jones123

Can someone explain to a simpleton (me) why bedding makes a difference? It seems to me that the lead is out of the barrel so fast that vibration, expansion, etc are all after the fact. I hear people in the know say it makes a difference, so I believe them, I was just wondering how.

Thanks

stubblejumper

That statement is untrue.The barrel is moving as the bullet moves down the bore.

gorse

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driftrider

Actually, the speed of sound in steel is something like 23,000fps, which is about 7-15 times faster than most bullets travel, so can and do effect the bullet while in the barrel (actually at the muzzle). As far as beddings effect on accuracy, it's mostly through consistancy that bedding makes a difference. Accuracy is synonymous with consistancy. Hypothetically, if everything happens exactly the same way every time a bullet is fired, the bullet will follow the exact same trajectory and hit the exact same spot downrange every time, hence perfect consistancy and therefore perfect accuracy. Of course, we live in the real world where there are so many variables in play, many of which we can't control, that perfect consistancy and therefore accuracy is impossible. Bedding is one of the variables that we can, to some extent, control. By providing solid and consistant bedding, the forces applied on the barrel and/or action are kept the same, shot to shot. If the forces applied to the barreled action are always the same, then the net effect on accuracy is zero, eliminating one accuracy robbing variable from the equation. That is one reason that free-floating barrels is popular. By free-floating the barrel the stock can have little effect on the harmonics and forces applied to the barrel on firing. Combine free-floating with a quality barrel that is consistant throughout it's length and you have the potential for excellent accuracy.

However, you've probably noticed, if you've looked, that there are a number of factory rifles that are not free-floated from the factory (the M700 is a great example). Most of these guns are pressure bedded, or in other words, have the stock touching the barrel at one or more points along its length. Pressure bedding has the advantage of damping the harmonics of the barrel to some extent, which can make a lower quality barrel shoot pretty well with a wider variety of ammo, but the drawback is that if the pressure applied by the stock ever changes, be it due to the barrel heating up, the stock getting hotter/colder and flexing, or warping due to moisture, etc..., it can cause the groups to open up, or the point-of-impact (POI) to shift unexpectedly.

Many factory rifles, and almost all custom/benchrest guns, are free-floated and use some type of bedding system to improve accuracy. Common types are glass bedding (non-permanently mating the action to th stock with a fiberglass/epoxy mixture to fill all the void space between the two), pillar bedding (where there are one or more steel or aluminum "pillars" embedded into the stock through which the action screws pass and the action is tightened down onto), or both. Some dedicated benchrest/varmint rifles are actually permanently glued into specially designed stocks (that have openings to allow the trigger and action to be adjusted/serviced) with epoxy.

So very simply, bedding makes a big difference, and a good bedding job can make a mediocre shooting rifle a lot more accurate. But as the saying goes, you can't polish a turd. If the barrel is poor/shot out, the action is as crooked as a politician, or the ammo sucks, the best bedding job in the world might not make a significant difference.

Mike

jones123

Thanks for the answers. I'm going to check my bedding out. My first move was to lighten the trigger. Immediate 100% improvement in group. Makes sense to me now that the barrel moves/vibrates as fast as the bullet.

And thanks for the bonus info about turds. Wish I'd known that before I went through so many buffer wheels! Guess I'll just grind them into fertilizer.

bigbulls

Exactly what gorse said.

Of course there are different types of bedding.

Glass bedding gives you 100% contact around the action or recoil lug so that nothing moves around on you from shot to shot. Basically it makes a form fitting shell for the rifle to sit in. It also strengthens the stock some what and keeps places like the recoil lug area from spliting.

Pillar bedding keeps the stock from compressing over time. This allows a person to get consistant torque on the action screws with out compressing the wood. When you take a rifle out of its stock and then put it back in and tighten the screws back you willusually turn them a little bit more each time and compress the stock. Also if you do not get the screws to the same torque each time your point of impact could change on you.

A bedding block is an aluminum "block" that is skeletonized and bedded into the stock. It is precicely machined to fit the barreled action and they mate up perfectly. This accomplishes both of the above but also adds extreme rigidity to the stock itself.

driftrider

Um, it's a metaphor...if you don't get it, well...nevermind. I'll play nice today.

Mike

jones123

Some times I wish we could see each other's faces. Then you'd know I just made a well intentioned but very poor joke, not a retort. I'm going to have to learn those smiley face things on the left. I can't figure out which one looks like me when I make bad jokes.

Sincere thanks for the answer - and the metaphor. I learnt something useful again.

driftrider

That's why I decided not to jump down your throat for it, because I couldn't tell if you were being a smart*** or just making a good natured response. The internet doesn't lend itself well to allowing people to fully articulate their intent like face to face contact allows (most of the time).

And, BTW, I'm happy to help.

Mike