How does bipod position (forward/back) affect accuracy?

[packrat]

I'm not a hugely experienced shooter but I know a little bit about physics, and this question has puzzled me for ages.

 

When I look at rifles and the positions of their bipods, I often find myself wondering why the maker/designer did not do their utmost to fix the bipod as far forward as possible. It seems to me that the further forward the bipod, the smaller the error introduced at the muzzle by a given movement at the rear of the rifle.

 

I've knocked up this handy (and massively exaggerated) diagram to show in simple terms what I'm on about. (Excuse the crap rifle )

 

 

I know that in general bipods are positioned forwards-ish, but for serious shooters, who spend a lot of time (and money) on optimising ammunition, weighing bullets, doing whatever else they do to wring the last tiny bits of accuracy and precision out of their kit, why are most of their rifles more like the top one of these than the bottom:

 

 

I think the rifle at the botton has a sizeable advantage over the top one, if guided by a human introducing the same error at the butt end, and all other variables being equal should always shoot better.

 

Precise and accurate shooting is all about minimising differences and controlling or eliminating variables, as I understand it, yet with this variable having what I would consider quite a big effect, relatively speaking, and being one which is pretty easy to optimise, I think I'm surprised so little attention is paid to it. And that makes me think that I may be thinking about this wrongly, or making some elementary error, because so many shooters can not possibly be wrong.

 

This all came to a head this evening as I was trying to fix a bipod to my AICS, this is a bipod that won't fit either the sling stud OR the AI spigot hole without some modification. The mod to fit it to the stud is easier than the mod to fit it to the spigot, yet the spigot mod would place the 'pod about 3 inches further forward. I could even extend the spigot mod to position it up to about 5 inches further forward... and then I got into thinking about the mechanics of all this and now I can't stop

 

So, please put me out of my misery... if this is a misunderstanding then can the panel explain where it is coming from, and why bipod position doesn't (or does) have as much of an effect as I think it should?

 

Would you do the more complex mod just to put the 'pod 3-5 inches further forwards? Or just do the simple mod to the sling stud, leaving it further back?

 

Cheers

[Gandy]

I can see you point and agree around the position of the pivot / fulcrum allowing any error induced to be magnified.

 

To challenge I would say that the error induced is irrelevant should it be consistent every time. If movement error is consistent i would think it can be addressed no matter how great.

[packrat]

I can see you point and agree around the position of the pivot / fulcrum allowing any error induced to be magnified.

 

To challenge I would say that the error induced is irrelevant should it be consistent every time. If movement error is consistent i would think it can be addressed no matter how great.

 

I see what you mean but if you don't have to concentrate on making that error consistent, you can concentrate more on all the other errors in your system. It's an easy error to fix.

 

Also, "consistently between 2mm and 5mm" (say) is much easier to achieve than "consistently zero", but if you have any variance at all, it will be contributing to the cumulative error of all the variables for a given shot, in a significant way.

 

Just thinking aloud really. Thanks for your input : )

[brown dog]

Packrat,

 

I think your theorising is spot on.

 

I think the reason bipods are often closer is 'reachability' for adjustment.

 

As with all things there's a trade-off in conflicting requirements.

 

Cant adjustment for the fellow with the blue rifle you've pictured would be problematic - but (as you explain) it's definitely a better place for a fulcrum.

[packrat]

 

Cant adjustment for the fellow with the blue rifle you've pictured would be problematic - but (as you explain) it's definitely a better place for a fulcrum.

 

What's needed to control cant, then, is a locking clutch that can be remotely operated by a wire, as in a bicycle brake cable, or remote camera shutter release (the old mechanical type), something like that. And for height, something similar but which can be turned to adjust the height screw. I might have a go at knocking something up, because I'm pretty sure this spigot mod I'm doing for my AICS is going to end up putting my cant & height controls out of reach.

 

I'd be surprised if this hasn't been done already, actually. Anyone heard of anything like it?

 

Cheers

[kent]

Although the theory is quite correct, field shooting requires adjustment of both cant and height as brown dog says. The bipod in the photo would be totally useless in the fields to myself as its not adjustable on the rough fields or moor. Sometimes the rushes are high and I need the long pod or sitting sticks. We control this tilt you mention by tracking back in a straight line, shoulder pressure or free recoil, back bags etc. My final point is illustrated well if we take shooting off the top of a dry stone wall, the tendency is for the shot to go high as the fulcrum is mostly nearer the shooter (nearer the action area) with no rear support. To combat this I might rest my arm on the wall (cap or soft objet between wall and gun) with the thumb of that forwards hand just lightly contacting the top of the forearm of the stock on its top edge to control rise and a set of bipod sticks under the toe of the stock to aid tracking.

Its tempting to over improve some things, taking it to the final degree you might end up with a full bench kit. Ok fine on the ranges just not so hot in the field

[The Gun Pimp]

Cant adjustment for the fellow with the blue rifle you've pictured would be problematic - but (as you explain) it's definitely a better place for a fulcrum.

 

Brown Dog - I'm puzzled by your 'cant' comment. Why would I want to cant the rifle once levelled and, if I did, why would it be 'problematic'?

 

I am of course the 'fellow' in the picture and, this is the rifle that won the 2011 European F Class Championship in the hands of Stuart Anselm (Osprey Rifles).

 

Having said all that - some shooters do use a bi-pod much further back and shoot very well (in F Class League matches) The one I'm thinking of also has spikes on his bi-pod whereas I've always favored 'skis'.

[packrat]

I am of course the 'fellow' in the picture and, this is the rifle that won the 2011 European F Class Championship in the hands of Stuart Anselm (Osprey Rifles).

 

 

 

Wow! What are the chances of that?! Please forgive my blatant borrowing of your image. And may I congratulate you on your most excellent bipod positioning

 

 

--

[brown dog]

 

Brown Dog - I'm puzzled by your 'cant' comment. Why would I want to cant the rifle once levelled and, if I did, why would it be 'problematic'?

 

I am of course the 'fellow' in the picture and, this is the rifle that won the 2011 European F Class Championship in the hands of Stuart Anselm (Osprey Rifles).

 

Having said all that - some shooters do use a bi-pod much further back and shoot very well (in F Class League matches) The one I'm thinking of also has spikes on his bi-pod whereas I've always favored 'skis'.

 

Sorry Vince, didn't realise it was you!

 

 

 

I was taking the question as a generalist bipod thing rather than focussed on the pretty unique requirements of F/TR (I’m assuming that’s an F/TR rifle?).

 

Why problematic? Presumably you have to crawl down the side of the rifle to reach the bipod and adjust cant and then crawl back to fire - that would be a negative embuggerance in many (non-F/TR) situations.

[kent]

Vince, Great bipod set up for FTR! darn near useless on the fell though, here we often need to have one leg out more than the other or lengthen both to get over the cover. Horses for courses

[The Gun Pimp]

 

Sorry Vince, didn't realise it was you!

 

 

 

I was taking the question as a generalist bipod thing rather than focussed on the pretty unique requirements of F/TR (I’m assuming that’s an F/TR rifle?).

 

Why problematic? Presumably you have to crawl down the side of the rifle to reach the bipod and adjust cant and then crawl back to fire - that would be a negative embuggerance in many (non-F/TR) situations.

 

 

OK Brown Dog - see your point now. Hopefully, you get set up level before the shoot but, if one leg sinks into the ground a significant amount then yes - you have to come out of position to correct it. It could - and does - happen but not a lot.

 

The latest version of the SEB joystick bi-pod addresses this with a built-in cant adjustment.

[jcampbellsmith]

I'm not a hugely experienced shooter but I know a little bit about physics, and this question has puzzled me for ages.

 

When I look at rifles and the positions of their bipods, I often find myself wondering why the maker/designer did not do their utmost to fix the bipod as far forward as possible. ...

I agree. One day, finance permitting, I will have a rifle with the bipod attached at the muzzle. A related topic which is worth a read up on is bloop tubes. Regards JCS

[bewsh]

 

much more stable waaay down the barrel than on the forestock

[varmintexpress]

I noticed you said you have an ai stock.

 

years ago I brought a cheap small Chinese bipod which has served me very well.

 

in fact I shoot with it much better than any of the harris or parker hail fitting into spigot of ai stock bipods which I have owned. interestingly enough the ai stock / parker hail / spigot connection made life hard for me and this was right at the front of the stock but with poor tilt support.

 

for me best accuracy is gained by a stiff bipod as close to the ground as possible near the end of the stock, stiff being the key for me.

[Mossy-dog]

On the same lines does it depend on the angle you are shooting at for POI?

 

In my mind a rifle pointing steeply up off a bipod would 'bounce' a lot more than one pointed well down or on a level?