AR-10 Recoil question.

[Warbone]

Bought a Cmmg AR-10 MK3 a few months back, found it had a over gassing issue, fixed that problem with a adjustable gass block, added a miculek muzzel brake.
I get geat accuracy if i open bolt load one round into magazine, load into rifle and release bolt. im talkking .5 moa or less.
If i load more than one accuracuy goes up to 1.0 to 1.5 moa.

Is this due to the bolt being locked back with the magazine on last round, vs bolt going forward and loading another round.
Is the bullet still in the barrel when the bolt is goind forward, or even slamming shut effecting accuracy.
If this is the case what is the proper shoulder hold for firing ar10? hard hold into shoulder ect?

 

[Ledzep]

Re: AR-10 Recoil question.

The bullet should be out of the barrel before the bolt carrier is moving backwards, so I doubt that it's a recoil-related problem.

I would tend to think it's something more along the lines of bullets being pushed into the case, or being yanked out of the case (inertia), or being pushed to one side or the other (runout) while in the magazine or in the chambering process.

Edit: It could also be upward pressure on the bolt carrier from the extra rounds in the magazine.

 

[Graham]

Re: AR-10 Recoil question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ledzep</div><div class="ubbcode-body">The bullet should be out of the barrel before the bolt carrier is moving backwards, so I doubt that it's a recoil-related problem.

I would tend to think it's something more along the lines of bullets being pushed into the case, or being yanked out of the case (inertia), or being pushed to one side or the other (runout) while in the magazine or in the chambering process.

Edit: It could also be upward pressure on the bolt carrier from the extra rounds in the magazine. </div></div>You're making this up, right?

 

[BCP]

Re: AR-10 Recoil question.

Probably technique. There are videos and writeups all over the internet but it is a bit hard to explain. Generally speaking it just takes time. Experimenting with different holds, different rests, different ammunition, finding what works for you, etc.

edit: firm on the shoulder, semi-firm pistol grip, gentle squeeze of the trigger, keep the rifle on target through firing cycle is best way I can put it.

 

[T2CH]

Re: AR-10 Recoil question.

This is all your position and the recoil of the rifle. By loading one round at a time you are only getting half the recoil impulse. You have to ride the recoil out on a gas gun, there is a lot going on when you pull the trigger compared to a bolt gun.

Are you shooting prone? From a bench? Bipod? Sand bags?

Are you back on target after the shot?

List of what to do:

1. Do some research, plenty of it right here on technique
2. Sign up for the online training provided on this forum
3. Stop loading one round at a time, you are negating the purpose of having a semi-auto
4. Practice what you read at the range.

 

[Graham]

Re: AR-10 Recoil question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: T2CH</div><div class="ubbcode-body">... there is a lot going on when you pull the trigger compared to a bolt gun. </div></div>http://archery.ar15.com/archive/topic.html?b=3&f=62&t=527099

 

[Warbone]

Re: AR-10 Recoil question.

The the purpose of loading on round at a time was to figure out if the barrel/rifle was capable of half min accuracy, it is. Now im just trying to figure out hold machanice, or if its another issue. I have searched internet and get 2 differant stories some say bullet is gone before bolt movment others say differant.
i have been shooting bench rest with front and rear bags. yesterday i did a 3 shot group right at .200 moa single load method. dont come close to that with 3-5 rounds in mag.
i have tried prone and bipod as well.
everywhere i read most people say its hold machanics. have tried many differant hold with poor results.
From what i can figure if the bolt is moving forward on a mid length gas system before bullet leaves barrel i could be my hold mechanics.
if bullet is already gone and i can shoot great group with single load and bolt staying back could it be a mag/bullet issue i.e. round pusing up on bolt, mag with round pushing up on bolt ect, upper and lower reciver mate?
I will not single load of course all the time but would like to figure out issue.

 

[T2CH]

Re: AR-10 Recoil question.

Tell ya what, clear the rifle and with the mag out release the bolt. Push your finger in the magwell and see if you can move the BCG. If you can not and the rifle shoots as good as you say it does loading one at a time then it is your mechanics.

 

[Warbone]

Re: AR-10 Recoil question.

Thank T2CH when i get home tonight i will check that out. That should tell me if bcg is loose in upper reciever. If it is that might be my issue.

 

[T2CH]

Re: AR-10 Recoil question.

If it is you would be having more issues than the grouping, like failing to feed and extract I would think.
Update after you check it.

 

[Warbone]

Re: AR-10 Recoil question.

i was having extraction issue thought it was over gassing shells where going to 1 oclock and every fith one would get jammed but a ajustable gas block fixed that issue shells going to 3 oclock and not a single jam after ajustable gas block installed.

 

[9H_Cracka]

Re: AR-10 Recoil question.

Always best to start out blaming the equipment rather than the driver.

When you single load, you break position, then rebuild position, with each shot.

When feeding from the mag, you lay on the thing and pump the trigger, shouldering the rifle, steering it with the grip, whatever it takes to get it back on target so you can get that next euphoric shot of serotonin in your brain as soon as possible.

The large frame ARs have a ton of bolt mass, independent of recoil, that effects where the rifle ends up after firing and loading. Staying on the rifle and shooting from the mag again often thwarts the stages of the shot process where you correctly build your position for the desired POI. Execution is a whole additional phase that has to be developed when shooting from the mag, staying on the rifle, that is different than single load execution.

In other words, shooting from the magazine is a leaned behavior of its own, just like single loading is a learned behavior of its own.

 

[Warbone]

Re: AR-10 Recoil question.

Thanks 9H, not sure if your first line was sarcasm or not. maybe i should have started my post with this.
After 3 months and over 1000 round i either have not been able to overcome the ar10 action in order to shoot accurate, or there is a problem with the gun.
I dont have a know tac drving ar10 to shot, nor do i know anyone that can shoot ar10 very accuratly so i cant figure out if it the gun or me that way.
I will be the first to admit its me when i can eliminate all other possible issues.

 

[okiefired]

Re: AR-10 Recoil question.

Hard to say whats giveing you problems without seeing ya shoot but I'd say you've gotten pretty good advice here from some. Keep the rifle in tight to your sholder without getting stressed and stay there while eveything settles after the shot. Speed will come after you become more comfortable with the system. One other thing, if your shooting reloads, make sure your bullets aren't being pushed back from chambering or recoil. .0015 neck tension has always kept my bullet seating depth stable in my AR10T. Oh and BTW, whomever told you it may be because your bolt is returning to battery before the bullet leaves the barrel has absolutely no idea what they are talking about. The bolt has'nt even unlocked to start the process of ejection bufore the bullet is long gone. Good luck.

okie

 

[hlee]

Re: AR-10 Recoil question.

It is "possible" that the gun chambers rounds more consistently when singly fed. Users here on SH have reported small amounts of "setback" being observed when rounds are loaded from a magazine. The cause is suggested to be the bullet tip ramming into the feed ramps at high speed. It is "possible" that this is the cause of your accuracy problem. You state that you have an adjustable gas block on your gun. You "could" recreate/simulate the recoil impulse of chambering the next round by turning down your gas block until the bolt will not engage the bolt catch- but still ejects the spent cartridge. If you find that your groups open up when you do this, then you may not be "riding the recoil" (in semi-auto mode) as another poster put it. If they stay consistent, then it could be that you are not rebuilding your shooting position (again in semi-auto mode) the same way that you do when you singly feed your rifle- as was suggested by another poster. If you have a caliper you could measure the cartride OAL before and after chambering. You "may" find that each round changes a different amount. But, the largest single source of variability and error remains the shooter, so that is where any troubleshooting should begin.

 

[T2CH]

Re: AR-10 Recoil question.

Just a thought as I read the other posts! Are you reloading? If so, are you full length resizing the brass?

 

[Warbone]

Re: AR-10 Recoil question.

Yes atm i am reload but have the same results with federal ammo, i FL resize brass, trim, ect. I am using a lee crimper i did find that my bullets would go from 2.800 oal to anywhere from 2.003 to 2.010 when i slam the bolt shut. With the lee crimper i have reduced that to 2.003 or less.
when i get home going to check the bcg for any play.

What i dont understand is that if the bullet is long gone before the bcg even begins to move how does the semiauto action effect accuracy. I always thought the bolt is atleast moving some before the bullet exits the barrel.
Again i have searched the internet count less time for this very info and finde differant answers.
The info i have gotten on this thread i think will help alot in narrowing it down.
Thanks to all those that have posted got some things to look at on the rifle as well as a few things to try at the range.

 

[Badshot308]

Re: AR-10 Recoil question.

Might want to recheck your numbers. If your col is going from 2.80 to anywhere between 2.003 and 2.010, you're pushing the bullet back into the case about 3/4 of an inch during chambering.

 

[Warbone]

Re: AR-10 Recoil question.

LoL sorry started at 2.800, after slaming bolt shut it would go anywhere from 2.803 to 2.810. After lee crimp i got it down to less than 2.803 most the time sometimes it wont even move. I never did check to see if the factory federal ammo moves at all because all the loads i test for this did not have any powder in them. i would hate to slam the bolt shut in my house with a live round and just happen to have a slamfire lol.

 

[Badshot308]

Re: AR-10 Recoil question.

OK, so when single loading them, the bullets are actually being pulled outward just a little. When measuring this, are you loading them into a mag and feeding them into the chamber from the mag, or are you putting the rounds through the ejection port and into the chamber by hand, and then closing the bolt?

 

[Warbone]

Re: AR-10 Recoil question.

Measuring,Locking bolt back, loading round into mag, putting mag in and pressing the bolt release latch, then ejecting round, and mesuring again.

 

[hlee]

Re: AR-10 Recoil question.

The shooting position is the foundation of rifle precision. Small differences in how you are setting up can have large differences down range. When you feed the rifle after each shot, you have to come off of the stock, load the gun, and then rebuild your position. When you are feeding from the magazine, you do not have to rebuild the position to stay on target. However, your position may still be changing from shot to shot- wrestling the gun back to point of aim, instead of rebuilding the position to achieve a natural point of aim.

Below is a link to a youtube video that seems to suggest that the bolt is not moving when the bullet leaves the barrel. Look to 2:13 for what seems to be the clearest shot... http://www.youtube.com/watch?v=fuQayLVbiSU

But, my rudimentary understanding of gas impingement systems would suggest that pressure on the gas key would increase immediately after the bullet passes the gas port. The pressure continues to build as the bullet traverses the barrel. The pressure is relieved when either; the bullet leaves the barrel, or when the bolt carrier begins to move. If the bullet leaves the barrel before the bolt carrier begins to move, then there is nothing to push the bolt carrier back (as the pressure in the system has its release valve- the muzzle). If the bullet is still in the barrel when the bolt carrier begins to move, then this movement could cause the accuracy difference between single feed and magazine fed.

I would love to see a super slow motion video of a ar10/ar15 firing, that included shots of both the muzzle and the ejection port. The ones that I have found seem to show one or the other, or not be slow enough to see a difference.

Most of what I have read here on the hide suggests the bullet is not clear of the barrel before recoil begins.

 

[Quarter Horse]

Re: AR-10 Recoil question.

It should be easy to determine if not rebuilding your position is the source. Simply get off the gun, give it about the time it takes you to to change mags and go back to the rifle. Let us know if you find a solution.

Also, I'm not following the numbers on OAL. Surely you do not mean your OAL is 2.0+ after chambering.

 

[Warbone]

Re: AR-10 Recoil question.

Quarter horse yes the oal numbers where a typo and corrected in a later post.
Maybe i didnt make my single shot, action clear.
I lock the bolt back, put round in mag, put mag into rifle hit bolt carrier lever the bolt slams forward and chambers the round, aim and fire. Then repeat process. I can do this 3 to 5 time and get less than half" moa groups with 3 shots and less that 1" moa groups with 5 shots, 90% of the time. In the action there are 2 differances from loading mage with more rounds.
1. bolt does not move forward it gets locked back with the mag.
2. there is not a round in the mag that may effect the bcg above it.
But if i load 3-5 rounds in the mag set up and fire 3 to 5 times. Slow controled fire with same hold and follow through as single firing. The groups open up to 1-2 moa.
What im trying to understand is what is causing this.
If the bolt is not even moving before the bullet leaves the barrel, then my hold shouldnt be the issue, it should be the way the rifle is loading the next round into the chamber, or the extra round in the mag effecting the bolt and round in the chamber.
if the bolt is moving backward while the bullet leaves the barrel then my hold still shouldnt be the issue. because with single loading accuracy is great, and bolt is still moving back.
However if the bolt is moving forward before the bullet leaves the barrel and im not adjusting for the mass of the bolt moving forward that could effect my accuracy.
Lol i dont even know if all that makes sense to anyone else.
But after 3 months and 1k rounds practicing its frustating.

 

[Badshot308]

Re: AR-10 Recoil question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hlee</div><div class="ubbcode-body">The shooting position is the foundation of rifle precision. Small differences in how you are setting up can have large differences down range. When you feed the rifle after each shot, you have to come off of the stock, load the gun, and then rebuild your position. When you are feeding from the magazine, you do not have to rebuild the position to stay on target. However, your position may still be changing from shot to shot- wrestling the gun back to point of aim, instead of rebuilding the position to achieve a natural point of aim.

Below is a link to a youtube video that seems to suggest that the bolt is not moving when the bullet leaves the barrel. Look to 2:13 for what seems to be the clearest shot... http://www.youtube.com/watch?v=fuQayLVbiSU

But, my rudimentary understanding of gas impingement systems would suggest that pressure on the gas key would increase immediately after the bullet passes the gas port. The pressure continues to build as the bullet traverses the barrel. The pressure is relieved when either; the bullet leaves the barrel, or when the bolt carrier begins to move. If the bullet leaves the barrel before the bolt carrier begins to move, then there is nothing to push the bolt carrier back (as the pressure in the system has its release valve- the muzzle). <span style="color: #FF0000"><span style="text-decoration: underline">If the bullet is still in the barrel when the bolt carrier begins to move, then this movement could cause the accuracy difference between single feed and magazine fed.</span></span>

I would love to see a super slow motion video of a ar10/ar15 firing, that included shots of both the muzzle and the ejection port. The ones that I have found seem to show one or the other, or not be slow enough to see a difference.

Most of what I have read here on the hide suggests the bullet is not clear of the barrel before recoil begins. </div></div>


Whether or not the BCG starts to move while the bullet is still in the bore will not have any thing to do with accuracy differences between single fed or magazine fed. The cartridge is already in the chamber when it's being fired and unless it's being damaged while being fed up into the chamber, that round doesn't care how it ended up in the chamber. Unless you're firing full auto, all movement of the gun has ceased between shots after the round has been stripped from the magazine and pushed into the chamber.

The OP is apparently getting some bullet jump when he's chambering the rounds one at a time from the magazine. What he might want to do is while at the range, fire some rounds from the magazine, letting the gun function normally, and then pull some rounds before firing them and measure their oal. The BGC is probably moving forward a little faster while being cycled by the gas system than when it's being locked to the back manually and released by the BCG release. Depending on just how much faster and harder it's being chambered, he may be getting more bullet jump. Depending on how the bullets are being fed from each side of the mag up into the feed ramps and then into the chamber, he may be getting some bullet set back. He'll have to measure some rounds at the range to find out.

 

[Badshot308]

Re: AR-10 Recoil question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Warbone</div><div class="ubbcode-body">Quarter horse yes the oal numbers where a typo and corrected in a later post.
Maybe i didnt make my single shot, action clear.
I lock the bolt back, put round in mag, put mag into rifle hit bolt carrier lever the bolt slams forward and chambers the round, aim and fire. Then repeat process. I can do this 3 to 5 time and get less than half" moa groups with 3 shots and less that 1" moa groups with 5 shots, 90% of the time. In the action there are 2 differances from loading mage with more rounds.
1. bolt does not move forward it gets locked back with the mag.
2. there is not a round in the mag that may effect the bcg above it.
But if i load 3-5 rounds in the mag set up and fire 3 to 5 times. Slow controled fire with same hold and follow through as single firing. The groups open up to 1-2 moa.
What im trying to understand is what is causing this.
If the bolt is not even moving before the bullet leaves the barrel, then my hold shouldnt be the issue, it should be the way the rifle is loading the next round into the chamber, or the extra round in the mag effecting the bolt and round in the chamber.
if the bolt is moving backward while the bullet leaves the barrel then my hold still shouldnt be the issue. because with single loading accuracy is great, and bolt is still moving back.
<span style="color: #FF0000"><span style="text-decoration: underline">However if the bolt is moving forward before the bullet leaves the barrel and im not adjusting for the mass of the bolt moving forward that could effect my accuracy.</span></span>
Lol i dont even know if all that makes sense to anyone else.
But after 3 months and 1k rounds practicing its frustating. </div></div>

The bullet has definately left the bore before the BCG has moved completely to the rear and started moving forward again. If the action was cycling that fast, there would be excessive pressure still in the chamber holding the case to the chamber walls, resulting in torn off rims, ruptured cases, ect.

 

[mavrick10_2000]

Re: AR-10 Recoil question.

If shooting 5 shot groups, load 6 rounds into the magazine, if shooting 10 shot groups load 11. Now try for groups again with 5 or 10 rounds being fired and report back.

Not breaking position should help you somewhat. Most LR308's like the pistol grip hand holding a little more firm than an AR15. Something to try as well.

Try these items one at a time to try to isolate the improvement of each. And then bring them all together for another group or two.

 

[okiefired]

Re: AR-10 Recoil question.

It takes time for pressure to build and to release. It takes time for pressure to move from one area to another. It takes even more time for mechanical things to move as a result of pressure. At 2600 fps a bullet is clear of a 24" barrel in 1/1300th of a second. In a little over 1/10th of a sec., it is well over 200 ft down range.

Now I realize this is all an aproximation on many levels and 3 bourbons may have scewed my math skills a bit

but..... an m16 runs about 700 rounds per minute. The bolt/carrier on my Armalite moves aprox 5" (after measureing, its actually much closer to 4") one way, thats 10" per cycle, 7K " per minute, < 117" per second. So in the time it takes the bullet to leave the barrel on a 24" .308 chambered AR, it is theoretically possible the bolt/carrier has moved aproximately 9/100ths ". Thats not even concidering how long it takes pressure to build and release at different times in the cycle.........I think. IMHO, b/c movement is a non issue before the bullet leaves the barrel.

okie

 

[Badshot308]

Re: AR-10 Recoil question.

One thing that has to be considered, on a full length gas system, the bullet travels about 12" before it passes the gas port. Looking at reloading manuals for 14" barreled .308 handguns, I'll guess the bullet is going between 2200 and 2400 fps as it passes the gas port and is accelerating towards the muzzle. Now the BCG wont move at all until the bullet moves past the gas port and a small quanity of gas is tapped off. Now this gas has to go up into the gas block, and then back 15.5" though the gas tube where it enters the gas key. On a 20" AR, that bullet is only in the bore for 8 more inches before it leaves the muzzle. Pretty good chance that the bullet has exited before the BCG starts to move. I would like to see some clear, high speed video that actually shows the bullet exiting the muzzle and bolt carrier movement at the same time. If the timing of the system is real close, then depending on size ofthe gas port, gas block design and pressure curve of the particular load, the BCG may start to open or remain closed while the bullet is in the bore.

 

[hlee]

Re: AR-10 Recoil question.

Maybe i didnt make my single shot, action clear.
I lock the bolt back, put round in mag, put mag into rifle hit bolt carrier lever the bolt slams forward and chambers the round, aim and fire. Then repeat process. I can do this 3 to 5 time and get less than half" moa groups with 3 shots and less that 1" moa groups with 5 shots, 90% of the time.

[...]

But if i load 3-5 rounds in the mag set up and fire 3 to 5 times. Slow controled fire with same hold and follow through as single firing. The groups open up to 1-2 moa.
What im trying to understand is what is causing this.
[/quote=Warbone]

Some people report that the first round from a mag prints differently than the subsequent rounds. Do you see a single flier and a tight group, or are the shots randomly dispersed? If you fired 5x5 shot mags, would each position in the mag group tightly, but separately from the rest?

Here are a few other threads on essentially the same issue we are discussing here...

I highly recommend reading through this one as the effects of recoil on POI are discussed...
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2715626&page=1

This one started as a question about buffer spring strength and accuracy...
http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=2846926&page=1

This one has a video that seems to show that on a piston gun there is pressure buildup in the gas system, but the piston does not appear to move until after the bullet has left the barrel.
http://www.snipershide.com/forum/ubbthre...mp;Search=true#

 

[Gildoom]

Re: AR-10 Recoil question.

Get a 22LR out, semi, and shoot. Then shoot your AR10. What 9H said, completely.

Sometimes my groupings open up, and I have to get back into everything fresh. I dry fire a lot when I see my groups opening up. Sometimes I have to just put the rifle down and think about something else for a bit. Sometimes I have to turn my sound down on my headset, noise cancelling I mean. Sometimes I have to just admit I have had a terrible day too.

99% of the time, when my groups open up, it is due to me screwing something up.

 

[maggitas]

Re: AR-10 Recoil question.

Warbone,

Here is my .02 cents worth.

I usually load my last round in the mag of my SR-25 with a dummy round, usually a snap cap. I find on my rifle the bolt catch causes my last round to usually fly about an inch high at the 11 o'clock position. As others have stated driving the AR platform takes more attention to details than a bolt gun. A tuned trigger down to 3.5 to 4 pounds and a palm swell will reap huge benefits on an AR platform. Also a low tech approach is to paint a dot on your stock to confirm that you cheek weld is in the same position everytime as the AR 10 platform has more recoil than you may think. Also have you tried putting the gun in a vice?

Johnny

 

[Warbone]

Re: AR-10 Recoil question.

Range report
See previous post for info and loading methods.
3 3shot groups using single load method avg .631
3 3shot groups using single load method, and gun slightly under gased so bolt would not get locked back by mag. avg .756
3 3shot groups, 3 loaded into mag avg 1.850.
This would seam to confirm i can shot a semi auto ar-10.
But that something is happening to the rounds that are being chambered after firing cycle.
Did some checking. (testing rounds after chambering)
Loading round into mag, inserting mag and releasing bolt. round started out at 2.809, after loading round was still 2.809. no unusal marks on bullet or casing.
loaded 3 round shot one, pulled next round from chamber and tested. Stared at 2.809, came out at 2.803. found a semi circle ring around the bullet about half way down from the tip of the bullet. Bullet is being pushed in.
One would think the forwad motion would move the bullet out a little bit.
i dont have a Concentricity tester so i dont know if chambering the round is knocking the bullet out of wack.
My guess is that it is and that's what is causing my accuracy issues when round is loading after firing cycle.
Anyone out there know what causes this issue
bcg?
barrel upper reciever issue?
mag issue with round in it?

 

[SPfeiffer]

Re: AR-10 Recoil question.

try a different mag. maybe the bullet is dragging and is deforming as it comes out of the mag... might be a big difference between Pmag and stock steel mag. I have had mags that flat would not feed at all.

 

[Warbone]

Re: AR-10 Recoil question.

I have 3 magpul 20 round mags i have been using, anyone recomend a good metal mag?

 

[hlee]

Re: AR-10 Recoil question.

Factory ammo or reloads? If you are getting setback (the bullet moving further into the case), conventional wisdom would suggest your rounds have insufficient neck tension. Do the three rounds from the mag print consistently? If you shoot the first round into a target, second into a second target, and third into a third target (for 3 mags) are the groups tight like the single feed groups or dispersed like the other groups?

Aside... How do you slow down the bolt carrier? That may be the solution.

 

[hlee]

Re: AR-10 Recoil question.

Of course, if the bullet is hitting somewhere as it chambers (which could cause both the semicircle ring and the setback, then a mag change could solve the problem. Can you determine where in the action the bullet is hitting (maybe with a sharpie marker)?

 

[Warbone]

Re: AR-10 Recoil question.

Both factory ammo and reload, ring and setback only happen when round is autoloaded after firing, the ring around the bullet going about 3/4 the way around would suggest it is not the mag making the mark as the mag would only hit half of it. I think that perhaps the round is being pushed up into the side of the throat causing the ring and the setback. That is the only part in the rifle i can think that would cause the damage. Like i say it doesnt happen with one round in and bolt release pressed.

edit. Or i wonder if the extra round in the mag is pushing up on the bcg causing the round to chamber high hitting the throat in the camber causing the marks and setback. In that case it could be the bcg, mag, or upper reciever.

 

[hlee]

Re: AR-10 Recoil question.

Look for some slow motion video on youtube that shows the cycle of an AR. You may be surprised how much rattling around a cartridge does before it settles down and chambers. There may be substantially less of this when being chambered via the bolt release. I am no AR expert, and I do not have a resolution for this...

 

[SPfeiffer]

Re: AR-10 Recoil question.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Warbone</div><div class="ubbcode-body">I have 3 magpul 20 round mags i have been using, anyone recomend a good metal mag?</div></div>

ohh shoot I figured you were using a crappy metal mag... P Mags are the best!that is all I have except the 2 stock ones...

 

[okiefired]

Re: AR-10 Recoil question.

Warbone, have you found your problem yet? If not, does your rifle have M4 type feed ramps? If it dosn't, opening them up to that type might solve your problem. M4 feed ramps seem to make the cartrage chaimber much easier. Good luck.

okie

 

[Warbone]

Re: AR-10 Recoil question.

Tried metal mag same problem, my next step im going to load some round at 2.795 oal and increase neck tension to about .002 see if i can stop the set back ect.

What do you mean by a m4 feed ramp, chamber, upper and lower are the stock cmmg no changes to it.

edit: checked with cmmg it does have m4 feed ramps.

 

[VKC]

Re: AR-10 Recoil question.

Always blame the equipment if possible, but...

Have you considered that your cheek-weld position maybe shifting slightly with recoil? If you shoot continuously from a fully loaded mag you may not be correcting you cheek-weld position and thus eye relief, etc. But when you single load, you bring your cheek all the way off and reset each time, and thus have the some check-weld position. The change or variation from shot to shot can be very slight, but can make a big difference.

The same thing was happening to me, until I finally figured it out.

After each shot, I move my head back and forth slightly to confirm the same exact eye relief and rotate side to side to get no optics shadow.

I also bring my non-firing hand up to my cheek and place it on the cheek piece, using it as a gauge to get the same position. To explain better, I use a PRS stock, and the cheek riser has a front lip or is higher then the rest of the stock. My proper cheek-weld position is just about one forefinger's width from the front edge of the cheek riser.

 

[hlee]

Re: AR-10 Recoil question.

It well could be shifting position when running a mag- and this was mentioned in a few posts above. However, the OP has identified setback as a potential source of the variability. If he were to recreate the setback by chambering and extracting live rounds (the way he identified the setback), then shoot them fed singly (the way he maximizes group precision), he could either confirm or refute the bullet setback as the cause of the variability. Of course, this experiment would be best if it were blinded such that the shooter does not know which cartridges are the controls and which are the tests.

 

[9H_Cracka]

Re: AR-10 Recoil question.

Setback? He's running FGMM, so assume 168 or 175 SMK - neither of which are jump variance intolerant projectiles.

A 308 semi is not a platform you'd be testing these minute of changes anyway, even if you were shooting a jump variance intolerant projectile.

I can year it now - next time I shoot an 8 offhand - "dang, I think my bullet jumped on THAT one..."

 

[okiefired]

Re: AR-10 Recoil question.

I think the OP said he was shooting reloads but that he had the same problem with FGMM. I dont know about FGMM out of an AR10 but changing my reloads COAL from 2.810 to 2.820 out of my long factory chambered LTR with 178 Amax's droped POI 1 moa. Group size remained consistant though. Of course, if I fired the two lengths together, group size would definately increase.

okie

 

[hlee]

Re: AR-10 Recoil question.

"I don't make the news, I just report it."

As it happens I am a scientist, not a journalist, so I just suggest experiments to rule out possibilities.

 

[Warbone]

Re: AR-10 Recoil question.

VKC: i think what you are saying is i can single load and reset my rest well enough to constantly print .5 to .75 moa groups, but somehow dont notice my cheek weld change when firing from auto load. i can tell you with positive assurance this is not the case i am well aware of my cheek weld firing both ways.

Bullet is being pushed back as much as .008, irregular marking on the bullet and possible bullet canting to one side or the other during autoloading. Groups from 1.5 to 2.0 moa.
None of this is occuring with single load method, and im getting groups between .5 and .75 90% of the time none abover 1 moa.

Something is happening when rifle fires and autoloads a new round. In my above post i have changed the Oal and crimp on the round but havnt had a chance to get back to the range.

 

[Low Sioux]

Re: AR-10 Recoil question.

I will just give you my experience with an AR10 T. Same issue with groups. I found that by allowing the carrier to chamber a round slowly with me guiding it with the charging handle that the meplat on the Sierra 168 was jamming into the flat section under the feed ramp. I could actually let the round stop the carrier when I eased the carrier forward by hand. Obviously it was changing the seating depth when stripping a new round at actual speed. Rather than mess with metal work I just tried some amax' s. Problem solved. hope this helps.

Sioux

 

[Warbone]

Re: AR-10 Recoil question.

Well trip to the range with 178g amax loaded from 2.775 to 2.295 oal, with .0020 crimp yeild same results, poor accuracy with autoloaded round.
Still getting marking on bullet, pushback and small canting. I am getting 3 differant grouping 1 set of groups from first shot which is a bolt slam, 2nd shot which is autoloaded from right side of mag goes down and left, 3rd shot which is autoloaded from left side of mag goes down and right.
The makings on the bullet look like the bullet is hitting the lands but i checked the chamber MAX OAL and its about 2.900.
In looking down the chamber it looks like before the lands there is a flat spot then a right angle lip, instead of say a 45 degree angle leading to the lands. I wonder if that is the part of the chamber the buller is hitting causing pushback and cant.
I guess it may be time to have a gunsmith check the chamber.