Accuracy Rest vs. Bag

[Lee King]

I bought a Larue upper about a year and a half ago. I was having a lot of problems with accuracy. I was getting groups of about 3 moa out of it. I tried playing with different ammo, with and without the comp etc. Then one day the groups suddenly went to just a hair under 1 moa. I realized on that particular day, I forgot to bring my rest and just layed the rifle on my gun bag.

The rest I had been using was a cheap Hoppes front rest. The saddle was metal with a felt lining. It was meant to mount to a piece of wood. But I never did. It was pretty unstable at recoil. Frequently I would have to catch the forearm as it fell off the rest. So I upgraded to a Caldwell Rock. It has a bean bag saddle. Wheel adjustment elevation. Wide base with the screw type spikes to level it. I use a simple bag saddle for the rear. I have a free float tube on my upper and was careful to rest only on it.

Yesterday I went to the range to do some actual homework on ballistics for my rifle. Chron, try to come up with an actual table vs. theoretical etc. I was using the caldwell rest. Again, my groups opened up to 2 moa at 100 yards. They were bad enough at 200 that I didn't get any useful data.

Any suggestions as to what I might be doing wrong? I felt like the gun was very stable. I'm running American Eagle XM193. At matches the gun shoots very accurately when I'm offhand or using barricades etc. I checked the scope mounts to make sure nothing was moving or loose.

Edited December 21, 2009 by Lee King

[Dan Sierpina]

What kind of bag do you have on the rest? What kind of rear bag are you using? Look at rear bags at Sinclair International. You want a sturdy bag packed pretty tight with sand.

Is your rear swivel contacting the bag when you shoot? That can do it too.

[Matt Cheely]

Are you holding it differently when you shoot off the bags? Too loose maybe?

[Lee King]

What kind of bag do you have on the rest? What kind of rear bag are you using? Look at rear bags at Sinclair International. You want a sturdy bag packed pretty tight with sand.

Is your rear swivel contacting the bag when you shoot? That can do it too.

The front bag is whatever that came with the caldwell rest. I'm not sure what it's filled with. Probably sand. The rear bag is a lot like the sinclair. Again I'm not sure what it's filled with. But it has the "ears" for the buttstock to rest in.

You bring up a good point. I have a M4 stock on the lower right now. I tried resting on the swivel but it is very awkward to hold position. The only other place with enough elevation is the lever that adjusts the stock in and out. Maybe this is my problem.

Do you think if I could get enough under the rear bag it would be better to rest the buttstock tube in the "V"? Maybe I should take some blocks or something next time to elevate the rear bag to try it.

[Lee King]

Are you holding it differently when you shoot off the bags? Too loose maybe?

I've tried tight and loose. I feel like when I hold it tight my heartbeat etc. moves the reticle around just a hair. The last attempt I held it loose and let the bags/rest take all of the weight. Then I tried to squeeze the trigger like the benchrest guys do. Almost pinching it with my thumb on the back of the grip and the tip of my forefinger on the trigger.

Usually, my off hand goes to the back and squeezes the "V" to make minute adjustments to elevation.

[Dan Sierpina]

Lee,

My experience with the AR is it likes as neutral a grip as possible. I hold the pistol grip lightly, but, move/squeeze the rear bag to readjust the crosshairs. If you could support the buffer tube rather than the adjustable stock, it would give much better results. I have A2 stocks on my rifles, and the rear bag contacts in front of the rear swivel.

[Jesse Tischauser]

Have a buddy or anyone else that may be at the range the next time you are out there shoot it too.

[bigbrowndog]

Lee, shoot the gun in your hands with a little support from bags and such, it is the way you will be shooting it at a match and you should do it that way at practice, the gun can give you untrue results shooting it differently than the way you intend to do so at a match.

Too many people get wrapped up in shooting the AR the way they see others shoot bolt guns, or target rifles, or the way the gunwriters tell us we should, hard contact with the fore end without extra support or a poor position even with a good solid hold can produce erratic results and be very frustrating. I had the issue once during practice and luckily a fellow shooter was there and told me the table I was laying on was moving all over the place, my holds were good and solid but the position was not.

When its in your hands use just a light wrap from the fingers on the fore end, and grip the pistol grip about like you would if you were shaking hands with a girl, just enough to control the gun from your chosen position.

Trapr

[Lee King]

Lee, shoot the gun in your hands with a little support from bags and such, it is the way you will be shooting it at a match and you should do it that way at practice, the gun can give you untrue results shooting it differently than the way you intend to do so at a match.

Too many people get wrapped up in shooting the AR the way they see others shoot bolt guns, or target rifles, or the way the gunwriters tell us we should, hard contact with the fore end without extra support or a poor position even with a good solid hold can produce erratic results and be very frustrating. I had the issue once during practice and luckily a fellow shooter was there and told me the table I was laying on was moving all over the place, my holds were good and solid but the position was not.

When its in your hands use just a light wrap from the fingers on the fore end, and grip the pistol grip about like you would if you were shaking hands with a girl, just enough to control the gun from your chosen position.

Trapr

I rarely use a rest for shooting my rifles in general. Especially for practice. You don't get to during a COF. That's part of my problem in that my technique could very well be flawed when I DO try to use one. I've been skipping the boring homework part of rifle to do the cool stuff. It's time to get serious and KNOW my holdovers etc. and not guess. I'm only using the rest so I can get (in theory) as consistent and repeatable results as possible. I know where my rifle should be shooting. I was trying to validate all of the parameters in the theoretical ballistics tables for my particular rifle. I was assuming, perhaps erroneously, the rest would take the nut behind the gun factor out of it so I'm measuring pure rifle/ammunition performance.

[bigbrowndog]

in that aspect then you are good to go, however trying to get accurate trajectory data directly from your rifle is a very big pain in the A**!!!!!!

i've tried on a few occasions thinking It would be better than using the published data tables, but its extremely aggravating, especially when conditions are not favorable or change constantly. Velocity, sight in zero, and then holdovers and unders are all I really worry about now. Getting the holdovers and unders is pretty simple you pretty much are just verifying that they are close to what the published data calls for, within an inch and I'm happy.

I would still check holdovers etc. from match shooting positions though.

trapr

[Lee King]

I'm going to thread drift myself here for a sec.

I only have a 200yd range to work with. I had zero'd my rifle for a theoretical 300 yd zero. About 2ish" high at 200. But that didn't work out so well at FB3G. Confusing the issue was, I hit everything at BRM3G including the 400ish yard target. But they were on a downhill angle so.. Ultimately, I came away from FB3G questioning myself.

I have the Burris XTR with the BDC. My plan was to come up with the closest numbers I could get, then keep a card for the subtensions and actually USE it instead of guessing at theoreticals. But the BDC is calibrated for a particular load. So my idea was to zero it at 100. Then measure the actually 200 yd drop. Cron the load. Then tweak the ballistic coefficient or muzzle velocity a little bit until the table was close to the actual. Then I could confidently say X line is on at say.. 330 yards.. Y at 460 so on and so on.

Am I somewhat on track with limited long range facility?

[bigbrowndog]

Lee, with 2ish inch high at 200 you are probably closer to a 250yd zero than a 300yd, try more like 4 or 5" high. I looked at a 69gr bullet at 2900fps, and its 5" high at 200 for a 300 yd zero.

even a 55fmj at 3150 is 4.5"high

Trapr

Edited December 21, 2009 by bigbrowndog

[Lee King]

So do most people shooting 55gr just shoot for 4.5" high at 200 and assume they're good to go beyond? Or do people generally do what I'm trying to do and actually figure up velocity and actual drop etc?

[bigbrowndog]

I personally would sight in 4.5" hi and then verify somewhere somehow. but have the confidence in knowing that you should be very close to correct. and get used to aiming slightly low for 200 and 100 yard targets, what scope do you use and how big is the aiming mark 2moa 4moa??????

You can use the dot to your advantage with your trajectory, Ex: 2moa dot, 250yd zero,......at 200yds its 4" across, so the top of it is 2" high at 200yds, the center of the dot should be dead on at 250yd, at 300yds the dot is 6" across and so the bottom is 3" below center, that puts it very close to on for 300yds. this allows you to still aim with the dot but actually hold slightly high or low depending on the target distance.

Trapr

[Dan Sierpina]

Geeze Trapr, Lee said he uses the Burris XTR.......

[AlamoShooter]

my groups are getting better off a table top now that I final listened to Trapr.

I have a Meopta and I use the (Top) of the dot at 200 yards with the power at 4x This lets me do the math with the 2 min dot and 2 min gap to the top of the post.

If I shoot at 100 and less yardage and the scope is at 1 x the bullets hit inside the top of the dot

this figures out to a 4" dot at 200 yards = 2 " above center line at 1x and 100 yards the dot is 8" ..or 4" above center line.

It is good to know the size of your retical at each power setting. If you have the standard rear focal plain retical.

The thing I am working on now is how to keep my tail from waging when I shoot.

[Dan Sierpina]

Lee,

I'm using the same scope, I think its the 1st Generation. I only have 100 yards to sight in, but, the 300 yard dot took out the Larue's with ease. In any case, the longer the distance you have to verify, the better off you are.

Are you using a decent ballistics calculator? There are a bunch of them out there. A good free one is the JBM. The site is...

http://www.jbmballistics.com/index.shtml

[Doug H.]

Run a ballistic table on your load using http://www.jbmballistics.com/calculations/calculations.shtml or similar and then you will have a better idea how high you need to hit at 200. I used a 275 yard zero last year using this method. I only have a 200 yard range to verify my loads and it worked out quite well for me.

Doug

[Lee King]

Yeah I've run the tables using the JBM calculator. The problem is "300" and "400" etc in the Burris BDC doesn't match what xm193 does.. or rather the JBM tables don't match the subtents of the BDC. I was trying to validate the tables, then know what the actual range of each line was. It makes a difference when you get beyond 300. Fortunately, I've only seen beyond at a match once. But I know it happens.

Thanks for all the input. This is very helpful. I think my next range trip to re-zero will also include some experimentation with different methods of resting the rifle... for zeroing purposes.

[jobob]

Doug's zero is real close to what I've been using. Sighting in on a 100 yd. range I sight 4" high. With my Accupoint TR21, amber triangle, I put the tip of the triangle on the bottom edge of the plate from 75 to 250. It's on at about 275 - 280ish. At 300 hold top of plate. 400 is an educated swag.

[HRider]

I have found that if I am standing, kneeling, sitting, etc. that my POI is different than when I am prone. I guess it is a difference in the way I am holding the rifle. I am zeroed for 300 (iron sights) but when I go prone, I have to treat it like a 200yd zero. I have done this at the range several times going back and forth from prone to standing and it holds true for me.

Hornady has a ballistics calculator on their website also that might be helpful.

Hurley

[Lee King]

Ok so here's a really dumb question back to the OP.

How do you set yourself up when you zero your rifle, test ammo etc.? When you want to get the best group possible out of the rifle?

Prone? Table? Rest? Sandbags?

[HRider]

To test ammo, I mount a scope on my rifle and put it on bags (front & rear) on one of the shooting benches at my local range. I let the front sit on the bag and hold the rear of the stock mith my left hand (I am right handed) just to steady the rifle for windage. This seems to work best for me.

For zeroing, I start using the same method, without the scope (I shoot irons), once I get it where I want it like that, I change to a regular hold, but steady the forend on the bags and make any fine adjustments needed.

I have only been shooting matches with the rifle for a few years now, so I am learning on a regular basis (now know a lot of things not to do )

Hurley

[Dan Sierpina]

I use a Hart front rest, (cast iron), a thick leather rear bag. My club has some heavy benches to shoot from, which helps. A light handling of the rifle on the rest gives the best groups. Then, I'll monopod from the prone postition to see how bad I am

[Lee King]

Anybody throw a bag over the top of the handguard?