Throating question

[bookworm]

When reading/shopping for custom rifles I notice some of them say they are "throated for 168gr and 180gr Berger VLD bullets" (or something similar).

What does this mean exactly and what is important or noteworthy about having this done?

 

[climb-101]

i am also new to the long range and custom rifle game and was wondering the same thing

 

[Gene]

You want the throat to be sufficient so that the base of the seated bullet is somewhare near middle of the neck This allows you to seat various bullets longer or shorter so that the ogive will touch the rifling. Once you know where it touches, you can seat the bullets longer or shorter, for either jump or jam. Of course, you will not be able to see where the base of a boat tail will rest, and you do not need to consider that part of the bullet when doing this.

When you have a gunsmith chamber a new barrel, tell him what bullet you intend to use, and he will run the reamer to desired depth. If you have a box magazine, keep the OAL short enough to fit.

 

[AZShooter]

Another factor that seems to be important is the throat angle.

Dave Kiff at Pacific Tool and Gauge recommended a 1 degree 30 min throat angle for the VLDs. It worked very well with a 257 Weatherby and a 7 Rem mag I had chambered. The Weatherby still had some freebore but less than the original Weatherby design. We made five rifles with the 257 Weatherby reamer and chose the longest OAL possible with good feeding from each rifle's magazine. Bullet jump was .070" to .100" and accuracy was great with the 115 VLDs. The 7 Rem mag had the 180 VLDs into the rifling .030" yet still fed fine. A loaded round could also be removed without upsetting the bullet's original seating depth.

Since using these two reamers I come to the conclusion that I won't have just any reamer a gunsmith has on hand to make a chamber. I prefer to have one made to my specs for bullet seating depth ( as previous poster mentioned) and throat angle. Typically I made a dummy round and ship it to Dave with some detailed instructions. Naturally I talk to Dave and ask pertinent questions before shipping. This approach has worked well with 12 reamers my friend and I own all made by Pacific Tool and Gauge.

 

[bookworm]

Thanks for the feedback...follow up question or two.

When you develop a dummy round (whether for smith or Pacific) you say that the base of the bullet should be somewhere near the middle of the neck. Does that mean the flat bottom of the bullet near the middle of the neck or where the last part of the bullet contacts the neck should be around the middle. Most of us shoot boat tails so I'm guessing it is the latter so you don't risk not having enough bullet-neck engagement.

Is there a rule of thumb on the minimum amount of bullet-neck engagement you want to have? I would have thought that you want to have at least half the neck engaged with the bullet....but maybe that is more than you need?

Also, what is the cost of the custom reamer?

 

[Buffalobob]

1 degree 30 min throat angle for the VLDs. It worked very well with a 257 Weatherby

It really does work great!

 

[Gene]

Forget the boattail. Try to keep the full diameter of ther base near the middle. You should not seat the bullet base too far forward, you could increase concentricity; i.e., run out. The bullet needs to be straight as possible in its contact with the neck.

 

[bookworm]

Got it. Thanks!