Better accuracy from homemade converted LC brass using Lee collet die.

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TreeTopFlier
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Better accuracy from homemade converted LC brass using Lee collet die.

Post by TreeTopFlier »

Thought I would share something interesting with you guys as a data point for our collective knowledge. Before I begin, I realize that we all have different dies, practices etc. I'm not looking to convert anyone to my process of making brass. I'm just sharing an observation.

I'm one of the folks that has used Lee dies for brass conversion from way back with no issues.

A while back I noticed that Lee now offers a collet die for the blackout https://www.midwayusa.com/product/25107 ... -sizer-set. If you are unfamiliar with the collet die concept, here is a run down.

The collet die is intended for custom brass. Meaning, the brass is only re-used in the firearm it was fire formed in and only recommended for bolt actions only. The die doesn't resize the brass at all or even push back the shoulder. The only function of the die is to squeeze the neck around a concentric mandrel to ensure exact concentricity.

I wondered if, since these dies were good for concentricity, would they improve a case that had already been formed/FL sized for use in a AR platform rifle? The answer seems to be YES.

I did a test with 125 SMK bullets in virgin LC formed cases. Half of the cases were just formed and trimmed and the other half had the added step of collet sizing to true up the neck. This was not a "worked up load" just a random one not tested in the firearm.

The 100 yd group on the left was without collet die, the group on the right was with collet die. I would say, in multiple test with two shooters the results were the same...on average a 50% reduction on group size.

Image

I think the collet die design is able to exert enough force on the neck brass to flow it into consistency much like neck turning.

Just info for the collective knowledge...TTF
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by TreeTopFlier »

Here's a cutaway of a collet die.

Image
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by rebel »

Make sense. Neck tension is everything, seating depth is everything else.
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by TreeTopFlier »

I was impressed how much difference it made with one extra simple step. I haven't had a chance to try it on fire formed brass yet but I assume it would improve it as well.

I got the idea watching an OLD David Tubb video about loading for long range accuracy or something like that. He made an off hand comment about removing the expanding ball so you didn't pull it back through the neck deforming it after you shaped it. It got me thinking about trying this die to true up already formed or resized brass.

The die is not marketed to use for semi auto application but if you full length size first. I would think any case would benefit from a process that swages the neck square.

Just to be clear, the collet die doesn't do anything the full length sizing die does.
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by dellet »

Check the internal neck diameter before and after. It may be that you are adding neck tension,
as much as "squaring the neck".

No doubt that getting the bullet square to the bolt face will help consistency.

Look forward to how it works for the AR.
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by TreeTopFlier »

dellet wrote:Check the internal neck diameter before and after. It may be that you are adding neck tension,
as much as "squaring the neck".

No doubt that getting the bullet square to the bolt face will help consistency.

Look forward to how it works for the AR.
Once again, my typing probably reads like a Dr Seuss story :oops:

All of the testing I did, to include the photo above, was in an AR. The brass I used was fresh cut down, formed LC 5.56 brass. The only difference between targets was I used the collet die on the rounds fired at the RH target. This was purposely a random/ undeveloped load to see how much difference the collet die would make.

The collet die is intended to be used on a case that isnt full length sized. Im saying, the collet die adds value, even IF the case has been sized or formed.

From Lee: ...A collet squeezes the case neck against a precision mandrel for a perfect fit with minimum run-out...

I measured a case that varied between .011 and .012 in neck wall thickness. After running it through the die it was a consistent .010. (calipers) It seems capable of putting enough force on the brass to cause it to flow. Would probably work even better on annealed cases.

The die clearly uniforms neck tension but it also improves uniformity in both square and thickness.

Anyway, all just to add another data point of possibility to everyone's thinking.

TTF
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by dellet »

TreeTopFlier wrote:
dellet wrote:Check the internal neck diameter before and after. It may be that you are adding neck tension,
as much as "squaring the neck".

No doubt that getting the bullet square to the bolt face will help consistency.

Look forward to how it works for the AR.
Once again, my typing probably reads like a Dr Seuss story :oops:

All of the testing I did, to include the photo above, was in an AR. The brass I used was fresh cut down, formed LC 5.56 brass. The only difference between targets was I used the collet die on the rounds fired at the RH target. This was purposely a random/ undeveloped load to see how much difference the collet die would make.

The collet die is intended to be used on a case that isnt full length sized. Im saying, the collet die adds value, even IF the case has been sized or formed.

From Lee: ...A collet squeezes the case neck against a precision mandrel for a perfect fit with minimum run-out...

I measured a case that varied between .011 and .012 in neck wall thickness. After running it through the die it was a consistent .010. (calipers) It seems capable of putting enough force on the brass to cause it to flow. Would probably work even better on annealed cases.

The die clearly uniforms neck tension but it also improves uniformity in both square and thickness.

Anyway, all just to add another data point of possibility to everyone's thinking.

TTF
I might have missed the AR part, no big deal.

What I meant about check the internal neck diameter was to find out how many thousandths it differed. One might be .306" from the regular die the other .305" from the collet.

The neck on converted brass is tapered about .0015", I doubt you are compressing out the taper. but it will form a much straighter and concentric path for the bullet.

Can't argue with the results on target.
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by TKO »

If I am understanding this correctly, the Lee die is to be used an additional step to processing AR brass that has been full length resized not in lieu of full length resizing?
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by TreeTopFlier »

dellet wrote:
TreeTopFlier wrote:
dellet wrote:Check the internal neck diameter before and after. It may be that you are adding neck tension,
as much as "squaring the neck".

No doubt that getting the bullet square to the bolt face will help consistency.

Look forward to how it works for the AR.
Once again, my typing probably reads like a Dr Seuss story :oops:

All of the testing I did, to include the photo above, was in an AR. The brass I used was fresh cut down, formed LC 5.56 brass. The only difference between targets was I used the collet die on the rounds fired at the RH target. This was purposely a random/ undeveloped load to see how much difference the collet die would make.

The collet die is intended to be used on a case that isnt full length sized. Im saying, the collet die adds value, even IF the case has been sized or formed.

From Lee: ...A collet squeezes the case neck against a precision mandrel for a perfect fit with minimum run-out...

I measured a case that varied between .011 and .012 in neck wall thickness. After running it through the die it was a consistent .010. (calipers) It seems capable of putting enough force on the brass to cause it to flow. Would probably work even better on annealed cases.

The die clearly uniforms neck tension but it also improves uniformity in both square and thickness.

Anyway, all just to add another data point of possibility to everyone's thinking.

TTF
I might have missed the AR part, no big deal.

What I meant about check the internal neck diameter was to find out how many thousandths it differed. One might be .306" from the regular die the other .305" from the collet.

The neck on converted brass is tapered about .0015", I doubt you are compressing out the taper. but it will form a much straighter and concentric path for the bullet.

Can't argue with the results on target.
I measured my homemade brass and it was all at .306. After running them through the collet die they were still a consistent .306.

I checked some Barnes I had and they were .307. After the collet die they were .306 so that seems to be the were the mandrel leaves it.

A couple of other points. Lee offers different diameter mandrels which might be nice for subs.

I saw a video where a guy had a contraption rigged up to use a breaking torque wrench to put consistent force on each case as he ran it through the die.

Last, I found a case that the neck wall thickness ranged from .010-.012. After the collet die it was an even .0095 so it definitely seems to be re flowing the brass a little.
Last edited by TreeTopFlier on Wed Sep 06, 2017 2:35 pm, edited 1 time in total.
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Re: Better accuracy from homemade converted LC brass using Lee collet die.

Post by TreeTopFlier »

TKO wrote:If I am understanding this correctly, the Lee die is to be used an additional step to processing AR brass that has been full length resized not in lieu of full length resizing?
Yes, the way I used it was to add this step AFTER full length sizing or forming. It is recommended that you full length size brass used in Auto loaders (AR's) or shared in different guns... so the collet die wouldn't normally be used in these applications. I'm saying, in my limited testing it still improved accuracy even on fully sized cases. Hope that makes sense.

I'm unintentionally a little over invested here. My hunch is, the better brass you start with the less value this will add. Im using homemade LC cases so I am seeing about a 50% reduction in group size.

Hope this helps someone.
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