To bed or to float

[MSC]

Hi, I am new to this forum & gun smithing, i have been shooting for many years but after reading some of the threads around here i must say that i had no idea that so many things could affect the accuracy of a rifle. The 1st. thing that i did was to check the barrel on my Marlin 25MN (22mag)  with a dollar bill, it would not even try to slide under the barrel so i was planning to float the barrel until i took it apart & realized that the stock seemed like it was bedded, so now i don't know what to do. I guess the question is why do some people bed a rifle barrel to make it more accurate & other people float the barrel to achieve the same results? These are two opposite processes, so how can they achieve the same results?

[trotterlg]

There are a lot of ways people try to make rifles more accurate.  Some are proven methods generally, in high powered bolt guns pillar bedding and floating the barrel is usually good, bench rest guys (some) just glue the enitre barreled action into a stock and are done with it.  Some actions are really not strong enough or stiff enough to support a barrel, so you bed the action and barrel to the stock, this sounds like what you have.  Before you mess with it you should see how it shoots.  There is no single solution, each rifle will respond a little differently.  Larry

[Luckyducker]

Both methods are a way of dealing with barrel harmonics.  I would rather float a barrel to enhance accuracy for two reasons, the first being that it is a lot easier to open the barrel channel than to open the inletting in the stock and  barrel channel and then apply bedding compound, and the second reason is that a bedded barrel really throws rounds after a little barrel warm-up where groups from the floated barrel will gradually open up.  I only have one fully bedded rifle, and after the third shot (sub MOA) the fourth shot from a slightly warm barrel will be 4" to 5" outside of group, where the floated barrels will throw the next round out +/- 1".   These numbers are with sporter weight barrels and heavy target barrels won't warm up nearly as fast as the thinner tubes and therefore won't show such adverse results.   This is the reason the benchrest shooters are inclined to fully bed their target rifles.  It all comes down to what will work or not work, and involves trial and error, especially when dealing with a problem child.

[MSC]

The barrel on this rifle is not that thin, it is heaver than my 10/22 & about the same as my .223, it is .615 at the end of barrel & .750 at the end of stock. I took the stock off & put a piece of duct tape sideways across the channel at the very end of the stock. It should be that the only place that the barrel is touching will be on the duct tape. What do you think this will do?

[Rangr44]

There's no way to tell how it'll do, except via shooting, MSC.

BTW - generally, I find that a thin plastic shim (credit card) or a piece of business card, placed in the bottom/center of a barrel channel about 1" to 1 1/2" from the tip of the forend, most effective.

A more permanent shim can later be adhered in place, if it works OK.

Shims, however, don't seem to work as well with synthetic stocks, in my experience - since they're more flexible in the forestock area, and will actually bend away from a barrel with shim pressure ILO putting an up pressure on the barrel.

.

[Flash]

For a rifle barrel to be accurate, it must vibrate (and it does) consistantly from shot to shot. It's refered to as harmonics. When you bed the action and float the barrel, it allows the barrel to do it's thing the same way from shot to shot. When there is pressure on the barrel from the stock, moisture being absorbed by the wood can increase the pressure and as it dries, the pressure is decreased. Well, guess what this does to your accuracy? When a rifle stock is Accura-glassed to the barrel and action, everything becomes one and it shoots consistantly. It's best to float the barrel and bed the action with the recoil lug screw being tight, always. A synthetic stock is somewhat forgiving when it comes to accuracy but still, floating the barrel on these, in my opinion, is best. The barrel can have a slight pressure point at the forend tip and after about 10 shots, the surface of that pressure point is hammered by recoil and it no longer serves the same purpose. With that said, always float your barrel and support the action with the tension being at the recoil lug.

[gunnut69]

First MSC welcome to the site and good luck. As you can tell from the various responses there are a lot of things that can help (or) hurt the accurqacy of a rifle. Heat distortion can cause a fully bedded barrel to 'walk' shots as it heats up, because the heat causes a lengthening of the barrel. Military rifles have dealt with this because the nature of their use predicts prolonged heavy use. The normal response was to put steps in the barrel as most mausers were built. This allows the barrel to lengthen without impinging on the barrel channel.. Why were the stocks full length? To allow a little easier handling with a very hot barrel! Tapered barrels as most sporters are can act like wedges as they lengthen from the heat.. Remington and others adressed that by applying the contact at the front section of the barrel in an area that was at least for a short distance, tubular, not tapered.. This helps by allowing the barrel to grow without altering the pressure on the stock appreciably. Barrels also can bend as the lengthen. This has several causes, a wandering bore(thin spots in barrel walls), metalurgical faults, or even uneven heating caused by something retaining heat over the barrels length(hand guard). If a barrel is bedded to the stock a tightly held sling can warp the stock/barrel enough to move bullet impacts. How do we decide? That's the real question of course. I usually free float and if the accuracy is sufficient that's where it stays. if accuracy needs improvement I can add pressure points ala the Remington pressure point technique with little difficulty. Pressure points usually make a barrel shoot better as it raises the frequency at which the barrel vibrates and higher frequencies equal less movement equals better accuracy. That's the reason bull barrels are usually considered to be more accurate..thicker walls equals high frequencies equal better accuracy. There are even devices that can be slipped over barrels to add weight to the barrel and alter it's frequency, called hamonic stabilizers they can be of some help. I prefer a simpler approach allowing the rifles bedding to solve the problem and not add accessories. The frequency alteration technique is kind of epitomized in Brownings BOSS system. This is a omni directionsal muzzle brake that can be screwed back and forth on the barrel and locked in place at the 'sweet' spot. This in effect lengthens (or shortens) the barrel changing the vibrations it produces. They do work but are falling from favor because of the increased muaale blast eh brake produces. Full length bedding a barrel is another kettle of worms. A common practice with mannlicker stocked rifles it seldom causes a problem. That's becasue even with thier normally slender tapered barrels they were not designed for use as sustained fire weapons. For hunting multiple shots are not usually needed. In fact seldom are more than three shots fired at a big game animal and even small game is won't stand around for a barrage. Full length bedding can make a rifle more uniform as the vibrations aer somewhat dampened by the full length contact with the bedding... I guess there is no positive answer and why there are still many techniques in widespread use.  A few notes. Synthetic stocks unless really well made flex too much to work well with pressure bedding and all but the heaviest(and even them to a small degree) will shoot away from a hard object touching the forestock. Also all rifles(bolt guns anyway) should be bedded (action) and the first few inches (2-3) of the barrel in front of the receiver ring, to produce NO movement when either of the action screws are loosened of tightened(neutral bedding) and the sequence of the bedding process can have a consiquence for the rifles accuracy. The glue in technique is called 'barrel Bedding' and is not used much any more..at least in target rifles. It is used in some instances with rifles such as the 10/22. This rifles aluminum action receiver doesn't have the strength to support a large barrel haning on the front in a free float situation so the solution is to bed the barrel tightly and allow the action to float in it's bedding. It's one of the designs limitations. the real fun is trying all this stuff out...!!

[gunnut69]

OH MY!! Forgive the book in my previous post!!

[bluebayou]

that was an awesome post, the part about:

 "Synthetic stocks unless really well made flex too much to work well with pressure bedding and all but the heaviest(and even them to a small degree) will shoot away from a hard object touching the forestock."

that really made me think for a minute about how my POI is different with the Stevens 200 in .223 when I am on a bag and off hand. 

Interesting

[bluebayou]

My preference is to "neutral bed" like you say with the scope/bases/rings on the receiver.  I want the unbolted barrelled action with scope to lay in the stock without levering forward due to the weight of the barrel.  I bed to a balance point on the barrelled action, like you say 2-3".  It might have been more on the Model 70 long action. 

[fox fire]

  I was pondering this very subject the other day, beded or floated,(LESS FILLING!! TASTE GREAT!!).     I had never heard anyone explain the difference between them, and as a bonus got a lesson about harmonics, always curious how they worked.   Matter of fact I posted a question asking someone to explain how the limb saver deresonator had effected the accuracy, trying to learn how they worked.  GOOD WRITE UP!!!   IS THIS A GREAT WEB SITE OR WHAT???

[gunnut69]

Thanks and we're glad to have helped.. I've not used the Deresonator but devices to alter barrel vibrations to improve accuracy are not new. Winchester used several variations of their target type rifles all the way back into the 30's. The Browning BOSS is another such device. Generally they fall into 2 types 1)alter the weight of the barrel to change the positioning of the vibratory nodes. 2)change the tension of the barrel which mimics shortening the barrel. The latter causes the barrel to vibrate at a higher pitch increasing the number of nodes but decreasing the distance over which the barrel vibrates. The first of these alters the weight of the barrel to in effect shorten the barrel. In other words the heavy barrel vibrates as if it were shorter producing the high pitches of vibration that usually give the best accuracy. The BOSS system works by moving the mass distribution of the barrel to give better vibration patterns,, The story is that the BOSS was developed because of the BAR's problem accuracy. If they didn't perform well the Browning shop would chop a bit from the barrel and re-crown. In many instances this fixed the rifles problems.  Some barrels don't vibrate enough to affect accuracy. Muzzle loader barrels were made from a very soft ductile iron and don't produce a tone when suspended and struck with a hammer. The full stocks on these rifles have little effect on accuracy(and they are quite accurate). There are other factors affecting the acccuracy of a rifle such as proper bedding of the action but that's another book!

[fox fire]

I love science... one of my favorite subjects in school.    I wish I could set down and pick your brain for a while, this is interestin stuff.   Thanx for the lessons.

[gunnut69]

Glad to help. I always loved science and science fiction which seems to provide a viw of the future direction of science.. along with reading everything I could lay hands on.. Traded guns before I could drive a car and my best fiends dad was one of the local gunsmiths and guntraders,, Started varmit hunting with a Winchester M43 in 218 Bee cortesy of the same guy. Love guns and all things gun oriented.. wrote papers in high school on weapons created and used in the 2 big wars..Vietnam was still being decided at the time and was still not called a war.. I always disputed that little omission... The science of guns can help make really good choices and see things more clearly. For instance the advantages of a cartridges shape on ballistics. Some of the short magnums claim to produce identical velocitis as their standard length campatriots but produce reduced recoil.. Do they actually perform this bending of physics? YES! The use slightly less by weight powder. They run pressures higher than the larger rounds and generate velocities AS HIGH AS the larger rounds. What the companies omit is the fact that if the techknowlegy to create the specialized powders were used for the larger rounds and their pressures allowed to rise to dangerous levels they would outperform the smaller rounds.. I heard it once expressed thusly, a cartrige is an engine and in engines, all else being equal, size matters///