Rear bag setup and technique?

[DenisA]

Hi all,

I use a Savage F-class stock that has a straight and flat toe that tapers from about 1" wide at the under side of the grip to approx 3/4" wide just before the butt plate. I have stock tape on it.
I use a Seb Bigfoot bag with a 16mm stitch gap and therefor the toe rides about 2/3 of the way up the ears, only the corners contacting.
I have the bag and the ears well compacted.

Shooting free-coil when load testing off a bench, I was getting tight groups but frequently had fliers. Being pretty anal with case and bullet prep I thought it could be the rear bag setup as I am always re-adjusting gross elevation at the front rest as the rear bag settles and I find the cross hairs are off the centre line when the rifles returned to battery. It takes shuffling the butt in the bag to reset.

As a temporary trial, I made a timber extension for the toe that's straight. It only fills the void between the original toe and the stitches. It tapers down to 16mm which allows the rifle to sit perfectly in the ears, on the stitches. The ears guide the butt snuggly.

I don't put any cheek pressure on the comb though I use only the weight of my hand to keep the butt down and try to reduce rifle torque.

The positives are:
The crosshairs always return to the point of aim
Theres no more rear bag settling and front rest adjustment.
The crosshairs are far less sensitive to slight body movement.
It feels solid.

The negatives are:
There's more resistance in tracking
A known good .284 load that I tested sprayed like a shotgun at 100m. That barrels never shot so badly, even testing bad loads.

A very cluey shooting friend of mine (who I hold in high esteem) suggested that being on the stitches is not good as there's less energy absorption. I translate that to the butt jumping, shuddering or jerking on recoil rather than being smooth.

I've read a post from a member here saying that he rides on the stitches.

Im interested to know everyones opinion on the ideal setup, hard bag or soft bag, hard ears or soft ears, riding the stitches or the ears?

Thank the shooting gods I made a temporary extension before re-shaping the stock.

Sorry about the long story. Just wanted to get my train of thought across.

If you've got to this point, thanks for persisting.

[johnk]

Denis,

I've had advice from some benchrest shooters that the toe should ride on the ears, not the stitching on the bag. Others suggest that how much the ears are filled (what control they offer, how much resistance is there) is the important thing. In your case, I have an inkling that the issue of resistance could be related to the quality of finish on the wood you've added & how much & what type of friction inhibitor you are treating your bags with.

What I believe I've demonstrated is important with the rear bag is to get it settled before you introduce the rifle to it. Pound it onto the ground to settle the sand then rip the ears apart before you set the stock in it. Obviously this will need a bit of preliminary fiddling to ensure that it's properly in alignment.

My stocks ride on the bag, not the ears.

John

[ecomeat]

Dennis, did you read the Speedy Gonzales comments re sand bags on Accurateshooter back in September ? It's not necessarily the answer to any part of your "enquiry" but the writer is certainly well qualified to be talking about front and rear bags
Tony
http://bulletin.accurateshooter.com/201 ... by-speedy/

[DaveMc]

Denis - one thing I did with my savage before almost anything else was took a plane to the bottom to make the stock 3/4 inch all the way through. I cannot for the life of me understand why they would do a reverse taper on the bottom of the butt. This acts as a wedge and stops it tracking correctly.

I ride the stitches on a big heavy bag that isn't packed too full - seems to work.

[DannyS]

Denis, I use a Seb bigfoot rear bag and a McMillan f class stock. I used to have a the ears packed pretty tight and used to ride on the ears, however, after a few shots the stock would settle deeper into the ears.
I removed some of the sand, so that the ears are more pliable and now run on the stitches, no more elevation changes, all my adjustments are from my seb neo rest.

I'm not saying its the best or the correct way but it works for me.


Cheers
Danny

[DenisA]

Ecomeat, thanks for link. I'll read through it.

Dave, I'm baffled by it too. It never seemed to present a problem until I started shooting the bigger calibers with it, hence more recoil and more emphasis on tracking.

Danny, I love those McMillan F-class stocks. I considered buying one a while ago, before I started modifying this one to suit. I may yet have one in the future.

Thanks for the replies so far guys. Its really interesting to hear how different stocks perform in different bags.

I spoke to Stuart E at BRT today and asked the same question. He recommended riding the stitches with firm but pliable bag and ears.
He also suggested that stock weight placement has a lot to do with it to reduce bounce and reduce the butt from jumping up. He said that the weight should be placed mostly forward of the action.

Its sounds like I might be on the right track, just need to keep working at it.

I'd still love to hear more perspectives.

[Cameron Mc]

Denis, I have found rifle balance to be very important. Rule of thumb for me is to have balance point slightly forward of action face. I have weight in the butts of my guns. I touched on this in another thread, when building a rifle I cant the action slightly to the rear. That is, the action axis is not parallel to the fore end flat. I feel this tends to force the rifle slightly downwards during recoil. I run my butt on the stitching.

Cam

[DaveMc]

On this balance point -The other thing I found with the savage stock Denis is the forend is quite short. When you start putting in 30+ inch straight 1.25 inch barrels they can get a bit front heavy. I added weight to the butt and also adjusted front stop so there was very little protrusion over the front rest which helped a lot. Before buying the offset dogtracker I was going to extend the forend with a lump of 3*1 (also getting away from the dovetail front end which in some bags pushes the boundaries on rule interpretation).

[DenisA]

Dennis, did you read the Speedy Gonzales comments re sand bags on Accurateshooter back in September ? It's not necessarily the answer to any part of your "enquiry" but the writer is certainly well qualified to be talking about front and rear bags
Tony
http://bulletin.accurateshooter.com/201 ... by-speedy/

Very interesting article Eco, thanks for making me aware of it.

I never even considered that it made such an obvious difference, I just "assumed" (MOAFU's) that harder and firmer had to be better. It makes a lot of sence now.

Its funny when people see you shooting off a coax rest at the range and they say "Thats not shooting, I could shoot one hole groups with that!".....................BS, LOL. There are so many tiny things to think about, not just a good barrel, good loads and technique. Every extra component we use in our setup introduces a new set of variables, required procedures and techniques that we need to understand and follow.

[IanP]

I'm using magnetite, (heavy fine sand) for the front bag and glass spheres (filter media) for the rear bag. The glass spheres are like grains of spherical sand and although not as heavy as garnet, its enough weight in a mini-gator or Seb bigfoot rear bag.

I now squeeze the bag in F T/R, (F-Open as well) and with the glass beads its really easy and linear in feel to achieve even adjustment. The ears with glass beads on the rear bag have really benefited my shooting. I squeeze the bag and not the ears but it can be done either way.

Glass bead filter media, look here: http://www.waterco.com.au/newsletter/ne ... -the-facts

Ian