Sand bags vs. solid rest - how much difference?

E

Economist

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I have been developing loads for my Ruger American in .270 Win and I can't seem to get them to 1 MoA no matter how much I play with charge weights, seating lengths, neck sizing or full length sizing, etc. My groups are usually fairly tight in the vertical axis, but tend to wander by a few MoA in the horizontal axis.

I had a flash of insight one day while I was going over my notes. When I do my testing at the 100 yard range, I shoot from a bench, but I don't have a solid rest. I use a front/rear sandbag setup. I am pretty sure I am giving up some accuracy with my setup, but how much?
 
Only way to find out is test a solid rest compared to what you normally do with sandbags.

I generally do all my testing with a bipod, and a solid rear bag. From what I've learned, if you have a solid rear sand bag (filled with heavy sand), and a front bipod, it makes for a pretty solid platform.
 
How much is mostly a guess ...

I am giving up some accuracy with my setup, but how much?
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I don't know if anyone but you, can give you a definite answer. I do know that there is a difference and have seen it more than once. Your sandbags will give you tighter groups. I have even seen a difference between sand-bags and Bi-pods. ..... :(

Be Safe !!!
 
The only way I see a rest being a better advantage is if its adjustable for vertical and horizontal movements vs using a sandbag setup. What loads have you currently tried with your .270?
 
If one hand holds a rifle to their shoulder when shooting it, soft bags are best. Otherwise, the pressure of the rifle's fore end on the bag will not be the same from shot to shot. It'll bounce off a hard surface unequally from shot to shot. The pressure of the stock's fore end on a hard bag can be enough to bend it so it touches a free foated barrel; a guaranteed accuracy destroyer as the muzzle axis no longer shoots bullets to the sight's point of aim on target.

Hard bags are best used with rifles whose stock are shaped to allow a 3-point support; one on each side of the fore end's tip and one just in front of the stock toe. Such setups are used firing the rifle by touching its few-ounce trigger then the rifle slides back in free recoil not touching any part of the shooter whatsoever.

Horizontal shot stringing is common with hand held rifles against ones shoulder as its fore end rests on something atop a bench. Us humans don't hold the rifle exactly the same way for every shot. Sitting at a bench puts ones body at a different angle to the recoil axis than field positions such as standing, sitting, kneeling or prone do. Zeros obtained from such bench shooting are typically about 1 MOA different in windage than those obtained from unsupported field positions.

I'm assuming the barrel's totally free floating. If not, then it may be contacting the side of the barrel channel in the stock.

Try laying down in prone with a soft bag under the fore end and another under the stock toe. I get much better accuracy that way than traditional benchrest shooting holding onto a rifle.
 
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Thanks Bart B, I guess I can't blame my equipment then, since I do hold the rifle to my shoulder. I will have to work harder on my inputs. The barrel is supposed to be free floating from the factory but I don't think I have ever actually checked. It might be time for some sandpaper.

I have tried different charge weights from 53 - 59 grains of H4831 with several types of 130 grain bullets. I had good results with Nosler BT and Hornady plastic tips, but they are too expensive for punching paper. I settled on Speer 130 grain BTSP because they are easy to obtain and relatively cheap. I'm using R-P cases because I have a lot of them and the Federal cases I have seem to have loose primer pockets. I'm using WLR primers.

My best so far with the Speer BTSP is 55.6 grains of H4831, bullet seated to touch the lands, neck sized R-P case. This yields about 1 MoA in the vertical axis but 2.5 in the horizontal.
 
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From what you just stated, I would def check the "factory free floating barrel" first before anything else. You're loads aren't far off from the ones I use from time to time and its usually pretty good if I do my part.
 
+1, make sure the barrel does not touch the stock when you are holding it, let someone else run a new dollar bill between the forearm and barrel when you are holding it on the rest. I bet you have a spot that is touching. The Ruger American stock flexes a lot. I have one in .308, nice and accurate with factory ammunition. Had to sand down one spot on the forearm right out of the box.

David
 
It's steadiness that counts whether it is sand bagged or on a solid rest. If the base the solid rest is on shifts (say it is a rock on sand), that's no bueno. Anyhow, as mentioned before, keep pressure away from the barrel.
 
I don't want to get to, to, pushy or technical.

There is a lot of difference between soft tissue (your hands) and a machine rest and 'sand bagging' is some place in the middle. Every change in stress/pressure will impact the dynamics of the recoil and harmonics of each weapon when fired.

With this said. What I would do:
Start with a full break down of the weapon, clean everything. Lube where needed and put a protective coating as needed as the weapon is put back together. Check the barrel channel for contact between the metal and the stock. Check the connection points between the receiver and the stock (some are pillars, some are cuts in the stock {if the latter and the stock is wood, think about glass bedding}, some are other means). Some receivers do better with tightening in a set sequence. Check with the manufacture on this if there is any question. The receiver must be held tight and stress free.
Moving on to the scope/sights. Check (degrease if appropriate) fit and tightness.
I use a pant leg from an old pare of jeans, sewn closed to hold a double zip lock bag of plain old rice that is packed tight with no ballooning with air. This bag set on my shooting box that is on top of a table. My hand is between the rice bag and the fore-end of the rifle. I don't hold on, just cradle. The butt-stock is pulled into my shoulder with my hand in place. Constancy is the desire.
I start with a box with a grid target taped to it at 35 yards. This is close enough I don't have to walk a lot (old broken fat men don't like to walk a lot, I also check my blood sugar to see it is in the right range, told you I was broken). This range is easy to get the sights in line with the desired condition.

I have found very few weapons that I was a better shot than the weapon could shoot.

I have always found it strange where some shooter goes out hunting and uses a mono-pod or by-pod and then free hand shoots. Then complains that there is something wrong with the weapon. I have though of tiring to get them all wound up so I could buy that no good hunk of junk for a song. It is just a thought :)

Hope I haven't bored you or irritated you. Just tiring to help.

To you question. All depends.. on the weapon, load, how it is all held.

Load with care,

OSOK
 
"...can't seem to get them to 1 MOA..." It's a hunting rifle. Some of 'em are just not capable of 1 MOA.
"...barrel's totally free floating..." Guarantees nothing. Some rifles, even two from the same maker, like a floated barrel and some do not. Check it for sure, but if it is floating try putting a pressure point in about an inch from the end of the forestock. A temporary point will do for testing. Just remember that an American is not a target rifle.
I'd lose the rear bag. Never seen much point in 'em. A front bag rest, at the proper height, doesn't get any more solid. Firm, but not hard.
 
What kind of surface you shoot off depends on how you are going to use the rifle. Guns tend to recoil away from hard surfaces, especially magnums. For hunting I use soft bags filled with cat liter. When shooting in the field from a rest I put my hand under the stock or fold a coat if there is time. Target shooters, on the other had, require a more consistent rest.
 
I would only add three things to the already excellent advice you've been getting here.

First, I've never been wild about using standard rifle primers with large quantities of slow burning powders, such as H4831. If it were me, I would go to a rifle Magnum primer, back off the powder charge 10% and work up carefully to your desired velocity again. I've found that when trying to get that last bit of accuracy out of reloads in a light sporter, the primer can make a difference in group size roughly equal to the amount you're lacking. Matter of fact, experimenting with several different primers was an integral part of my load development. You can't assume that a popular primer will give the best results in your rifle just because it is well thought of.

Second, check your guard screws for tightness.

Last, don't get the idea that boat tail bullets will automatically deliver better accuracy than spitzers just because they're boat tails. I used the 130 grain Speer spitzer exclusively in three different .270 bolt guns and all delivered MOA accuracy with them. According to the gun writers, the biggest advantages of boat tail bullets are long range energy retention and the fact that it allows the manufacturer to turn out a high quality bullet easier than with a spitzer. So say the gurus. In all of my loading, the rifle liked what it liked, and that could be either type of bullet without rhyme or reason. Hope this helps.
 
Check the action screws !
Bags and you allow the fluid motion of the recoil.
A mechanical rest doesn't have that fluid motion and still has bounce.

Maybe your too close to the lands allowing too much pressure.

I haven begun to reload yet , but I have done some experiments with factory ammo, tangent and secant ogive.

I wanted to know why some bullets did good and others didn't so I bought a comparator.

I got good groups with scirocco by rem. 3006 150 gr. Secant shape.
Same with 150 gr power shoks.
I bought a oal gauge and found the secant was a .090 " jump.
The shoks were on a .048 " jump. ( tangent )
I'm just learning myself , but this is what I've come to know so far !
 
There needs to be more clearance than a dollar bill's thickness (1/250th inch thick, allows easy passage with 1/200th inch clearance) between the barrel and stock fore end. 1/16th inch is good at the front tip and 1/32nd inch at the receiver. Maybe more for flimsy stocks.

Many rifles are heavy enough that their own weight bends the fore end tip up the thickness of a bill and touches the barrel of a rifle resting its fore end on something. Measure yours with a dollar bill and see if it slides easy under the barrel on a horizontal rifle resting its fore end tip on something. And the stock toe resting somewhere.
 
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