Bag hardness ?

[fishbone]

Tony Boyer points out in his book that hard front bags opens group.
My front bag is rock hard. I'm not sure how softening it would help.

Using a shade tree front rest, my vertical travel range works it self 'up' as I shoot, and needs several coarse downward adjustments during a shooting session. I can't figure where that's coming from. Bags are rock steady, as is the front rest to the bench. The gun returns to battery well. Seems strange.

 

[Jerry W]

Having to move the rest down during your shooting session could be caused by the rear bag settling during firing. The sand may be becoming "unpacked" during transport. After setting your equipment on the bench, try pounding down on the buttstock while sliding the rifle back and forth in the bags. That may help settle the rear bag.

I'll be interested to hear if anyone can define what a "too hard" front bag feels like. I've struggled with this in the past and have been doing as suggested in Tony's book and fluffing up the bag by squeezing and massaging it every once in a while. That seems to have helped.

Jerry

 

[Hal D.]

TB couldn't possibly be right. Keep that bag as hard as possible.

Tony Boyer points out in his book that hard front bags opens group.
My front bag is rock hard. I'm not sure how softening it would help.

Using a shade tree front rest, my vertical travel range works it self 'up' as I shoot, and needs several coarse downward adjustments during a shooting session. I can't figure where that's coming from. Bags are rock steady, as is the front rest to the bench. The gun returns to battery well. Seems strange.

 

[Butch Lambert]

fishbone,
I believe the directions on the Shadetree website address this. You need to center your stick in the lowest position. Settles the butt of your rifle in the rear bag. I pound mine in. Now start with your aiming point about 1"-2" below the lower part of the target. 2 shots and your rear bag will be settled and your joystick travel will take care of any vertical that you need.

 

[thumper4fun]

You need to center your stick in the lowest position. Settles the butt of your rifle in the rear bag. I pound mine in. Now start with your aiming point about 1"-2" below the lower part of the target. 2 shots and your rear bag will be settled and your joystick travel will take care of any vertical that you need.

Works well for me.

 

[John Kielly]

I also rip the ears of the bag apart before jamming the butt in.

 

[Terry Balding]

"My front bag is rock hard."

Is this legal?

 

[Butch Lambert]

Terry, if the bag is filled with sand, it is legal. Tony B. is right, a hard front bag can contribute to vertical.

 

[goodgrouper]

"My front bag is rock hard."

Is this legal?

Technically, no. At least in the NBRSA. Rules state that the bag must be able to be deflected 1/4" by finger pressure. Of course, that is very vague, and I've never seen a M.D. enforce this rule. But you don't want a rock hard bag anyway. Was it TB who said that the bag should feel like a ripe orange? That is a good description to go by.

 

[Greg Walley]

Hard Sandbags = Vertical

Technically, no. At least in the NBRSA. Rules state that the bag must be able to be deflected 1/4" by finger pressure. Of course, that is very vague, and I've never seen a M.D. enforce this rule. But you don't want a rock hard bag anyway. Was it TB who said that the bag should feel like a ripe orange? That is a good description to go by.

We’ve fixed a lot of bad guns-barrels-scopes-actions over the years by simply removing a bit of sand from both sandbags.

Greg Walley
Kelbly’s Inc.

 

[CYanchycki]

Technically, no. At least in the NBRSA. Rules state that the bag must be able to be deflected 1/4" by finger pressure. Of course, that is very vague, and I've never seen a M.D. enforce this rule. But you don't want a rock hard bag anyway. Was it TB who said that the bag should feel like a ripe orange? That is a good description to go by.

If one thinks about it, a 1/4" inch in a bag is QUITE a lot. I still for the life of me CANNOT figure out how to keep sand in the sides of the bag trying to keep it that soft. I will bet that if a front bag check were done 75% would fail.

 

[goodgrouper]

If one thinks about it, a 1/4" inch in a bag is QUITE a lot. I still for the life of me CANNOT figure out how to keep sand in the sides of the bag trying to keep it that soft. I will bet that if a front bag check were done 75% would fail.

I'll bet it would be more like 95% fail.
This rule is pretty antiquated if you ask me. They should either dump it or change it.

One of the things on my list on the benchrest wishlist thread from awhile back was a front bag and rear bag that have seperate, sewed-off compartments for sand. Imagine how nice it would be to have the sides of the front bag seperated from the bottom with a simple row of stitches. You could leave the bottom half empty and the sand from the sides wouldn't fall into it. Only then could you possibly follow the rules of 1/4" horizontal deflection.

 

[Wilbur]

First, your bag needs to be at least 1/4 inch thick. From there it's a simple matter of finding somebody with strong enough fingers.

 

[Charles E]

We’ve fixed a lot of bad guns-barrels-scopes-actions over the years by simply removing a bit of sand from both sandbags.

Speaking of "over the years," way back in the last millennium, a lot of people were bag squeezers. Then came the joystick rests.

In the old days, what we'd do is to slam the rear bag down on the bench till it made that "I'm solid" sound (no flat bottoms allowed, remember?). Then, we'd pound the butt into the groove between ears. Next, fluff things up so you could aim.

How many still slam (or even plop with vigor) the bag down & pound the stock into the ears, but skip fluffing the duff because the adjustable joystick front will let you aim?

So, the rear's easy. Don't get the ears too full, and have the base so you could shoot by squeezing the bag. In fact, if you've got a RBRP, you might be surprised to see how fast you could shoot. I know, no RBRPs out there anymore...

I can't think of any way to get the front bag like a ripe orange. Well, I can, but it may not be legal. Just in case anyone wants to test the rules, here's how.

The front sandbag is just going to be hard, no matter what you do You can't fluff it with each shot. Trick would be to also make it thin, like an old Hohen bag. Now used some closed-coat foam between the bag and the top. Bag is still filled with sand only, just like the rule states The softness comes from the rest. Bag is like the skin of the orange, the ripeness comes from the rest. Problem is to design things so there's no left-right or front-back movement.

* * *

Here's one from column B. In long range, I've become bewitched by the .338s. There is a lot of torque generated in firing a 300 grain bullet down a 10-twist barrel. The forearm twists a lot, so the sand in the front bag gets "reoriented" pretty quickly -- sometimes with less than 10 rounds (5 sighters, five for record). When that happens, the rifle doesn't shoot so well.

That won't happen with a PPC or 30BR in 10 rounds. But over time? Probably. You gotta fluff the front bag from time to time, too. Once a yardage? Once a match? I don't know.

I do know if you're going to buy into bag hardness being a factor -- and you probably should -- you're going to have to get innovative. Bags & rests have developed technically along a path where that gets harder & harder to do.

 

[Boyd Allen]

On the subject of "fluffing" the front bag, if you seem to be caught in a dilemma of not being able to keep enough sand in your front bag's ears, you might try backing off the side tension adjustments quite a lot, taking the entire top assembly out of the base (talking ancient Hart style rest here)turning it over, and giving it a few shakes. After you do that, carefully replace the assembly in the base, the rifle in the bag, and then readjust your side tension. This will trap some sand in the ears for a number of shots, but the procedure will have to be repeated from time to time.

Many years back, I had been shooting a loosely filled cordura bag, one of the thin ones, on an early design Hoehn windage tops. I decided that it would probably track better if I filled the bag so that it was harder, and retained its shape better, form shot to shot. After adding more sand it tracked better, and shot worse. There was an immediate, and significant increase in vertical. I took the sand back out, and decided that since there was not tracking trophy, that I could live with having to adjust aim more, from shot to shot.

 

[Charles E]

...l I decided that it would probably track better if I filled the bag so that it was harder, and retained its shape better, from shot to shot. After adding more sand it tracked better, and shot worse. There was an immediate, and significant increase in vertical. I took the sand back out, and decided that since there was no tracking trophy, that I could live with having to adjust aim more, from shot to shot. [emphasis added]

Bravo, Boyd. Worth repeating -- Bravo.

All we ever see these days is "tracking, tracking, tracking." Tongue firmly in cheek, maybe they could grow the IBS by giving a tracking trophy. Betcha we could get UPS & FedEx to fight over sponsorship...

 

[goodgrouper]

Those who talk about the importance of tracking are doing it in the context of free recoil shooting with a "knob tweaker" type front pedestal rest. Obviously, tracking won't apply (as much) to bag squeezers or Farley users. There is an art to getting things set right for free recoil/pedestal. If it won't track without giving vertical, it's time to look for another type of bag, front or rear or both.

 

[Boyd Allen]

I know that you have spent a lot of time and resources getting those details right. How close does your rifle return...on average?

 

[goodgrouper]

I know that you have spent a lot of time and resources getting those details right. How close does your rifle return...on average?

Well, I shoot a 36x Leupold with a dot reticle and on average, I'd say my dot is within a bullet diameter of center mothball---- IF my rifle is in tune. If it's really hummin', it'll be spot on. When my load starts getting too hot, it can be a full ring or two to the right of the mothball.

I've also found that bags are only part of the equation to tracking straight. The stock must be straight and riding surfaces must be parallel too. Also, the barrel (or muzzle) must not be pointed downhill in the stock. If it is, it will lift the rear end of the butt up and out of the rear bag and almost always make the crosshairs low on the target (this is a super common problem with so called "varmint" type factory rifles).

 

[Charles E]

I do believe a rifle that employed Vaughn's recoil isolation device -- flextures, he called them -- would be immune to issues of bag hardness. Along with several other problems...

Anybody ever build a competitive BR rifle along these lines? I never heard of one.