New barrel tenon length and nose clearance issue

[SpencerC87]

Got a new barrel spun up for my BRM and found the end of the barrel to the shoulder is .015" short. This led me to measure headspace and nose clearance. The headspace is ok at .0025-3, the nose clearance however is about .027" total or .017 over max (.020 over ideal). How would you expect this to be fixed? Since the headspace is correct and others are short, the only way to do it is cut the chamber longer and recut the shoulder. Would you trust not chopping off existing tenon length and re-doing at least 50% of the chamber? It is a heavy palma and already to length.

 

[LVLAaron]

Need to set it back.

 

[Walt Krafft]

To get it right, set it back. What action? Flat or coned breech?

 

[DaveTooley]

Compare the amount of exposed case with a Remington 700. Remington's from the factory are around .165"-.170" Unless you're past that I wouldn't worry about it.

If you choose to set it back there's no need to do anything but move the shoulder forward and set the HS.

 

[SpencerC87]

To get it right, set it back. What action? Flat or coned breech?

It's a cone breech. Measurement was verified through several techniques and compared against my current barrel which all measures in spec.

 

[Walt Krafft]

Cone breech you must fix it. Pita I know, btdt.

 

[SpencerC87]

What is the minimum amount you would set it back?

 

[DaveTooley]

Cone breech you must fix it. Pita I know, btdt.

Walt
Why is this a must? In my experience cone bolt faces are shallower than many flat face bolts.

 

[DaveTooley]

What is the minimum amount you would set it back?

If you need .015" then take that off the shoulder and deepen the chamber.

 

[DaveTooley]

Measure the depth of your bolt face. Add the .025" to it and tell us the number.

 

[urbanrifleman]

Compare the amount of exposed case with a Remington 700. Remington's from the factory are around .165"-.170" Unless you're past that I wouldn't worry about it.

.

This man is wise in so many ways.

 

[SpencerC87]

Measure the depth of your bolt face. Add the .025" to it and tell us the number.

.925 from the face of the action, .148 from face of bolt

 

[DaveTooley]

So you have .148" of exposed case? I set Remington 700's up with .160" exposed. That gives me anywhere from .010" to .020" end clearance depending on the bolt.

 

[SKWERLZ]

.925 from the face of the action, .148 from face of bolt

.148 is a decent number on the actions I’ve worked with
That basically just the rim and extractor clearance cut on many cartridges exposed.

 

[SpencerC87]

Maybe I'm misunderstanding something. My headspace gauge in the barrel that is correct, is flush with the end of the barrel and the cone of the bolt and cone of the breech has about .008" clearance. The barrel in question, the headspace gage is proud of the barrel by about .015" and measured cone to cone clearance is .027-.028" total. That barrel threaded onto the action, the headspace is correct

 

[DaveTooley]

Not sure you're getting an apple's to apple's comparison. Your .015" gage to barrel measurement is only good if on the barrel the transition from cone to barrel is the same. Make up a 30 degree gage. 1" in diameter, maybe a 1/4" cylinder section. Early in my career I made these up for 25 and 30 degree cones. Easy to duplicate a barrel and easy to do a barrel with the number in my log book.

 

[SpencerC87]

Yes, That is one of techniques I used to measure it. I started with a gage ball but was too hard to hold steady so I made a tapered gage. Also used layers of scotch tape on the bolt face and feelers gages between the bolt handle and action body, all of which gave the same numbers

 

[Walt Krafft]

Walt
Why is this a must? In my experience cone bolt faces are shallower than many flat face bolts.

My experience is mainly with t2ks. They have a recessed bolt face plus the cone. The bolt face to chamber edge is .150 to .160. 0.018 over that is asking for a case failure. Saw one with a 6br. Shooter would be blind if he didnt wear safety glasses.

 

[jackieschmidt]

You never said what case.
BR and PPC Cases are very limited on the length of the solid part of the head. I would thing that .028 clearance might uncover the solid portion of the case head.

Start over. Do it right. If somebody else did it, send it back.

Years ago, when Jerry Stiller developed his drop port on the Viper Action, he used a Remington style bolt head and extractor that allowed the case to fall out the bottom.

When he fired it the first time at a practice day in Denton, it ruptured a case. (6PPC). He found out that he had to maintain no more than .005 nose clearance in the counterbore. If you bought one of those, he included instructions saying just that.

 

[SpencerC87]

It's a .308 which is also why I'm asking about how much set back is needed to correct it. If adjusting just that .015" or so, that's not much room on the chamber walls to ensure a nice cut. Alignment would have to be zero assuming initial setup would be a couple/few tenths. I paid for and am expecting a 30" barrel. A 29" with 1" shorter breech on a new heavy palma doesn't cut it for almost $1200. I'm just really frustrated with this whole thing.