Seeking Advice from FTR Bag Squeezers

[rckendall]

I will humbly accept advice from anyone, I just tried to narrow the particulars a bit. When I first shot F Class in FTR I quickly got frustrated with all there was to learn and moved on to F Open. My scores improved but after a couple years I knew the equipment was responsible for my progress. So I went way back and started playing with a couple faux M40-A3 type rifles with Harris bipods. It was fun and I learned a lot.

Fast forward to today and I have a much bigger challenge along the same lines, sort of? I purchased an Armalite AR-50A1 50 BMG. Wow what a surprise. I broke the barrel in according to the owner's manual and progressed to testing some hand loads. To say I was shooting 8" groups at 100 yards would be generous. The rifle has a very effective brake on it so it doesn't kick, but pushes I guess and hits everything beside and behind with muzzle blast.

I upgraded the bipod and trigger so the rifle itself is really good as far as I'm concerned and I have a load the gave ES of 12 and SD of 5.1 so equipment is good. My groups have improved but I have commonly experienced large vertical dispersion, sometimes two close together in one spot and another two close together higher, by maybe 4" while my horizontals are 1 1/2".

I have been concentrating on fundamentals, staying on the gun despite the big boom, loading the bipod, etc. I struggled with proper eye relief initially because the rifle is so tall, I found that I need to elevate my chest with my trigger arm, similar to a sling shooter. I saw David Tubbs shooting that way on a video of KO2M. I am almost always left of the target when the rifle settles and I have been shifting my body left to compensate but it doesn't always help.

I am using a Protektor rear bag with bunny ears. It has a hard bottom and is soft enough that I can squeeze it to adjust for elevation requirements. The ears did seem to be grippy, so the last time out I tried the dryer sheet trick on the ears and that seemed to help the butt slide.

I tried real hard to be consistent the last time with the rifle pointing a couple inches high and a couple inches right on the target. This got me really close after I shouldered the rifle and got my proper eye relief, cheek weld. After squeezing the bag for final adjustment I tried to let everything settle to see if I maintained proper NPA, then just held the bag to keep it from collapsing during recoil.

I shot pretty well that day with a group of 4 of 1 1/4" and the flyer at 1" higher and 2" right. I also discovered that session that I could squeeze the trigger without a firm hold on the grip. I guess I was looking to see what influenced what. I'm making good progress but it is a little expensive to shoot so my practice sessions need to be purposeful.

Please offer any advice you think appropriate. I will say that I don't know what is considered the NPA when shoulder position, cheek weld, and squeezing the bag all enter into sight alignment. Also, using a tight hold on the grip might help with torque reaction of the rifle?

Thanks,
Richard

 

[BoydAllen]

I will humbly accept advice from anyone, I just tried to narrow the particulars a bit. When I first shot F Class in FTR I quickly got frustrated with all there was to learn and moved on to F Open. My scores improved but after a couple years I knew the equipment was responsible for my progress. So I went way back and started playing with a couple faux M40-A3 type rifles with Harris bipods. It was fun and I learned a lot.

Fast forward to today and I have a much bigger challenge along the same lines, sort of? I purchased an Armalite AR-50A1 50 BMG. Wow what a surprise. I broke the barrel in according to the owner's manual and progressed to testing some hand loads. To say I was shooting 8" groups at 100 yards would be generous. The rifle has a very effective brake on it so it doesn't kick, but pushes I guess and hits everything beside and behind with muzzle blast.

I upgraded the bipod and trigger so the rifle itself is really good as far as I'm concerned and I have a load the gave ES of 12 and SD of 5.1 so equipment is good. My groups have improved but I have commonly experienced large vertical dispersion, sometimes two close together in one spot and another two close together higher, by maybe 4" while my horizontals are 1 1/2".

I have been concentrating on fundamentals, staying on the gun despite the big boom, loading the bipod, etc. I struggled with proper eye relief initially because the rifle is so tall, I found that I need to elevate my chest with my trigger arm, similar to a sling shooter. I saw David Tubbs shooting that way on a video of KO2M. I am almost always left of the target when the rifle settles and I have been shifting my body left to compensate but it doesn't always help.

I am using a Protektor rear bag with bunny ears. It has a hard bottom and is soft enough that I can squeeze it to adjust for elevation requirements. The ears did seem to be grippy, so the last time out I tried the dryer sheet trick on the ears and that seemed to help the butt slide.

I tried real hard to be consistent the last time with the rifle pointing a couple inches high and a couple inches right on the target. This got me really close after I shouldered the rifle and got my proper eye relief, cheek weld. After squeezing the bag for final adjustment I tried to let everything settle to see if I maintained proper NPA, then just held the bag to keep it from collapsing during recoil.

I shot pretty well that day with a group of 4 of 1 1/4" and the flyer at 1" higher and 2" right. I also discovered that session that I could squeeze the trigger without a firm hold on the grip. I guess I was looking to see what influenced what. I'm making good progress but it is a little expensive to shoot so my practice sessions need to be purposeful.

Please offer any advice you think appropriate. I will say that I don't know what is considered the NPA when shoulder position, cheek weld, and squeezing the bag all enter into sight alignment. Also, using a tight hold on the grip might help with torque reaction of the rifle?

Thanks,
Richard

You reported your ES and SD as if you think that having low numbers equates to your load being tuned. Not so. The questions that you asked about how different ways of shooting the rifle affect your groups is best answered by you at the range. I will say that even though your load may not be in perfect tune, you should be able to detect gross differences in how different shooting styles work. Why not set up your phone so that you video yourself shooting the rifle, from a side view. You might see things reviewing the video that you were not aware that you are doing, and you could post it here in the hopes that someone might have some insights.

 

[CharlieNC]

On a rifle which has significant taper on the toe, upon recoil it is not unusual for the muzzle to point upwards as the taper slides backwards on the bag which leads to vertical stringing. And for me it is also difficult to maintain the squeeze perfectly on the bag. Correcting this situation probably contributed to improving your fclass scores. As an experiment you can cut a wood wedge and tape onto the toe to achieve a nominal 5 degree taper and use your flat top fclass bag to minimize muzzle rise upon recoil. Or don't use a rear bag, just support the butt by cupping your hand onto the shoulder. While a highly tapered toe provides rapid, easy vertical adjustment but can be a pain to control vertical poi.

 

[BoydAllen]

I have shot a lot of sub half inch groups with tapered buttstocks, with factory rifles, and short range benchrest LV and HV rifles are required to have angled butts. One thing that I would look to with all of that concussion, is scope related issues. From the bench, with good light and a suitable target, I can reliably shoot under an inch and a half. Many times I have done quite a bit better. My point is that if your rifle has irons, you might want to compare what you get with them to what you get with your scope.

 

[Ned Ludd]

The standard Harris- and Atlas-type bipods have a relatively narrow footprint, meaning torque will be more of a consideration when using one. Many years ago, I switched to using a Long Range Accuracy bipod in F-TR for that very reason. The LRA bipods are sort of like a giant Harris/Atlas with a much wider footprint. In conjunction with the LRA, I use a large squeezable rear beanbag from Triad Tactical (i.e. Tactical Pillow):

Red Tac Gear Tactical Pillow

triadtactical.com

Having used this setup for many years with F-TR rifles that don't have anywhere near the recoil of your 50 BMG, even with the brake, it wouldn't surprise me that if you're using a bipod with a more narrow footprint and an eared rear bag, they might be contributing factors. Regardless of how much you are able to "squeeze" it, an eared rear bag is simply not the right choice when pre-loading a bipod. You want a rear bag that was designed to be squeezed in order to adjust and control elevation, something the eared rear bags were not designed to do. Eared rear bags are awesome when you're shooting off a ski-type bipod or rest, where they allow the rifle to track straight back under the recoil impulse. For a pre-loaded (i.e. traditional) front bipod, some kind of large rear [squeezable] bean bag is a much better choice.

The good news is that you don't necessarily even have to purchase any new and expensive equipment in order to carry out a few tests to determine whether a different rear bag might improve your precision with the 50 BMG. Dried beans/peas/etc. are relatively inexpensive and can be placed in any small cloth bag and used with your existing traditional bipod to determine whether it is an improvement to the eared rear bag. If you think a rear bean bag might work better for you after such an experiment, you can think about buying a new one at that time.

The other concern I would have given your initial description of the problems you are having is what evidence do you have the that rifle/ammunition are actually capable of better precision? I can certainly understand that your setup should be doing a lot better than 8" at 100 yd. However, you stated that your groups have improved to ~4" high x 1.5" wide. How much better precision, if any, is that setup actually capable of? The only way to really know that with certainty is to use some type of support that largely mitigates the recoil. Using a heavy and very stable front rest combined with your eared rear bag might be one approach. If you know someone that has a Lead Sled-type weighted shooting rest/rifle support that helps to minimize movement of the rifle during recoil, perhaps they would let you borrow it for some testing. Until you have definitive proof of what level of precision the rifle setup is capable of, you may be thinking the problem is all on you and your setup when perhaps it actually isn't. If you know definitively how accurate/precise the setup is, it will give you the confidence and motivation to continue adjusting the setup and your position/technique behind the rifle until you are shooting it to its full potential. If there are additional contributing factors to the poor precision such as the ammunition used or even the rifle itself, it's better to know it than spend significant effort trying to correct something else that may not be the problem, or at least may not be the entire problem.

 

[rckendall]

Thank you everyone who has responded. I am actually using the LRA F Class bipod and think it is a fine choice. It does have a little slack in the legs which leads directly to the loading of it. The ammo I am loading is LC brass that has the primer pockets uniformed and the flash holes cleaned up inside. I have mostly been using Vihtavuori 24N41 powder because that was what I could find early on. The projectiles are 650 gn M33 machine gun bullets that have been pulled, sized, and weight sorted. I also have a Jewell trigger set at about 1 3/4#. My scope is a Nightforce 5-20.

The internet seems to say these projectiles are good for 2" groups at 100 yards and if I were able to shoot that regularly I would be happy. But the vertical dispersion is more common than not. I trust the rifle and ammo more than I do my ability to shoot it.

I do have a sand sock or two that I can try but that seems like a step backwards compared to the bunny ear bag, but I certainly do trust your expertise. Can someone enlighten me on their checklist or procedures to establish NPA etc?

Thanks again to everyone,
Richard

 

[BoydAllen]

When squeezing a eared rear bag, I set up so that the cross hairs are centered and perhaps a half inch higher than my desired point of aim. I place the palm of my non trigger hand on the front of the base part of the bag, with my thumb at the base of the ears on one side and two fingers in the same place on the other, squeezing the base of the ears between thumb and fingers brings the cross hairs down to the point of aim. Of course follow through with the bag hand is important. How are you dealing with friction between the stock and the bag? Is there any part of the stock that is on the bag, or slides into contact during recoil that interferes with a smooth slide. Generally, if your ears are leather, baby powder lightly dusted on the ears is the lube of choice. If you look at the bottoms of benchrest stocks you will see a smooth surface, with nothing that can catch on a bag.

 

[rckendall]

Again, thanks for the feedback. I believe I squeeze the bag similarly except maybe my hand is a little lower, more in the center of the bag portion. I did remove some sand so that it would be more flexible. I am now also using a dryer sheet on the ear area to reduce the drag.

I now feel that I will go back to a firm hold on the grip. The last time out, I found that in a position that gave me good eye relief, I had firm cheek weld and a solid hold at my shoulder. This gave me confidence enough to release the trigger without much contact with the grip, similar to how an F Open shooter might do. I now feel that is wrong with this rifle and that a firm hold on the grip might help control the torque.

I know that being consistent will be the key to all this and I will report back with my progress, and maybe we all can profit from this.

Thank you,
Richard

 

[RegionRat]

"I have a load the gave ES of 12 and SD of 5.1 so equipment is good. My groups have improved but I have commonly experienced large vertical dispersion, sometimes two close together in one spot and another two close together higher, by maybe 4" while my horizontals are 1 1/2".


So, I won't try and give advice on the rests, but for a moment I will state that you are under sampled on your stats and it may give you a misunderstanding of the source of the vertical dispersion. Next session, try and get velocity for all your shots, not just some of them.

When the ammo and gun are normal, we call that a Gaussian Distribution. If the SD and ES are "normal", meaning your ignition and internal ballistics are not erratic, your ratio indicates you are not seeing the full ES.
The ratio between the ES and SD should trend toward 6X when your process is stable. It can get worse but lets assume your loads have no erratic flyers for this example. Your ES would be more like 5.1X6= 30.6 or your SD would be more like 12/6= 2. It will likely be more like that 30.6 in reality.

Taking enough samples of that ammo will give you a better view of the ES and the vertical at distance. If at all possible, run a LabRadar on whole practice string or two. When you have somewhere between 15 to 30 samples, you will see those stats show a relationship between the SD and ES trending closer to the truth.

Those velocity stats are only an indicator of the ammo/gun relationship, but it takes all of the above advice combined with load development to achieve your goals. Stay with it and good luck!

 

[Ned Ludd]

I would not view using a bean bag or sand sock as a "step backward" from using an eared rear bag, I would merely view it as using the correct equipment for the given application. No matter how you slice it, the eared rear bags were not designed to be used with a pre-loaded bipod. They just weren't. Even if you can "squeeze" one and make it work, that is not how they were designed to be used. The eared rear bag is designed to allow the rifle to track straight back under the recoil impulse, which is exactly what you're trying to minimize or prevent when pre-loading a bipod.

There are several reasons and some physics that underly that statement that I don't have the motivation to go into detail about right now. Instead, I will point out that while there are obviously operational differences between using a pre-loaded (traditional) bipod with a bean bag of some sort in the rear, and a ski-/sled-type bipod with an eared rear bag, there is also a similarity in that each of the two styles of shooting/bipod use has specific aspects that are critical for them to work properly. With a ski-type bipod and eared rear bag, it is absolutely essential that the rifle track straight back under the recoil impulse. Therefore, body placement and arrangement of the rifle and rear bag are critical factors. An eared rear bag is specifically designed to allow the rifle to track straight back during the recoil impulse. That is it's major function as part of that type of setup.

With a pre-loaded bipod, the major key is the amount of pressure used to pre-load the bipod. It must be the same for every shot or excessive vertical dispersion will be the result. Tracking of the rifle is less critical with a pre-loaded bipod, because the whole reason for pre-loading it is so that the rifle doesn't move backwards appreciably during the recoil impulse. Muzzle hop when using this type of setup is really secondary to using constant pressure to pre-load the bipod because it most often means body alignment behind the rifle is not correct. When the body position behind the rifle is correct AND constant pressure is applied when pre-loading the bipod, the muzzle should move very little. Now the term "very little" is perhaps a misnomer when applied to shooting a .50 BMG, but I think you understand what I meant.

Regardless of which method you prefer and end up using, you are going to have to experiment to find the body position that is correct for you. Not everyone's body is that same. Height, weight, and the angle of one person's shoulder pocket can be different than another's. So there really is no "perfect" position that fits every single person, or only a single "correct" way to do it. Obviously, there are some general positional requirements and places to start, but you already know that stuff. My guess is that you're going to have to do a fair bit of experimentation with respect to body position, keeping constant pressure on the bipod, perhaps even exactly where on the bipod rail the bipod is situated. All these seemingly little details are important, and you have to find out what works best for you. There is no substitute for testing in order to determine this. In this instance, I would recommend having someone with you that can observe, possibly even record, the details of both body and rifle movement during the recoil impulse that you cannot see while you're shooting. Having someone watch and/or record you from the side and from behind might offer some useful insight into what your body and the rifle is doing that will allow you to formulate some plan to correct it. That's much harder to do when you're by yourself.

 

[davidjoe]

RC, the AR 50 is an awkward gun to shoot. But man I’m glad to see a post on one. I’m honestly surprised you located a new one, which I infer from your mention of breaking it in according to the manual. I had scoured the internet myself a number of times, zero. You are very lucky, as one that has two of them, I consider them to be among the best new rifle values on the market across every segment and at best very sporadically made.

In saying that it’s “awkward” to shoot, I don’t mean to imply it won’t shoot small groups. They absolutely can shoot small. I mean only that the rear butt (maybe toe is the correct word, but the bottom) is not angled, yet the heavy gun uses a traditional bipod. This is practically a contradictory concept in the accurate rifle game, at least with a huge gun that is not very maneuverable, with legs that are not easily adjustable on the fly.

By not putting an angle on the butt, almost NO amount of pinching rabbit ears will just happen to coincide with the elevation you need, while at the same time enveloping the stock in the leather securely, the way that feels right in your hand. You may have the stock perched almost on top of fully squeezed ears. You may have it crushed down so low that pinching the ears doesn’t help.

You literally need three or four rabbit ears of different sizes and boards of different thicknesses to use the gun on targets of different heights. Then the cheek piece never feels quite comfortable. Welcome to the AR 50, uncomfortable before you pull the trigger, let alone after. This is about the mail delivered, not the (un)happiness of the shooter, and it’s peerless in both respects, but it’s great for 50’s if that counts.

I don’t know your loads. I’d almost wager that that any group bigger than 2 inches at 100 even with ball surplus involves some “bracing” up movement in the lock-time-eternity that the huge firing mechanism needs. Especially since you show good SD. (These big bullets do follow each other, we know that from video.) That bolt by itself weighs something like 4 or 5 pounds, with huge, belligerent internals. You have to consciously freeze every part of your body, and bear hug the gun. The bipod needs to be as far as possible forward to minimize your movements. No one gets good accuracy letting these recoil when a bipod is up front pushed down by almost all of the 34 pounds, and so I’d wrap my hand whether or not required by your trigger.

In the acquainting yourself with it, judge it only at 300 and beyond with Hornady A-Max 750 factory loads to start. It should group in the neighborhood of very good hunting rifles out to about 500, then, it will go on a rampage in the wind compared to smaller BC, with its 1.0 plus G1 and its unbeatable mass until gravity ultimately wins.

 

[rckendall]

Wow, more good input from you fellows. Thanks. I'll try to address things in order. Since the National Forest is closed now to shooting, because of fire season, I am limited to my local range which has a 200 yard bay that they have allowed me to use a couple times. There I can handily use my LabRadar, but it is all but impossible on the 100 yard line where they have had me shoot lately. I'll see if I can work something out with them for a future visit. I love the technical aspect of all this, but I still kind of feel that I am the weak link.

I follow the logic of using a bean bag and I have a couple packed in my gear for tomorrow. I'm happy that I am receiving so much encouragement, and each suggestion is helpful in this journey!

I can a add couple things that might show some of where I've been. Since I have been using a bag from when I shot FTR, I have several suede shims that I can use to minimize the amount of squeeze required, but it is time consuming to keep experimenting with them, but maybe Ned's suggestion will alleviate the need for all of this. The bean bag approach follows along with my thinking that I need to hold on to that thing when it goes boom, and stay on it.

I have a few A-Max bullets to shoot but I really want to get the basics down a little better before shooting a bunch of them. I did shoot two 3 shot groups last time out, and the first group was about 1 1/4" and the other had the dreaded vertical pattern. Two in one hole, but almost 2" vertical from the other!

I really do thank all of you for your contribution. I no longer feel like I am on this road by myself. What a great community this site is!

Richard

 

[rckendall]

I went to the range today and I'll do my best to share what happened. As I had stated before, I had a couple bean bags with me to test, along with my regular bunny eared bag with dryer a dryer sheet covering the ears. As I was unloading my truck, I received a call from Dave at Protektor who wasn't available yesterday to talk. I told him about the situation that I was in and asked him outright if the eared bags were meant to be squeezed. He said some people do and some don't, but if one does want to squeeze the bag, the taller ears are better. In order to squeeze the bunny ear bags, sand would need to be removed from the base, which I have done.

One thing I did different today was to place the bipod directly on the concrete, where before I had always used a piece of carpeting underneath. I thought the rubber mesh on the bottom of the carpet would be helpful, but I'm not so sure now.

I felt really good about my shooting today, everything felt solid and I was able to stay on the rifle each shot. I still wound up left of center but it was consistent. The first string of five were scattered, but the next two strings of five had 3 or 4 in a respectable group and either one or two flyers. I think I can attribute a couple shots to abnormalities in the ammo. I noticed this during the reloading session and made a mental note to watch for theses two rounds during the strings.

I have the OK from the range officers to set up on the opposite end of the firing line where the ground is level to set up my LabRadar. I warned my buddies who normally shoot at that end and they just said they would move to the other end. I also have some Mil Surp powder on the way which will made it a little more affordable to shoot. But I will also do some testing with the A-Max bullets to really see the accuracy potential of everything. I'll keep posting here as I progress.

Thanks everyone,
Richard

 

[davidjoe]

Richard, it’s been a while since I shot mine and you’ve inspired me to take one to the range tomorrow that needs a zero, since I stole its idle scope, and see what it’s doing with a few Amax and a few FMJ.

I don’t like to shoot these at 100 but I’ll zero at 200 and put up some picks of my set up and groups.

 

[Tempest]

A buddy of mine and I both have that same gun. After he spent a fair amount of time tweaking 750g AMAX loads and testing, we both came to the conclusion it's not F class accurate at 100-1,000 yards.

IMO it's better for suited for ELR shooting.

 

[davidjoe]

A buddy of mine and I both have that same gun. After he spent a fair amount of time tweaking 750g AMAX loads and testing, we both came to the conclusion it's not F class accurate at 100-1,000 yards.

IMO it's better for suited for ELR shooting.

The F-Class rules on .35 cal limit would keep it out, but it is the parent design for the smaller A-Tips like the 190 that Open shooters I believe it is, have bought up all of recently.

I think the bullet itself is as accurate as the other A-Tips, Agree that the AR50/Amax combo is good “hunting rifle only” or maybe sniper rifle accurate through midrange, getting better after that.

About to have a look at close range in a couple hours.

 

[davidjoe]

I did mention already these are not comfortable to shoot?

A loaded RSAUM round weighs 495 grains. A 50 AMax bullet by itself weighs 750 grains.

 

[davidjoe]

Relative strike point of two different loads.

Had to use left hand finger tops as shims under metal toe of stock and on top of bag. Not ideal.

 

[davidjoe]

Richard that’s par or a bit better with good ammo on this at 200. Definitely 3 shot would have hit the sharpie marker at 200.

Once scope corrected for AMax and thick paper inserted under rest group vertical was good at 200.

My pictures get rotated sometimes but the group and pen is horizontal.

The stock makes me think of how hard it would be to use an Fclass rifle stock in a PRS match.

I know the gun handling could be better on my part, as I anticipate back blast. If that factors in, these shoot center to center as I often see with my very accurate rifles.

 

[Tempest]

The F-Class rules on .35 cal limit would keep it out, but it is the parent design for the smaller A-Tips like the 190 that Open shooters I believe it is, have bought up all of recently.

I think the bullet itself is as accurate as the other A-Tips, Agree that the AR50/Amax combo is good “hunting rifle only” or maybe sniper rifle accurate through midrange, getting better after that.

About to have a look at close range in a couple hours.

Understand, I shoot F class. My point is, its not a 1/4 MOA gun and better suited to shoot ELR or through cinder blocks!