Neck Tension for AR-15's ??

[shadow4]

Started reloading for my M-4 Clone about 2 months ago. I've been loading for bolt rifles for years. A friend scanned some pages from the sierra reloading manual for gas operating rifles and I read what was on them. When I got to the part about neck tension it said that for semi-auto rifles that .003-.004 neck tension was preferred in order to keep the bullet from sliding forward while getting "slammed" into the chamber (basically re-seating itself longer). According to the article there are two ways to get this done. By bushings dies (of course) or by using a drill and emery cloth to remove a couple thousandths off of the expander ball (therefore creating more neck tension).

Up until this point I had just been using the Sizing die like I have with any other full length die. After reading the article I measured my neck tension that I had on my rounds just from the sizing dies themselves (with no modifications). My redding FL die gives .0015-.002 MAX neck tension. My Extreme spread was around 40fps sizing this way.

After reading the article I drank the cool-aid and went to work on my expander button to create more neck tension. I now have .004 neck tension but my extreme spread is ridiculous (90fps).

Has anybody had any issues with their regular FL sizing dies not creating enough tension to the point where the slamming forward motion seats their bullets out further?

How much neck tension do your FL dies create on your .223 brass?

I really do not want to crimp,.... any ideas or should I just stick a new expander ball back in there and call it good enough?...................... btw, the brass in Remington once fired brass.

Thanks

 

[tfsron]

Re: Neck Tension for AR-15's ??

Dear S4:

I am not sure that there is an "answer" to your question(s), at least not one that you can count on as your brass changes.

Here is my interpretation:

1. Before changing a load that works I would have run a few cartridges through the clip, let the bolt pick them up and chamber them. Eject them by hand and measure the overall length to see if there is a problem to begin with. If the load is shooting good I would stick with it regardless. I think the expression is " If it's not broke, don't fix it."

2. The actual neck tension is a complex function of the brass hardness at the neck and the amount of expansion that happens when you seat the bullet. I would not expect sizing the neck .004 to give you twice the neck tension; if it does, it may be different yet the next time that you load the brass.

3. Sizing .004 under bullet diameter may also bring concentric problems with the loaded round.

4. Crimping and working up a new load may turn out to be the easiest solution if there is indeed a problem with the COAL changing in the magazine or chamber.

Good shooting,
Ron

 

[918v]

Re: Neck Tension for AR-15's ??

Check it out:

Neck tension alone does not keep bullets in place. It is the friction between the inner neck and the bullet shank. As little as .0005" is enough if the neck is completely free of carbon and rough enough to bite into the bullet shank.

You have to be sure you don't have any lube in the neck.

I take a bronze brush chucked in a power drill and spin it at high speed inside the neck. At first it spins easily due to the lubrication provided by the carbon fouling. After a while it heats up the case and you feel the bristles bite down into the brass. At that point I keep spinning for three more seconds and then remove the brush. The result is bare brass. No carbon at all. When I seat the bullet into the neck it feels like I'm using virgin brass. I have so much friction I don't have to crimp or worry about bullet setback with the normal amount of neck tension my dies furnish.

 

[shadow4]

Re: Neck Tension for AR-15's ??



<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ron Morrison</div><div class="ubbcode-body">1. Before changing a load that works I would have run a few cartridges through the clip, let the bolt pick them up and chamber them. Eject them by hand and measure the overall length to see if there is a problem to begin with. If the load is shooting good I would stick with it regardless. I think the expression is " If it's not broke, don't fix it."
</div></div>

Thanks Ron,

I actually just got done doing what you recommended. Funny thing is I was probably doing it as you were writting that. I was just logging on to say disregard my post I found the solution.

You are right though, I should have just done that first. My first loads that I put through the rifle weren't that impressive (2-2.5 MOA). A friend recommended the Sierra reading to me and basically I got the idea that my accuracy could possibly improve with more neck tension. My thought was that my bullets were getting seated further out from the action of being jammed into the chamber, therefore messing up my accuracy.

I just went and measured the OAL of ten rounds that were loaded using the previous .0015-.002 neck tension brass. I marked the OAL on the side of each round with a magic marker. Well, after slamming each one into my chamber about 7-10 times a piece there was literally no change in seating depth. So as it turns out, .0015-.002 neck tension is enough.

Thanks!

 

[tfsron]

Re: Neck Tension for AR-15's ??

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 918v</div><div class="ubbcode-body">Check it out:

Neck tension alone does not keep bullets in place. It is the friction between the inner neck and the bullet shank. As little as .0005" is enough if the neck is completely free of carbon and rough enough to bite into the bullet shank.

You have to be sure you don't have any lube in the neck.

I take a bronze brush chucked in a power drill and spin it at high speed inside the neck. At first it spins easily due to the lubrication provided by the carbon fouling. After a while it heats up the case and you feel the bristles bite down into the brass. At that point I keep spinning for three more seconds and then remove the brush. The result is bare brass. No carbon at all. When I seat the bullet into the neck it feels like I'm using virgin brass. I have so much friction I don't have to crimp or worry about bullet setback with the normal amount of neck tension my dies furnish. </div></div>

This is good!
It never entered my mind, but I got it now.
Thanks
Ron

 

[gnfiter3]

Re: Neck Tension for AR-15's ??

Using an RCBS Comp. Die Set, and noticed the force need to seat the bullet varied substantially sometimes. I have not had a problem to date, but I don't really understand how to adjust the tension. One article stated that the loader removed the expander ball completely.

It isn't broke so I'm not inclined to fix it, but I'd like to know the process. I also understand different balls can be ordered.

Mixed brass may be why I noticed this.

 

[Mag 300]

Re: Neck Tension for AR-15's ??

Best not to mix brass if possible there surprisingly different in the neck area at least enough to vary the neck tension by 50%
I have used .003 and its worked well. consistancy is the key in my opinion
Bill

 

[gnfiter3]

Re: Neck Tension for AR-15's ??

Ok, now I have to admit, since no one described the process, how do you check it?

I take it there's a guage? I hate it when I don't know something that could be the difference between 1,1/2, 1/4, moa. Interseting that the mix brass, separated after loading, hasn't made 1 moa difference when loaded with the same charge. My AR-10 shoots moa or better with 41.5 of 4064, regardless of brass. 40X ragged 5 shot hole with 43.0 grs. 4064, mixed brass. I can call anything outside of that, operator error.

AR-15 shoots sub with Varget, which is out of stock everywhere. Admittedly, 1 moa from my AR isn't squat at 100yds. When the load is tuned and my head is on straight, ragged five shot hole is what I look for. When they are all in a 1" grid and not touching, I'm not happy. Now that may be a function of mixed brass, neck tension, but I usually think, it's me. Just looking to take another variable out of the game.

So now please, describe the process and tools required. One day I hope to shoot out to 1K and it may really matter then.

 

[myerfire]

Re: Neck Tension for AR-15's ??

To adjust neck tension, you need a neck sizer die with interchangable bushings.
myerfire

 

[shadow4]

Re: Neck Tension for AR-15's ??

You can also use a FL Redding type S die that uses bushings. Or, you can take some emery cloth and drill and remove a thousandth or two from your expander ball. Unfortunately this is permanent. I did this but I also had an extra expander ball on hand, just in case.

<span style="font-weight: bold">Gnfiter3</span>, You measure neck tension by taking one of your cases that you have FL sized, and measure the outside diameter of the neck with your caliper. You then load that case with the bullet you are using and again measure the outside of the case neck diameter. Subtract the unloaded from the loaded and you now know how much neck tension you have on your bullets. Measure more that one, some times this can vary up to .001"

 

[gnfiter3]

Re: Neck Tension for AR-15's ??

Professor Shadow 4, Thank you.

I posted to a member and told him that if he posted a question here, and waited long enough; some Professor of Reloading would answer his question.

The guys here are a library of knowledge, from basic to advanced.