Skip to main content
Topic: Neck tension, something I've been working on: a full neck "crimp" (Read 502 times) previous topic - next topic

Neck tension, something I've been working on: a full neck "crimp"

This has probably been tried before but I'm the type that needs to make my own mistakes  ;D

I use Lee collet dies for neck sizing, not to say there isn't anything better, but for a shooter who doesn't turn necks, it's an elegant solution that's inexpensive. I got this crazy idea to adapt a Lee collet die so it puts a full neck "crimp" on a finished round. Why you ask, good question. I ask why not? I've read about some of the benefits resulting from crimping, this is an extension of that.

Anyway, below is the basic anatomy of a Lee collet die; the piece I named the "collar" may not be the correct name; it's the tapered part that when used to apply force to the collet, causes the collet to compress the neck.



In order to use a Lee collet die to compress the neck of a finished round we need to remove the mandrel; the new mandrel will be the bullet. One problem remains; the mandrel for a 6.5 bullet is .262 or so, no way will a .264 bullet fit in the hole. So, I replaced the collar (which the mandrel runs through) with one from a 7mm-08 Lee collet die. This allows the bullet to pass freely through the collar.

I adjusted the die so that my CoAx cams over to where I can feel the squeeze without leaving collet marks on the brass. I observed a reduction in neck O.D. of about 0.0005". I get this from a Mitutoyo caliper with 4-digits, I don't believe it's that precise but, uncrimped cases measure firm to 3-digits every round. So, there's some reduction in O.D. but I don't want to overstate the case (ahem).

The first (and so far only) trial appears to favor the "crimped" rounds. This is a small sample, but I am encouraged to push on and see where it goes. These results use 7x fired Alpha brass case, wet tumbled, annealed, body sized and bumped 0.001, Lee collet neck sized with standard mandrel to roughly 0.002 neck tension. I also lubed the necks with OneShot based on observations by HufD63. All bullets were seated 0.013 OTL on top of 40.5 gr H4350 ignited with CCI BR-2 primers. Rifle used was my trusty Browning X-Bolt 6.5 CM 28" target.

Lab Radar chronograph results:

Three 5-shot un-crimped groups:
Avg/High/Low/ES/SD
2742 / 2754 / 2723 / 31 / 12.5
2747 / 2763 / 2733 / 31 / 11.2
2739 / 2759 / 2711 / 47 / 18.2

Two, (one 6-shot and one 5-shot), crimped groups:
Avg/High/Low/ES/SD
2737 / 2748 / 2731 / 17 / 6.9
2733 / 2739 / 2729 / 9 / 4.2

These were fired out of order so as not to thermally favor any group.

I may well be going down another obsessive rabbit hole with no end in sight but hey, that's what makes this hobby fun and keeps us young :)
Chris

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #1
😁😁😁
Grant

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #2
Chris,

Thanks for sharing that. Very interesting, to say the least.
You may be stumbling on something and I'll be looking for future results.
Did you see any difference in the grouping at all?
The most misused words in the English language are "can't" and "won't".

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #3
I experimented with crimping once a long time ago but could not see any difference on the target. I had no chronograph at the time so was strictly judging results off the target.

Keep us updated on your findings it is interesting.
Dave

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #4
I don't know what it did on target but it sure made a difference on your es and sd even though its a small sample... I suspect its creating a more consistent bullet grip..
Grant

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #5
Chris,

Thanks for sharing that. Very interesting, to say the least.
You may be stumbling on something and I'll be looking for future results.
Did you see any difference in the grouping at all?

Steamer, I was looking more to the velocity metrics for validation rather than groups at 100 yards. I would be lying if I said I didn't care about group size and wasn't shooting for groups, lol. In this case the groups were decent, all in the sub-MOA range.

I think it was member Regnar who mentioned that ES/SD metrics become more important as the distance to target increases, since I don't have any place to shoot past 300 yards without driving a long ways, I've always accepted his assertion.

In any event, I've got enough time on my hands to move forward to see if this approach bears fruit. I was very cautious the first time out not wanting to make the cork so tight so as to cause a kaboom.
Chris

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #6
chris I actually think your decreasing neck tension by doing this... wouldn't be by much though.. when your squeezing that neck into the bullet your squeezing the bullet a smidge too... when you back the die off the brass springs back a little but the bullet wouldn't have any springback to it... at least that's what I envision whats happening there...could very well be wrong though ...
Grant

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #7
I think of the neck as an imperfect collar for lack of a better word. We've all probably looked at necks under magnification; it's a moonscape.

My thinking on this one is to increase the amount of brass in contact with the bullet which should result in more bullet grip.

Looked at another way, bullet bearing surfaces are imperfect, necks are imperfect. If the end game is to have this interface be closer to perfect, there are any number of ways to go about it. This approach is to take the hand I'm dealt and coerce the two surfaces to come closer together, like a shotgun wedding I guess.

Using only what I see, I'm thinking a jacketed bullet is more perfect surface-wise than any neck I've seen. I really don't want to deform the bullet which I don't think would happen since brass is quite malleable. 

Chris

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #8
Something to try chris.. measure the bearing surface on your bullet.. then seat it and crimp the neck like your doing.. then pull the bullet and measure the bearing surface again. See if it changes any..
Grant

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #9
chris I actually think your decreasing neck tension by doing this... wouldn't be by much though.. when your squeezing that neck into the bullet your squeezing the bullet a smidge too... when you back the die off the brass springs back a little but the bullet wouldn't have any springback to it... at least that's what I envision whats happening there...could very well be wrong though ...

Way too little data to draw any conclusions. However, the lower muzzle velocities in the “crimped” rounds would support Grant’s thought here.

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #10

“Looked at another way, bullet bearing surfaces are imperfect, necks are imperfect. If the end game is to have this interface be closer to perfect, there are any number of ways to go about it. This approach is to take the hand I'm dealt and coerce the two surfaces to come closer together, like a shotgun wedding I guess.”

Chris I see your logic here and it brings out the point that bullet grip is not just a function of neck tension. One point worth considering though is that brass (as an alloy) demonstrates spring back, while the metals in the bullet (copper and lead) are very malleable but don’t demonstrate a spring back response.

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #11
I agree, it would be interesting to see one of these rounds dissected. Lets see how much that bullet is deformed.

My favorite 223 loads have had a light collet crimp for years now. I have to look under a magnifying glass to even see it They work great in my gas guns. The factory crimp did not help my 6.5 loads at all though.
The most misused words in the English language are "can't" and "won't".

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #12
I don’t have as much experience reloading for 6.5 Creedmore as you guys have , but tell me how is this process
Different from using Wilson hand dies with a correct bushing for neck tension as I do
I may be missing something
When I started I spoke with Lester Bruno and he walked me through the whole process and what to get
How is this different

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #13
Let me hit a few things here:

I will pull a bullet to see if there's any sort of deformation or other artifacts caused by this process. I'll pull an uncrimped one as well so I have something to compare if to. Unfortunately I don't own a collet puller I've got the old hammer style beater.

From what I've read it's very difficult to compress solids. Solids my be deformed of course, but that's just moving the material around from one location to another. I've generally felt that the proper use of a Lee collet die should result in complete contact of the neck with the mandrel without leaving visible collet marks on the outside of the neck, I followed that same operating procedure with the second crimp. Of course a bullet is softer than a stainless mandrel...

To me, true crimping using a bullet with a cannelure is an entirely different program. The net result may be similar if, and only if, the crimp I'm experimenting with does in fact increase bullet grip.

Chris

Re: Neck tension, something I've been working on: a full neck "crimp"

Reply #14
I don’t have as much experience reloading for 6.5 Creedmore as you guys have , but tell me how is this process
Different from using Wilson hand dies with a correct bushing for neck tension as I do
I may be missing something
When I started I spoke with Lester Bruno and he walked me through the whole process and what to get
How is this different

Piper11, the step described here is purely experimental and is in addition to all other steps, it could be applied to your finished rounds as well. But, if you are seeing single-digit SDs with your finished rounds, I doubt it would be of any any interest, your'e already there.
Chris