Why two die sets for semi auto??

[Pauliedad]

So I started shopping for my latest focus, loading 7.62 x 39 for some accuracy. There are several two die sets and the a separate crimp die available. I get why this is done for cartridges that are common in both bolt and semi but for the AK/SKS round? Seems like that would be a no brainer.
Thoughts?

[CSACANNONEER]

There are bolt action 7.62x39s.

BTW, I think you mean that you want to load for "precision" not "accuracy". "Accuracy" is nothing more than properly adjusted sights.

[Pauliedad]

Oops. Yup, precision. That's it.
Here's a thought, not being cheap but trying to avoid waste.
I have a couple of extra die sets I've acquired somehow.
.308 and 30-30. Would those crimp dies get the job done?
I realize I could just set it up and try but thought I'd go the ask first route.

Thanks

[Bornonthe4thofJuly]

I don't think the .308 or 30-30 crimp die will work, because they are .308 and the 7.62 x 39 is .310-.311 diameter.

[CSACANNONEER]

I don't think the .308 or 30-30 crimp die will work, because they are .308 and the 7.62 x 39 is .310-.311 diameter.

I'm pretty sure that can be adjusted for. But, I've never tried using a crimp die not labeled for the specific cartridge I'm loading so, while I think it should ork, I can't be positive.

[ElDub1950]

There are bolt action 7.62x39s.

BTW, I think you mean that you want to load for "precision" not "accuracy". "Accuracy" is nothing more than properly adjusted sights.

Is 'precision' defined more as consistency of the shots? Or?

Example: if all rounds go through the same hole, that's precision. If that hole is exactly where you're aiming, that accurate. People confuse me when they use them interchangeably

[CSACANNONEER]

Is 'precision' defined more as consistency of the shots? Or?

Example: if all rounds go through the same hole, that's precision. If that hole is exactly where you're aiming, that accurate. People confuse me when they use them interchangeably

You are correct. Many people, including firearms manufacturers use the term "accuracy" incorrectly.

[ElDub1950]

^ Great, Thanks

[chknlyps2]

Oops. Yup, precision. That's it.
Here's a thought, not being cheap but trying to avoid waste.
I have a couple of extra die sets I've acquired somehow.
.308 and 30-30. Would those crimp dies get the job done?
I realize I could just set it up and try but thought I'd go the ask first route.

Thanks

I don't think they would, a 7.62x39 is much shorter than a 30-30 or .308, so when you lifted the ram, the shell holder would hit the bottom of the die before the neck of the 7.62x39 was up in the area of where the crimp took place.

I have only tried a Lee crimp die for .223, I don't crimp rifle rounds and when I tried the Lee crimp die I saw no difference in "precision".

Is 'precision' defined more as consistency of the shots? Or?

Example: if all rounds go through the same hole, that's precision. If that hole is exactly where you're aiming, that accurate. People confuse me when they use them interchangeably

So if all shots went through the same hole that you were aiming at would that be precisely accurate?

[M1NM]

With RCBS 2 die rifle sets they will crimp if the seating die is screwed down. Run the ram with a shell in it all the way up - screw the seating die down till you feel it hit the top of the shell. About 1/4 turn more will crimp the shell.

[Divernhunter]

^^ like this or if you are like me use no crimp. I have not had any trouble no crimping for my SKS.
Adjust the die so there is just a light crimp. If you over do it you will crush the shoulder and the round will not feed and allow the shell to fully chamber.

[Pauliedad]

Good stuff. Thanks. I will order the RCBS two die set.
I tend to crimp in fear of setback. It's not like I'm going to notice setback in a magazine before I pull the trigger and when I've checked, checked, and rechecked my non crimped rounds the OCD gets the better of me and I become more worried about that than just enjoying the shooting.
Yup, I've resigned my self to be a crimp guy if there's a magazine or clip involved.

['ol shooter]

It can be adjusted. I use the same Lee factory crimp die for .30-30 and .32 Special with no issues. I like the factory crimp die because there is no way you can collapse a case neck with it. I started using them after wasting a couple .444 Marlin cases, them babies aren't cheap.

[bigedp51]

So I started shopping for my latest focus, loading 7.62 x 39 for some accuracy. There are several two die sets and the a separate crimp die available. I get why this is done for cartridges that are common in both bolt and semi but for the AK/SKS round? Seems like that would be a no brainer.
Thoughts?

Many people prefer to seat and crimp in separate operations, and a two die set means readjusting the seating die for the separate crimping operation. And this is why a separate crimping die is sold, and "why" the Lee factory crimp dies are so popular.

And you do not need to crimp the bullet if you decrease the diameter of the expander button which increases the case neck grip on the bullet.

[sunborder]

I have only tried a Lee crimp die for .223, I don't crimp rifle rounds and when I tried the Lee crimp die I saw no difference in "precision".

Were you shooting using a chronograph? Have you tried it with a round that actually has appreciable recoil? Crimping may allow additional precision by allowing a more uniform starting pressure (and therefore unoform fps at muzzle or chrono). It DEFINITELY changes pressure and velocity.

It can also change precision by getting the round to the right velocity to hit the sweet spot in the barrel harmonics, without including additional powder. I've found that it decreases the spread between high and low velocities in groups. Some feel that it changes the outer surface of the bullet, making the aerodynamics change, and thus impeding accuracy. I haven't generated enough data to have an opinion on that.

I would only consider crimping a factor in improving precision when you have a load that is giving you big swings in fps within a shot string, where you suspect inconsistent ignition. The .223 probably isn't a round where you will see massive changes, unless you are using an oddball powder/load recipe.

Then there's the issue of bullet setback in certain types of firearms (think heavy-for-cartridge bullets in magnum revolvers, tube magazine-fed rifles, or autoloading rifles with stiff recoil), which is a safety matter.

I crimp my 556 rounds, because I've found it lowered the SD of my loads, and the bullet/brass combo I am using is one that makes me nervous about setback. Also, if I ever use a bullet as a "tool" to drop a mag, I don't want to set the bullet back in the process. YMMV.

And you do not need to crimp the bullet if you decrease the diameter of the expander button which increases the case neck grip on the bullet.

Depends on what kind of bullet you are loading. Any kind of cast bullet (and people DO load cast in the 7.62x39), you need the extra expansion and crimping. Also, depending on the jacketed bullet (flat base, thin jacket, etc...) you don't want too much neck tension, especially if you haven't deburred/chamfered your brass adequately after trimming. Can scratch up the jackets quite fierce.