Post by Bullshop on Apr 27, 2024 16:37:34 GMT -7
Its been kind of slow here on the forum and its raining here so I am going to sit and ramble on a bit about the 300 AAC Blackout. What got me started with it quite late in its game was the desire to add it to our inventory of ammo offered by the Bullshop. What I quickly discovered was that the ammo market for this cartridge is so saturated with so many different types of loads with both sub sonic and supersonic velocities and bullets weights and types that it is very confusing. Adding yet other loads to the glutted market can only confuse it further so I have given up on the idea of selling 300 BO ammo
The thing is that about two years ago I bought a rifle to test ammo with so thought I should at least develop some loads for my own use. Initially I wanted to develop a heavy bullet subsonic load for the market and I did but as I said for people buying their ammo its about impossible to figure out what ammo they need for their intended purpose . The load I initially developed was with a 240 grain custom design exclusive to The Bullshop. It is a smooth side without lube grooves semi round nose boat tail a perfect design for subsonic velocities. The semi round nose keeps the length for weight shorter than the very high BC long pointy bullets. Those types of high BC bullets are designed and intended for high ballistic efficiency at super sonic velocities. The semi round nose of our design is perfect for total subsonic flight.
This bullet drops from the mold at .307" diameter and when powder coated will measure between .308" and .309" . Anyway I partly achieved my goal with that bullet in developing a good accurate subsonic load. The market thingy part failed. I should give a little better description of this bullet. It has a short ogive ending in what I will call semi round nose meaning its close to a spitzer nose shape but not quite but the not a blunt round nose either so semi round nose or semi spitzer if you prefer. The bulk of its length is bearing surface ending at its base with a gentle angle boat tail.
As cast it required such deep seating that the 300 AAC case ran out of room for powder. Enter the nose die ! Too many years ago to remember I had a nose sizing die made to size 30 cal bullet noses to .301" diameter to aid in chambering bullets with over size nose diameter. This gave some versatility to a lot of other 30 cal molds for bullet seating depth. That covers a lot of ground and I wont even try to get into that here but will say that the nose die mated with this bullet design makes this bullet a perfect fit for any 30 caliber cartridge. In effect it allows the bullet bearing length to be adjusted to perfectly fit any case neck length. In this case for the 300 BO the bearing length the .308" part is adjusted to put the bullet base exactly at the base of the case neck with no bullet protruding into the powder volume of the case.
Its allows a perfect fit no matter the 30 caliber cartridge. Another positive point about this bullet design and another point where the semi round nose shape comes into play it that it keeps the total bullet length much shorter that if it were a high BC long pointy design. The difference is that the hugh BC design requires a faster than standard rifling twist rate which in 30 caliber is 10". This heavy for caliber 240 grain bullet will stabilize in the 30 cal standard 10" twist where the long high BC bullets being used in the 300 BO for long range sub sonic loads require a much faster twist which for the 300 BO is 7" With our design you can so to speak have your cake and eat it too in that it gives the low drag subsonic performance but is usable in most any vintage of 30 caliber rifle once the bearing length is adjusted to fit the case neck length of the cartridge being used.
Wow it looks like I may have strayed from my intended 300 BO thread into a custom bullet design thread. Let me try to fix that. This week end since I had a birth day I took an extra day off and just fiddles with the Ruger American 300 BO just for fun and also to develop some usable loads for my own use. Since I have the rifle why not right. I had kind of abandoned it after deciding there was no ammo market there for us and its been sitting for a couple years. Actually for a cast bullet shooter its quite an interesting cartridge delivering good performance with a very modest appetite for powder.
The cartridge does present a rather unique challenge in developing top end loads for the cartridge with cast bullets. It combines a rather small case volume with a very fast for caliber rifling twist rate. That 7" rifling twist rate is very torquey when approaching top end pressures for the cartridge which can exceed 50,000 psi. Combine that with the slight case volume which dictates rather fast burning rifle powder and you have a classic catch 22 situation in which when you gain at one end you loose at the other.
I watched a bunch of youtube videos and all use book recommended powders the center of which is at about H-110 in burn rate. These type of powders that I will call magnum hand gun powders work great when pushed to their optimum pressure window which is always near top end for pressure. That is great when trying to push the little cartridge to its limit but when your trying to cut that top end velocity nearly in half to produce a subsonic load the very same powders are also listed in load manuals. Truth is it cant work well both ways.
From watching the youtube vids I see most are shooting at 25 or 50 yards. Most dont show targets but those that do ar in my opinion rather poor for such close range. Some show 2 to 3" groups at 25 yards which for me is totally unacceptable. The issue I believe is that much faster burning powders than those listed for subsonic loads are needed. To find the perfect burn rate for best ballistic uniformity for subsonic loads in the 300 BO will take me some time but at least in my long week end I believe I have a foot in the door.
For a subsonic load that stays inside the two inch mark at 100 yards this week ends effort produced this load,
case - PMC 223 reformed
bullet - Accurate molds 215gn FN-PB BHN-20 .308" diameter Lotak lube
primer - CCI # 500 SP
powder- 3.5gn IMR high score 800 X
That subsonic load turned in excellent results for accuracy and penetration at 100 yards. I started the load development at 4 gn but some shots were producing the supersonic crack and the barrel was beginning the get grey streaking showing about the limit for the plain base bullet. Backing down to 3,5gn eliminated the streaking in the barrel as well as the occasional supersonic crack. Repeated shooting with this load showed very consistent accuracy. A simple penetration test was to put a dry pine log at 100 yards and shoot into it end grain. End grain is harder to penetrate than cross grain. At 100 yards this load penetrated 8 7/8" into the dry pine end grain. Maybe it doesn't sound like much but a factory 30-06 with 180gn soft points will not go much farther if at all. Granted to 30-06 shreds a lot of wood from entry to stopping where as the 300 BO just made a 30 cal hole but the Accurate Molds bullet have a fairly large for caliber meplate should perform well on animal tissie well beyond what its slight velocity might indicate. I hope to fine out. Might be a perfect load to use for deer from the reapers roost where shots are short and head shots the rule.
Having time with the extended week end I also wanted to do something I had not yet done with this cartridge which is to work up top end loads with both heavy and light weight cast bullets. That endeavor was also a success so I will also list those loads.
case - PMC 223 reformed
bullet Lee 118gn FN-GC
primer - CCI #400
powder - 15.7gn Ramshot Enforcer
case - PMC 223 reformed
bullet - RCBS 30-180 .310"
primer - CCI # 450 SRM
powder - 15.6gn WC-842
Note that the top end loads with the slower powders required hotter primers for best ignition.
So that is it for this week end. I feel good with that like I have accomplished something. It has also sparked an appreciation for the little cartridge that can offer a lot of shooting with a range of different type of loads at little cost. At first when it came out and was all the rage I didn't know what all the tado was about but now I am beginning to see it really is a neat little cartridge rivaling the 30-30 at its top end able to duplicate cartridges like the 32 S&W at its low end but at its middle performance range able to accurately deliver a heavy for caliber projectile in near total silence.
The thing is that about two years ago I bought a rifle to test ammo with so thought I should at least develop some loads for my own use. Initially I wanted to develop a heavy bullet subsonic load for the market and I did but as I said for people buying their ammo its about impossible to figure out what ammo they need for their intended purpose . The load I initially developed was with a 240 grain custom design exclusive to The Bullshop. It is a smooth side without lube grooves semi round nose boat tail a perfect design for subsonic velocities. The semi round nose keeps the length for weight shorter than the very high BC long pointy bullets. Those types of high BC bullets are designed and intended for high ballistic efficiency at super sonic velocities. The semi round nose of our design is perfect for total subsonic flight.
This bullet drops from the mold at .307" diameter and when powder coated will measure between .308" and .309" . Anyway I partly achieved my goal with that bullet in developing a good accurate subsonic load. The market thingy part failed. I should give a little better description of this bullet. It has a short ogive ending in what I will call semi round nose meaning its close to a spitzer nose shape but not quite but the not a blunt round nose either so semi round nose or semi spitzer if you prefer. The bulk of its length is bearing surface ending at its base with a gentle angle boat tail.
As cast it required such deep seating that the 300 AAC case ran out of room for powder. Enter the nose die ! Too many years ago to remember I had a nose sizing die made to size 30 cal bullet noses to .301" diameter to aid in chambering bullets with over size nose diameter. This gave some versatility to a lot of other 30 cal molds for bullet seating depth. That covers a lot of ground and I wont even try to get into that here but will say that the nose die mated with this bullet design makes this bullet a perfect fit for any 30 caliber cartridge. In effect it allows the bullet bearing length to be adjusted to perfectly fit any case neck length. In this case for the 300 BO the bearing length the .308" part is adjusted to put the bullet base exactly at the base of the case neck with no bullet protruding into the powder volume of the case.
Its allows a perfect fit no matter the 30 caliber cartridge. Another positive point about this bullet design and another point where the semi round nose shape comes into play it that it keeps the total bullet length much shorter that if it were a high BC long pointy design. The difference is that the hugh BC design requires a faster than standard rifling twist rate which in 30 caliber is 10". This heavy for caliber 240 grain bullet will stabilize in the 30 cal standard 10" twist where the long high BC bullets being used in the 300 BO for long range sub sonic loads require a much faster twist which for the 300 BO is 7" With our design you can so to speak have your cake and eat it too in that it gives the low drag subsonic performance but is usable in most any vintage of 30 caliber rifle once the bearing length is adjusted to fit the case neck length of the cartridge being used.
Wow it looks like I may have strayed from my intended 300 BO thread into a custom bullet design thread. Let me try to fix that. This week end since I had a birth day I took an extra day off and just fiddles with the Ruger American 300 BO just for fun and also to develop some usable loads for my own use. Since I have the rifle why not right. I had kind of abandoned it after deciding there was no ammo market there for us and its been sitting for a couple years. Actually for a cast bullet shooter its quite an interesting cartridge delivering good performance with a very modest appetite for powder.
The cartridge does present a rather unique challenge in developing top end loads for the cartridge with cast bullets. It combines a rather small case volume with a very fast for caliber rifling twist rate. That 7" rifling twist rate is very torquey when approaching top end pressures for the cartridge which can exceed 50,000 psi. Combine that with the slight case volume which dictates rather fast burning rifle powder and you have a classic catch 22 situation in which when you gain at one end you loose at the other.
I watched a bunch of youtube videos and all use book recommended powders the center of which is at about H-110 in burn rate. These type of powders that I will call magnum hand gun powders work great when pushed to their optimum pressure window which is always near top end for pressure. That is great when trying to push the little cartridge to its limit but when your trying to cut that top end velocity nearly in half to produce a subsonic load the very same powders are also listed in load manuals. Truth is it cant work well both ways.
From watching the youtube vids I see most are shooting at 25 or 50 yards. Most dont show targets but those that do ar in my opinion rather poor for such close range. Some show 2 to 3" groups at 25 yards which for me is totally unacceptable. The issue I believe is that much faster burning powders than those listed for subsonic loads are needed. To find the perfect burn rate for best ballistic uniformity for subsonic loads in the 300 BO will take me some time but at least in my long week end I believe I have a foot in the door.
For a subsonic load that stays inside the two inch mark at 100 yards this week ends effort produced this load,
case - PMC 223 reformed
bullet - Accurate molds 215gn FN-PB BHN-20 .308" diameter Lotak lube
primer - CCI # 500 SP
powder- 3.5gn IMR high score 800 X
That subsonic load turned in excellent results for accuracy and penetration at 100 yards. I started the load development at 4 gn but some shots were producing the supersonic crack and the barrel was beginning the get grey streaking showing about the limit for the plain base bullet. Backing down to 3,5gn eliminated the streaking in the barrel as well as the occasional supersonic crack. Repeated shooting with this load showed very consistent accuracy. A simple penetration test was to put a dry pine log at 100 yards and shoot into it end grain. End grain is harder to penetrate than cross grain. At 100 yards this load penetrated 8 7/8" into the dry pine end grain. Maybe it doesn't sound like much but a factory 30-06 with 180gn soft points will not go much farther if at all. Granted to 30-06 shreds a lot of wood from entry to stopping where as the 300 BO just made a 30 cal hole but the Accurate Molds bullet have a fairly large for caliber meplate should perform well on animal tissie well beyond what its slight velocity might indicate. I hope to fine out. Might be a perfect load to use for deer from the reapers roost where shots are short and head shots the rule.
Having time with the extended week end I also wanted to do something I had not yet done with this cartridge which is to work up top end loads with both heavy and light weight cast bullets. That endeavor was also a success so I will also list those loads.
case - PMC 223 reformed
bullet Lee 118gn FN-GC
primer - CCI #400
powder - 15.7gn Ramshot Enforcer
case - PMC 223 reformed
bullet - RCBS 30-180 .310"
primer - CCI # 450 SRM
powder - 15.6gn WC-842
Note that the top end loads with the slower powders required hotter primers for best ignition.
So that is it for this week end. I feel good with that like I have accomplished something. It has also sparked an appreciation for the little cartridge that can offer a lot of shooting with a range of different type of loads at little cost. At first when it came out and was all the rage I didn't know what all the tado was about but now I am beginning to see it really is a neat little cartridge rivaling the 30-30 at its top end able to duplicate cartridges like the 32 S&W at its low end but at its middle performance range able to accurately deliver a heavy for caliber projectile in near total silence.
