AR10T - first round accuracy

MikeeBooshay

MikeeBooshay

Recoil Sponge
Full Member
Minuteman
Aug 31, 2009
953
8
Houston TX and Hackberry LA
#1
I spent the weekned at the ranch with a bunch of friends, we had a great time, shot some axis and pigs, drank some nice bourbon and in general forgot about the world for three days.

Shot several of my sticks, I have steel out to 600 yards, but had real trouble with my AR10T. The rifle is a real hammer, shooting 118LR in subminute groups, EXCEPT for the first round. No matter how I load it, single, from the mag, full mag half mag, one round in the mag, it is nowhere close on the first round. Tried two different lot numbers of ammo, different mags, press check/no check, nada, no change. Never throws one low, always high, usually left, sometimes way left ( off paper at 100 yds ) most of the time, 2+ mils high.

I'd appreciate some ideas of what to look for, cleaned the bore, checked the gas block, stripped/cleaned the bolt etc. Only thing I have noticed different, is that the first round does not always feed from the mag correctly, sometimes it is good, others not. Never had that issue before. No misfeeds on any subsequent rounds.

Thanks in advance for your ideas and help.

Mikee
 
#2
Re: AR10T - first round accuracy

Is this the first round of the day or the first round of every group? If it's the first round of the day, is there any lubricant or solvent left in the barrel from when you last shot and cleaned it? I run acetone or gun scrubber through the bore with several patches if the weapon's been lubricated and stored away. I have an AR10A4 that's not even free-floated and there's no real POI differance between the first and subsequent shots. When you say the first round doesn't always feed correctly from the mag, is it nosediving and missing the feed ramps?
 
#3
Re: AR10T - first round accuracy

Yep, more info would help. Do you mean it is off paper to the left most the time AND 2+ moa high? How far is off paper? I assume that to be WAY off. Like Badshot asked, first round of every mag or of the day? Right off the bat, make sure you dont have a feeding issue thats jamming the first round bullet back into the case. Feed one like normal then eject and check condition.

okie
 
#4
Re: AR10T - first round accuracy

Ok more info - it is the first round of every mag. Not just the first shot of the day.

Not every first round off the paper, just some, but all are left of POA for sure. All first rounds also high, 1-2 mils at 100 yards. Off the paper is about 2.5 mils, FWIW.

I have tried all feeding methods, loading from a full mag and a half mag. Loading one only from the mag, I have also had an empty mag, and hand fed them thru the ejection port. No real success with any of these methods. After the first round from the mag, the rest are right on target. I put a half dozen into a less than 1" group several times yesterday, after wasting the first round of the mag.

I'll check the OAL on a couple rounds tonight, I don't think there will be much change, the 118LR rounds have a lot of neck tension. The misfeeds that it gets are only the first round, and not every time, not even half the time. And yes they are hanging on the feed ramps on the barrel extension.

Something has changed on the rifle, it did not use to do this.

Oh and I also tried a couple different mags, all gen2 type. And yes, bolt does lock back on empty mag.
 
#6
Re: AR10T - first round accuracy

Haha - yes it does! It ain't me....

I saw your build write up, and believe I saw something you wrote on another site. Nice work!

This is very frustrating for me, I had five rifles at the ranch, all were shooting very very well, except this one. This one had not previously had this issue, which is the source of some head scratching/concern. Your ideas and questions are welcome!
 
#8
Re: AR10T - first round accuracy

Are you easing the bolt forward, using the bolt release, or, pulling the bolt ALL the way to the rear, with the charging handle, and letting the bolt fly forward??
 
#9
Re: AR10T - first round accuracy

That's very strange. In theory, feeding the first round from the mag and letting the bolt fly <span style="font-style: italic">should</span> be the same as when the gas system cycles the bolt.

First round blank in every mag?
grin.gif


ETA: yep, no idea if a blank would cycle the gun at all
 
#10
Re: AR10T - first round accuracy

Pulling the bolt all the way back, letting it fly, when loading from mag. I have tried press-checking, no change, the bolt in completely in battery. Easing the bolt forward, in my experience, is not the way to operate one of these.

LW - empty mag, hand feed into chamber, at least a dozen rounds, same result, all high, mostly left, some more high and left than others. Tried a couple with no mag also, same result.

FWIW, cleaned bore and bolt, no change. Rifle still shot the rest of the mag very well. Also, I don't leave anything in the bore post cleaning. It is just associated with the first round from the mag, not just the first of the day.
 
#12
Re: AR10T - first round accuracy

Very interesting. I dont think "you" can duplicate the cycle of an auto loader by hand. I just cant help but think that with that much deviation in POI there has to be some sort of deformation of the cartraige during first round feed. If you cant find it after examination, I'd call Armalite, thier CS has always been outstanding for me. Keep us posted.

okie
 
#13
Re: AR10T - first round accuracy

I see you tried a couple with out a mag. Have you tried firing an entire 5 or 10 shot group,all hand fed with no mag in the gun whatsoever? If your getting the problem when "empty mag, hand feed into chamber, at least a dozen rounds, same result, all high, mostly left, some more high and left than others", then you're eliminating the possibility that the bullet impacting the feed ramp on the way to the chamber as a possible cause. How many inches off center are these rounds at 100 yards? Has any work been done to the rifle such as removing the free float tube or barrel? Have you changed out the scope with a known good scope. I'm starting to think loose barrel nut, or loose lens element somewhere in the scope. The weird thing is the consistancy of the error.
 
#15
Re: AR10T - first round accuracy

It is common for auto loaders to throw the first round after hand charging, but for me it has been consistant, I had an m1A that threw it 2 inches to the left after charging, hand charging doesn't mimic a firing sequence, the rifle goes through different harmonics when fired and recoil impulses, my ar10 throws the first round to the right and high 1 moa, my 223 doesn't, so I consider myself lucky on that rifle.
 
#16
Re: AR10T - first round accuracy

Posted this by mistake on the other AR-10 feeding thread; it makes more sense here.

I have the same gun and had the same problem, but not quite as extreme as you describe. I found that in shooting Sierra Bullets that the meplat was hanging on the load ramp and stuffing the bullets further back into the case. Try loading and ejecting that first round and measure it to see if its getting stuffed. My final solution was just to switch to Amax bullets. the poly tip does not hang on the ramp like a hollow point can.
 
#17
Re: AR10T - first round accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mikee Booshay</div><div class="ubbcode-body">LW - empty mag, hand feed into chamber, at least a dozen rounds, same result, all high, mostly left, some more high and left than others. Tried a couple with no mag also, same result.
</div></div>

I am far from an expert on these, but if it were my rifle I would check to make sure the barrel nut was tight first. Especially if hand feeding is not producing nice tight groups.
 
#18
Re: AR10T - first round accuracy

Going back to the ranch this Friday, hope the rain stays away. I'll check barrel nut and float tube, plus OAL on rounds, and see what develops.

The really wierd thing about this is not the consistency of the error, but how well the rifle shoots after the first round. I'll try to remember to take a couple pics before we paste targets.
 
#19
Re: AR10T - first round accuracy

Been keeping up with this thread Mikee. Hope you will let us know what you find this weekend. I'm a big time fan of the AR10T and have owned one for about seven years. Its certainly my favorite heavy AR. Good luck.

okie
 
#21
Re: AR10T - first round accuracy

Question, once the nut has been properly torque and the gas tube installed and aligned, wouldn't the gas tube be deformed if the nut has moved?
Also, doesn't the tube aid in keeping the nut from coming loose?
 
#24
Re: AR10T - first round accuracy

Hookay... back from the ranch, no solution yet. First thing, I checked a couple of theideas given here. The barrel nut is tight, gas tube not in a bind.

Removed, stripped and cleaned the bolt again. All good in there. Cleaned the lug area again in barrel extension.

Chambered several rounds, measured OAL before and after, no change. All same lot of M118LR. I did not get to try with TAP 168's, the other load this rifle likes.

Range report - same first round flyers, THIS time, they are flying low, not high.

IMG_0711.jpg


POA was center rectangle, bottom corner. The two holes left and down are two first rounds, single fed, no mag. The two down and right are from a POA same rectangle, right corner. The cluster of holes at the bottom corner are from the mag after a first round. Right to left wind about 15-20mph. The three left of the right corner are from the rest of the mag, when aiming at the right corner.

Still looking for ideas and solutions, any ideas welcome.
 
#28
Re: AR10T - first round accuracy

Have you tried swapping scopes yet? You may have something loose inside that is shifting differently when you close the action chambering the first round vs the harmonics that are generated when the action cycles during the firing cycle. It's a long shot but ya never know...
 
#29
Re: AR10T - first round accuracy

Bad shot,

Nope, haven't tried that yet, I am going to do that and swap ammo a couple times also. It took me several tries to find what feeds reliably and shot well, seems as if I could get one or the other. I got to thinking, this started when I got a new batch of ammo, I think. Only thing that changed....I think.
 
#30
Re: AR10T - first round accuracy

Thats some serious gear there. You know what your doing I am shure. This is a "go to thread" can't wait to see what happens or what it was. I just bought my first AR10 its an Armalite with I have been told a Eagle Arms Upper or Noveske "still researching that. Anyways It ran and fed everything I gave it. Hand loaded 175s Sierras hole are touching at 200 Federal 168s first and second shots toughting. Win brass, Lc, Fed, all ran great. This is scary bc I hope it stays this way. Good Luck man.
 
#31
Re: AR10T - first round accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EagleI79</div><div class="ubbcode-body">Thats some serious gear there. </div></div>

Not all mine, but yes it was a lot of fun! My buddy had not shot his TRG out to long distance yet, I have a hill in the middle of a couple box canyons with steel in them. I have a 100 yard range at the house, in the pics. The canyons I can shoot to over 1000 yards in them, steel is presently out to 600, adding more soon. The first steel 6", 9" and 12" @ 400, 500 and 600.

IMG_0652.jpg


My nieghbor has steel out to 1600, with steel every 25 from 250 to 1000. It is his fault that I have gotten into this stuff....

I am about to think this is an ammo problem, the same new lot#, is hard to close the bolt on in a bolt gun I have. Old lot number, not so. That rifle is pretty tight, wondering if this one is too. Will try again with different ammo weekend after next, can't go this week.
 
#32
Re: AR10T - first round accuracy

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mikee Booshay</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: EagleI79</div><div class="ubbcode-body">Thats some serious gear there. </div></div>

Not all mine, but yes it was a lot of fun! My buddy had not shot his TRG out to long distance yet, I have a hill in the middle of a couple box canyons with steel in them. I have a 100 yard range at the house, in the pics. The canyons I can shoot to over 1000 yards in them, steel is presently out to 600, adding more soon. The first steel 6", 9" and 12" @ 400, 500 and 600.

IMG_0652.jpg


My nieghbor has steel out to 1600, with steel every 25 from 250 to 1000. It is his fault that I have gotten into this stuff....

I am about to think this is an ammo problem, the same new lot#, is hard to close the bolt on in a bolt gun I have. Old lot number, not so. That rifle is pretty tight, wondering if this one is too. Will try again with different ammo weekend after next, can't go this week. </div></div>
This was going to be my second guess...sounds like it's just not fully seating the rounds using manual bolt manipulation...just enough to throw off accuracy. OAL, bullet type, radius/ogive difference, more jump than before...wouldn't take much. Under (semi)auto-cycle, it's fully seating the round just enough to cure the problem. If it wasn't doing this before, then it should be a process of elimination back to the last thing you changed which sounds like the ammo.
What a nice place to shoot, BTW.
 
#33
Re: AR10T - first round accuracy

Wow, cant believe "this" after what I experienced today. Great day on the range, perect day, great friends and great rifles. My pards 40X chambered in '06 and my LTR in .308. Shooting .5 moa grps consistantly then we both started experiencing tightness when locking down the bolt, yes, both fairly close to the same time in the session, go figure. On both rifles the groups opened up to 1+ moa at the same time as the tight bolt lock appeared, you could literally almost match the tight chaimberings with the flyers. First time I've ever seen such obvious proof of how critical this is. Maybe some of the pro's will weigh in on this. Anyway, hope you're closing in on your problem and that it is an ammo issue, thats an easy fix
smile.gif
.

okie
 
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