Crimp VS. No Crimp food for thought

[res45]

I,m posting this from another post I read on some testing a gentleman did on this subject. Which ever way works for the individual reloader is up to them this is just his results after and extensive test. I have also found similar results using the Lee factory crimp die with all my rifles from my Mosin M44 down to my YUGO SKS using a light to Med. crimp.

50 Rd. 30-06 168 Gr. Match bullet 25 Crimped 25 Uncrimped.

Uncrimped:
Group #1 >> .750 @ 100yds (No fouler shots)
Group #2 >> .485 @ 100yds
Group #3 >> .500 @ 100yds
Group #4 >> .645 @ 100yds
Group #5 >> .843 @ 100yds

Chronograph on above was all at 2650fps with a SD of 12fps!!

The Crimped loads however totally suprised me!! Shocked
They grouped better and the SD was alot better also!!

Crimped:
Group #1 >> .620 @ 100yds (No foulers)
Group #2 >> .600 @ 100yds
Group #3 >> ONE HOLE!! Shocked
Group #4 >> NO!! Not Again ONE HOLE Laughing
Group #5 >> .375

Chronograph was same at 2650fps but the SD was 4fps!!!

 

[Linear Thinker]

Confirms both Lee's advertising and my observations. I would like to see the phenomenon explained, but until then I will keep on crimping all my ammo.

In magnum revolver loads, the crimp assures the pressure buildup before the bullet jumps, proven to increase accuracy. Perhaps the same happens in rifle rounds.
LT

 

[Walkalong]

You need something to give good start pressure. It can be good neck tension and a good crimp, or just seating into the lands a bit with no crimp and light neck tension.

 

[Bad Flynch]

For more years than I have walked the earth, conventional wisdom has been that one should avoid crimping except in specific applications. Well maybe so and maybe not. I have walked the earth for many years now and am ready to try to explain some of this that I have observed.

I believe that it is better, more uniform powder burning that gets it done, whether it is simply the initial start resistance and pressure build-up or if the added resistance of the cimp continues beyond that. I don't have any way of proving it one way or another, but it does sometimes work.

 

[ArchAngelCD]

Even though I'm not reloading for 40 years I read a lot, listen to those who have reloaded for 40 years and take in everything I hear. I have never reloaded a 30-06 yet as some who read this forum a lot will know from the recent threads I've started. I have reloaded a lot of handgun rounds in the past, and I mean A LOT. I use a Lee FCD on all of them and have found the rounds to be more accurate than those crimped with the seating die. I figured if it works with handgun rounds why not for rifle rounds. I should be getting the delivery of dies on Monday and a Lee FCD will be included for the 30-06.

From all I have read and heard I'm guessing it's not really the crimp that's aiding in the accuracy of my ammo but the final resizing that's done with the FCD. If your rifle round is perfectly formed by the FCD as the last step I'm sure it has an effect on the accuracy of the bullet.

I could be wrong because like I said, I'm no expert.

 

[Jim Watson]

The rifle factory crimp die closes a 4-jaw collet on the case mouth. It does not post-size the loaded round like the carbide factory crimp die for straight pistol cases.

 

[birdbustr]

Lee Factory Crimp dies have me sold!

No feeding issues in my pistols or M-4 since I started using them. The accuracy seems improved also. When I get a new caliber weapon to reload for, I will definitely buy the Lee factory crimp die in addition to the pacesetter dies.

 

[ArchAngelCD]

The rifle factory crimp die closes a 4-jaw collet on the case mouth. It does not post-size the loaded round like the carbide factory crimp die for straight pistol cases.

Thank you Jim, I was wrong again, as usual LOL!!

At least the rifle FCD is getting good reviews here, so It's probably money well spent.

 

[Fatelvis]

Is there any way to adapt the FCD to work with a progressive press, like the 550B?

 

[Owens]

For my match loads in a .308, I partially neck size, no crimp and seat the bullets .030" off the lands. I experimented with this some myself and found no crimp a bit better. However, after reading this thread, it does make me want to do some more trials using a FCD and see if things get even better.

 

[Walkalong]

The FCD is giving folks good "start pressure" that they were not achieving some other way. Personally, I would achieve it some other way myself, but I am sure they work fine.

 

[30Cal]

What bullet?

 

[Rod B]

I use the Lee FCD on all my pistol & rifle calibers.

However I don't over do it. just enought to remove the expander flare. (I load a lot of cast bullet rifle ammunition)

I really like the post sizing feature on the pistol calibers. Most of the time you barely can feel it working. Occasionaly it seems to require more pressure & I feel this is indicative of a thick case or a slighly oversize bullet. I think it improves the reliability of the ammunition.

 

[redneck2]

I saw an ad last week for an internet site that sells some kind of gizmo that measures neck tension on bullets. Their spin was that consistent tension aids in consistent burn rates and consistent velocity. Maybe the crimp die does the same thing.

 

[jeepmor]

I'm in agreement with the crimp die making the cartridge more uniform, improving accuracy. I'm also in agreement with the crimp making the neck tension more uniform, also improving accuracy by making the initial burn more consistent.

As in all things technical, less variation is better. This is why a lot of those uber long range sniper type shooters work their case necks over. I'm personally not there yet and don't have that desire as of yet. However, when I do find a good place to make those Loooonnnngg shots and start working at that level, I'm sure I'll get there. Particularly because you only do this type of work to the brass once.

Before all this, I think I would deburr my flashholes in hopes of creating more consistency also since it's a one time deal.

 

[BsChoy]

I begrudgingly got an FCD die for my M1 rounds and lo and behold, everyone who told me they would shoot better was right...I crimp all M1 rounds now and will probably start with my german mauser even though it shoots nices groups without it

 

[oldgold]

Found a FCD in a bunch of stuff I got at a yard sale . Since it was in .308 and I was working on wifes target rifle I tried a little experiment. Loaded twenty rounds , full length resized and then crimped ten . Shot three, 3round groups. Average was 3/8ths smaller for the crimped rounds. Sorry I doubted the crimp die. Now I have one for everything I reload.

My 550 Dillion is set up with FCD .223] in the last hole. Seater is backed out to where it seats but not crimps. This setup also eliminates the occasional shoulder buckle from a long case. Gotta get some more powder....

 

[jhansman]

Glad it's working for you, but I have gotten better results neck sizing than crimping for my bolt .223. Now the only round I crimp is .357mag.

 

[peterotte]

ArchAngelCD , don't give up on your theory just yet. This might be one of the many complicating factors at play. I am working on a simple trial to test this aspect of reloading. I'll let you know what I find - either way! (Which could also be inconclusive).:banghead:

Peter

 

[peterotte]

res45 , was there any shift in POI from crimped to uncrimped? And from group to group within crimped or uncrimped?

It would be interesting to see how this phenomena extends to other loads and bullets. (Easy for me to say - test like that could cost a bit of time and money)!

Peter

 

[f4tweet]

I remember reading a year or so back in a reloading magazine that the one single thing that had the most impact on a round's accuracy was the crimp. They had changed the primers from standard to magnum, varied the powder charge, and bullet weight. The crimp had the most impact. FWIW

 

[peterotte]

So, here is room for some fun experiments! I have heard some say crimp is best with hornet while others have found different. Also, some have found pistol primers work best with crimp while others say rifle primers and no crimp. The powder they are using has interesting characteristics and might show up those differences more. This is interesting!

Peter

 

[res45]

peter I didn't see any change in POI I didn't have to readjust the scope on the scoped rifles any or the iron sights on those type rifles all I experienced was tighter groupings with all crimped rounds vs. non-crimped

 

[stubbicatt]

Fatelvis says:

Is there any way to adapt the FCD to work with a progressive press, like the 550B?

Works on my Super 1050 just fine!

 

[Gewehr98]

Huh?

Is there any way to adapt the FCD to work with a progressive press, like the 550B?

My Lee Factory Crimp dies sit in the 4th station of my Dillon 550B with no problems whatsoever. I don't know why they would have to be "adapted" to a press, since they're the standard 7/8" die size...