Varmint Hunters Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
2 Posts
Discussion Starter #1
Need advise. I shoot a 17M4/17 Fireball. I bought lapua 221 Fireball brass and necked it down to 17 cal. The accuracy went to hell. When I tried to pull the bullet heads they were very difficult to pull from the cases, the neck brass is to thick. Please advise on how and what is need to turn the necks?
Thanks Please get back to my email [email protected]
 

·
Registered
Joined
·
4,691 Posts
Neck turning

It sounds like you have a chamber of unknown dimensions - typical of any custom/wildcat chamber. And, any time you resize from a larger caliber to smaller, the thickness of the brass thickens (it has to go somewhere, right?).

Two schools of thought (depending on the job the gun is to do): tight neck (or sometimes "fitted" neck) cases - reserved for precision or competition applications, or standard chambers.

We'll get to tooling in a minute. But, first you need to know to .001" what the chamber neck ID measurement is. Once that is known, then then the neck OD of the loaded round combination of bullet diameter + 2xthe neck wall thickness needs to be less than the chamber neck OD by a specified amount to allow expansion when firing: up to ~.0015 to .002" larger than loaded case neck wall diameter is typical for benchrest or precision shooting, or .006" clearance for factory chamberings.


Tooling:

In the end, my chamber neck ID is .200"
I desire my loaded necks to be .200" MINUS .002 for expansion (a "tight neck" specification) or .198"
The difference between bullet OD (.172") and loaded neck wall OD (.198") is the TOTAL thickness of each surrounding neck walls or .026/2 = .013 for NECK WALL THICKNESS.

I use a K&M neck turner with a .171 (lubed inside the neck) mandrel and cutter adjusted to a final cut of .013" after the final fine cut.

I use a Wilson bushing die with a .097 ID to neck size only my brass in preparation for loading, and it works well.

NOTE: The smaller the bullet diameter, the more critical the variations in dimensions of the case neck become to accuracy/consistency.

My accuracy with my rig is such that I can print 5 inside a dime at 100 yards with a 20 gn Berger hollow point, which is fine for rats, possums, coons, ans squirrels out to 200 yards. More precision would no doubt tighten up the groups some, but NONE of the varmints around here have complained yet!:rolleyes:
 

·
Registered
Joined
·
1,034 Posts
You have some good info to chew on re previous replies.
One other tidbit for now or later on in your reloading career, necks that are too long. Check the mouths of fired cases for hints of land and groove marks. This happened to me a long time back...trimming was needed. Be safe, have fun.
 
  • Like
Reactions: Paul Workman

·
Premium Member
Joined
·
197 Posts
45TAJ has struck on a much overlooked fact or reloading. Brass grows and can be very apparent when you measure the length of your cases. I like to trim mine to .10 under the length to the lands. That crimping action on a too long case will spike chamber pressure out of sight.
 
1 - 6 of 6 Posts
Top