Crimp-Velocity

[coop2564]

Lee FCD will give you better and more consistent neck tension, been using for years, it will increase pressure slightly. So don't crimp a load worked up at max without crimp and expect it to shoot okay. I don't really see a overall velocity change from crimped max to uncrimped max. But I see a charge weight change to get max velocity and pressure. Crimped loads reach max with slightly less powder. I'm talking Lee FCD crimp. YMMV

 

[RAGGED EDGE]

Taper or roll? How about shank def?

 

[chav0_12]

I don't crimp but have found increasing neck tension to as much as .007 has improved sd/es and accuracy in slow for application powders. I have more than few loads that have .0005-.002 in small cases and start there in overbore cases. Crimping can act the same way if you cannot adjust neck tension.
With my 270 H4831 has .002 neck tension 8es over 5 shots and will shoot sub 1/2moa Same gun same bullet case and primer RL26 shoots tighter groups with es of 3 over 5 shots. But only with .007 neck tension I turned the neck down and that load opens up everywhere. Would a crimp be a better option. I will never know.
I read something from Kirby Allen about RL33 wanting some resistance during ignition to clean up es/sd quite awhile ago. I started looking at that with slower burn rates and have found I can clean up most load numbers with just more neck tension. Some examples are RL19 and RL26 sd's went from low teens to single digit 10 shot es and sub 3fps sd in 6.5CM
The above 270 load
7rm for both my brother and myself run .004 or.005 with retumbo and RL26 both are below 11es
Bottom line light neck tension works with faster powders in moderate cartridges very well. It can work well in tighter chambers as well as when using just a neck sizer. When it doesn't don't be afraid of clamping the **** out of a bullet to find a load. It may just be whats needed to get a consistent enough ignition to make your rifle preform like you hope it will.

I might have to try that and see how much it works for some of my stuff. When do you know that you need to "clean up" a load"? I guess how far do you take it before just playing with neck tension?

To the OP, I only crimp handgun loads and AR loads. I crimp the handgun loads because I have to remove the bell, and on the 44 mag to keep the cylinder from locking up on me I needed a Lee FCD. The 223 loads get crimped because there's a lot that's happening when a semi-auto runs a round into its chamber. I should play with the crimp amount and run it over my chronograph and see what it looks like. But really I'm not too worried about it.

 

[Muddyboots]

The term crimp is really how much? Tough to measure in combo seating die unless pistol who cares... Some rifle bullets will shoot better but you need something like a Lee FCD where you can easily adjust the amount of crimp. Even then, you are not measuring the force of the crimp but measuring how much by marking the die in 8ths. Pretty much how @ButterBean has suggested and I found it works really nice. I have shot same load at different "crimp" settings and you really do see ES SD changes.

But you cannot do anything without a chronograph!

 

[ButterBean]

The LEE FCD is as valuable as any tool on the bench if used correctly

 

[ButterBean]

Pressure builds Velocity. Any guess what potential velocity you might lose by not crimping? I do not have a chronograph to check velocity.

Yes pressure builds velocity and the LEE FCD is tunable to adjust this, I will add that when on the top end of a load the FCD is invaluable for precise tuning, from 1/8th turn to a 1/2 turn you will see a huge difference in pressure signs

 

[dougduey]

I tested Lee Factory crimp using Oehler Ballistics Lab almost twenty years ago. I don't remember a pressure or velocity increase. I do remember that the accuracy and ES/SD number were far better just by using the crimp. Only thing I could think of was it helped with creating consistent tension which aided ignition/ powder burn. YMMV.

You're spot on here. If you read through the Lee loading manual, Mr Lee talks about crimping. Basically, you get consistent neck tension that creates a consistent pressure build up before the bullet is released. He said it's basically like seating a bullet into the lands which so many competitive shooters prefer.
I crimp everything. You can "tune" a load using the Crimp die, too. You'll also find that factory ammo is crimped.

 

[dougduey]

Yes pressure builds velocity and the LEE FCD is tunable to adjust this, I will add that when on the top end of a load the FCD is invaluable for precise tuning, from 1/8th turn to a 1/2 turn you will see a huge difference in pressure signs

Bean you answered while I was typing!!!
Listen to Bean

 

[xsn10s]

You're spot on here. If you read through the Lee loading manual, Mr Lee talks about crimping. Basically, you get consistent neck tension that creates a consistent pressure build up before the bullet is released. He said it's basically like seating a bullet into the lands which so many competitive shooters prefer.
I crimp everything. You can "tune" a load using the Crimp die, too. You'll also find that factory ammo is crimped.

Hey that's good to know! Mr Lee knows far better than me. Thanks for sharing!

 

[dougduey]

Hey that's good to know! Mr Lee knows far better than me. Thanks for sharing!

You can learn a lot of if you really read through the front of the load manuals.
And, yes, Mr Lee may know a thing or 2

 

[xsn10s]

You can learn a lot of if you really read through the front of the load manuals.
And, yes, Mr Lee may know a thing or 2

I learned about Lee Factory crimp from Ken Waters "Pet Loads". Been reading that since the 80's.

 

[Mike Matteson]

Pressure builds Velocity. Any guess what potential velocity you might lose by not crimping? I do not have a chronograph to check velocity.

I am not trying to beat you up. The chronograph it one of the most important pieces of equipment needed to be reloading and shooting. Otherwise you are only guessing. It's a whole lot faster to figure out what's going on and determine what the drop is going to be. A couple of hundred yards no big deal, and beyond that the chronograph is almost a must.

 

[436]

I crimp "most" my reloads using a Lee Crimp die, but not for velocity reasons I like a few here have found some good reasons to do so with my landlords, which works for me and others here it seems. I also noticed sometimes the cartridge "neck and bullet" concentricity are a little better, but that's getting into cannelure and non-cannelure bullet stuff.

Now with that said; I have always used a very heavy LEE crimp with my subsonic loads to allow the small about of fast-burning power in the case to get to the same pressure environment in the case before the bullet is released giving me better working SD and external velocity. So, does a crimp help with velocity? well here it does. Just my 0.2 Cheers.

 

[scpaul]

it won't tell you how much velocity you are gaining or losing, but you could load 2 sets of rounds as identical as possible except 1 group crinped. Shoot the target with the same hold and see if the crimped group prints higher. I would let the barrel cool between groups. If you pick up much velocity I would think the group would be higher.
Be sure to watch for pressure if you are even remotely close to a max load.
I agree with the others, if you are serious, you need a chronograph. I have 2 just in case. Some aren't very expensive and work surprisingly well.