constructor
05-27-15, 08:33
This is only to show max loads- any load between 58-60k should be considered max. Start 1.5-2gr lower and work up while looking for accuracy.
120SST---------2.3"OAL-- IMO apx 30-31gr is max fill for ball powders and the 120 sst loaded to 2.295
For that reason CFE, Lever, 2520 and 748 are too slow.
This test run with an 18" 5R barrel, pressure could be higher with 6 groove barrels or with barrel made with a higher land -groove ratio/smaller bore area.
33gr Lever-2497fps and 49201psi-compressed max fill
31gr 8208-2558fps and 56923psi-compressed max fill
31gr H335-2542fps and 57091psi
30gr Xterm-2506fps and 57279psi
33gr 2520-2584fps and 54789psi-compressed max fill
28.2gr 2200-2609 and 57312psi
29gr 2200-2652fps and 59778psi
29gr 1200R-2597fps and 59703psi
27.5gr Norma200-2536 and 58060psi
29.5 N530-2612fps and 57kpsi
28.2gr 10X-2561 and 55900psi
95gr TTSX-Top performing powders, any slower burning powders will produce less velocity
29.5gr 2200-2801fps-54260psi--28.5gr has shown to be accurate with the 95TTSX and 110gr bullets. est pressure 51500psi
30.5gr 2200-2889fps-57928psi
30.5gr RE7-2905fps-58100psi
29gr Norma 200-2819fps-55052psi
29.gr Norma 200-2862fps-57954psi
30gr N530-2709fps-50974psi
27.8gr 1680-2854-58163psi
85TSX---Top performing powders, any slower burning powders will produce less velocity
1680-30gr-3047-56728psi
2200-32gr-2994fps-53313psi
Norma 200-31.5gr-2993fps-53348psi-max fill
RE7-31gr-2945fps-53436psi-max fill
6.8 data-
Take a look at page 14 of the Accurate Arms load data for the 6.8. It shows 28.6gr AA2200 with a 110 HPBT creates 57,900psi and pushes the bullet to 2657fps from a 20" barrel.
Page14 6.8 data---- http://www.accuratepowder.com/wp-con...d_data_3.5.pdf
ACCURATE 2200
85 BARNES MPG--------28.0 2,737 ----31.1 3,020 54,997 2.235
90 SIERRA HP ----------28.2 2,699 ----31.4 2,988 58,481 2.260
95 BARNES TTSX------ 27.1 2,626 -----30.2 2,915 57,953 2.260
110 HDY HP ------------25.7 2,410----- 28.6 2,685 57,899 2.260
110 HDY V-MAX------- 25.7 2,439 ------28.6 2,711 58,020 2.260
110 SIERRA SPT PH --26.1 2,454-------29.0 2,685 58,410 2.260
115 SIERRA HPBT MK 25.2 2,372-------28.0 2,614 58,221 2.260
120 HDY SST ---------24.5 2,289 -------27.2 2,543 58,500 2.260
130 NOSLER B-TIP--- 24.2 2,205-------26.9 2,434 54,333 2.260
140 NOSLER B-TIP--- 23.0 2,094-------25.6 2,298 53,506 2.260
140 SIERRA HPBT GK 23.4 2,128.------26.0 2,342 58,293 2.260
That should be a reference point everyone can use. That load when used with Hornady or SSA brass and CCI450 or CCI41 primers will not flatten or crater at that pressure UNLESS the shoulder of the resized case has been pushed back too far and there is excessive headspace because of it.
I have been saying primers do not crater and brass does not flow into the ejector hole until apx 58,000 since the 2008 performance report below. If you look through the report you will see the primers are all CCI41 and look normal until they pass that 58,000 psi level. At apx 62,000 psi the primers are blown from the cases. At 70,000 psi the base of the case is swelled to look like a belted magnum. I read primers to tell me when the primers are about to fail. If using CCI400 primers they will fail at a much lower pressure. It doesn't matter what the case, bolt or rifle can handle if the primers are failing, the primers will always fail first. CCI 450s and CCI41s will crater between 58 and 60k in an AR15. That little hole in the bolt face is just about the best gauge we can use. Peak pressure on the inside of the primer trying to push a constant thickness metal through a constant size hole.
Today I pulled out the pressure trace system after not using it on a 6.8 barrel in years(results above). Went through the normal calibration steps and checked it against that 28.6gr 2200 load. The pressure read 57,114 and 2665fps from an 18" barrel. IMO dead on what it should be for a high performance chamber VS the SAAMI spec chamber. These are the loads, velocities and pressure obtained from an ARP 5R barrel. Using a barrel with 6 grooves and a 50:50 L-G ratio could raise pressures by 3-4000psi.
That should give everyone a rough idea of what pressures are with some of the heavy loads.
Reviewing the traces shows a secondary pressure spike when using CFE and Lever. That spike is a result of the bullet out running the powder...the powder is too slow.
8208, H335 and the 2200 does not show a secondary spike. 2520 shows a broad peak and good trace. Lots of area under the curve explains why it produces good velocity at a lower peak pressure. IMO 8208 is likely the best burn rate for the 130gr bullets but the case may not be large enough to get peak velocity.
The secondary pressure spike near the muzzle may decrease accuracy.
With every increase of 1 gr of powder I see from 50-90fps and apx 3000-3500psi.
Velocity is not a product of peak pressure but the area under the curve. Peak pressure is an important part but not the ONLY part. Peak pressure happens during the first few inches of bullet travel. The freebore and engraving force (depending on hardness of alloy and shape/ratio of the lands) and forcing cone angle can effect the peak pressure and pressure curve. Barrels that have a 50:50 l-G ratio like the old 6 groove barrels will have a higher engraving force than barrels with a 25:75 ratio.
The effects of engraving force and bore area on pressure-
http://www.dtic.mil/dtic/tr/fulltext/u2/a431357.pdf
CONCLUSIONS
1. The baseline heptagonal barrel will exhibit peak chamber pressures about 15 to 20%
higher than the same cartridge loaded in a standard M240 barrel. This is due primarily to
the increased resistance pressure early in the in bore travel of the projectile.
2. The increase in peak chamber pressure could be reduced by either increasing the free run
of the projectile prior to the start of engraving or by reducing the forcing cone angle in the
barrel.
3. A slight decrease in resistance force was observed for the 2.5 deg half angle forcing cone
compared to the 1.2 deg half angle forcing cone found on the M240 barrel baseline. It is
believed this difference is due to a reduction in the plastic deformation of the M80
projectile in the 1.2 deg barrel.
4. The addition of lubrication to the M80 projectile exterior increased the engraving force in
the baseline M240 barrel with 1.2 deg half angle forcing cone, while it decreases the
engraving forces in the 2.5 deg half angle forcing cone barrel. Likewise the push force
standard deviation increased with lubrication in the 1.2 deg half angle forcing cone, and
decreased in the 2.5 deg half angle forcing cone.
5. Projectile construction and elastic modulus appear to play significant roles in the
resistance pressure of small caliber projectiles.
Thermal hog hunt video-https://www.youtube.com/watch?featur...&v=jfAWKfYsUUY
120SST---------2.3"OAL-- IMO apx 30-31gr is max fill for ball powders and the 120 sst loaded to 2.295
For that reason CFE, Lever, 2520 and 748 are too slow.
This test run with an 18" 5R barrel, pressure could be higher with 6 groove barrels or with barrel made with a higher land -groove ratio/smaller bore area.
33gr Lever-2497fps and 49201psi-compressed max fill
31gr 8208-2558fps and 56923psi-compressed max fill
31gr H335-2542fps and 57091psi
30gr Xterm-2506fps and 57279psi
33gr 2520-2584fps and 54789psi-compressed max fill
28.2gr 2200-2609 and 57312psi
29gr 2200-2652fps and 59778psi
29gr 1200R-2597fps and 59703psi
27.5gr Norma200-2536 and 58060psi
29.5 N530-2612fps and 57kpsi
28.2gr 10X-2561 and 55900psi
95gr TTSX-Top performing powders, any slower burning powders will produce less velocity
29.5gr 2200-2801fps-54260psi--28.5gr has shown to be accurate with the 95TTSX and 110gr bullets. est pressure 51500psi
30.5gr 2200-2889fps-57928psi
30.5gr RE7-2905fps-58100psi
29gr Norma 200-2819fps-55052psi
29.gr Norma 200-2862fps-57954psi
30gr N530-2709fps-50974psi
27.8gr 1680-2854-58163psi
85TSX---Top performing powders, any slower burning powders will produce less velocity
1680-30gr-3047-56728psi
2200-32gr-2994fps-53313psi
Norma 200-31.5gr-2993fps-53348psi-max fill
RE7-31gr-2945fps-53436psi-max fill
6.8 data-
Take a look at page 14 of the Accurate Arms load data for the 6.8. It shows 28.6gr AA2200 with a 110 HPBT creates 57,900psi and pushes the bullet to 2657fps from a 20" barrel.
Page14 6.8 data---- http://www.accuratepowder.com/wp-con...d_data_3.5.pdf
ACCURATE 2200
85 BARNES MPG--------28.0 2,737 ----31.1 3,020 54,997 2.235
90 SIERRA HP ----------28.2 2,699 ----31.4 2,988 58,481 2.260
95 BARNES TTSX------ 27.1 2,626 -----30.2 2,915 57,953 2.260
110 HDY HP ------------25.7 2,410----- 28.6 2,685 57,899 2.260
110 HDY V-MAX------- 25.7 2,439 ------28.6 2,711 58,020 2.260
110 SIERRA SPT PH --26.1 2,454-------29.0 2,685 58,410 2.260
115 SIERRA HPBT MK 25.2 2,372-------28.0 2,614 58,221 2.260
120 HDY SST ---------24.5 2,289 -------27.2 2,543 58,500 2.260
130 NOSLER B-TIP--- 24.2 2,205-------26.9 2,434 54,333 2.260
140 NOSLER B-TIP--- 23.0 2,094-------25.6 2,298 53,506 2.260
140 SIERRA HPBT GK 23.4 2,128.------26.0 2,342 58,293 2.260
That should be a reference point everyone can use. That load when used with Hornady or SSA brass and CCI450 or CCI41 primers will not flatten or crater at that pressure UNLESS the shoulder of the resized case has been pushed back too far and there is excessive headspace because of it.
I have been saying primers do not crater and brass does not flow into the ejector hole until apx 58,000 since the 2008 performance report below. If you look through the report you will see the primers are all CCI41 and look normal until they pass that 58,000 psi level. At apx 62,000 psi the primers are blown from the cases. At 70,000 psi the base of the case is swelled to look like a belted magnum. I read primers to tell me when the primers are about to fail. If using CCI400 primers they will fail at a much lower pressure. It doesn't matter what the case, bolt or rifle can handle if the primers are failing, the primers will always fail first. CCI 450s and CCI41s will crater between 58 and 60k in an AR15. That little hole in the bolt face is just about the best gauge we can use. Peak pressure on the inside of the primer trying to push a constant thickness metal through a constant size hole.
Today I pulled out the pressure trace system after not using it on a 6.8 barrel in years(results above). Went through the normal calibration steps and checked it against that 28.6gr 2200 load. The pressure read 57,114 and 2665fps from an 18" barrel. IMO dead on what it should be for a high performance chamber VS the SAAMI spec chamber. These are the loads, velocities and pressure obtained from an ARP 5R barrel. Using a barrel with 6 grooves and a 50:50 L-G ratio could raise pressures by 3-4000psi.
That should give everyone a rough idea of what pressures are with some of the heavy loads.
Reviewing the traces shows a secondary pressure spike when using CFE and Lever. That spike is a result of the bullet out running the powder...the powder is too slow.
8208, H335 and the 2200 does not show a secondary spike. 2520 shows a broad peak and good trace. Lots of area under the curve explains why it produces good velocity at a lower peak pressure. IMO 8208 is likely the best burn rate for the 130gr bullets but the case may not be large enough to get peak velocity.
The secondary pressure spike near the muzzle may decrease accuracy.
With every increase of 1 gr of powder I see from 50-90fps and apx 3000-3500psi.
Velocity is not a product of peak pressure but the area under the curve. Peak pressure is an important part but not the ONLY part. Peak pressure happens during the first few inches of bullet travel. The freebore and engraving force (depending on hardness of alloy and shape/ratio of the lands) and forcing cone angle can effect the peak pressure and pressure curve. Barrels that have a 50:50 l-G ratio like the old 6 groove barrels will have a higher engraving force than barrels with a 25:75 ratio.
The effects of engraving force and bore area on pressure-
http://www.dtic.mil/dtic/tr/fulltext/u2/a431357.pdf
CONCLUSIONS
1. The baseline heptagonal barrel will exhibit peak chamber pressures about 15 to 20%
higher than the same cartridge loaded in a standard M240 barrel. This is due primarily to
the increased resistance pressure early in the in bore travel of the projectile.
2. The increase in peak chamber pressure could be reduced by either increasing the free run
of the projectile prior to the start of engraving or by reducing the forcing cone angle in the
barrel.
3. A slight decrease in resistance force was observed for the 2.5 deg half angle forcing cone
compared to the 1.2 deg half angle forcing cone found on the M240 barrel baseline. It is
believed this difference is due to a reduction in the plastic deformation of the M80
projectile in the 1.2 deg barrel.
4. The addition of lubrication to the M80 projectile exterior increased the engraving force in
the baseline M240 barrel with 1.2 deg half angle forcing cone, while it decreases the
engraving forces in the 2.5 deg half angle forcing cone barrel. Likewise the push force
standard deviation increased with lubrication in the 1.2 deg half angle forcing cone, and
decreased in the 2.5 deg half angle forcing cone.
5. Projectile construction and elastic modulus appear to play significant roles in the
resistance pressure of small caliber projectiles.
Thermal hog hunt video-https://www.youtube.com/watch?featur...&v=jfAWKfYsUUY