Gemsbok405
03-28-2016, 04:06 PM
Have been a BHP owner for good 40 years, and lately putting some effort to fine tuning accuracy variances. Current pistol is the MK11 with fixed sights and parkerised finish
Best load ever found was some old Hirtenberger 124gr FMJ (RN), and good (POA=POI) for under 2”groups at 10yds off bench.
The worst factory load ever fired was some only S&B 9mm berden primed 115gr FMJ (RN), and which could just keep on an A4 target at 7m! Barrel was very dirty after shooting and could be the rifling cutting through the cupro nickel steel jackets into core?
My old standby CB load was the RCBS 09-124CN and was always good for club social shooting at 7-10m with loads in 1000 fps range. These loads were loaded short relative to throat and sized 0.357”and commercial cast with beeswax lube. For close combat style and steel plate shooting, were good enough.
Had some 115gr swaged bullets 115gr (sized .355) with TL (some form of wax) and leaded something horrible and many went through target sideways!
The latest experiment has been some 123gr commercial CN ( Magma 09-122FP BB / sized .357”), and at the 1000 fps loading were close to point of aim vertical but a consistent 2”left of point of aim. I tried increasing the load to a 1075 fps range and were on POA horizontal, but about 4-5” below POA. These rounds has similar recoil to factory 124gr FMJ ammo.
At the 1100 fps est, and at same 7 metres, started moving left again, but huge vertical spread…about 6” plus. Let other shooters try this load in my BHP and similar story. Leading/fouling at chamber end was minimal (no gas cutting), but more of a wash type of leading/residue at muzzle end. 3-4 strokes with a P/Bronze brush with mc-7 and barrel was clean. No remaining leading smeared into grooves!
But this is where gets interesting, the last (1075+) loads were seated long, with the bullets just off the leade (with drop test for function). My thoughts are that the bullets was lying loose into throat downwards (gravity), and upon ignition, was bounced upwards and bullet engraving slightly off centre in barrel. I.e. base of bullet low in barrel and front band high. With a 4”rifled section of barrel combined with 1:10 twist, the bullet nose would have rotated close to 5.00 O’clock as exits the muzzle. However, it would only stabilize once clear of muzzle and by that point would be closer to say 7 o’clock and POI left of POA.
With the slightly offset nose axis, it would exit the muzzle nose down relative to flight path, and gyro effect would maintain this relationship (nose down). The low impact suggests this is likely scenario. Some of hits, say 2 of 10 would be very low and left and almost off the target.
While many suggest a 1:16 twist is better, and may be all is needed, said twist would cause exit closer to 9.00 O’clock, and would hide problem to a larger extent, but would still be there...
Many on this forum say size to 0.358 for accuracy. A generic Yes, but perhaps this extra diameter fills out the throat, and prevents bullet misalignment as engages throat. Thicker brass cases will also help with alignment and improve accuracy. Also seating short with thicker brass will provide a more liner alignment of bullet into throat as won’t have time for bullet to “bounce” skew. However, with the SAAMI throat angle of 2*, it’s a very easily alignment for the bullet from case to leade, and would not expect much if any ‘tilt’ as bullet enters barrel. A SWC design will prevent the nose ‘bouncing’ the bullet skew…as may happen with a full diameter TC or RN bullet.
A bullet lubed with a carnauba red mix will most likely prevent leading even with a .357 bullet in a .357 bore (Browning is claimed to be 0.3572”groove diameter) due to its high pressure sealing resilience at CB rifle pressures. The 9mm Luger has more in common with a 30k-psi CB rifle load than most handguns in 10-18k-psi loadings. The 30k-psi bump on ignition is also sure to obturate the CB to fully seal the barrel…
A light taper crimp to remove bell and just permit “drop test” would keep bullet in case aligned with throat on ignition. Current case mouth (crimped) is right on 0.380”
A thought as to why as approach the super-sonic velocity level and accuracy sometimes goes to pieces in the 9mmP BHP. Could it be that the laminar flow from a cone (TC) profile separates from the main body at the “kink” at back of cone and end up with a low pressure region around the main body? With the gyro effect and limited pressure on bullet body, could become unstable in flight.
From my limited understanding of supersonic wave forms over foils, if the bullet speed is just below supersonic, there will be a subsonic zone right behind the nose…but with a “truncated cone” and as it stretches back towards the main body, the compressed airflow can accelerate into supersonic range and create a supersonic wave at the join of TC to main body. A supersonic wave at this point will most likely create huge instability on the bullets axis as well as a lack of laminar flow behind and close to the main body of the bullet. This may or may not be a problem? The Magma 122gr bullet (at est. 1100 fps) as detailed above suggests there symptoms may in effect be the cause
The Keith Type SWC with its large front band and recessed nose diameter, will most likely collapse any tendency in the airflow at the back of the nose from accelerating and going supersonic
The 147gr 9mm cast bullets are very long relative to a say 124TC, and with mild nose ogive the airflow is unable to separate…and most always are very accurate.
Most of 357 magnum in cast swc or KT all shoot well in this velocity range, and in say a Colt Python with 1:14 twist at full power have a similar rotational spin as the 9mmP at supersonic level.
I would suggest that the KT front bands “sharp edge” is sufficient to break the laminar flow at this point, and cause airflow to “tumble” (turbulent flow) closer to the bullet body, re-form thereafter into laminar flow and maintain pressure on bullet body and prevent gyro instability… But, even here the odd mould such as Lyman # 357446 SWC does not work at lower velocities as its smaller diameter front band does not collapse the airflow alongside body of bullet until pushing into transitional supersonic velocity ranges…
The 1911 type barrels in 9mmP are usually 1:16 pitch, so have substantially less gyro effect against reduced airflow... and why are much more accurate with a TC bullet, such as the various Lee, Lyman and RCBS CB in 120-124 gr range.
The Lee 9mm -105 SWC shoots well in both 1:10 and 1:16 twists. Perhaps the front band is doing its “magic” here…
There is almost no other SWC moulds in 9mm available, and the ‘odd’ commercial cast versions of the “long nose” H&G 68 styles in 9mm are better suited to velocities well below supersonic and transitional ranges…about 800 to 900 fps max.
The obsolete Lyman 358480 / 133gr SWC has been known for sometimes decent accuracy. Only issue is have to shoot ‘short’ in that much beyond 1.060”COL the front lube groove is exposed. So is unlikely per above to be able to seat out far enough for decent throat engagement. The front band is also substantially shorter than the Mountain Mould “MM” item detailed below…
The Hornady 9mm .356 HAP has many of attributes of the CB CN style bullets. However, most loadings are just under / close to supersonic levels, and may also be impacted by laminar flows on the shoulder. Best accuracy reports have been in the Colt 9mm carbine with velocity levels in 1260 fps (at muzzle) and still just supersonic at 50 yds. At 100 yards, are well below supersonic and accuracy seems to fall off… The said bullet in a .38 super should be a superb performer!
My current experiment is a custom Mountain Moulds 0.357” 125gr SWC Truncated Cone (BR) mould. With a relatively long body and small (full diameter) SWC shoulders, hope to get good alignment when loaded “long”, and with an under-size bore ride shoulder of 0.330 to generate “tumble” of the laminar airflow to keep the gyro effect stable and prevent a supersonic wave forming at the bend from TC to main body. It also has an extra lube groove as many 9mm Lugers lead towards the muzzle, and hope the extra lube will be an improvement here, together with the use of a Carnauba lube. The bullet is very similar to the RCBS 09-124TC profile wise, but with an extended BR shoulder and extra lube groove / body band.
164752
The above is very similar to the Lyman RN item, with its small shoulder and twin lube grooves, but a TC vs. a RN design. Also the TC design has a longer bearing surface…
The bullet, as cast, comes out just at 0.595” LOA, with a 0.240” nose and .100”front band. Seated to 1.050”COL overall, it has a combined nose (with part of front band exposed) of 0.305”, with est. of 0.065 “full diameter” exposed front band engaging the leade. Drop test appears to record light contact of front band into leade, but does not bind. The round chambers nicely when manually rack the slide, but can feel the final engagement as bullet lines up in leade.
Weight without lube with range lead (with some antimony in mix) comes out at 125.5 gr on average. Size as cast is just under 0.358 and after sizing in RCBS (0.357”) lube die comes out close to 0.3572” on average (decent micrometer measures).
It was tested with RCBS green lube as well as Rooster HVR red / carnauba lube
This design and seating depth, should prevent hot high pressure propellant gases from eroding the lube in the transition from throat into barrel…and blowing the lube down the barrel ahead of the bullet!
The COL of 1.050 is same as Winchester silvertip 115gr JHP, and drop test is same headspace as said WW round.
The current load is 4.2 gr of Somchem MP200, similar to Unique…but a bit faster, with Somchem data suggesting about 1000 fps. The factory data is for a cast under-sized bullet @ 0.356” (in BHP) and may have been subject to gas cutting and blow-by in said test data. However, with full size (0.357”) bullet, pressure may be up a small amount...
Somchem recommend a COL with the RCBS 124TC bullet at 1.060 and powder range of 3.9 to 4.4 gr of MP200. The RCBS item is 0.595”, same as the mountain mould design, so in effect are seating the “MM” bullet 0.010 deeper…but still towards bottom of load range!
First test.
Made up 30 pce per above with RCBS green lube and 30 pce with Rooster HVR red carnauba lube.
Brass was once fired S&B. Interesting in that was no case bulge after loading which would suggest that said brass has more internal relief for longer bullets such as various 147gr loads…
The RCBS 9mmP expander plug shows approx. 0.200” parallel section excluding the flare, so is just a bit short for bullets with larger bearing surfaces. Tested some cases with the RCBS 38 spl cowboy expander seated 0.050” deeper into the case and shows a very fine expansion of case ( behind bullet depth) with S&B brass. Similar with vintage HP/Hirtenberger (124gr) brass. Vintage SPEER brass is the thinnest and shows no expansion ring at all. Vintage Norma shows a huge ring as though tapers inside case much sooner than other brands. Will test this cowboy expander at 0.025 deeper as well…
At range loaded up with green lube bullets…and almost every bullet was tumbling sideways through the target at 7m range. After 30 rounds pulled barrel and no leading. Just a bit of antimony wash in barrel. Feeding was fine except for a short stroked round following a weak load. Was loaded with little dandy #7 rotor, but powder was quite an old batch.
Followed up with the carnauba load, and bullets flew straight without fail. After a mag to season barrel with new lube, was grouping 7 of 10 shots 2” low and in line horizontal in a nice 1-1/2” group(standing – not bench shooting).
Another shooter tested with 4 rounds, and 3 almost under ½”with a single “called flyer”
Pulled barrel again, and bore was shiny and clean, the usual appearance after shooting with carnauba lube.
Loads were very similar in recoil to other 1000 fps cb loads and brass landing in a neat pile with the carnauba loads.
The explanation for the softer green lube flyers could be lube “gas blow by” and lower velocity causing unstable flight…long bullet/short nose requiring decent velocity…as with the 357446 bullet detailed earlier. The bullet lube grooves are fairly shallow, compared to lyman RN bullet pic detailed above.
Went back to range last week and fired 10 rounds to ‘season’ barrel with the carnauba lube (Rooster HVR). No tumbles at all and grouping good enough for SD purposes. But the second round of 10 shots tightened the group back into 2”range. Group in vertical plane was a good 2” low at 7m, but horizontal right on.
No FTF at all with this batch.
The BHP MK11, for whatever reason has the back sight mounted lower than front sight by about 0.025” and would explain the POI being below POA. A new rear sight is planned shortly…
Best load ever found was some old Hirtenberger 124gr FMJ (RN), and good (POA=POI) for under 2”groups at 10yds off bench.
The worst factory load ever fired was some only S&B 9mm berden primed 115gr FMJ (RN), and which could just keep on an A4 target at 7m! Barrel was very dirty after shooting and could be the rifling cutting through the cupro nickel steel jackets into core?
My old standby CB load was the RCBS 09-124CN and was always good for club social shooting at 7-10m with loads in 1000 fps range. These loads were loaded short relative to throat and sized 0.357”and commercial cast with beeswax lube. For close combat style and steel plate shooting, were good enough.
Had some 115gr swaged bullets 115gr (sized .355) with TL (some form of wax) and leaded something horrible and many went through target sideways!
The latest experiment has been some 123gr commercial CN ( Magma 09-122FP BB / sized .357”), and at the 1000 fps loading were close to point of aim vertical but a consistent 2”left of point of aim. I tried increasing the load to a 1075 fps range and were on POA horizontal, but about 4-5” below POA. These rounds has similar recoil to factory 124gr FMJ ammo.
At the 1100 fps est, and at same 7 metres, started moving left again, but huge vertical spread…about 6” plus. Let other shooters try this load in my BHP and similar story. Leading/fouling at chamber end was minimal (no gas cutting), but more of a wash type of leading/residue at muzzle end. 3-4 strokes with a P/Bronze brush with mc-7 and barrel was clean. No remaining leading smeared into grooves!
But this is where gets interesting, the last (1075+) loads were seated long, with the bullets just off the leade (with drop test for function). My thoughts are that the bullets was lying loose into throat downwards (gravity), and upon ignition, was bounced upwards and bullet engraving slightly off centre in barrel. I.e. base of bullet low in barrel and front band high. With a 4”rifled section of barrel combined with 1:10 twist, the bullet nose would have rotated close to 5.00 O’clock as exits the muzzle. However, it would only stabilize once clear of muzzle and by that point would be closer to say 7 o’clock and POI left of POA.
With the slightly offset nose axis, it would exit the muzzle nose down relative to flight path, and gyro effect would maintain this relationship (nose down). The low impact suggests this is likely scenario. Some of hits, say 2 of 10 would be very low and left and almost off the target.
While many suggest a 1:16 twist is better, and may be all is needed, said twist would cause exit closer to 9.00 O’clock, and would hide problem to a larger extent, but would still be there...
Many on this forum say size to 0.358 for accuracy. A generic Yes, but perhaps this extra diameter fills out the throat, and prevents bullet misalignment as engages throat. Thicker brass cases will also help with alignment and improve accuracy. Also seating short with thicker brass will provide a more liner alignment of bullet into throat as won’t have time for bullet to “bounce” skew. However, with the SAAMI throat angle of 2*, it’s a very easily alignment for the bullet from case to leade, and would not expect much if any ‘tilt’ as bullet enters barrel. A SWC design will prevent the nose ‘bouncing’ the bullet skew…as may happen with a full diameter TC or RN bullet.
A bullet lubed with a carnauba red mix will most likely prevent leading even with a .357 bullet in a .357 bore (Browning is claimed to be 0.3572”groove diameter) due to its high pressure sealing resilience at CB rifle pressures. The 9mm Luger has more in common with a 30k-psi CB rifle load than most handguns in 10-18k-psi loadings. The 30k-psi bump on ignition is also sure to obturate the CB to fully seal the barrel…
A light taper crimp to remove bell and just permit “drop test” would keep bullet in case aligned with throat on ignition. Current case mouth (crimped) is right on 0.380”
A thought as to why as approach the super-sonic velocity level and accuracy sometimes goes to pieces in the 9mmP BHP. Could it be that the laminar flow from a cone (TC) profile separates from the main body at the “kink” at back of cone and end up with a low pressure region around the main body? With the gyro effect and limited pressure on bullet body, could become unstable in flight.
From my limited understanding of supersonic wave forms over foils, if the bullet speed is just below supersonic, there will be a subsonic zone right behind the nose…but with a “truncated cone” and as it stretches back towards the main body, the compressed airflow can accelerate into supersonic range and create a supersonic wave at the join of TC to main body. A supersonic wave at this point will most likely create huge instability on the bullets axis as well as a lack of laminar flow behind and close to the main body of the bullet. This may or may not be a problem? The Magma 122gr bullet (at est. 1100 fps) as detailed above suggests there symptoms may in effect be the cause
The Keith Type SWC with its large front band and recessed nose diameter, will most likely collapse any tendency in the airflow at the back of the nose from accelerating and going supersonic
The 147gr 9mm cast bullets are very long relative to a say 124TC, and with mild nose ogive the airflow is unable to separate…and most always are very accurate.
Most of 357 magnum in cast swc or KT all shoot well in this velocity range, and in say a Colt Python with 1:14 twist at full power have a similar rotational spin as the 9mmP at supersonic level.
I would suggest that the KT front bands “sharp edge” is sufficient to break the laminar flow at this point, and cause airflow to “tumble” (turbulent flow) closer to the bullet body, re-form thereafter into laminar flow and maintain pressure on bullet body and prevent gyro instability… But, even here the odd mould such as Lyman # 357446 SWC does not work at lower velocities as its smaller diameter front band does not collapse the airflow alongside body of bullet until pushing into transitional supersonic velocity ranges…
The 1911 type barrels in 9mmP are usually 1:16 pitch, so have substantially less gyro effect against reduced airflow... and why are much more accurate with a TC bullet, such as the various Lee, Lyman and RCBS CB in 120-124 gr range.
The Lee 9mm -105 SWC shoots well in both 1:10 and 1:16 twists. Perhaps the front band is doing its “magic” here…
There is almost no other SWC moulds in 9mm available, and the ‘odd’ commercial cast versions of the “long nose” H&G 68 styles in 9mm are better suited to velocities well below supersonic and transitional ranges…about 800 to 900 fps max.
The obsolete Lyman 358480 / 133gr SWC has been known for sometimes decent accuracy. Only issue is have to shoot ‘short’ in that much beyond 1.060”COL the front lube groove is exposed. So is unlikely per above to be able to seat out far enough for decent throat engagement. The front band is also substantially shorter than the Mountain Mould “MM” item detailed below…
The Hornady 9mm .356 HAP has many of attributes of the CB CN style bullets. However, most loadings are just under / close to supersonic levels, and may also be impacted by laminar flows on the shoulder. Best accuracy reports have been in the Colt 9mm carbine with velocity levels in 1260 fps (at muzzle) and still just supersonic at 50 yds. At 100 yards, are well below supersonic and accuracy seems to fall off… The said bullet in a .38 super should be a superb performer!
My current experiment is a custom Mountain Moulds 0.357” 125gr SWC Truncated Cone (BR) mould. With a relatively long body and small (full diameter) SWC shoulders, hope to get good alignment when loaded “long”, and with an under-size bore ride shoulder of 0.330 to generate “tumble” of the laminar airflow to keep the gyro effect stable and prevent a supersonic wave forming at the bend from TC to main body. It also has an extra lube groove as many 9mm Lugers lead towards the muzzle, and hope the extra lube will be an improvement here, together with the use of a Carnauba lube. The bullet is very similar to the RCBS 09-124TC profile wise, but with an extended BR shoulder and extra lube groove / body band.
164752
The above is very similar to the Lyman RN item, with its small shoulder and twin lube grooves, but a TC vs. a RN design. Also the TC design has a longer bearing surface…
The bullet, as cast, comes out just at 0.595” LOA, with a 0.240” nose and .100”front band. Seated to 1.050”COL overall, it has a combined nose (with part of front band exposed) of 0.305”, with est. of 0.065 “full diameter” exposed front band engaging the leade. Drop test appears to record light contact of front band into leade, but does not bind. The round chambers nicely when manually rack the slide, but can feel the final engagement as bullet lines up in leade.
Weight without lube with range lead (with some antimony in mix) comes out at 125.5 gr on average. Size as cast is just under 0.358 and after sizing in RCBS (0.357”) lube die comes out close to 0.3572” on average (decent micrometer measures).
It was tested with RCBS green lube as well as Rooster HVR red / carnauba lube
This design and seating depth, should prevent hot high pressure propellant gases from eroding the lube in the transition from throat into barrel…and blowing the lube down the barrel ahead of the bullet!
The COL of 1.050 is same as Winchester silvertip 115gr JHP, and drop test is same headspace as said WW round.
The current load is 4.2 gr of Somchem MP200, similar to Unique…but a bit faster, with Somchem data suggesting about 1000 fps. The factory data is for a cast under-sized bullet @ 0.356” (in BHP) and may have been subject to gas cutting and blow-by in said test data. However, with full size (0.357”) bullet, pressure may be up a small amount...
Somchem recommend a COL with the RCBS 124TC bullet at 1.060 and powder range of 3.9 to 4.4 gr of MP200. The RCBS item is 0.595”, same as the mountain mould design, so in effect are seating the “MM” bullet 0.010 deeper…but still towards bottom of load range!
First test.
Made up 30 pce per above with RCBS green lube and 30 pce with Rooster HVR red carnauba lube.
Brass was once fired S&B. Interesting in that was no case bulge after loading which would suggest that said brass has more internal relief for longer bullets such as various 147gr loads…
The RCBS 9mmP expander plug shows approx. 0.200” parallel section excluding the flare, so is just a bit short for bullets with larger bearing surfaces. Tested some cases with the RCBS 38 spl cowboy expander seated 0.050” deeper into the case and shows a very fine expansion of case ( behind bullet depth) with S&B brass. Similar with vintage HP/Hirtenberger (124gr) brass. Vintage SPEER brass is the thinnest and shows no expansion ring at all. Vintage Norma shows a huge ring as though tapers inside case much sooner than other brands. Will test this cowboy expander at 0.025 deeper as well…
At range loaded up with green lube bullets…and almost every bullet was tumbling sideways through the target at 7m range. After 30 rounds pulled barrel and no leading. Just a bit of antimony wash in barrel. Feeding was fine except for a short stroked round following a weak load. Was loaded with little dandy #7 rotor, but powder was quite an old batch.
Followed up with the carnauba load, and bullets flew straight without fail. After a mag to season barrel with new lube, was grouping 7 of 10 shots 2” low and in line horizontal in a nice 1-1/2” group(standing – not bench shooting).
Another shooter tested with 4 rounds, and 3 almost under ½”with a single “called flyer”
Pulled barrel again, and bore was shiny and clean, the usual appearance after shooting with carnauba lube.
Loads were very similar in recoil to other 1000 fps cb loads and brass landing in a neat pile with the carnauba loads.
The explanation for the softer green lube flyers could be lube “gas blow by” and lower velocity causing unstable flight…long bullet/short nose requiring decent velocity…as with the 357446 bullet detailed earlier. The bullet lube grooves are fairly shallow, compared to lyman RN bullet pic detailed above.
Went back to range last week and fired 10 rounds to ‘season’ barrel with the carnauba lube (Rooster HVR). No tumbles at all and grouping good enough for SD purposes. But the second round of 10 shots tightened the group back into 2”range. Group in vertical plane was a good 2” low at 7m, but horizontal right on.
No FTF at all with this batch.
The BHP MK11, for whatever reason has the back sight mounted lower than front sight by about 0.025” and would explain the POI being below POA. A new rear sight is planned shortly…