Redding bushing dies for neck tension Fed AE 7.62x51 168 gr m1a

[InfoLoader]

Hi, I was wandering if anyone has sugested using a bushing die for better neck tension on fc ae 168 gr otm cases when seating bullets for use in a scar 17? Not sure if its needed but i did read where someone did ask sierra about crimping bullets and they said something like no crimp needed just as long as your neck tension is couple thousanths less to hold bullet tight. Any thoughts on subjust and suggestions on what type of redding die type s full length small base bushing die or their type s full length standard bushing die? Also what size neck bushings to purchase if you think this is a good route to take for extra assurance of a tight bullet hold in case for scar 17 . Thanks for those that respond with some good feedback on the subject matter.

 

[InfoLoader]

If it's not needed and tension from rcbs ar small base t/c dies are sufficient let me know as well. Thanks yall....

 

[Bart B.]

I would just use a standard full length sizing die. That rifle will do fine with reloads from it. Is its bolt face squared up with the chamber axis? If not, new cases will be more accurate than resized ones from any die.

 

[30Cal]

Yeah, a standard FL sizing should be fine.

 

[USSR]

While I use Redding bushing dies, I use them for precision bolt guns where I want less neck tension, not more. You will be fine with standard dies for your autoloader.

Don

 

[Blue68f100]

To determine your bushing size, measure a completed round at the neck. Then take 0.001"-0.002" that will be your bushing size. If you want more just go to the next smaller size. For bushing dies to work best your necks need to be relative close to the same wall thickness, all the way around. The negative on bushing dies is that it seams you need a different size for every mfg of brass you have, unless you go to the trouble to turn necks or use high quality brass.

If you need more neck tension than your std dies are giving you just turn down the expander a little more.

 

[243winxb]

Sierra - Reloading for Semi-Autos and Service Rifles http://www.exteriorballistics.com/reloadbasics/gasgunreload.cfm
See- Neck Tension

Photo from http://www.handloadersbench.com/view_topic.php?id=28771&forum_id=91&jump_to=265433#p265433

Guy was using
a valve spring pressure tester.

 

[Bart B.]

My issue with those bullet psi numbers is they're misleading.

A bullets force on its base to push it out of the case is measures in pounds in USA military arsenals. 7.62 NATO service ammo has been 60 pounds minimum; 20 for M118 match ammo. It takes at least 260 psi to push a match bullet out, 790 psi to push a service bullet out.

You can replace those psi numbers directly to pounds add they'll be meaningful. Multiply them by 13 to get the approximate pressure in the 7.62 case needed to push them out.

Those neck and die numbers are the interference fit; a dimension difference. Tensions are measured by the force one thing has against another. Depending on contact area between case neck and bullet, surface friction and mating force, a given interference fit will require different forces to push the bullet out. The throat (inside the neck) cross section area of 308 Win and 7.62 case is about .0745 square inch. For every 100 pounds per square inch (psi) of pressure in the case, there's 7.45 pounds of force on the bullet.

The force needed to seat bullets seldom equals the force to push them out.

 

[243winxb]

My issue with those bullet psi numbers is they're misleading.

Think of it as a comparator.