Any difference - CFCD vs Bullet seating/crimp die

[gemini1]

I had a chance to chrono some of my loads using just the Lee bullet seating/crimp die.
On one of my test loads, using 4.4 gr of Accurate # 2 and extreme 115 gr plated RN with a COAL on 1.100" My chrono results were AV 966.2 ES 48.58 and SD 16.88 for a 10 shot test

From my previous loads, with the bullets separately crimped with the carbide factory crimp die, and using the same components but seated at 1.115-1.121"
My 10 shots had a chrono result of AV 1001, ES 77.65 SD 20.09

So what do you think happened here? why did the test loads that were separately crimped with the carbide crimp die show higher readings, even though it was seated higher?
I did follow the video instructions to adjust the bullet seating/crimp die, and I've check the bullets were indeed crimped.

[ExtremeX]

My guess...

The Lee FCD carbide insert is sizing down everything even more slightly lowering case volume and increasing pressures by giving more tension on the bullet. I guess the increase in ES and SD might be attributed to different brass thickness if using mixed brass.

The standard seat/crimp die crimp function is very different from the FCD as it may touch the brass again after the initial sizing/decap function in step 1 compared to a standard seater.

You might want to use a micrometer and measure the plated bullet before and after use of the FCD. You might be swaging it down a little too.

Just my guess, I could be completely wrong.

[sofbak]

The factory crimp die "rolls" the leading edge of the case mouth into the circumference of the bullet, and bites into it a tiny bit (if used properly). This extra bite gives the case more grip on the bullet, and thus requires more pressure to free the bullet and push it out of the case. Higher pressure equates to higher velocity.

I have no idea what ES is....

The broader standard deviation (SD?) could have resulted from differences in case lengths used. In my experience with the FCD, the amount of crimp is sensitive to case length. From however you have it adjusted, if you then use a slightly longer case, you get a little more crimp, and conversely with a slightly shorter case-less crimp. And by 'slightly" I mean even one thousand can make a difference on the amount of "roll" that is formed into the case mouth. So if all the cases used in your test were not the same length, some minor deviations are introduced via the minor variances in crimp depth.

[ExtremeX]

The factory crimp die "rolls" the leading edge of the case mouth into the circumference of the bullet, and bites into it a tiny bit (if used properly). This extra bite gives the case more grip on the bullet, and thus requires more pressure to free the bullet and push it out of the case. Higher pressure equates to higher velocity.

I have no idea what ES is....

The broader standard deviation (SD?) could have resulted from differences in case lengths used. In my experience with the FCD, the amount of crimp is sensitive to case length. From however you have it adjusted, if you then use a slightly longer case, you get a little more crimp, and conversely with a slightly shorter case-less crimp. And by 'slightly" I mean even one thousand can make a difference on the amount of "roll" that is formed into the case mouth. So if all the cases used in your test were not the same length, some minor deviations are introduced via the minor variances in crimp depth.

ES = Extreme Spread

Pretty sure both standard and FCD are both taper crimps, and are both effected by case length when setup correctly.

The FCD can be setup NOT to crimp, and when it is setup like that, it still has a carbide sizing insert which may resize brass and or bullets.

I suspect the issues are with the carbide sizer, not the actual crimp function.

[sofbak]

ES = Extreme Spread

Pretty sure both standard and FCD are both taper crimps, and are both effected by case length when setup correctly.

The FCD can be setup NOT to crimp, and when it is setup like that, it still has a carbide sizing insert which may resize brass and or bullets.

I suspect the issues are with the carbide sizer, not the actual crimp function.

If you have an FCD, take it apart and check it. The only "action" piece in it is a machined collar that has a radiused reduced diameter inside. This radius is what forms the crimp.

The carbide ring in my .45 colt set is .004" to .006" larger in diameter than the seating die, and .008" larger in diameter than the carbide ring in the re-sizing die, so it doesn't do any appreciable sizing/crimping to the case that wasn't done in either of the previous dies.

[ExtremeX]

If you have an FCD, take it apart and check it. The only "action" piece in it is a machined collar that has a radiused reduced diameter inside. This radius is what forms the crimp.

The carbide ring in my .45 colt set is .004" to .006" larger in diameter than the seating die, and .008" larger in diameter than the carbide ring in the re-sizing die, so it doesn't do any appreciable sizing/crimping to the case that wasn't done in either of the previous dies.

I am familiar with the makeup of the die.

Guess it depends on the die, tolerances in manufacturing, and brass thickness...

I use 45 xtreme plated bullets which are made at .452" and if I hit it with a Lee FCD it swages down a bit closer to .451"

It feels like its going though the sizing process again when using the die. Sometimes it doesn't, and that's attributed to the fact I use mixed brass and they have different wall thickness.

I've also read reports of cast lead users who got major leading issues after using a FCD due to the swaging of the bullets.

[sofbak]

I am familiar with the makeup of the die.

Guess it depends on the die, tolerances in manufacturing, and brass thickness...

I use 45 xtreme plated bullets which are made at .452" and if I hit it with a Lee FCD it swages down a bit closer to .451"

It feels like its going though the sizing process again when using the die. Sometimes it doesn't, and that's attributed to the fact I use mixed brass and they have different wall thickness.

I've also read reports of cast lead users who got major leading issues after using a FCD due to the swaging of the bullets.

I have three sets, .40, .45acp, and .45 colt, and all mine feel like nothing is happening (little if any resistance on the handle) in the FCD until that reduced radius hits the top of the case. For each caliber, I'm using all brass from the same mfg, and same lot...I can see how a mixed variety could cause that.

If they're swaging, then I would think they have it adjusted too deep maybe, or mixed length brass. I adjust mine in very, very small increments, and just until I can barely see a shiny burnished ring right at the top of the case. Usually get about a one thou to one and a half thou reduction in case diameter right at the mouth....

[ExtremeX]

I'm referring to the carbide insert swaging the bullet, not from over crimping... I can back out the crimp adjustment on the top and get the exact same results.

Its simply due to a .452 bullet and thick case walls... There is no way around it unless I remove the carbide sizing ring.

My original reason for buying the Lee FCD was to remedy problems with a tight chambered 1911 and feeding issues. So my ammo was already crimped in the seat/stage operation and ran it though the FCD without allowed the crimp adjustment to engage the top of the brass.

The bullet swaging issue was just an observation... Its not a persistent issue, and I don't use the die for anything except for that one pistol. For everything else, the standard seat/crimp die works fine.

Going back to the OPs topic, I suspect the velocity and SD/ES variations MAY be attributed to some or all the things mentioned above.

[3RDGEARGRNDRR]

I think extremex is correct in post #2. There are many variables at work here, not just simply a change in oal. Also the bullet jump may be hitting the rifling sooner causing a pressure jump that could cause higher velocity as well, if the bullet was setback there are sometimes two pressure curves and a change in the powder burn

[gemini1]

Yeah, maybe I should measure one that will go through a FCD and one with just the bullet seating/crimp die only. I do use mix brass and never bothered to measure it, once it pass the gauge test via the barrel chamber.

[J-cat]

I'm just a tool, but I do know that 9mm brass weights vary from 50grs to 65grs and that changes the internal case volume. The less volume the more pressure the more velocity you get. For example, WCC+P brass increases velocity by 50 FPS over older pre-"dot FC dot" FC brass.

The velocity difference you're seeing is due to your use of mixed brass. Sort your cases and you will see more consistency.