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hungstart, A bullet fired from a 9mm Blackhawk travels through the throat, which is like a bore with no rifling. It then contacts the forcing cone and travels down the bore, just like any other revolver. The length of the throat has very little, if any, influence on accuracy.
I own 2 Blackhawk 357/9mm Convertibles and have tested accuracy with both of them. I used a Browning Hi-Power and a CZ-75b 9mm semi auto pistols in comparison. These two guns are well rated for accuracy in relation to other 9mm pistols. First, 9mm cartridges are not very accurate in any gun. Have you ever seen a match grade 9mm? Neither have I. That said, my 9mm 6 1/2" Blackhawk Convertible is more accurate than either of my 9mm pistols buy a notable amount. With standard 124gr factory loads, my CZ and Browning are hard pressed to shoot groups under 2" at 25 yards. Using the same ammo at the same distance, my 4 5/8" Blackhawk will shoot about 1 1/2" groups but my 6 1/2" 9mm Blackhawk will shoot an inch group at the same distance. 115gr bullets are notably less accurate in both revolvers and pistols. 147gr 9mm bullets are a bit more accurate in both pistols and revolvers.
Here's the kicker ..... both of my Blackhawks will shoot half-inch groups at 25 yards with 38 Special 148gr hollow base wad cutters, which qualifies for "match grade". They will also shoot 1" groups with most jacketed bullets in 38 Special or 357 Mag. When most gun owners run similar tests, they usually come to the same conclusion .... 9mms are just not as accurate. Why?
There are several reasons but the three most important are excessive headspace, rifling twist rate, and bore diameter. You will find most 9mm cases are about .010" shorter than the SAAMI standard to minimize feeding malfunctions. Because 9mm cartridges headspace on the case mouth, short cases will result in excessive headspace .... about .020". This is excessive for any cartridge but especially for cartridges with a tapered case. The reason is simple .... when the cartridge is backed out of the chamber by .020" until it touches the recoil shield, the tapered case and tapered chamber prevents the bullet from aligning perfectly with the throat. This condition is known to damage bullets, which in turn makes them fly a bit goofy. A 38 Special or 357 Mag case has straight walls .... no taper, and will typically have .006" headspace (distance from the case head to the recoil shield). This keeps the bullet in perfect alignment with the cylinder throat and bore and keeps bullet damage to a minimum.
357/9mm Blackhawks have a 1:16 rifling twist rate, which keeps bullet stabilized for a considerable distance. Typical 9mm pistols, such as my CZ or Browning have a much faster 1:10 twist rate. The faster twist rate is needed to maintain stability with 9mm bullets that have very poor ballistic coefficients. So .... when 9mm bullets are fired in a slower twist rate barrel, accuracy is less than stellar, especially at distances longer than 25 yards. Then why is a 9mm cartridge more accurate out of a Blackhawk than a good quality pistol? Primarily, it's the headspace issue.
Bore diameter gets blamed for poor accuracy in a Blackhawk, although being somewhat true, it is the least of your worries. Typical 9mm pistols have a .355" bore whereas a Blackhawk has a .357" bore. The Blackhawk's bore dimensions between lands is about .345" so even a .355" bullet is going to get engraved by rifling (.005" deep per land) but because jacketed bullets don't expand in the bore like lead bullets (called obturation) they don't get as good of a seal in the bore, like .357" jacketed or .358" lead bullets. This coupled with excessive headspace and a slower twist rate will cause something less than optimum accuracy.
So here's my test conclusions for my 4 5/8" and 6 1/2" Blackhawk convertibles. The most accurate in both guns are .358" lead bullets with 148gr LHBWCs being the absolute best. The next most accurate are LRN 158gr bullets in 38 Special. Jacketed bullets in 38 Specials are next followed by jacketed bullets in 357 Mag cases. Last and certainly least are jacketed 9mm bullets .... the lighter the weight, the worse the accuracy. That said, 9mm accuracy in my Blackhawks is still notably better than in a good quality semi-auto pistol. I contribute poor pistol accuracy to sloppy barrel-to-slide fit.
I own 2 Blackhawk 357/9mm Convertibles and have tested accuracy with both of them. I used a Browning Hi-Power and a CZ-75b 9mm semi auto pistols in comparison. These two guns are well rated for accuracy in relation to other 9mm pistols. First, 9mm cartridges are not very accurate in any gun. Have you ever seen a match grade 9mm? Neither have I. That said, my 9mm 6 1/2" Blackhawk Convertible is more accurate than either of my 9mm pistols buy a notable amount. With standard 124gr factory loads, my CZ and Browning are hard pressed to shoot groups under 2" at 25 yards. Using the same ammo at the same distance, my 4 5/8" Blackhawk will shoot about 1 1/2" groups but my 6 1/2" 9mm Blackhawk will shoot an inch group at the same distance. 115gr bullets are notably less accurate in both revolvers and pistols. 147gr 9mm bullets are a bit more accurate in both pistols and revolvers.
Here's the kicker ..... both of my Blackhawks will shoot half-inch groups at 25 yards with 38 Special 148gr hollow base wad cutters, which qualifies for "match grade". They will also shoot 1" groups with most jacketed bullets in 38 Special or 357 Mag. When most gun owners run similar tests, they usually come to the same conclusion .... 9mms are just not as accurate. Why?
There are several reasons but the three most important are excessive headspace, rifling twist rate, and bore diameter. You will find most 9mm cases are about .010" shorter than the SAAMI standard to minimize feeding malfunctions. Because 9mm cartridges headspace on the case mouth, short cases will result in excessive headspace .... about .020". This is excessive for any cartridge but especially for cartridges with a tapered case. The reason is simple .... when the cartridge is backed out of the chamber by .020" until it touches the recoil shield, the tapered case and tapered chamber prevents the bullet from aligning perfectly with the throat. This condition is known to damage bullets, which in turn makes them fly a bit goofy. A 38 Special or 357 Mag case has straight walls .... no taper, and will typically have .006" headspace (distance from the case head to the recoil shield). This keeps the bullet in perfect alignment with the cylinder throat and bore and keeps bullet damage to a minimum.
357/9mm Blackhawks have a 1:16 rifling twist rate, which keeps bullet stabilized for a considerable distance. Typical 9mm pistols, such as my CZ or Browning have a much faster 1:10 twist rate. The faster twist rate is needed to maintain stability with 9mm bullets that have very poor ballistic coefficients. So .... when 9mm bullets are fired in a slower twist rate barrel, accuracy is less than stellar, especially at distances longer than 25 yards. Then why is a 9mm cartridge more accurate out of a Blackhawk than a good quality pistol? Primarily, it's the headspace issue.
Bore diameter gets blamed for poor accuracy in a Blackhawk, although being somewhat true, it is the least of your worries. Typical 9mm pistols have a .355" bore whereas a Blackhawk has a .357" bore. The Blackhawk's bore dimensions between lands is about .345" so even a .355" bullet is going to get engraved by rifling (.005" deep per land) but because jacketed bullets don't expand in the bore like lead bullets (called obturation) they don't get as good of a seal in the bore, like .357" jacketed or .358" lead bullets. This coupled with excessive headspace and a slower twist rate will cause something less than optimum accuracy.
So here's my test conclusions for my 4 5/8" and 6 1/2" Blackhawk convertibles. The most accurate in both guns are .358" lead bullets with 148gr LHBWCs being the absolute best. The next most accurate are LRN 158gr bullets in 38 Special. Jacketed bullets in 38 Specials are next followed by jacketed bullets in 357 Mag cases. Last and certainly least are jacketed 9mm bullets .... the lighter the weight, the worse the accuracy. That said, 9mm accuracy in my Blackhawks is still notably better than in a good quality semi-auto pistol. I contribute poor pistol accuracy to sloppy barrel-to-slide fit.
