Neck Tension?

[CaptnC]

As some of you know this is my first gasser to reload for.


My die set didn't come with a crimp die...I have one for my 6.5CM that could be used if it's not too deep...just thinking out loud...

Any way, don't care to crimp my brass, so back to resolving neck tension to keep from pushing bullets back in the case.

Bolt guns tend to be .002 and i've read .003 is best for semi's.

Any one here pull the expander ball and seat the new bullets?

Brass is hard to recover so I'm not sure I want to anneal any cases for this caliber. In a hunting situation most will be lost...

[NugginFutz]

Cap,

I used to crimp the Grendel, but no more. I use the Redding Type S bushing die. I set the neck tension to .003, with no expander. No issues with setback (verified).

[Crusty]

I've removed the expander balls from my dies. I size down to .259" ID with a bushing die, then bring it back to .261" with an expander die and then seat my bullets. My groups have been tightening as I pay more attention to consistent neck tension and bullet release.

[FLS]

Similar to above. I use a full length sizing die with decapping stem and expander ball removed. I expand the neck with a .262 carbide mandrel. It give very consistent neck tension, low SDs and ES.

[centerfire]

Full length sized, no expander, and a .262 neck sizing mandrel. New brass is trimmed and expanded with a mandrel.

[ported45]

My Hornady expander is 0.262 and sized brass comes out at 0.258 id. Bullets moving until I put a pretty firm crimp from the Lee DVD on it. Crimp looks similar to a military crimp. It is leaving a crimp ring in the bullet. Heavier than I crimp 5.56 or Blackout. Never had them move before, but a slight crimp seemed to help accuracy a smidge.

Brass was tumbled and necks brushed before sizing.

What gives?

This was my first real run with this upper because of throat issues with the first two scrappy BCA uppers.

Today the first 15 of 120 Nosler bt was just over 1" and first 15 of 129 Nosler ABLR was just over 2" at 100 yards. Both with 8208 starting loads.

The neck tension seems to be an issue right now. One bullet got stuck because I chambered it twice on my first range trip yesterday before I thought to check bullet movement while chambering.

[ricsmall]

My Hornady expander is 0.262 and sized brass comes out at 0.258 id. Bullets moving until I put a pretty firm crimp from the Lee DVD on it. Crimp looks similar to a military crimp. It is leaving a crimp ring in the bullet. Heavier than I crimp 5.56 or Blackout. Never had them move before, but a slight crimp seemed to help accuracy a smidge.

Brass was tumbled and necks brushed before sizing.



What gives?

This was my first real run with this upper because of throat issues with the first two scrappy BCA uppers.

Today the first 15 of 120 Nosler bt was just over 1" and first 15 of 129 Nosler ABLR was just over 2" at 100 yards. Both with 8208 starting loads.

The neck tension seems to be an issue right now. One bullet got stuck because I chambered it twice on my first range trip yesterday before I thought to check bullet movement while chambering.

[Klem]

ported,

I don't crimp anymore after comparing the differences between crimping and neck tension over 300 shots. In the chart these are four-rd groups at 100yds from the bench. The bullet was the 120NBT which as you know does not have a cannelure. I found no practical difference in accuracy between crimping and neck tension but as crimping is an extra step and also deforms the case mouth it was an easy decision to stop doing it.

The way I determine neck tension is to measure the OD of a sized neck and subtract this from when a bullet is seated. The reason for this is I don't use an expander and also bullet diameters vary fractionally between manufacturers. By including the bullet this is the actual tension rather than assuming it by measuring the die and case.

[Mad Charlie]

Once you exceed the yield point of any material, with an interference or press fit, you only get so much "squeeze" left over. If you get past the point where the brass doesn't spring back to a dimension close to what it was before the bullet was pressed into it, after the bullet is removed manually you only have a certain amount of "tension", no matter how much the original press fit was. Try seating a bullet into a resized case (dummy round) and let it set for a few days, pull the bullet and measure the inside of the neck, the difference between that dimension and the bullet will be the actual "neck tension". (I am tired and I don't think I am explaining what I mean very well, sorry bout that). Personally, I think .002-.003 press fit is plenty, depending on purpose.

[ported45]

I appreciate the responses so far guys.

But the problem is not set back of the bullet. It is being inertia pulled when stopping in the chamber. I had one bullet stick in the lands when it was chambered twice without firing. Nothing about the feed ramps or magazine lips would cause this.

Almost feel like giving up on it. Took three uppers from BCA to get one with an appropriate length throat and now this. Maybe I need to pick up a box of factory ammo and give it a try. My cases were once fired Federal. Maybe that brass is junk.

[Crusty]

[ported45]

Cases are corncob media cleaned and then I use a nylon brush to clean the inside of the necks and make sure that no case lube gets anywhere near the cartridge mouth while sizing. Maybe I will use a q-tip with break cleaner to swab the inside of the necks and see what happens.

Bullets are seated to 2.245" on the 120 BT and 2.270" on the 129 ABLR. The base of the bullet is well below where the neck & shoulder join.

I use all the same procedures on my 5.56 and .300 Blackout ammo and had never had bullets sliding forward out of the case when chambering before. Just something new I am experiencing with the 6.5.

[Crusty]

Do you know your neck ID before the bullets are seated? Are your cases trimmed to 1.620" or shorter? The other measures that you're taking seem adequate to me. FWIW I used a vibrator cleaner for quite a while and then finally broke down and bought a cheapo HF rock polisher and some SST pins and that's resulted in a step up in the quality of my finished rounds because the primer pockets and neck IDs get cleaned at the same time.

Does the primer of a loaded but unfired round get a slight indent from the firing pin when the bolt slams home?

If all of that's OK then I'd be changing brass because most other things that could be causing it have been eliminated.

[ported45]

Once you exceed the yield point of any material, with an interference or press fit, you only get so much "squeeze" left over. If you get past the point where the brass doesn't spring back to a dimension close to what it was before the bullet was pressed into it, after the bullet is removed manually you only have a certain amount of "tension", no matter how much the original press fit was. Try seating a bullet into a resized case (dummy round) and let it set for a few days, pull the bullet and measure the inside of the neck, the difference between that dimension and the bullet will be the actual "neck tension". (I am tired and I don't think I am explaining what I mean very well, sorry bout that). Personally, I think .002-.003 press fit is plenty, depending on purpose.

I get it. Plenty good explanation. I will try this and Klem's method of "before and after seating the bullet" outside neck measurements.

[ported45]

Do you know your neck ID before the bullets are seated? Are your cases trimmed to 1.620" or shorter? The other measures that you're taking seem adequate to me. FWIW I used a vibrator cleaner for quite a while and then finally broke down and bought a cheapo HF rock polisher and some SST pins and that's resulted in a step up in the quality of my finished rounds because the primer pockets and neck IDs get cleaned at the same time.

Does the primer of a loaded but unfired round get a slight indent from the firing pin when the bolt slams home?

If all of that's OK then I'd be changing brass because most other things that could be causing it have been eliminated.

Trimmed to Hornady Manual recommended length (1.615"?) and inside is 0.258" before seating of the bullet.

Primer shows the fp strike on unfired rounds.

I will try extra effort in cleaning the inside of necks and be sure they are degreased to eliminate any loss of friction between the brass and bullet and see what that gets me.