1/30/2024 0 Comments Subsonic 223 recipesThe info indicated that if fillers are used (especially on these types of marginal loads) then all the powder is contained in the rear of the case against the primer and that a much more consistent string of shots could be produced as a direct result. Finally I read a few articles about case fillers. You have not reached the point of SEE (detonation) but you have reached the point where upon ignition your powder burns irratically from round to round and you get variations to measured speed between identical weight loads. When you get down to a certain point you have a small amount of powder laying randomly in the bottom (actually along the side since the case is parallel to the gound) of the case. R wrote:i think you have the same problem that goes on in larger 30 cal calibers when downloading for subsonic. Once you get your powder measuring down look around the net for loads using fillers and check it out for yourself. TB might not be the best for 223 in subsonic. IMR SR4759 is a nice bulky powder that lends itself to subsonic loads. My loads are hand weighted with a trickler and an Ohaus M-5 scale. The only drawback is about every 3-4th rd I see what looks like a small puff of snow out my suppressor. My speeds increased within the 20-30ft/sec range and IMMEDIATELY all my chrono speeds became extremely consistent. I broke down a tried, taking a single sheet of of TP, cutting it into 1/4s with sissors then placing one in each case packing all powder to the bottom of the case. These articles indicated that in general a 20-30ft/sec increase would be seen. I think you have the same problem that goes on in larger 30 cal calibers when downloading for subsonic. I don't have a bolt gun to check the results and see if the dropping velocity is something unique to a semi-auto with a gas system, or what. I'm thinking that 5.2 grains of TrailBoss might be the load I go with for an likely average velocity of somewhere around 1050 fps What I find is that the first shot is the fastest, and typically each shot is slower, and slower (with an occasional exception) This is what I am seeing (just the powder weight is listed) I am just getting an idea of where I am, so 5 of each: ![]() The components are: Hornady V-Max 55gr Moly Coated, Primers are CCI Small rifle, Powder is IMR TrailBoss. The time in between finishing one group of the same powder charge and starting the next was perhaps a minute or two (if that matters) I load the magazine for the next load and start over. From one shot to the next is perhaps 15 to 20 seconds. I shoot one shot across the chronograph, record the speed, pull the charging handle, ensure I am not pointing at the face of chronograph, and pull the trigger. The firearm is suppressed with my Form 1 can. The subsonic rounds do not cycle the action, making this into a 'straight pull' bolt gun. No modifications have been made to the gas system. The firearm is an AR-15 SBR with a 11.5" barrel 1:9 twist. This powder yields very stable results from my 300/221 (300 Whisper) The powder is all from the same 8lb keg I have been working from for a couple years now. I don't use this method for regular reloading, but when I am making 5 or 10 of one charge, then 5 or 10 of another, I take extra care to ensure that the charges were as identical as I can make them. Then I pour it into a RCBS 1010 beam scale to double check it. ![]() I have found that my scale doesn't like to hold its zero, so I pour my charge into another powder pan, zero the scale and weigh it again. 223 subsonic round I am working upįirst, my method: I weigh the charge using a RCBS 750 electronic scale. I'm working on load development and I have noticed something very unusual going on with a.
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