.223 AR neck tension issue - Update

[ReaperDriver]

I just posted this on the Hide rifles forum but it occured to me it was more of a reloading issue - so I though ya'll could learn from this and I'd be interested in some comments/feedback to see if anyone has seen this issue before.

Link to original post

Reader's digest version: I initally was having issues with my 1st load development rounds using 77 SMKs and LC brass loaded with Redding S-Type Match FL bushing dies with a .245 bushing. The loaded round measured .246, so that was only giving me .001 neck tension. Every 1st round of a 5-shot string was significantly low (about 1-1.5") from the rest of the group when releasing the bolt from the mag release button on a new mag. I experimented with some rounds I loaded this week to see if the bullet was changing seating depth when the bolt slammed home and sure enough the bullets were seated about .003-.004 LONGER after being chambered this way. So I tried another batch of the same components but this time used a .243 neck bushing instead and the extra .003 tension kept the bullet from moving when being chambered. SO hopefully when I shoot them this week, I won't see the POI shit I did previously.

 

[Suasponte]

Re: .223 AR neck tension issue - hopefully resolved

Watch low neck tension on Semi's! With only that much neck tension there is a good possibility that the bullet is being pushed back into the case when closing the bolt. I have seen guys at the range acutally have the bullet pushed all the way into the case to the point that the poweder got past the bullet back into the chamber and mag area!

I like to have good solid tension on my AR loads. I typically run them thru the LEE factory crimp die.

Terry

 

[ReaperDriver]

Re: .223 AR neck tension issue - hopefully resolved

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: suasponte</div><div class="ubbcode-body">Watch low neck tension on Semi's! With only that much neck tension there is a good possibility that the bullet is being pushed back into the case when closing the bolt. I have seen guys at the range acutally have the bullet pushed all the way into the case to the point that the poweder got past the bullet back into the chamber and mag area!

I like to have good solid tension on my AR loads. I typically run them thru the LEE factory crimp die.

Terry </div></div>

Actually, my experiment showed just the opposite. I think the momentum of the bolt slamming home with light neck tension allowed the bullet to keep moving forward. My measured COALs after chambering were always about .003-.004 LONGER than the the pre-chmabered rounds.

 

[MitchAlsup]

Re: .223 AR neck tension issue - hopefully resolved

Both effects can happen when the neck does not adequately grip the bullet. Bullet set-back can happen in the magazine and on the feed ramps. Bullet set-forward can happen as the bolt rams it home.

 

[Grand]

Re: .223 AR neck tension issue - hopefully resolved

I stumbled on an easy solution to neck tension. I polished the expander ball in my RCBS FL die about .001 smaller. Plenty of tension without the crimp.

 

[Pogo57]

Re: .223 AR neck tension issue - hopefully resolved

My setup gives a .003" neck tension and no crimp with any bullet I'm using in my AR. I've had 0 problems with bullets moving. When I originally had around .009" neck tension, I was getting pressure signs. These have gone away with the lessened tension.

I do a quick check by pushing the tip of the bullet on a loaded round against the edge of my bench. No movement and it's GTG. Some cases with thin walls will allow a bullet to move.

 

[TT]

Re: .223 AR neck tension issue - hopefully resolved

How much jump to the lands when loading to mag. length? If it is a factory chamber the 0.003 - 0.004 increase in seating depth may not be signicant (pressure etc.). What may be significant is the bullet axis becoming slightly canted or shifted off center thus losing concentricity which we all know affects accuracy.

I mention this because of the die you are using. The bushing die does not resize as much of the neck as the non bushing version of the die. This results in (1) less total friction for a given neck tension and (2) less "effective" case neck to keep the bullet aligned.

I found this out awhile ago after contacting the folks at Redding. I now use the standard Redding full length die in my AR but special ordered it with the neck reamed to the desired inside diameter. Just sayin'...

 

[Clark]

Re: .223 AR neck tension issue - hopefully resolved

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ReaperDriver</div><div class="ubbcode-body">

Reader's digest version: I initally was having issues with my 1st load development rounds using 77 SMKs and LC brass loaded with Redding S-Type Match FL bushing dies with a .245 bushing. The loaded round measured .246, </div></div>

If I use a FL Redding "S" die with .246" bushing, and there are no problems with 96LC brass. The loaded ammo measures .248~ .249".
I do have a few problems with a .247" neck sizer.

Has someone been turning your necks?
Are your bullets undersized?

 

[jarheadkp]

Re: .223 AR neck tension issue - hopefully resolved

On a semi, you should have no less than .003 neck tension. The battery of a loaded round going into the chamber and the recoil with rounds in the mag, will change COAL with anything less. Soft seating(.001 neck tension) is not a good practice unless its a bolt rifle, single load only. Only for the use in Benchrest or High power 1000yds disciplines.

 

[ReaperDriver]

Re: .223 AR neck tension issue - hopefully resolved

Well, I shot about 35 rounds throught the rifle yesterday comparing identical loads with the original neck tension (.001) and the same load with .003 neck tension. I thought at 1st it was getting better, but in all honesty - most of the groups really sucked for what I've gotten out of the rifle in teh past with factory match loads. Best group was still > 1 MOA with most being about 1.5-2" with mostly verticle stringing. In fact they ALL had very noticable verticle stringing. Two different shooters duplicated these shitty groups. So either I'm doing something wrong with my handloads or something is messed up with the rifle and or the scope.

My last resort before I send the upper back to Larue is I'm going to go out and buy a box of BH .223 77 blue box and shoot it to see how it does. This gun had previously EASILY shot tight .6 to .7 groups with the Black Hills stuff. If I repeat these results with the factory ammo, something's definitely broken

 

[jarheadkp]

Re: .223 AR neck tension issue - hopefully resolved

Do you have a flash suppressor on this rifle? If not, check the crown on see if its has been damage. Another thing to check is make sure the gas rings in the bolt are spaced so their 1/3 from the openings, not stack in the same position. This can cause vertical displacement. Going to factory loads see a good ideal, but check the gas rings first.

 

[Rovieairto]

Re: .223 AR neck tension issue - hopefully resolved

Make absolutely sure that there is nothing contacting the barrel.
I once had the vertical stringing problem until I noticed that the sling loop (connected to the FSB) was touching the sandbag I was firing off of.
I removed it and all is better.

Is there any odd play in your barrel relative to your FF tube?

I almost always see my OAL get longer with auto chambering, especially with the heavier bullets and larger calibers like .308.