Bolt design: advantages and disadvantages?

[FromSA]

Hi everyone,

Having retired a couple of years ago, my dad has taken on a number of design projects that have always interested him but that he never had time for while working. His most recent one is to build his own custom action. I've been helping him with information where possible (because, by his own admission, he is digitally challenged). In the process I've also learnt some very interesting things about bolt design processes. One question I have (out of pure curiosity) is if there is anything lost in terms of accuracy if a bolt is a full body design (I think some call it a fat bolt design) as opposed to the designs with lugs that slide in raceways in the action body. Or is it simply a case of the quality of workmanship that determines the precision produced by an action?

As far as I can tell T/C, Ruger and Weatherby at least make some of their actions using the full body design. I think I've also seen some Savages with this design but I could be mistaken.

Any experiences regarding accuracy of different designs would be appreciated.

 

[hank440]

accuracy is 90% the barrel the action has very little to do with it

 

[dkhunt14]

accuracy is 90% the barrel the action has very little to do with it

This is not true. Fire control has a lot to do with accuracy. The action has to be good enough to bed and hold the barrel securely. Especially when you start hanging 30 inch 1.250 and up barrels on it. In actions where the lugs are in the rear there is bolt deflection from bolt thrust. Matt

 

[J E Custom]

Hi everyone,

Having retired a couple of years ago, my dad has taken on a number of design projects that have always interested him but that he never had time for while working. His most recent one is to build his own custom action. I've been helping him with information where possible (because, by his own admission, he is digitally challenged). In the process I've also learnt some very interesting things about bolt design processes. One question I have (out of pure curiosity) is if there is anything lost in terms of accuracy if a bolt is a full body design (I think some call it a fat bolt design) as opposed to the designs with lugs that slide in raceways in the action body. Or is it simply a case of the quality of workmanship that determines the precision produced by an action?

As far as I can tell T/C, Ruger and Weatherby at least make some of their actions using the full body design. I think I've also seen some Savages with this design but I could be mistaken.

Any experiences regarding accuracy of different designs would be appreciated.

In my opinion a one piece bolt is easier to blue print because there are no moving parts that have to have some clearance to operate. With that said, There are lots of multiple piece bolts that shoot great if set up correctly.

I blue print "ALL" of the actions I deal with because they all need some truing no mater who makes
them.

I subscribe to the philosophy that less is more in most cases, and easier to trouble shoot if there is a problem.

I feel that the barrel is the heart of an accurate rifle but all other components can have a major
impact on the rifles overall performance.

If I were to build an action from scratch. It would be similar to a 700 rem. the 700 rem action
is the most copied action made for a good reason. Most hand made bench rest action are based on the 700 Rem action with the owners personal likes added. (I love the Sako bolt release when installed on a 700 Rem.

I agree with dkhunt14 that the lugs need to be as close to the case head as possible for the best performance on high powered rifles/cartridges.

Just my opinions and likes

J E CUSTOM

 

[hank440]

This is not true. Fire control has a lot to do with accuracy. The action has to be good enough to bed and hold the barrel securely. Especially when you start hanging 30 inch 1.250 and up barrels on it. In actions where the lugs are in the rear there is bolt deflection from bolt thrust. Matt

Do you know anyone hunting animals with a "30 inch 1.250 and up barrels on it" ?

 

[dkhunt14]

Almost everybody I know has a 30 in plus barrel on their hunting guns. Mine is 36 inches and 1.450 Diameter and some of the guns we hunt with are up to 46 inches. My gun is actually fairly light so we can carry it in. It only weighs 45 pounds. Some of my buddies guns weigh 95 or so. We do all our shooting off of chain drive benches. Go see Long range hunting articles on Dan Liljas site. We sit all day and watch whole mountains. In fact if you go to page 30 on this forum and look for the thread pictures of my hunting gun you will see pictures of the bench and stock that I made. Matt

 

[hank440]

dang is that hunting or shooting ? It doesn't seem sporting gun)

 

[hank440]

DK that's not a rifle it's an alien space laser weapon type device

 

[WildRose]

dang is that hunting or shooting ? It doesn't seem sporting gun)

When you've made your first shot on game beyond 800yds you'll understand why it is very much "sporting".

This is "The Long Range Hunting" website... .gun)

 

[hank440]

Wildrose I have

 

[tinkerer]

Any bolt made on the interrupted thread concept can be inherently accurate. Naval 16" guns are all barrel with no cartridge and a bolt for closure only and can place a 2600 pound shell in a football field at 26+ miles.

I always wondered how interesting it would be to start with grade 8 chrome moly bolts and a solid body and a barrel.

Post results.

Larry
Tinkerer

 

[zfastmalibu]

A full diameter bolt is just easier to machine. You dont have to broach or edm race ways in the action body. It wont affect accuracy. Matt is right, ignition is a huge part of accuracy. The firing pin needs to be guided the whole way, and must not rub or bind in any way. Just because it goes bang doesnt mean its ok. Other than that if the threads, lugs, bolt face, and action face are all square and parallel then it will be accurate.

 

[SansSouci]

accuracy is 90% the barrel the action has very little to do with it

I agree.

 

[SansSouci]

This is not true. Fire control has a lot to do with accuracy. The action has to be good enough to bed and hold the barrel securely. Especially when you start hanging 30 inch 1.250 and up barrels on it. In actions where the lugs are in the rear there is bolt deflection from bolt thrust. Matt

There are a lot of things that will affect accuracy, but none as much as barrel. If a barrel is not up to snuff, not even match ammo will produce decent groups.