Barrel-Receiver Threaded Joint Motion

[TScull]

In Harold Vaughn's book "Rifle Accuracy Facts", he dedicated chapter 6 to dealing with barrel joint motion. One of his proposed solutions was to thread the barrel using a ramp-thread design called "Spiralock" by Detroit Tool Industries instead of the standard V thread. Has anyone used this approach? Is there an ongoing concern with this issue? Do you just use the standard thread and apply a high torque with a good thread lubricant (such as Teflon tape)?

 

[chino69]

Spiralok

In Harold Vaughn's book "Rifle Accuracy Facts", he dedicated chapter 6 to dealing with barrel joint motion. One of his proposed solutions was to thread the barrel using a ramp-thread design called "Spiralock" by Detroit Tool Industries instead of the standard V thread. Has anyone used this approach? Is there an ongoing concern with this issue? Do you just use the standard thread and apply a high torque with a good thread lubricant (such as Teflon tape)?

It was my understanding that the Spiralock thread was initially conceived and designed for the aircraft industry where high cyclic rate & vibration could typically loosen a standard fastener. I think it's a cost prohibitive thread for many applications but could be wrong.

The other interesting piece in Vaughn's book was the discussion about pre-stressing or stretching the fastener. This is routinely done in the power generation facility for large turbine components, reactor heads, etc. The studs are actually elongated with a stud tensioning device that puts a pre-load on the fastener. These studs never work loose during thermal contraction, expansion, and vibration.

Lou Baccino
Chino69

 

[Boyd Allen]

You might want to check with Greg Tannel of Gre-Tan Rifles. I believe that he has used the thread design you are interested in.

 

[Charles E]

Has anyone used this approach? Is there an ongoing concern with this issue?

Yes. Jerry Stiller has written about this -- numerous posts on BR Central Centerfire forum. The problem is galling. You could do a search & get his exact words.

Another solution is to this "maybe" problem is to use a barrel block, and put the scope base on the block. That way, where ever the barrel is pointing, so too is the scope.

 

[TScull]

I did try searching before posting my question but I didn't do a very good job of it. I now have found Jerry Stiller's comments on his concern relative to galling as well as Gene Beggs comments about his experience.

The reason I posted my question on this forum is because I believe the concern is much more relavent to the magnum cartridges that many use for 1000 yard BR than for the 6 PPC. I believe Vaughn makes a compelling case that for many rifles, joint motion is a real accuracy concern. I like the suggestion of the barrel block. I haven't been thinking along that line for a while now but I will reconsider that as my design approach.

Tim