Effects of Having Bolt Lock up in the Barrel

[South Pender]

(Not sure just which sub-forum to put this into, so chose this one. If it should be somewhere else, perhaps mods will move it.)

A number of newer bolt-action hunting rifles have the bolt lock up in the barrel. I believe the newer Anschutz centerfire rifles lock up this way, and all the switch-barrel hunting rifles pretty much have to--Blaser, Sauer, Schultz & Larsen, and now Sako. Note: I'm not including switch-barrel benchrest rifles built on conventional actions.

I’m wondering what the effect on accuracy would be when compared with rifles that lock up in the conventional way, with the lugs engaging recesses in the action, rather than the barrel. Related to this, perhaps, is the question of how tight the lock-up will be; can the lugs lock up as tightly into the recesses in the barrel as they do in a well-tuned rifle with conventional lock-up? Will the barrel harmonics be different—better or worse—with a barrel lock-up?

So, does anyone on the forum have a theory about this, or perhaps better, some empirical evidence with these newer rifles?

 

[762plinker]

cost is my guess. the ar family has a "bbl extention" (lugs) screwed to the bbl for bolt engagement.
not new at all

 

[Walt Krafft]

Look at the Barrett Advance Sniper Rifle (ASR). It locks up in an extension and the accuracy requirements are very tight.

 

[DaveTooley]

The Sig Cross uses an extension also. No complaints on the barrels I've done.

 

[BoydAllen]

To the OP, all rifles that have screwed in barrels are prime candidates for being used as switch barrels. They have the additional advantage of being able to choose any barrel manufacturer or chambering. Additionally, if the action has interchangable bolt heads, that really opens the caliber choice to anything that can fit in the magazine, assuming that to be an issue. It sounds to me like you may have never seen a barrel switched, which is in no way a put down. Most have not.

 

[gunsandgunsmithing]

There's a outfit not far from me that builds 50 BMG's on their own actions using milsurp 50bmg barrels that use and extension similar to an AR. I forget what they call the gun that the bbls are intended for. Wanna say it's a helicopter gun of some designation.

Anyway, It shoots well enough to make most people very happy but I've yet to see one shoot well enough for myself and a lot of people on this site.

Can't say why, but it shoots better than average maybe.. but not what'd want, myself. Just pointing out that example and that it uses a milsurp bbl with a bbl extension setup. They are chrome lined, IIRC...fwiw.

 

[Coyotefurharvester]

My TC Dimension(have 204,223,22-250 barrels) are all very accurate. Very little poi change if removing reinstalling same barrel and bolt. Fired brass sizes easily and will fit other rifles of same caliber. Looking/watching for a 7rem mag barrel (have the d-bolt) and a 30TC barrel.

 

[South Pender]

To the OP, all rifles that have screwed in barrels are prime candidates for being used as switch barrels. They have the additional advantage of being able to choose any barrel manufacturer or chambering. Additionally, if the action has interchangable bolt heads, that really opens the caliber choice to anything that can fit in the magazine, assuming that to be an issue. It sounds to me like you may have never seen a barrel switched, which is in no way a put down. Most have not.

Yes, I get your point about screwed-in barrels. This is not what I was referring to and should have been clearer in my post. I was thinking instead of the kind of switch-barrel rifles made by Schultz and Larsen (and others), in which the barrel just slips into the action and is tightened down by two cross bolts on a clamping extension below the receiver ring. Before tightening the barrel down, the bolt has to be closed on the loose barrel to control headspace. Here’s a brief YouTube video of how this works. It is 6 minutes long, but, if you skip to the 3-minute mark, you’ll get the picture. I’ve wondered about whether this kind of barrel attachment and having the locking lugs engage the barrel, rather than the receiver, might have a negative effect on accuracy.

 

[FNSafari]

Yes, I get your point about screwed-in barrels. This is not what I was referring to and should have been clearer in my post. I was thinking instead of the kind of switch-barrel rifles made by Schultz and Larsen (and others), in which the barrel just slips into the action and is tightened down by two cross bolts on a clamping extension below the receiver ring. Before tightening the barrel down, the bolt has to be closed on the loose barrel to control headspace. Here’s a brief YouTube video of how this works. It is 6 minutes long, but, if you skip to the 3-minute mark, you’ll get the picture. I’ve wondered about whether this kind of barrel attachment and having the locking lugs engage the barrel, rather than the receiver, might have a negative effect on accuracy.

S&L has always had a very good reputation for accuracy and build quality. As far as I know, they are not imported into the US and haven't been for quite a while. They are pricey.

 

[Ray123]

I watched the video...I was unimpressed.
I've seen similar expensive setups that were not accurate..and then changed the barrel it was more acceptable in the different caliber. The 50 BMG was more accurate then the big 375, which was absolutely horrible, at $10 per shot...But it was a switch barrel! An expensive crap shoot...so big no for me. I can build a complete rifle for the cost of an extra barrel on many switch a barrel rifles ...and it will be accurate.

 

[lb-ft]

The Sig Sauer SSG 3000 is based on the Sauer 200/202. Accuracy is exceptional and remarkably consistent. Benchmark Barrels offers replacements too, no slouch in the precision department.