Barrel bedding question

[Big Dog Dad]

Should the front sling swivel stud protrude through a wood stock and press on the barrel? I always thought you should be able to slide a dollar bill between the barrel and stock from muzzle back towards the action.

 

[Reloadron]

No, not that I have ever seen. I have seen adjustable pressure points that rest on the barrel, never used them but have seen them. The sling swivel should not touch or apply pressure to the barrel.

Ron

 

[sage5907]

You didn't say but I assume you're asking about a bolt action rifle. When bolt action wood stocks are made at the factory they are usually set up so the barrel fits tightly in the wood and some upward pressure is supplied by the wood to the front of the barrel. If someone opens the barrel channel with a piece of sandpaper the upward pressure would be removed and could allow the barrel to touch the sling swivel stud. If the sling swivel stud touches the barrel the adjustment would be to remove the sling swivel stud and either file it shorter or grind it shorter on a bench grinder. I would grind it shorter and then use a file to taper the end lightly so the threads start easily. That situation would not be good for accuracy. The situation of sliding a dollar bill under the barrel all the way to the action is neither good or bad. The best situation on a classic sporter is for the barrel to fit snugly in the stock as the manufacturer intended without any contact from the sling swivel stud. If someone has taken a piece of sandpaper and opened up the barrel channel it may not be good because the barrel could walk back and forth from side to side over a period of time bumping one side and then the other. This situation is corrected by glass bedding the rear two inches of the barrel around the chamber area. The glass bedding holds the barrel in one place.

 

[MachIVshooter]

Sounds like someone put the rear swivel stud up front, or just plain used a too long stud.

Fix that problem post haste. No good can come of it.

When bolt action wood stocks are made at the factory they are usually set up so the barrel fits tightly in the wood and some upward pressure is supplied by the wood to the front of the barrel.

Not by design on any modern rifle. Sometimes there is contact either because proper fitting was not done, or because a wood stock warped a bit, but it isn't supposed to be that way.

 

[CoRoMo]

Ruger M77's are made this way. The barrel is not free floating. The stock has a spot under the barrel that presses upward on the barrel.

 

[jmr40]

Some rifles are designed with some upward pressure at the tip. Some gunsmiths full length bed the barrel for consistent pressure. Most find fully free floated works best on most rifles. But the sling swivel stud should never touch the barrel

 

[sage5907]

The term "modern rifle" can mean something good or something bad. Free floated barrels started being built in the 1960's for the sole reason to reduce production costs. Labor costs were so high that manufacturers didn't want to take the time to fit the barrel to the wood. The available poor quality wood and poor quality composite stocks on the cheaper rifles fit right in with free floated barrels. With the advent of the CNC machines it became easier to get a better fit between the metal and wood, or between metal and composite stocks. Some of the manufacturers produced free floated barrels and some continued to fit their barrels to the wood, especially on the more expensive rifles. Then came the advent of the precision long range rifles where free floated barrels became the excepted norm and cost more than most can afford.

 

[Bart B.]

Free floated barrels started being built in the 1960's for the sole reason to reduce production costs.

Rifles were built in the 1950's with free floating barrels. And precision free floated barrels getting best accuracy was championed by the short range benchrest folks and those shooting NRA high power match rifles through 600 yards in the 1950's long before precision long range shooting became possible with good, heavy large caliber hollow point bullets in the 1960's.

Winchester (in the '60's?) changed their Model 70 sporting stock fore end channel making it a bit wider to free float their factory rifle barrels. Worked very well and they shot more accurate with that stock than the original that had multiple, inconsistent contact points on the barrel. That plan was scrapped when so many customers didn't like that 1/16" gap between fore end and barrel; didn't have that "perfect fit" for appearances.

Anyone who can hold the rifle vertically and slide a dollar bill between the barrel and fore end and have it move around easily should also rest the rifle horizontally on its stock toe and fore end tip to see if that bill still slides easily. Sometimes it doesn't; the weight of the barreled action bends the fore end up closer or against the barrel. Most barrels vibration amplitude at the fore end tip is much greater than a dollar bill's thickness.

=========================

Whose side are you on?

One side of this issue is that a free floating barrel will whip and vibrate the same for every shot fired in all positions; no external force will get transferred through the fore end to the barrel.

The other side's basis is a contact point stabilizes or modifies the barrel's whip and wiggle to be more consistent or perfect for every shot; the fore end force on the barrel is always constant regardless of the shooting position.

One of the above is physically impossible. You decide.

 

[Sunray]

"...a free floating barrel will whip and vibrate the same for every shot..." There's absolutely no way to guarantee that will happen. The only thing that is guaranteed is that if a barrel is touching the stock on one side or the other or is inconsistently touching, the shot will not go where you want it.
Free floating barrels guarantees nothing. Some rifles just don't like it. And there's no way of telling without trying it.
The really important part is for the receiver bedding to extend into the barrel channel as far as under the whole chamber area and no more if floating helps.

 

[Bart B.]

The really important part is for the receiver bedding to extend into the barrel channel as far as under the whole chamber area and no more if floating helps.

Why does that bedding have to extend an inch further under a barrel in a given receiver to the end of the chamber (its mouth) for different cartridge case lengths? A given caliber barrel chambered for a .308 Win. would need its bedding pad half an inch shorter than that of a cartridge case half an inch longer.

I used to think that's the best way util a National Champion suggested I try it testing loads at long range but cut it back half an inch from the 1.5 inches that bedding pad had in front of the receiver for a test group at each pad length. Groups had vertical shot stringing that eventually went to zero after all the bedding pad was removed.

Such bedding pads under barrel chambers are not popular in match rifles. If they really worked as people think, every match-winning record-setting rifle made would be built that way.

There absolutely is a way to guarantee that totally free barrels will whip and vibrate the same way for every shot fired. Shooting a few dozen shots 20 seconds apart starting with a cold barrel from one in a machine-rested free-recoiling rifle into less than 2 inches at 600 yards seems like a pretty good way to prove it. Or shooting 30 shots from a 30 caliber magnum the same rate of fire into 6 inches at 1000 yards. Besides, a given barrel's structural properties don't change from shot to shot (in the temperatures typically shot in) so as long as the external force (the cartridge firing) shocking it into vibrating and/or wiggling, if any at all, is the same from shot to shot, so will be the barrel's physical behaviour.

 

[sage5907]

Bart B, if you think about the number of rifles sold in the 1950's compared to the number that had free floated barrels it could have been 1 rifle in 10,000, or less. For the average hunter who owns a rifle today most of the accuracy level in his rifle is in the quality of the barrel rather than the bedding method as long as it has the original manufacturers stock without some problem like the sling swivel stud touching the barrel. The example that you gave about removing the bedding around the chamber may have only applied to that one rifle. That's why it is so much fun to take a rifle and tweak it to get it to shoot accurately. I have the utmost respect for the long range precision shooters because when they set a rifle up to shoot accurately it isn't long before they are tweaking on it again, or changing barrels.

 

[murf]

and check the barrel with that dollar bill when it is hot (as hot as you think it is going to get out in the field). barrels expand and wood bends when warmed up. you may have to do a little extra relieving of that barrel channel for a good free float.

murf

 

[Bart B.]

Anyone thinking any stock fore end with a pressure point somewhere between it and the barrel will always have the same force and direction against the barrel needs to do the following.

Measure how much the bore axis moves relative to the line of sight in different shooting positions and different holding parameters. Easy to do and an eye-opener to most. No ammo required and can be done in your shop, front room or bathroom.

With plenty of clearance from the barrel to the fore end, the force against the barrel will always be zero.

The example that I gave about removing the bedding around the chamber applied to thousands of rifles. They're the ones getting the best results in competitive shooting with all sorts of barrel profiles using all sorts of cartridges. And based on hundreds of rounds proving it.

 

[MCMXI]

It's much easier to obtain consistent barrel harmonics with a free floated barrel. There really shouldn't be any doubt about this. It's also possible to obtain consistent results with a bedded barrel (I have such a rifle), but why go that route and add more variables to the accuracy equation? All of my long range precision rifles have free floated barrels. I've often wondered if ARs are considered free floating due to the gas tube making contact with the upper half of the receiver.

 

[PowerG]

Yes. I have had better results overall with floated barrels...that said, one of the most accurate rifles I've ever owned has a bedded barrel. It was bought used at a pawn shop, when I took it apart I found a very neat barrel bedding job. (It's one of the old BDL Varmint Specials, in 7mm-08.) I figured I'd try it before any modifications, it still has the bedding.

 

[Bart B.]

I've often wondered if ARs are considered free floating due to the gas tube making contact with the upper half of the receiver.

No, they're not free floated. Neither are M1 and M14 barrels. They're all fixed to the gas system that goes back to receiver and bolt parts. M1 and M14 rifles have several pounds of barrel pull down pressure at the stock ferrule so they're definitely not "free floated" at that area. They are "pressure fitted" according to the 'smiths at the USN match conditioning unit that built their Garands for competition.

That said, the best match conditioned ones would shoot all day long inside 4 to 5 inches at 600 yards with good lots of commercial match ammo or good handloads with new cases.

Free floating means the barrel touches nothing but the receiver. At least in most folks vocabulary.

 

[scythefwd]

I can think of a couple OLD target rifles that had adjustable pressure points under the barrel at the tip of the forearm. Never have I seen a target rifle that was built for any type of precision have the sling swivel touch though...

 

[M-Cameron]

"...a free floating barrel will whip and vibrate the same for every shot..." There's absolutely no way to guarantee that will happen. The only thing that is guaranteed is that if a barrel is touching the stock on one side or the other or is inconsistently touching, the shot will not go where you want it.
Free floating barrels guarantees nothing. Some rifles just don't like it. And there's no way of telling without trying it.
The really important part is for the receiver bedding to extend into the barrel channel as far as under the whole chamber area and no more if floating helps.

oh yes there absolutely is.....i suggest you look into "barrel tuning"......

it is essentially tuning your barrel to resonate in a distinct and consistant pattern, this tuning accounts for changes in velocity of your ammo, negating the effect of a hot or cool round.

adding a "pressure point" in a barrel interferes with natural barrel harmonics, making it MUCH harder, if not impossible, to tune correctly.

i do not know of ANY serious competetive shooters that are not using a free floated barrel.

 

[sage5907]

What's been lost in this discussion is that only a small portion of rifles are target rifles or long range precision rifles that use free floated barrels. The original question applied only about the sling swivel stud touching the barrel. Most people who own a rifle will never shoot at anything over 200 yards, and most rifles shoot far better than the capability of their owners. Most hunters who take to the field this fall are not concerned whether their rifle barrels are free floated or solid bedded.

 

[Panzerschwein]

No. It should absolutely NOT do that.

Use a shorter screw, or trim the current one, if this happens.

 

[scythefwd]

sage - I think we got that point. Our point is if the guys chasing accuracy (the target shooting guys getting paid for very small groups) aren't having swivels or bolts sticking through touching the barrel, then its probably detrimental to accuracy and it shouldnt be that way...

There are a LOT of rifles now, even cheap rifles, that come free floated. Many r700's do, the savage axis does, the remington american does, etc... Its becoming a common feature, even on budget rifles. In other words, the industry has pretty much agreed that free floating is the better option. The remington 40x was the last target rifle that I know of that used pressure points on the barrel for tuning, and that was mostly in their 22's, and that was stopped decades ago.

 

[Bart B.]

What most people do not understand.....

All rifle barrels change their bullet departure angle when anything interferes with their natural frequency's harmonics. The more inconsistent that interference is, the less accuracy is. Doesn't matter how far away the target is. It's the bore axis at the muzzle that directs the bullet down range. A 1/3 MOA change from normal moves bullet impact 1/3 MOA at all ranges.

All rifles shoot bullets more accurate by themselves in free recoil than when some human holds onto them; doesn't matter if the human rests the rifle on something while they hold onto it or not. Us humans have a heart pumping blood into our muscles that makes us wiggle. None of us hold onto the rifle exactly the same for every shot fired. Our variables add to that of the rifle and ammo making all our test groups much larger holding onto the rifle while shooting it.

Most people will shoot rifle bullets more accurate slung up properly in prone resting the stock on something than sitting crooked at a bench holding onto the rifle.

 

[scythefwd]

exactly bart.. which is why the harrell tuner, and like devices, are so common in 22 bench shooting.. so that you change the balance and weight of that barrel tip so that the bullets exit (ideally) at the stop between the upward and downward movement during the oscillation.

 

[Bart B.]

...a free floating barrel will whip and vibrate the same for every shot..." There's absolutely no way to guarantee that will happen.

Well, nobody's disproved it. As long as no external force moves the barrel, it'll whip at exactly the same frequency and harmonics thereof for each shot.

Our point is if the guys chasing accuracy (the target shooting guys getting paid for very small groups)

What competitive shooting discipline does that?

.. which is why the harrell tuner, and like devices, are so common in 22 bench shooting.. so that you change the balance and weight of that barrel tip so that the bullets exit (ideally) at the stop between the upward and downward movement during the oscillation.

Wrong. So darned wrong. That's the worst place for bullets to exit on average which they will because of muzzle velocity spread. Same for the stop between the downward and upward movement at the bottom of its swing. In both instances, half the bullets will be shot out in the wrong direction. Can you figure out why? And it is done to change the resonant frequency the barrel whips at; nothing else.

The Brits figured that out over a hundred years ago with their .303's doing so well in long range matches. There's even a web site documenting it.

If the rifle's built right and held right by the shooter, the free floating barrel won't whip vertically at all.

 

[scythefwd]

Bart, benchrest shooters, specifically the guys that are sponsored. They get paid either in materials or cash to consistently win, which is a direct result of consistently and accurately printing small groups on target.

I'd be interested in hearing the best place to tune a barrel for ammo you cannot control the extreme spread of, like rim fire. The harrell tuners are very much about dampening the vibration or at least changing the timing of that vibration. Whatever they're doing works. Most every purpose built small bore bench rifle I've put eyes on is using a micrometer adjustable tunrer of some sort.

let me clarify my over simplifed post. Ideal is to fully stop the barrel and if every round had the same exact MV, top or bottom as it transitioned would be the longest time period the barrel isn't in motion. In a nonideal setting, like real world, that doesnt happen. Most folks tune on the up swing so faster bullets, with less dwell time in the barrel, exit at a lower point in the up swing of the barrel while slower bullets exit a little higher in the up swing, making them impact the same point. At least that seems to be a fairly common theory on what the tuners are doing. Thats the difference between ideal and real world. If these guys running fully customized win 52's, remmy 40x's, suhls, and anschutz's are seeing changes in the groupings with a tuner, then it is messing with the harmonics in some manner. I'd hardly argue that their barrels aren't made properly, so if its not vertical ocilations, then how are groups being shrunk?