamber pressure is required to increase barring dimensional changes or technology advancement in propellant to produce said velocity. Think horsepower vs. Fuel consumption at a constant volumetric efficiency.

[BWT]

Velocity isn't free. Chamber pressure is required to increase barring dimensional changes or technology advancement in propellant to produce said velocity. Think horsepower vs. Fuel consumption at a constant volumetric efficiency.

Ah. I think we're talking about two different things.

I'm talking about the early adoption of 5.56mm in traditional cannelure 55 FMJ in M193 format versus .223 Remington 55 FMJ.

You're talking about M855A1.

Standard XM193 is around 62k PSI versus 50-55k of .223 Remington.

So they took the same weight projectile and increased the pressure/velocity of the loading in that instance.

ETA: I'm talking about when the M16 was first accepted and then modified to fit military needs. I may be mistaken about reliability being the only reason. But I do know it played a part.

[Unobtanium]

Ah. I think we're talking about two different things.

I'm talking about the early adoption of 5.56mm in traditional cannelure 55 FMJ in M193 format versus .223 Remington 55 FMJ.

You're talking about M855A1.

Standard XM193 is around 62k PSI versus 50-55k of .223 Remington.

So they took the same weight projectile and increased the pressure/velocity of the loading in that instance.

ETA: I'm talking about when the M16 was first accepted and then modified to fit military needs. I may be mistaken about reliability being the only reason. But I do know it played a part.

Here. This will explain it all.
http://www.thegunzone.com/556dw.html