[ENGLANDER]

Hello from Scotland

I have a .308 Mirkou M-bolt stainless/synthetic 22" barrel, which im smitten with its very light, shoot very straight, and is pleasing to the eye.
At recently i have been putting factory 180 gn Winchester silver-tips and 180 gn Nosler balistic tips it shoots both to the same point of impact dispite different powder and loads.
At some point i want to try cast gc bullets of 180 gn in it. This brings me to me question to crimp or not to crimp ? As with all topics many seem to have differing opinions on the subject, some say crimp for better accuracy others not.
I was planning to use collet neck die only full length sizing when the fireformed cases started getting tight ? As i would also like to get maximum life span out of my brass ?
What do you guys think ??

Regards Englander

 

[arkypete]

Englander

Most of my cast bullet reloading is for straight sided cases and crimps are not an option.
Now with my 375 Whelen, based on the 30-06 case, I do not crimp the case neck.
I use the Lyman M die for, I think, 37 caliber. All of my cases have had their necks turned to uniform case wall thickness, length of the case trimmed uniform.
I removed the expander portion and chuck it into a power drill. I polished the shank portion to bright shine and reduced it's diameter, while leaving the flaring part alone. The neck tension of the case holds the bullet tight without a crimp.
Jim

 

[MikeG]

Englander,

There are two basic classifications of cast bullet loads for rifles in cases like the .308.  One is a light load of a fast-burning pistol/shotgun powder (Unique, etc.) that generates modest velocities (1,000fps to ~2,000fps).

On the other hand you can work up to full-power hunting loads, with velocities comparable to jacketed bullets.

So keep that in mind when you read this answer.  For the light loads, many recommend no crimp, light neck tension, and the bullet seated so that it just contacts the rifling when the bolt is closed.  Theory is that the fast burning powder isn't so hard to ignite so a crimp isn't as necessary.

For the heavy loads, you would probably be better off with full neck tension (similar to what you'd get with a jackted bullet), and "probably" a crimp.  It might not be required but it's a variable that you should plan on experimenting with.

If you crimp, AND you want to seat the bullets out near the rifling (which is probably a good idea regardless), then you may need the Lee Factory Crimp die, which will allow you to crimp anywhere on the bullet.  Otherwise the crimping groove might not line up with case mouth, depending on the throat dimensions of the rifle.

I think that the collet die is the way to go.  With the light loads especially, the brass may have a tendency to not completely seal the chamber, unless it has been previously fireformed.  Not a big danger but the cases might come out all dirty.  And using brass that has been formed to the chamber is a help to accuracy.

Make sense?  Like a lot of things with reloading, there is room for experimentation.