Proper placement and use of a rear bag with an angled stock

[Alexander-M]

Until a few weeks ago, I had always shot, whether from the bench or prone, by holding the stock of the rifle against my shoulder with my left hand (I am right-handed). I adjusted the Harris bipod legs for rough elevation, and did the final adjustment with my hand. This had worked fine for me for many years, and I was able to shoot sub-MOA regularly up to 200 yards, and at or very close to MOA at 300 and 600 yards with my DPMS Panther 308.

Now I have a new (bolt action) rifle that I would like to use for F-Target Rifle, and I am trying to use a rear bag. I like the fact that I don’t see my heart-beat as sometimes I did when using just my hand to hold the stock, and it is easier to line up the cross-hairs with the target when using the rear bag.

I started using the bag with my DPMS, which has a MagPull stock with a flat bottom. The stock rode backwards rather evenly on the bag, and it was easy to follow through and get back on target with very little effort.

But the new rifle, a Savage 12 F/TR, has an angled stock, and I am not sure how to use the rear bag with it. I made a 3/4" stock extension, which I put between the stock and the rubber recoil pad, and I trimmed the recoil pad such that the extension and the pad create a flat surface almost two inches long at the end of the stock.

I tried placing the end of the stock (the extension and the recoil pad) in the “V” made by the two rabbit ears of my Caldwell bag, and this works OK, but not as nicely as with the DPMS with its flat bottom stock. I squeeze the bag for fine elevation adjustment after I adjust the CenterShot bipod that I bought for the Savage 12. I really like the CenterShot bipod!

I then tried putting the Caldwell Rabbit Ear Bag under the angled portion of the stock, closer to the front, and this works very nicely as I can slide the rifle forward or backwards just a little for fine elevation adjustment. But the recoil causes the rifle to slide back and down on the bag, and I am concerned as to how this affects elevation accuracy.

I believe it takes just under a millisecond for the bullet to travel the length of the 30” barrel, but the stock will also be sliding back AND down during this time, and this made me wonder if the shot would also not be affected by this vertical motion.

What is the proper way to use a rear bag with an angled stock?

Thanks for your help!

Nando

 

[jsthntn247]

For an angled stock, you need a protektor dr rear bag. I've been having trouble with rear bags myself and just ordered one 10 minutes ago. The wrong bag will cause verticle issues as I have found out the hard way.

 

[Lapua40X]

Nando ... I believe you have to keep in mind that any rear bag used with the stock design you describe, whether its a Protektor DR with the slanted support or something more traditional, will only allow you to maintain a constant butt elevation from shot to recoil recovery with solid shoulder contact. If you choose to use a free recoil technique the rifle butt will drop, regardless of the butt bag you select.
With a sporting (hunting) rifle style stock, relying on your shoulder with that left hand to do the fine tuning for vertical is still, IMO, the best method for maintaining a relatively static horizontal plane for the rifle barrel.
If you're dead set for using a butt bag, try finding something that supports just the toe area of the stock while you maintain good shoulder contact. You may find it provides the solid vertical hold, squeezing as necessary, and greatly reduces the butt drop at recoil.

 

[snakepit]

If you choose to use a free recoil technique the rifle butt will drop, regardless of the butt bag you select.

How about if you use a benchrest stock that is flat at the rear with no bottom slope and use a rear bag such as a Protektor DR flat top custom bag with no slope, will the rifle butt drop during the recoil if you use a free recoil technique? If it does drop how much if any does this affect your vertical?

 

[Lapua40X]

If you choose to use a free recoil technique the rifle butt will drop, regardless of the butt bag you select.

How about if you use a benchrest stock that is flat at the rear with no bottom slope and use a rear bag such as a Protektor DR flat top custom bag with no slope, will the rifle butt drop during the recoil if you use a free recoil technique? If it does drop how much if any does this affect your vertical?

The bench rest stock design uses a flat fore-end, a flat or nearly flat comb and a straight flat bottom between the lower end of the pistol grip and the toe. All that "flatness" sets up a relatively uniform platform for the stock to move straight back during recoil and the greatest drama occurs at the muzzle, where you'd expect it. Because of those factors, with the rear of the stock resting on a butt bag there isn't much chance for the rear of the stock to drop. That's not to say that the recoil will induce a perfectly flat horizontal movement in the rifle. There are other physics involved here too. I relied on free recoil with my benchrest gun when I was on the bench. I used it for a while in long range prone, resting on a bipod, where free recoil was counterproductive and my shoulder behind a butt bag proved to be a better choice.

 

[snakepit]

Lapua40x, since I only shoot 6 BR benchrest and free style due to a bad shoulder and have the benchrest stock that I described to you, would you recommend a custom Protektor DR flat top bag or the regular Protektor DR bag with a slope.

 

[Lapua40X]

Lapua40x, since I only shoot 6 BR benchrest and free style due to a bad shoulder and have the benchrest stock that I described to you, would you recommend a custom Protektor DR flat top bag or the regular Protektor DR bag with a slope.

I would choose the flat top.

 

[BoydAllen]

I think that you may want to shoulder the rifle solidly enough that it cannot recoil very much. To do this, you will need to pull it into your shoulder with the second and third fingers of your trigger hand. Shooters often have the opinion that they need to touch a rifle as lightly as they can. Many times this is not the case, I suggest that you shoot with a variety of techniques and see what works the best for you. If you are shooting using a bipod, you may want to figure out some way to load the bipod legs. By trying out a lot of different techniques you will learn a lot about what works best for your rifle.

 

[moose1223]

While practicing for Raton, my son was having some accuracy issues so one day at pracice with the Michigan FTR team he tried a bag from a fellow team member. The coach said just hold on the x and fire four to five times and dont worry about wind (Now with the original bag he was shooting some nines and even an occaitional 8) so the next five shots were in a 3 inch circle at 1k yards. There was now, no doubt that the rear bag can play a huge role in accuracy. Again during the Nationals in Raton he was strugling with fiers, so during a practice session before the Worlds he decided something had to be done. He readjusted his whole setup with relation to rear bag placement and instantly 10s and Xs. We have learned that load devlopment is very important but, it cannot solve all of your accuracy problems and at some point you are just burning up lead. The devil is definitly in the details and most are not willing to admit that it may not be the gun or the load but its the shooter and his setup that needs to change.

 

[Alexander-M]

Every one of your responses is a valuable lesson, most informative, and I thank you.

As I mentioned earlier, I was able to create about a two-inch long flat bottom at the end of the stock with the added extension and trimmed stock pad. This allows the rifle to slide relatively evenly (flat) on a rear support if the support is placed at the end of the stock (toe?). I have tried a couple of different bags, including the rabbit-eared Caldwell, but they do not hold their shape consistently. I ordered a Protektor 13A as it looks that it would be more solid, and should receive it in a couple of days. I’ll try it and let you know.

I also tried a three-inch long ‘U’-shaped piece of 0.020” thick plastic tack-glued in the ‘V’ formed by the Caldwell rabbit-ears. Although this allowed the stock to slide freely, for some reason it did not work as well as I had expected. Perhaps it was because it constituted a hard-on-hard surfaces; i.e. hard stock on hard plastic?

I have tried to hold the stock firmly against my shoulder by exerting pressure on the pistol grip with my right (shooting) hand, and so far I do not believe that it has affected my trigger pull, which I have set at 1 lb – the AccuTrigger. When I shoot the DPMS 308 (AR10 style) with the MagPull stock, the shape of the stock allows me to push on the stock against my shoulder with my left hand.

Now I am waiting for a day without wind so I can properly evaluate the various approaches. Up to now I have managed 1-1/4” to 1-1/2”, 5-shot groups and 1-7/8” to 2”, 10-shot groups at 300 yards, which is sub-MOA.

But when I tried 600 yards, the 10-shot groups have ranged from 4-7/8” to 6”. The 4-7/8” group looked fine, and seven of the 10 shots had a vertical dispersion of just over one inch and horizontal dispersion of 4-7/8” (there was a slight wind). But the other three shoots, although centered horizontally, were three inches apart vertically, and this was caused by me.

I am new at this, I am learning a lot, and there is a lot to learn!

Thank you for taking the time to reply!

Nando

 

[BoydAllen]

When you get out to 600 yards, I believe that you have to also look at your loads. Long range shooters are weighing their charges to very tight standards many to .02 gr.), and in many cases regularly annealing their case necks on a regular basis, both to reduce the extreme spread of their velocity within groups. The best way to sort out whether this is the issue that you need to address is to use a chronograph. While the use of these methods is not universal at 600, looking at chronograph results will tell you if you might need to try either or both. It sounds to me like you are doing pretty well with your bag and buttstock situation but I have a suggestion if you want to try to stabilize your bag. A while back I mounted an old soft bottom bunny ear Protektor bag on a spacer that has a raised edge, and stacked them both on a piece of 3/4" plywood, that I had cut cord clearance grooves in the bottom of. I ran cord around the whole thing, between, directly in front of and directly behind the ears, very tightly binding the stack, and stabilizing the base of the bag to a remarkable degree. The reason that I did this was to see if I was loosing any accuracy with the base as it was, shooting my 6PPC from a bench. It worked. My point is not that you should duplicate what I did exactly, but that with a little imagination, you might come up with something similar that fit your situation. My first bench rifle, built for informal bench shooting, was built on a 40X prone stock, which has an angle on the bottom of the butt. With it, I was able to reliably shoot groups right at 5/16" at 100 yards, early in my bench shooting experience. Since then I have gotten better wind flags, and become more experienced at reading them, so I might be able to do slightly better, but I changed stocks on that rifle, and it is glued in the new one. I guess that my point is that having an angled stock toe may not be as big of an issue as you might think. In short range benchrest they are required, and if you look at the match results, I think that you will see that they can do reasonably well.

 

[Lapua40X]

I'm liable to catch some flak from the BR guys for this, but I'll risk that.
Take a look as this video:
http://www.youtube.com/watch?v=weBuYmnpg38
Take enough time to view it several times and pay close attention to the details offered by the instructor.
If every shooter would watch this (or others that are as well done as this is) before focusing on loads as the cause of accuracy problems there would be a lot less stress at the reloading bench.

 

[aj300mag]

If you are shooting using a bipod, you may want to figure out some way to load the bipod legs.

You don't load a Center Shot Bipod...

 

[BoydAllen]

Good catch. I flew right by that, after picking up Harris at the beginning. Went and studied the Center Shot. Looks well made, and thought out.

 

[Lapua40X]

You don't load a Center Shot Bipod...

You have a better eye than I have. I missed that also. Never used one so I can't speak to the benefits or proven best use techniques. Seems unnatural to me; shooting off a platform resting on a sled.
Nice job of catching the important stuff, aj300mag

 

[Trex]

I'm new to using a rear bag myself and enjoying learning how to use it well, so interesting to read this thread, lot of good comments which I'll read in depth later when time is available.

An alternative suggestion, if you have installed a rear butt spacer might be to do similar to the Remington and TRG examples on the linked page. Also interesting the elevation adjustable bag rider, turn the elevation knob rather than squeeze the bag?

I know Davy ships abroad but a lot of shooters have a lathe and mill or a friend who does, nothing complicated about the design itself.


http://shootingshed.co.uk/oscom/index.php?cPath=32

 

[Alexander-M]

Regarding loading the bipod.
I had talked with John Weil before deciding to buy the bipod, and he had told me that his Center Shot bipod should not be loaded, so you guys are right on. I will look at how to best adapt the Protector bag I ordered, which should be delivered today, for my stock.

Regarding the hand vs. a bag – for some rifle configurations.
Yesterday I had to confirm the scope on an FN Scar 17S at 200 yards, and while trying to use a rear bag, I ran into the same issues. Of course, this rifle is not meant for a rear bag, but I gave it a whirl anyway.

Using its Grip-Pod (foregrip with deployable, small bipod) in the front and just my hand to steady the collapsible/folding stock against my shoulder, I shot a Ø1-1/2”, 8-round group (nearly perfect equilateral triangle!) after two elevation adjustments. I was impressed with this out of a 16”-long barrel, so I tried placing a rear bag to steady the stock. But regardless of how I arranged the bags I had, the shots where all over, several inches away from each other. So I tried my hand again for five shots, and was able to keep them in just under an inch.

Powder load measuring.
I have been measuring the loads for the Savage 12 by trickling and weighing them with my venerable Lyman M-5 (Ohaus). I try to get the beam exactly lined up with the graduation marks, and can detect a difference of ±1 particle of Varget. I suspect the accuracy of my loads this way is within 0.05 grains. For the loads I use in other rifles, such as for the Scar 17S mentioned above, I have been using a Lyman 1200 DPS, which I believe to be about ±0.1 grain at best.

Lapua40X
That is one great video! Although the bipod they use (Harris?) is meant to be loaded (as I have on my DPMS rifles), the pointers they give are great for F/TR. Interestingly, I am a decent Across-the-Course shooter with my RRA National Match AR15, but I had not transferred some of those techniques to F/TR, and they most certainly apply.

Thanks again!

Nando

PS. I will return to the range tomorrow and will shoot at 300, and maybe at 600 if the winds are calm.

 

[Alexander-M]

Yesterday I received the Protektor #13A rear bag. I was impressed with the quality of the materials and workmanship, and was surprised by how hard it was. They must have a pressurized method for filling the bag, as it is impossible to press on it and alter its shape of ‘dent’ the surface. It is not the conventional type of bag that can be squeezed for elevation adjustments.

I went to the range this morning with my new Protektor bag, but wasn't able to shoot at 600 yards because that range was reserved for a match, so I shot at 300-yd, prone.

What a difference the Protektor bag made!

I rested the end of the stock (the toe?) between the bag’s rabbit ears, about in the middle, and adjusted the Center Shot bipod for the correct elevation. For fine elevation adjustment I was able to use two methods. I found that I could slide the stock on the bag back and forth, and this changed the elevation ever so slightly. I could also squeeze the ears together just a bit, and this would also change the elevation slightly.

Bottom line was that between the Center Shot bipod and the very slightly adjustment possible with the bag, I could line up the cross-hairs with the target and keep them aligned with almost no effort. After shooting, the rifle remained pointing almost on target, and it was very easy to follow through and look at the target through the riflescope.

I shot six, 5-shot groups that ranged from Ø1-1/4” to Ø1-3/4” (about .4 and .6 MOA), but better yet, I had no flyers! Three of the groups were rectangular in shape, with their heights being half as much as their widths, and the other three groups were more evenly clustered.

With this part of the shooting resolved, I can now concentrate on learning the best posture with the Protektor bag, and develop loads and proper bullet seating for this rifle.

I definitely want to thank you all for your help, as well as John Weil, Denys Beauchemin, and Benjamin Steinsholt for the hints they shared with me.

Nando

 

[22BRGUY]

How helpful and reminding all you guys are on this post...Thanks Much!

 

[Alexander-M]

In case this may be helpful to others who are learning as I am . . .

Attached are a couple of pictures of how I am using the Protektor #13A rear bag with my Savage 12 F/TR. I have tried the bag in both positions ; i.e., slant forward and slant backwards, and it works fine for me either way. In one case, the stock drops slightly when it slides back, and in the other case it tends to rise. Either way the stock doesn't move much at all, and it is very easy to reacquire sight alignment.

The target picture is of my second five shots this morning after sighting in. These were shots numbers six through 10, and were the best - a 1-5/8" group at 600 yards. I fired shots 11 through 20 at three other targets (at each corner of the large target) but they were progressively not as good. The problem was the mirage from the barrel. By the time I fired shots 16 through 20, the target appeared to be moving or floating about half the diameter of the Ø6” black. I need to figure out how to improvise a mirage shield, which I have never used.

About the target itself. I print the hour numbers and the distance from center (in red numbers) so it is easier for my wife to call out the shots when she is in the pits. We use walkie-talkies. BTW, the 'black' is Ø6" (3" distance from center).

Thx -

Nando