Accuracy - Glass bedding - Please explain this

tedsalad

Well-Known Member
Ive always been taught not to put my left thumb on the barrel when shooting as this effects accuracy -Never understood why.

The scope is fixed firmly to the action and when zeroed both scope and rifle are pointing at the same place. The barrel cannot move or flex regardless of how much pressure you exert on it.

When I had a Pro Hunter, the stock seemed to be made of flexiboard but it shot superbly., with or with bipod attached.

I recently stuffed my action 1 Sako into an action 3 composite stock that I had roughly power filed to size and still it shot 1/4inch at 100 yards without re-zeroing.

Can someone please explain it.
 
The action and attached barrel are mounted together to the stock with only the action having contact. The barrel does not touch the stock hence, free floating.

Bedded rifles have the barrel in contact with the stock, tends to be a more traditional method.

Brithunter is more knowledgable on this.

Stan
 
A free floting barrel is free to vibrate at a certain frequency when fired, (the world of harmonics) and if you do anything to alter the frequency at which the barrel vibrates it will affect accuracy.

Thats the simple explanation.
 
Hi Ted,
I'm open to correction from anyone with a greater knowledge, and there are sure to be many on here. I'll give it my best shot to explain as I understand it :-

The barrel of your rifle is not quite as rigid or inflexible as it might first appear. As the bullet travels down the rifling grooves the barrel will in effect try to untwist in the opposite direction. You are fixing the breech end with your shoulder and body weight. the length of unsupported barrel *assuming it is free floated*, can however whip and twist, just for that split second as the bullet passes through. Providing this whipping twisting movement is always the same the bullet will arrive pretty much where you point the rifle. Anything which alters the way the barrel is allowed to flex, i.e. your thumb or the tree the barrel might be leaning against will adversely affect the point at which the barrel is when the bullet finally exits at the muzzle. It will now have a different path of flight, and so will not arrive consistently at the same point on the target some distance away.

On a bedded action the barrel is supported along it's entire length or at points along it's length. The theory is that the barrel will now behave exactly the same way each time you fire it.

Bit like religion, different people have faith in different systems. I trust metal to be fairly consistent within the ranges of temperature normally found. wood however is in my opinion not as stable, and so I would choose a free floated barrel. Like I said others will have a different take. Just like religion I don't care to argue with them about it, I just have faith in what I believe.

Pretty much the same explanation as Dan Gliballs and Stan, with just a bit more info/flannel.

Mark.
 
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Imagine when you fire the rifle a sine wave moves up the barrel in both horizontal and vertical planes and when the bullet get to the end of the barrel the barrel will be in a particular position due to vibration the key is to the barrel being consistently in the same place each time for the best accuracy.

I would argue that the best results would be from a rifle with a bedded action and a free floating barrel. You also need consistent ammo that will produce consistent pressures and velocities and ideally you want ammo specifically loaded so its optimised for the barrel it is to be fired from.

Dave
 
Just to add a little clarity. In general terms a 'bedded' rifle is taken to mean the action has been bedded into the stock to form a near perfect union between the action and stock by the addition of a fine layer of an impervious compound and another generalisation of a bedded rifle is that the barrel will not make contact with the stock and is therefore free floating. This means that the vagaries of weather/temp/ method of holding/strength of grip will have minimal bearing on the harmonics of the barrel during the shot taken, although some have a single pressure pad in the barrel channel, this usually on wooden stalking weapons where the clearance is not great and it is thought preferable to have a known contact rather than variable pressure due to vagaries of hold.
It has long been an adage among precision shooters that a movement of one thou' of an inch at the muzzle equalls one inch at 100 yards. It takes very little difference in the stress you apply to your rifle to alter the point of impact, this is why consistancy of hold/technique is paramount to wringing the Nth degree of accuracy from your rifle.
 
Longlowdog has it right.

As to the barrel being inflexible. Well, I was shooting a short barreled Brno .22 last week and getting some rather unpredictable results shooting off a front rest. I finally put it on twin sand bags and got very distinct horizontal grouping depending on my cheek weld. I finally went back to only the front rest but this time, pulled down hard on the foreend. The POI dropped 1" at 25M and the groups settled. The barrel channel had excessive pressure on barrel. This barrel is about the diameter of many CF barrels but with only a .22 bore. It was easily flexed, as are most rifle barrels. I relieved the wood from the rear sight bolster to the fore-end tip and the problem was solved permanently.~Muir
 
most cf rifles have free floating barrels but most bedded rifles only have the action bedded the barrel is still free floating. i dont really know of any smiths that bed the barrel.

though some have been know to bed the 1st inch or so in the barrel channel if the action has a very heavy profile barrel on it.
 
If a manufacturer makes a rifle that is bedded on the action and say at the tip of the fore stock as well, don't try and be too smart and relieve the wood to make it free floating - It may make for worse groups.
I speak from experience - I used to have a Ruger 77 mk1V with a heavy barrel. It shot ok (1.5" groups at 100 yards) but the trigger was too heavy for precise work.So I bought a Timney trigger and fitted it which meant cutting wood out from the stock around the trigger assembly. That went fine and the grouping got a bit better so next I thought I'd bed the action in resin. That too went well but I foolishly then decided to free float the barrel by cutting the barrel groove clear at the front end (The stock was made so that the barrel rested on about half an inch of wood at the front of the stock) This free floating resulted in groups of 4" to 5"!!:doh:!! I realized my mistake and reversed my error by glass bedding the barrel at the front end so that it again nicely supported the barrel. and bingo - 0.5" groups!!:D!! It stayed like that till I finally sold the rifle after 15 years!
I think that the heavy varmint barrel was maybe flexing the action and it was flopping around without the support. Who knows - In that case Ruger did! What they made worked!
 
If a manufacturer makes a rifle that is bedded on the action and say at the tip of the fore stock as well, don't try and be too smart and relieve the wood to make it free floating - It may make for worse groups.
I speak from experience - I used to have a Ruger 77 mk1V with a heavy barrel. It shot ok (1.5" groups at 100 yards) but the trigger was too heavy for precise work.So I bought a Timney trigger and fitted it which meant cutting wood out from the stock around the trigger assembly. That went fine and the grouping got a bit better so next I thought I'd bed the action in resin. That too went well but I foolishly then decided to free float the barrel by cutting the barrel groove clear at the front end (The stock was made so that the barrel rested on about half an inch of wood at the front of the stock) This free floating resulted in groups of 4" to 5"!!:doh:!! I realized my mistake and reversed my error by glass bedding the barrel at the front end so that it again nicely supported the barrel. and bingo - 0.5" groups!!:D!! It stayed like that till I finally sold the rifle after 15 years!
I think that the heavy varmint barrel was maybe flexing the action and it was flopping around without the support. Who knows - In that case Ruger did! What they made worked!

so yours was pressure bedded from factory ? soem old sako's where like this to
 
My take... it is 2011 and I don't believe in voodoo.
In the meantime precision rifle builders world wide are capable of procucing
rifle after rifle with the same accuracy.
These rifles are built quite similar after the same principles.
Especially rifles for police work or military do not have the freedom of designing
a load to suit the rifle, they must all work with a factory load.
As far as I know...they do not pressure bed.

edi
 
A very useful reference for all things accuracy, compensation, bedding etc
Target Rifle Shooting
Reynolds and Fulton 1972

Written for the TR service/shooter in mind but asrelevant today as it was 40yrs ago.
 
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