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Posted: 8/15/2006 9:25:01 PM EDT
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Stag Upper and Lower in a 16" 1:9 twist AR-15. Factory ammo ejects to the side and roughly 1 foot behind me. Im reloading now, M193 55gr FMJBT, Mixed brass, trim to 1.751 +- .001 IMR 4895 Surplus 26gr. (also had powder at 24, 24.5, 25, 25.5 with the same issue) but my rounds are ejecting to the side but roughly 1 foot forward now. Nice group on the cases on the ground but has anyone seen this before or possibly have suggestions? Im not seeing any issues with loading, or ejecting, everything is smooth, no case markings, nice groups at 100 yards completely acting like well loaded ammo and the AR eats it up and spits out nicely. My intial thought was longer trim lenght but ill have to wait until my brass stretches back out to test that or, get some new brass in. Any thoughts would be appreciated. |
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4895 burns slower than the standard powders used in the rifle which leaves higher residual pressure in the bore at unlock This translates to the spent case being more pressure bound to the chamber side walls ata unlock, which leads to more momentum of the B/C being lost on pulling the bound spent case, which leads to less of a impact of the buffer off the back of the receiver extension (less buffer stall at end of stroke). Bottom line is the buffer-B/C is stalling less at the rear of stroke before moving back forward due to the gun powder being used, and instead of the spent case being pivoted off rearward at the stall, it's being pushed off the bolt face as the bolt starts to move back forward. As long as the rifle is ejecting the spent case cleanly (not being thrown into the front of the ejection port), don't worry about the spent case flight path. To add, with the 55gr bullets, your giving up a lot of speed using the 4895, and in fact these light loads may be contributing to the light buffer impact off the back of the receiver extension. Best guess with the 4895 is that you are getting around the 2700 FPS or less, and nowhere near the standard 3200 FPS mark of real M-193. If you are just shooting around 100 yards, don't worry about it, but if you are trying to push out past the 300 yard mark, the wind/drop is going to eat you alive. |
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Thank you for that feedback and information it is greatly appreciated. I chronoed all my loads from 24. to 26 in .5 increments.. at 26 grains I am getting an average of 2930 fps with a pact I chrono out about 10 feet from the bench. Which seems to be inine with the reloading manuals getting 3100 with a 20" barrel. But its good to know I dont have any real issue. I had a good deal on the powder.. once I burn it up.. (16lbs of it) im going to work up something standard for the rifle. Thanks again. |
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Spent case ejection can be a real problem especially in highpower matches where you are positioned every 8 feet or so apart. A 3:00 oclock ejection pattern can introduce a hot cartridge case down the neck of the shooter next to you. If the shooter next to you is a lefty you can literally put one in his shooting eye. I always hate it when a black gun is next to me on the line and brass starts to rain down on me during a string. I was told a GI was killed on a KD range many years ago when Army did training on Known Distance Ranges with shooters about eight or ten feet apart. The story goes one GI was shooting standing and a hot case went down neck of shooter next to him. In his involuntary reaction to the hot case he turned and subconciously pulled the trigger killing GI on next point. The Army stopped such training (shooters close together) many years ago and now shooters are separated maybe 30 feet apart shooting in lanes at multiple targets. Spent cartridge cases exit the gun above 200 deg F. A 160 deg F exposure to bare skin for one second can and will cause 3rd degree burns. National Burn Victim Foundation estimates (found on line) a one second exposure to 160 deg F for one second will cause 3rd degree burns. These are paticulary nasty as they are prone to infection. If anyone doesn't believe this--I Took polyethylene .8mil trash bag from kitchen and fired some TW72 M193 ball on it from about three feet. Cases landed on bag and started to melt bag, just stuck to it. It permanently deformed the bag. Per the internet low density poly melts at 115C. Since it deformed and left permanent deformation in bag I figure it was lower so lets say 110C. 110C equals 230 deg F or damn hot. That is what I figure If anyone knows a better way to check this without exotic instrumentation let me know. I have personally sustained 2nd degree burns from shooting AR left handed from hip for three quick shots without a shirt. Brass ejected, hit my stomach and departed immediately. I had three very nice burn imprints of the case on my stomach including the shoulders and necks of the cases for weeks. If you are shooting with no one around but yourself this is not that big a deal. The ideal case ejection pattern is between 1:00 and 2:00 and should be strived for if shooting near any other person such as matches, informal plinking etc. You can change the ejection angle by several methods. You can adjust your loads. Bet you have noticed that hand load ejection impacts are much closer spaced than factory loaded ammo. This is because your handload ammo is most likely loaded to a more uniform pressure and the same energy is presented to the bolt carrier each shot. This is directly related to carrier velocity which is related to ejection. Assuming you have a receiver with the "bump" to the immediate rear of the ejection port there are several things you can do to change where the hot brass is directed. One is you can degrease the bump and attach one of the small rubber adhesive backed pads you can get as furniture protectors. I found a sheet of black rubber ones about 3/8" diameter. The most effective thing I have found is I went to Home Depot and found some industrial velcro strips with a very tenacious backing. I cut a section about 3/4 long, peeled one back and stuck it to the forward face of the "bump". Next I peeled the other backing and stuck a piece of foam rubber on that. I found that placing is so that the forward part of the foam is even with the firing pin retainer hole in the bolt carrier or about 1/2" over the opening. You won't be able to close the dust cover but you will protect your shooting partner to your right. This combination gives me a nice neat ejection at 1:30 to 2:00 with M193 loads. It also doubles as a case protector and allows the case to be ejected without deforming the case mouth making it easier to reload. Hope this gives you some idea of what you need to accomplish. |
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Thank you Humpy70 it sounds like I am right on then.. My ejections are at the 1 o clock they are ejecting and landing in the rough in front of me to the side.. Basically benches are on cement and my brass is landing in front of the rifle ion the grass 1 foot away to the right. . Nice group too all of its in a 2 foot circle. The wolf I shot before my reloading supplies were all at 3 to 6 o clock and probably had a 10 foot circle of brass. I was just thinking it was normal for brass to release to the right rear and not right front. |
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I have seen brass from good handloads group better on the ground than shooter did on target. I have seen 10 rounds in maybe a 8" circle. Your ejection pattern is perfect. Try the bit with the foam pad, think you will like that too. I was at a police auto weapon demo last Monday. They had a M4 shooting SS109 and I saw 120 rounds in a fan from 2:00 to 4:00. Such a ejection pattern is a accident waiting to happen and there is no need for it. Sooner or later a sharp attorney is gonna get a injury suit against a gun manufacturer for having such a design and then it is gonna hit the fan big time. I have a good friend who was gov't lawyer and I told him about such and he told me if I ever heard of anyone getting killed as a result, call him, he will be glad to take the case as he wanted to retire early anyway. |
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