DCMJ Posted October 24, 2012 Share Posted October 24, 2012 I built up an AR15 sorta M4 have to do things myself but lessons were learned so I'm good with the costs. DPMS Oracle carbine upper 1-9/DPMS-built, RRA LAR15 lower. A little daylight between upper and lower, but no movement at all (lucked out there), DPMS guts and no complaints about the trigger. Magpul CTS stock fully extended, good cheek weld I think but I'm taller and this thing is tiny! I was shooting American Eagle 55Gr FMJ. First shots at the range I noticed that recoil/muzzle rise is minimal but with painful mechanical impact and an odd thing is happening. I have virtually no barrel rise, but a movement to the right no matter what I do. It is pretty obvious and I'm uncertain what causes it. Hold? Flash hider/muzzle brake clocking slightly off? A4-pattern hider. Is the impact normal or do I need to look into making changes? Right now I'm running a standard carbine buffer and spring, all mil-spec. Fun! Link to comment Share on other sites More sharing options...
RiggerJJ Posted October 24, 2012 Share Posted October 24, 2012 Probably torque. Counter it with a decent comp that is tuned for it. jj Link to comment Share on other sites More sharing options...
dhill Posted October 24, 2012 Share Posted October 24, 2012 The Rolling Thunder comp can be tuned for your particular shooting style. Link to comment Share on other sites More sharing options...
Hi-Power Jack Posted October 24, 2012 Share Posted October 24, 2012 I recoil/muzzle rise is minimal but with painful mechanical impact and a movement to the right Jim, I'm confused. You see no recoil, but "painful mechanical impact" and gun moves to the right? What position are you shooting from? Is gun being fired level, or canted? Link to comment Share on other sites More sharing options...
DCMJ Posted October 24, 2012 Author Share Posted October 24, 2012 (edited) Jack, As far as I am aware, firing from level with no cant. Maybe what I am feeling as impact is the buffer bottoming out in the buffer tube. Inspecting the buffer, I don't see evidence of of it; no scuffing, etc. But a stripe of grease pencil on the bumper will clear up that question next trip. The sensation is like someone hitting me on the collar bone with a small hammer. I suppose the movement might even be reflexive, like getting tapped on the knee/knee jerk due to that tap on the collar bone. It seems delayed but that observation is clouded by the time that has passed since that range session. It was one of those "that's really strange, what am I doing wrong?" moments. Being aware of it didn't change the reaction on following shots. Edit> Position was standing/freehand, no added support, no sling. Edited October 24, 2012 by DCMJ Link to comment Share on other sites More sharing options...
benny hill Posted October 24, 2012 Share Posted October 24, 2012 If you want a soft gun, never use a carbine length gas system. There is a reason most top shooters use a rifle length system w/ a good comp. Link to comment Share on other sites More sharing options...
DCMJ Posted October 24, 2012 Author Share Posted October 24, 2012 If you want a soft gun, never use a carbine length gas system. There is a reason most top shooters use a rifle length system w/ a good comp. It's like I said, I have to do it all myself, lol. No experience with AR's to base this on, I'm working against a lot of "is this normal?". I'm planning on moving to a rifle setup, especially after realizing the pull on a carbine is too short by inches. If that will give me the "Cadillac ride" on top of better ergos, kewl. Link to comment Share on other sites More sharing options...
co-exprs Posted October 24, 2012 Share Posted October 24, 2012 (edited) If you want a soft gun, never use a carbine length gas system. There is a reason most top shooters use a rifle length system w/ a good comp. +1 The hop to the right is caused by the BCG and buffer impacting the back of the tube. It causes your body to torque slightly right. The carbine length gas runs a much higher pressure and unlocks the bolt sooner than rifle length gas. Not all of the powder has had time to burn off and the BCG comes back with more authority. Some of that can be countered by running the rifle more to the inside of your shoulder pocket and with the butt down, so that it doesn't stick up above your shoulder. Ultimately, you will need to tune out some of that gas with an adjustable gas block and add a comp. Edited October 24, 2012 by co-exprs Link to comment Share on other sites More sharing options...
DCMJ Posted October 24, 2012 Author Share Posted October 24, 2012 (edited) ...caused by the BCG and buffer impacting the back of the tube. That makes sense to me, thanks! As does the gas system comment. Edited October 24, 2012 by DCMJ Link to comment Share on other sites More sharing options...
Sleepswithdogs Posted October 24, 2012 Share Posted October 24, 2012 (edited) Jack, As far as I am aware, firing from level with no cant. Maybe what I am feeling as impact is the buffer bottoming out in the buffer tube. Inspecting the buffer, I don't see evidence of of it; no scuffing, etc. But a stripe of grease pencil on the bumper will clear up that question next trip. The sensation is like someone hitting me on the collar bone with a small hammer. (Edit for brevity by Sleepswithdogs) Both?? Is it possible you are resting the butt of the gun on your collar bone? Most AR's have a virtually no comb, and little drop at the heal, so I typically see some odd firing positions required to bring the stock up to where it needs to be for a good sight picture. Quite often the butt ends up way high on the shoulder where it could possibly be coming in contact with the clavicle. I can see where coupling the straight stock design with in impulse from a carbine length gas system, this might be pushing a very hard butt plate against your collar bone. The rifle might not be starting out there but might be getting there during the shot? Tar Edited October 24, 2012 by Sleepswithdogs Link to comment Share on other sites More sharing options...
DCMJ Posted October 24, 2012 Author Share Posted October 24, 2012 The butt plate ends up pretty high on my shoulder rather than in the pocket. I just added the enhanced butt pad, should soften the impact a bit but the final solution may be to go with a A1/A2 or similar setup. More LOP, and the longer buffer system. That said, I am embarrassed after a great deal of mental replay to admit I know what's up. Two words. Brass Catcher. I couldn't fathom how I felt the recoil impulse and then the muzzle moved right. The energy transfer when the case was ejected and hit the bag, then weight of the brass hitting the bag makes it swing. With a half-dozen or more hulls in the bag I ended up with a bit of massy brass flapping back and forth over there. Duh. But I appreciate the help/advice and probably now a bit of muttering under one's breath. No worries, I did! Link to comment Share on other sites More sharing options...
Sleepswithdogs Posted October 24, 2012 Share Posted October 24, 2012 Not to worry. IMO, the best part of life is people working together to help each other. 3g people are a good bunch and most always willing to pitch in and help. Tar Link to comment Share on other sites More sharing options...
DCMJ Posted October 25, 2012 Author Share Posted October 25, 2012 Tar, In my line of work, folks may know so much there's the temptation at times to think we know it all. The reality is that the more I learn, the less I realize I know. When I get in to a corner I can't find my way out of on my own, I frequently find the solution to the problem as I talk it out with someone else. Similar experience here on the forums. Sometimes it is just finding an ear, a little exchange, and I find the answer talking it out. Even if I don't, I get acquainted with other members, learn something new. Win/Win Thanks for joining the conversation, Tar, co-exprs, benny hill, Hi-Power Jack, DHill, and RiggerJJ. -jim Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now