ar15 vertical string

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uspsamaster

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the gun is a heavy barrel 16" dpms with a free float hand guard and It will constantly group (5 shots) about 1/2 wide and 1 1/2 high. I am shooting off of a bench with sandbags. is there a technique I should try or something on the gun I can tweak in order to improve the vertical string (have tried allot of load changes/tweaks) I have tried several ways of holding the rifle but if there is a best way please let me know.
 
Are you using a front rest with a fore-end stop? If so, is it touching the barrel or gas block in front of the float tube? I've seen that cause headaches in the past...
 
The a2 stock on the back sucks even off bags a bad design for bench shooting. The 16'" probably has a flash hider so that and the bang clang recoil mechanism reduce muzzle rise but cause gun movement. Try holding the back of the sock where the sling swivels are with your left hand.
Do not steer the gun with the pistol grip. the forend A2 or round turn and tilt on bags easily. Use front bag and rear or a rolled up towel. Hold underhand on forend cupping downward into bag slight pressure to shoulder. Heavy
trigger pull imparts movement to the groups. If scope is mounted high enough place hand over top of barrel and free float guard. Use only 1/4 inch of tip of index finger on trigger. After firing make sure gun is in the exact same place on the bags shoulder and pistol grip. Bang clang realign shooter position, sight picture target acquired, exhale 2/3 air hold light and briskly snap trigger. Repeat. Try loading one round at a time. Also dry firing.
 
Have someone else shoot the rifle and see if the same problem exists. Often times we will look at every other solution in the world other than ourselves. If it does the same thing for another good shooter than run down the list of possible solutions.
 
AR off the bench

All excellent advice, and if I may add: M.L.McPherson did an interesting article on this very subject in the Oct. 2001 issue of "Precision Shooting", titled "A ? of Bag Placement and Gun Design". He found that groups will be the smallest, with the AR, when the front bag (sandbag as in both mine and your usage/ doesn't work well with my Sinclair front rest), is placed as close as possible to the front of the receiver, without touching. He started with the bag at the front of the handguard = worst groups. In the center of the handguard = better. Almost touching the front of the receiver = best. If your scope is mounted on the carry handle, that may also be a problem. I get my best groups from my flatop where the scope centerline is less than 2" above the bore, as compared to 4 1/4" on the carry handle. I also use my Protecktor #14 bunny eared rear bag, and remove the rear sling swivel. The top screw is adequate to hold the butt plate ass'y. together. I do hold the rifle very tight, and get my best groups firing from a magazine loaded with 5 rounds, so there is no changing of position (cheek weld) between shots. Just some thoughts that may (or may not) help.
 
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First more about the gun it is a low-pro upper (no forward assist/shell deflector/ ejection port cover and no flash hider, with a flat top and a extra heavy wall thickness A2 style stock)
I have tried single loading and loading 7 in the mag but only counting the middle 5 (my thinking here is the middle 5 are all self loaded with the gun chambering the next round, not first loaded by hand and the last with the bolt locking back) there is not much extra room to move the sandbags back on the handguard (it is a short handguard) but I will give it a try. I have tried front and rear sandbags to no avail. I will also try my hand over the handguard as suggested by DaRealViper.
Thank you all for your time an considerable knowlege, I posted this on a large AR specific site and got lots of you just need to shoot more, shooting more with out changing rifle or techniqe doesn't help it is like doing the same thing and expecting diffrent results. I did however get one .25" 5 shot group (it was with 45gr winchester white box no less, that made me think about load development) but not being able to duplicate it with that ammo or any other I evetually decieded it was a random fluke
 
Try but-stock pressure

You may want to try placing your shoulder behind the butstock, and keeping constant pressure on the gun, but be careful on the rear bag, keep things consistent from shot to shot.

Kind of treat it like a hunting rifle, or one with a 2 piece forend, keep the front rest as close to the lower, without having the lower receiver touching the rest, as previously mentioned.

Have hard from reliable sources that failure to place sufficient force on the butt of the rifle will cause vertical stringing. The reciprocating mass of the bolt and buffer assembly can have a negative impact if shot free recoil, or closer to it. What type of front rest and rear bag are you using?

Can you secure a flat adapter to the front tube to give you a 3" wide foreent that will ride the bags more uniformly? There are a couple of people out there that make such an adapter that attaches to a front tube that has the slot for a front hand stop.
 
I'd never even held an AR until a couple of years ago when I finally broke down and bought one. Mine has a 20" "heavy barrel" with a round free float handguard. After fiddling with it some I just went to using a Harris bipod on the front with a piece of carpet under the bipod's feet so that it would slide instead of bounce. Trying to shoot free-recoil did NOT work at all. Too much stuff moving around that wants to be held, so I pull it tight into my shoulder.

It won't shoot with my bolt guns by a long shot, but for a factory .223 it's not bad with 10 in an inch at 100 yards if I don't screw up. Me screwing up seems to get more common the older I get too. :eek:
 
Not the load or rifle, it is your breathing

What you describe sounds like breathing issues. If you pause at different intervals in the natural breathing cycle (where we all grew up with the bad advice being exhale halfway), it can cause that vertical variation. it is hard to train yourself to pause halfway thru the breathing cycle exactly at thet same place, espeically if your heart is really pumping. try pausing at the bottom of the breathing cycle, where you have totally exhaled, and pulling the trigger there. Dont pause more than a few seconds at that low point.

Jim
 
I mostly let the gun free recoil (the trigger is factory set at awful) so that may be the problem as well. The gun is not one of the piston setups. The bags are old bluejeans filled with sand and sewn shut (not perfect but very cheap and I don't compete but it is good enough to get .25-.45 regarluy out of my mostly factory bolt guns). I breath out half way, is it any diffrent with an AR? If so, I can try it. It is only time at the range and ammo both of which is fun to spend (money on the other hand is a little harder to come by at my house)
 
Mr. IPSC, I'm curious where the first and seventh shot hit.
 
Adjustable gas regulator?

From what I can tell, the shooters who "benchrest" their ARs have generally turned off their gas systems. A gentleman who posts here a lot and is familiar with ARs is "mike in co", hopefully he will chime in on this one, as he is knowledgeable about this topic, more so than most.

Try putting shoulder pressure behind your gun and not shooting free recoil, if you can not turn off your gas DI system.

Pistol shooters can chime in on this as well, on several models of pistol, if you "limp wrist" the shot, some will fail to function, as the inertial portion of their recoil system is defeated, when the pistol free recoils and does not have the resistance of the shooters hand to allow the action to function.

To an extent you may be having the same overall effect in free recoil shooting your AR, creating a bunch of variance in the function of the carrier/bolt/buffer system.

Several good 2 stage triggers out there, but they are pricey!

Have a god one and enjoy shooting, that's what this is all about!
 
I have a 24" Wilson 1x8tw barrel Flat top ar15. Also a Mini-14 17.25" 1x9 tw barrel a Savage 12fv and a .222 Thompson Encore.

The following works in several rifles. In Desert warm climates low altitude.

Try 23.6-23.7gr H4895 CCI400PR 55grFMJ Fed Brass 2.255"OAL.

69gr SMk 23.0gr H4895 remainder same as above.


High altitude cooler climates could try 23.1gr AA2015BR 55gr fmj remainder same as above.


The 45gr are difficult to get good groups with in 1x9 and 1x8tw barrels.
takes more development to get nice groups.
 
thank you again for all the tips. As for recomended loads, thank you but I need them to be suitable for varmit hunting (is the SMK?) as that is the main purpose of the rifle is preditor calling and a walk around varminter. As for where the 1st and 7th shot? the 7th usually gets ejected or waits for a new mag to start a new group. the first if my memory serves me it goes about 1/2" high and a little to the right. again if memory serves me it is the same as my barrel fouling rounds but it has been awile since I payed attention and not just put the rounds at a dirtclod or a broken clay pidgen/old 12ga shell ect
 
This first thing I would do is put a good trigger in it. Best bang for the buck in regards to shooting smaller groups. Most AR factory triggers are junk. Jewell and Geissele make a good one for the AR's. Save up...they are well worth it.

Also, check for parallax issues on your scope.
 
Vertical

I skimmed this quick and didn't notice this, but did you remove your rear sling stud from the stock? I get most vertical from shoulder pressure, besides the stud.

How are you charging your reloads, weighed or thrown, with ball or extruded? How much variation in charge weight and what kind of extreme spread are you getting in velocity? Do you crimp your reloads?

If your loads aren't showing any pressure you may try working up .3 gr at a time and see if vertical decreases.

Just different thoughts. nhk
 
I will try removing the stud as well as i have not tried that. the current loads are with blc2 and it seems to throw very close so I weigh every 3rd or so. I don't know what the extreem spread might be as I don't have a chrono. I am at max load so I don't want to go more but as I was working up to it, it seemed to have the same shaped groups. I need to go shoot some more so I can more definitvely answer some of these questions.
 
BLC-2 Ball c-2 in my mini-14 was a problem. When I first started accurizing at 50yds it wouldn't group good inside a pie plate now I shoot asprin and thumb tacks with it. Blc-2 gave me a round circle group holding on a dot the size of a BB the groups looked like a clock dial 1" round. I never used the powder again. H4895 is a much better powder. If you want to use a ball powder try Win 748 Hodgdon 335 These ok (AA2230 and Ramshot TAC).

If I'm shooting Semi Auto out of a clip I crimp mildly with a Dillon Die. Lee Factory Crimp works nice also.

As for the bullets. Weight is the main factor.
With the loads I provided I used Remington 55gr an 45gr Spire Points for killing power . You could use a Hornady vmax or A Speer 52gr TNT.

As for the SMK that is a Sierra Match King which is a hollowpoint and very effective on live targets as well. With that same load a 64gr Spire Point winchester bullet is very effective.

Once a load is worked up correctly you can change bullets and seating depths to suit your needs. 2.24"oal Is another good starting place for
cliped round Overall Lenght.

If you want to try different bullets then this is my suggestion:

http://www.bulletsamples.com/Stock.html



Hodgdon used to sell

Xperimental Packs will be in limited supply.

4 different 4 oz cans

Light Varmint: H322, Benchmark, H335, Varget

Lots of people Like Varget for Heavy bullets I don't I use Alliant Reloader 15.
Its cleaner and shoots better in a gas gun. H4895 is a good choice for both light and heavy bullets and happens to have uniform ignition characteristics for reduced loads.



I've developed reduced loads suppressor loads Hunting loads target loads
gallery loads squib loads cast and jacketed in the following calibers: .45acp, 9mm, 32acp, 250 Savage, 300 Savage, 22-250 Remington, .243 Winchester, .308 Winchester,
.222 Remington, .223 Remington, 6.8 Spc Remington.



For a copy of my free reloaders spread sheet follow the links on my shooting
page :


http://maxpages.com/thejedilair/Firearms_Shooting


In the 3rd photograph right hand side the BLc2 clockwork pattern is what I was refering to:

http://wumingta.tripod.com/pub/id3.html

Notice my groups in the smiley faces and above the blue tape those are my recommended loads. As for one shot one kill look at the eyes and the mouth of the Smileys.
 
Shooting technique

From the results you get from your bolt guns I don't think your technique is the problem.

I've been working with two 16" barreled ARs with 1:9 twist barrels and they are a little tricky. Both have round free-floating tubes. There is no load data specifically for them, but I think faster powders (H322, X-Terminator) are the best bet*. The 55 gr poly tipped bullets don't do bad in the 1:9 twist. I'm convinced they are 1 MOA rifles though. I've used both sandbags and bipods.

I sighted in an AR carbine for another person at the range with 69 gr Federal Match Ammo and fired a second round to check zero and it went through the same hole. He shot three rounds then and bracketed my two with a 1" group.

*H4895, TAC and Varget do OK, but I got into pressure with H335. The ball powders are more temperature sensitive and don't perform well in the cold weather. I haven't chronographed the Ramshot powders (X-Term, TAC) over a range of temperatures, but they may not do too bad(?). I'm waiting to get my hands on the new IMR 8208 XBR :) nhk
 
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