Crimp-Velocity

Fatcatbuster said:
Pressure builds Velocity. Any guess what potential velocity you might lose by not crimping? I do not have a chronograph to check velocity.
Click to expand...
If you want to find out the actual velocity of your load out of your rifle, resolve this first. I have a few Lee crimp die sets but have yet to find the need to crimp. But I know a few here that swear by it.

 
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Fatcatbuster said:
Pressure builds Velocity. Any guess what potential velocity you might lose by not crimping? I do not have a chronograph to check velocity.
Click to expand...
You definitely need a chronograph to answer that question . I don't think you will be over pressure ,unless you're on the ragged edge with your load, and then how much of a crimp will change things also . BOTTOM line get a chronograph.
 
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.
 
I think the biggest reason for crimping , is a little extra insurance of not having the bullet move , depending on neck tension etc . Some of the other benefits are reducing extreme spread from shot to shot for better accuracy . I don't think many hand loaders load to increase vel , pressure etc , at least I don't , some bullets and cartridges I crimp and some I don't . I do see some benefit in crimping , but it isn't absolutely necessary , unless it is a very heavy recoiling rifle , cartridge etc . Then safety plays a big part ,I.M.O.
 
Hard rock said:
I think the biggest reason for crimping , is a little extra insurance of not having the bullet move , depending on neck tension etc . Some of the other benefits are reducing extreme spread from shot to shot for better accuracy . I don't think many hand loaders load to increase vel , pressure etc , at least I don't , some bullets and cartridges I crimp and some I don't . I do see some benefit in crimping , but it isn't absolutely necessary , unless it is a very heavy recoiling rifle , cartridge etc . Then safety plays a big part ,I.M.O.
Click to expand...
I use a crimp for mostly the same reasons. Just to insure there isn't any bullet movement mainly in lever gun and semi autos. I don't crimp bolt action rifles for the most part. My loads have been accurate without a crimp. It is an option if accuracy is suffering. I have some LFC dies somewhere. I haven't used them in years.
 
Searching for accuracy in a rifle is much like hunting, if you you're looking and not finding what you're looking for in the usual places, look somewhere else. On one of my rifles, an old husqvarna 1640 30.06, crimping made an improvement. Most of my other rifles, not so much, you don't absolutely need a chronograph to determine the accuracy potential of crimping, but for all the other numbers involved, it's a must
 
I bought several Lee factory crimp dies and loaded my regular recipe for two rifles. I was curious, and maybe a little bored, but I wanted to see if ES and SD would get better. That was in December and I have not been to the range except to shoot pistols since that time due to 40 MPH to 75 MPH winds every weekend. I hope that I don't lose interest by the time the weather clears up.
 
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.
 
This thread has me thinking. I may polish up my expander ball and decrease the diameter a bit for my 260 AI. That should aid in case stretch and give me more neck tension. I'm using ball powders and the ES/SD isn't quite up to my liking. Mag primers would be the best solution but hard for me to get. Wondering if increased neck tension might be a cheap fix.
 

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