View Full Version : First round in a group shooting high and 30cal suppressor on 223 accuracy questions
Eurodriver
07-26-16, 06:39
200 yards. Krieger .223 Wylde, 77gr TMK handloads
I have two separate questions. The first involves a consistent first round flyer out of rifle. This is not from a cold bore. The barrel was very well warmed up at this point from long range steel shooting. The two groups were shot probably 3-5 minutes apart from one another.
Could it be that the first round was loaded from an open bolt and all the subsequent rounds had the bolt ride over top of them?
http://i1328.photobucket.com/albums/w521/6234987u02/IMG_0499_zpskpiyfvyz.jpg
For the 3rd group, I inserted the magazine on a closed bolt and racked the CH to load the first round. That seemed to eliminate the flyer, but then my group opened way up to ~0.9" (which, with a sample size of one, doesn't really prove anything)
http://i1328.photobucket.com/albums/w521/6234987u02/IMG_0524_zps4wwnezwl.png
Unfortunately, that was all I had time for but I'm beginning to wonder if I should load the first round from a closed bolt from now on? Has anyone else experienced this? ETA: I should mention the group POI differences are because I was adjusting my scope.
Also, for the first time I was using my .30cal can on my precision rig. I no longer have any .30cal suppressor ready rifles, and like having dedicated cans for guns. Since this thing is already long and heavy, adding a long and heavy 30cal can doesn't seem like it matters. I was wondering if that may have any effect on precision. Given that I have two groups that are almost 1/2 MOA I am wondering if that increase in size may be due to the larger bore diameter of the suppressor. Normally at that distance my groups would be consistent with the group in the top right of the first picture (all 5 should be touching)
Two thoughts,
One, open bolt on a warm barrel is a barrel filled with air/even pressure to the surrounding environment. Subsequent shots from closed bolt would be through a warm barrel that has only one opening (other is essentially plugged by the cartridge) and at a different gas state/pressure than surrounding environment, kind of like the first round pop out of a can.
When I am at a shoot, I always fire two rounds as "foulers" at the beginning of each match. Now the barrel is already fouled and warm before firing the two "foulers" but they do a couple of things that I feel are important. One, they do not count for record or as a sighter I will trust, instead they clear any particualtes like hardening carbon or dust/debris from the bore before I take record shots. Two, they fill the bore with gasses that will be present for the remainder of that match. I have a certain amount of time that I will keep a bolt opened or closed to try and maintain this, as well as to not heat up a live round too much.
Two, darn good shooting, I would be curious to see what that thing could shoot if you had wind flags available to read.
Eurodriver
07-26-16, 14:14
Interesting. I would have thought it was related to the actual BCG cycling over the bullet somehow since it didn't appear to happen as significantly in the third group. However, based on what you're saying it may have been that the third group was not exposed significantly to outside air because the bolt was closed before the groups were fired.
Still, it is kind of surprising to see almost a 1 MOA shift up just from that. Is that typical/normal in your experience?
Similar yes, though I'm not shooting through a can which may be exacerbating the situation.
You could test to see by firing a five shot group but taking some time between shots to allow the barrel to clear the gasses, keeping the bolt open, then fire another five shot group normally at the same point of aim to see if it what I am suggesting is happening.
I may be wrong, but it was my first thought when I read your post.
I have heard for many years on semi auto, racking the first round it will always be a flyer, now im sure once in awhile you will luck out and not get a hand racked flyer ! And i believe this because i have seen it so many times in my ARs and even my 1911 45 acp
Interesting. I would have thought it was related to the actual BCG cycling over the bullet somehow
I'm highly doubtful of this. There are indeed nasty gasses suspended in the barrel/can after shooting it. I remember pulling the bolt on a gun and looking down the bore. It was so thick, I couldn't see out the barrel at all.
I'm wondering if there isn't a body position issue for you, as the shooter. I.E. are you on the gun slightly different for the first shot compared to the follow ups where you're running the bolt? Just a thought.
Eurodriver
07-26-16, 18:23
Body position stayed the same for sure. It's a semi auto not sure if I mentioned that.
Maybe it is the gassed, and maybe it's exacerbated by the 30cal can as I certainly don't recall this happening with my 5.56 can. That is a 5" shift at 500.
I'll have to do what Masan said and see if the bore gasses affect the first round. It certainly has to be "something" because it is consistently high and consistently the first round.
If you really want to test it I would make sure to wait a good while between shots to ensure that the bore is clear of anything but the surrounding air.
Body position stayed the same for sure. It's a semi auto not sure if I mentioned that.
Maybe it is the gassed, and maybe it's exacerbated by the 30cal can as I certainly don't recall this happening with my 5.56 can. That is a 5" shift at 500.
I'll have to do what Masan said and see if the bore gasses affect the first round. It certainly has to be "something" because it is consistently high and consistently the first round.
I certainly dont think its BAD GAS !
Have you talked to the manufacturer of the can ?
Eurodriver
07-27-16, 12:40
If you really want to test it I would make sure to wait a good while between shots to ensure that the bore is clear of anything but the surrounding air.
How long is a "good while"?
Have you talked to the manufacturer of the can ?
Why would I do that?
long enough that you can be sure the bore is in the same state as the previous round, clear of any visible gas would likely work
How long is a "good while"?
Why would I do that?
Because the manufacturer has experienced all the problems you could ever have had, and most likely have a solution to your problem !!!!
Try blowing out the barrel and closing from an open bolt each shot for a 5 round group.
Try it without blowing out the barrel.
I highly doubt is has an impact, it the same pressure inside the barrel as outside by time you take the next shot, and it's not like a frp since the bullet seals off the propellant. I don't thing the residual gas has enough mass to affect velocity, but I don't know everything.
Try blowing out the barrel and closing from an open bolt each shot for a 5 round group.
Try it without blowing out the barrel.
yeah. Maybe with one of those keyboard cleaner cans. It would be interesting.
The 30 cal can should not be a problem. My most accurate gun is a 223 5R rem 700 bolt gun. I took an AAC M42k off (Mark gave me copious amounts of shit for jacking with the most consistently accurate gun in the stable for us) and dumped a Gemtech quicksand on it. Quite frankly it made me nervous. But the gun still shoots bug holes.
But every gun and every can combo has its own relationship. But I doubt that's your issue.
Best of luck big guy.
PB
Does the first round flyer occur with factory ammunition? How far are you setting the case shoulder back at the datum line when resizing brass?
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