How much crimping is too much crimping?

F

freeflight

Sergeant
Full Member
Minuteman
Sep 15, 2011
204
3
California
#1
Hi there,

I am working on a 5.56 load on my Daniel Defense M4 carbine. I found SMK 77gr, 24.8gr TAC, LC 10 brass, COAL=2.25 give me the best 5 shot groups right now. It is about 0.8 MOA at 100yd. But the standard deviation of velocity is about 12-15 fps, which I would like to reduce. I do use the Lee factory crimp die to reload for semi-auto, mainly for safety concerns. The above recipe was achieved with a "normal" crimping.

Lee talked in length about the benefits of using his factory crimp die. So I want to play with different amount of crimping, see if I can reduce the group size or std dev. The image below shows bullets with "light", "normal", and "heavy" amount of crimping, which I will explain.

7628161652_e980e85938_b.jpg


1. The left most bullet was done with light crimping. I didn't feel resistance when crimp the cartridge, and felt the amount of force to pull bullet out is about the same as without crimping.

2. The right most bullet was done with normal crimping, I turned the Lee factory crimp die for another 1/12th of a turn. I barely felt the resistance when crimping the cartridge. When pulling the bullet, I have to use more force to pull it out.

3. The middle three bullets were done with heavy crimping, with another 1/12 of a turn of Lee factory crimp die. I definitely felt the resistance when crimping the cartridge. I had to use a lot more force to pull these bullets out.

Normal crimping is safe to shoot out of my AR. Is it safe to shoot the cartridge with heavy crimping shown above?

Which crimping gives the best accuracy or std dev according to your experience?

Thanks,
Kevin
 
#2
Re: How much crimping is too much crimping?

Stop crimping. The FCD may cut your sd's, but what good is that if it comes at the cost of deforming bullets? IMHO, if you want a good firm crimp, buy some cheap FMJ's; don't waste money on quality bullets if you're going to smash them.

Edit, 77gr smk's are available w/ can. I think that's a waste, but if you have to crimp them, that would be the bullet to use.
 
#3
Re: How much crimping is too much crimping?

I run .004 neck tension on mine and cycled them through the AR action and saw no change in OAL, this from the bolt stop position and rapidly cycling the charging handle.
 
#4
Re: How much crimping is too much crimping?

I think it's safe, or we would be reading horror stories. I could be missing them, though.

I tried the Lee FC dies with several chamberings. I never saw any obvious accuracy improvements.

They may have a valid application preventing bullet setback in rounds that are subjected to repeated heavy recoil in magazines.

If the bullet needs it, it also needs a cannelure to receive the crimp. <span style="font-style: italic">Any</span> deformation of a non-cennelured bullet is distortion, and may degrade accuracy.

I no longer use the Lee FC dies.

Greg
 
#5
Re: How much crimping is too much crimping?

You can crimp if you want but only need a tad. Not much at all. You don't even really need to crimp especially if you are crushing bullets.
 
#6
Re: How much crimping is too much crimping?

An SD of 12-15 is not bad at all. You can try adjusting crimp pressure, another option might be more brass prep, but I wouldn't expect any substantial improvment. If 0.8MOA isn't good enough for you, try a different powder, I like TAC, for high volume loading, I generally get MOA or just a bit better results, but I haven't been able to make it touch the accuracy RE15 or Varget deliver.
 
#7
Re: How much crimping is too much crimping?

If your ammo is not feeding without bullet setback you have a feeding problem.
There are very few handloading applications that require a crimp. Autoloaders are not one of those applications , believe it or not.
 
#8
Re: How much crimping is too much crimping?

Thanks for your replies.

So the consensus is no crimping, or the lightest crimping. I will find some time to shoot the "light" and "normal" crimped ammo group, and see how they group. Still undecided whether to shoot the "heavy" crimped ones or not.
 
#9
Re: How much crimping is too much crimping?

No need to crimp even in an AR. I've loaded for the AR-15 for many years. I tried crimping, no crimping and came to the conclusion; crimping isn't necessary in an AR-15.

The other thing is you should not crimp rifle bullets that do not have a cannelure. If you want to crimp the 77 GR. Sierras, they do make one with a cannelure. It has a light cannelure. They made it for the Military, who required it in their specifications.
 
#10
Re: How much crimping is too much crimping?

This is one of the hottest debated "options" out there. Personally I like a light crimp. I have never had a bullet setback on me, but a reloader friend of mine has. My rifles aren't cheap, but a Lee crimp die sure is! I call it cheap insurance (literally cheap too). I crimp anything that goes near the auto loaders. There is no need to crimp so much you deform the bullet, a light one will do fine. That heavy a crimp will be hell on your brass too!
 
#11
Re: How much crimping is too much crimping?

Lee's collet crimper is the best available IF it's used correctly; if used incorrectly it may be the worst. I don't blame any tool when I fail to use it correctly.

Crimping is just one arrow in our quiver. If you're interested, try it. If it helps, keep doing it. If it doesn't help, don't crimp any more. But there is no way any of us can tell you what it may do for you. Saying crimping anything did or didn't help me isn't a very sound basis for saying it will do the same for anyone else. ??
 
#12
Re: How much crimping is too much crimping?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Devil W C</div><div class="ubbcode-body">This is one of the hottest debated "options" out there. Personally I like a light crimp. I have never had a bullet setback on me, but a reloader friend of mine has. My rifles aren't cheap, but a Lee crimp die sure is! I call it cheap insurance (literally cheap too). I crimp anything that goes near the auto loaders. There is no need to crimp so much you deform the bullet, a light one will do fine. That heavy a crimp will be hell on your brass too! </div></div>

This is precisely why I use crimping in the first place. But it seems even my "normal" crimping is too much. The "light" crimping is better.

I have never use any reloads without crimping in my AR. I may just load 10 rds to see how they group.
 
#13
Re: How much crimping is too much crimping?

When I have the Lee crimp die set to how I like it, I can see the crimp but it's not blatenly obvious. In this video the guy sounds a little distracted but the picture at the end is worth waiting for. I've done lighter, and a little heavier then what he calls the "proper" crimp with no adverse effects on accuracy out to 200. Can't tell you what happens after that, because unfortunately that's my limit for now.

http://m.youtube.com/index?desktop_uri=/&gl=US#/watch?v=3NOWqX0BX6o
 
#14
Re: How much crimping is too much crimping?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Devil W C</div><div class="ubbcode-body">This is one of the hottest debated "options" out there. Personally I like a light crimp. I have never had a bullet setback on me, but a reloader friend of mine has. My rifles aren't cheap, but a Lee crimp die sure is! I call it cheap insurance (literally cheap too). I crimp anything that goes near the auto loaders. There is no need to crimp so much you deform the bullet, a light one will do fine. That heavy a crimp will be hell on your brass too! </div></div>

What happened to your friend? Did a bullets setback cause isses w/ his rifle? If he had an over pressure, how would he know it was bullet setback? Years ago, I purchased some reloads from a local shop. They had neck tension issues. I removed several setback cartridges from my rifle. The way I found them was to eject a cartridge from the rifle. By the number of setback cartridges I happened to find and the number of cartridges I fired, it's extreamly likely that I fired mulitple setback cartridges. By setback, I mean the bullet was setback to the point where powder could spill out. This was a .223 fired in an AR. If this was a pistol cartridge like a 9mm or similar, I'm sure the gun would have exploded in my hand, but rifles are much, much more forgiving. YMMV.
 
#15
Re: How much crimping is too much crimping?

Thanks. The picture compare three cartridges with crimping is very good.

I think I saw the collects move when he retract the cartridge, but it could be the lighting in the video creates illusion though.
 
#16
Re: How much crimping is too much crimping?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MtnCreek</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Devil W C</div><div class="ubbcode-body">This is one of the hottest debated "options" out there. Personally I like a light crimp. I have never had a bullet setback on me, but a reloader friend of mine has. My rifles aren't cheap, but a Lee crimp die sure is! I call it cheap insurance (literally cheap too). I crimp anything that goes near the auto loaders. There is no need to crimp so much you deform the bullet, a light one will do fine. That heavy a crimp will be hell on your brass too! </div></div>

What happened to your friend? Did a bullets setback cause isses w/ his rifle? If he had an over pressure, how would he know it was bullet setback? Years ago, I purchased some reloads from a local shop. They had neck tension issues. I removed several setback cartridges from my rifle. The way I found them was to eject a cartridge from the rifle. By the number of setback cartridges I happened to find and the number of cartridges I fired, it's extreamly likely that I fired mulitple setback cartridges. By setback, I mean the bullet was setback to the point where powder could spill out. This was a .223 fired in an AR. If this was a pistol cartridge like a 9mm or similar, I'm sure the gun would have exploded in my hand, but rifles are much, much more forgiving. YMMV. </div></div>

I'm not sure what the outcome was or what happened. He still has both hands and all his fingers so nothing too catastrophic. He has way more experience then myself, and loads too many calibers for me to count. I asked him if he ever had a problem with setback and if I should crimp. His response was "If it makes you feel better to crimp, then crimp. My preferred load uses military brass, a long 77gr pill, and Varget which fills the case. It's almost a compressed load, and a setback probably wouldn't blow my rifle up. BUT! With 3 of my auto loaders being bullpups with the chamber next to my face, it certainly does make me feel better.
 
#17
Re: How much crimping is too much crimping?

If you use a compressed load the dangers of "creep forward" are much more likely than setback.
If you have to crimp due to lack of neck tension then you have an annealing problem(brass is too hard from working). You solve that problem with a torch, not a crimping die OR a bushing die.

I guess I am lucky cause I never have these problems, even after many thousands of rounds loaded.
 
#18
Re: How much crimping is too much crimping?

In which case I'd have feeding issues. I don't have either problem, and I also don't have a problem with neck tension. As of now I don't anneal, I just toss my brass.
 
#19
Re: How much crimping is too much crimping?

Like some other poster replied, Stop crimping!! I dont see how you can improve accuracy when youre putting a crimp in the bullet jacket.
 
#20
Re: How much crimping is too much crimping?

I use .002 neck tension in my ar 15 match rifle and never had a bullet move. I use the same neck tension in my garand with no crimp and no problem. My 338 lapua doesnt have an issue either. Only cartridge i crimp is my 375 h&h
 
#21
Re: How much crimping is too much crimping?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MtnCreek</div><div class="ubbcode-body">Stop crimping. The FCD may cut your sd's, but what good is that if it comes at the cost of deforming bullets? IMHO, if you want a good firm crimp, buy some cheap FMJ's; don't waste money on quality bullets if you're going to smash them. </div></div>

My sentiments exactly. There are better ways to work on your SD without ruining a perfectly good bullet, i.e. consistent neck tension through superior brass prep. If Hornady/Sierra/Berger wanted dents in their bullets, they would have designed them that way.
 
#22
Re: How much crimping is too much crimping?

There no gaged or SAAMI specificed amount of crimping that must be achieved or things start to blow up. IF we choose to crimp at all, it seems obvious that when the crimping damages our cases or bullets it's likely we've gone a bit too far. ??
 
#24
Re: How much crimping is too much crimping?

I finally got a chance to shoot these cartridges. Here are the results,
1. No crimping just doesn't group well with my Daniel Defense M4. 5 shot group size range from 1.2 to 1.6 MOA.
2. Light crimping groups are around 1.0 - 1.15 MOA.
3. Normal crimping (the right most bullet of the 1st post) groups about 0.8 to 1.0 MOA.
4. Didn't try heavy crimping due to safety concern.

Going over my reloading log, it appears Varget groups better than TAC. But TAC offers about 150FPS advantage over Varget. Tough decision.
 
#26
Re: How much crimping is too much crimping?

So does FGGM, all factory match uses a light crimp. A light crimp will not hurt accuracy one bit. Think about it, sending a bullet down the bore causes more deformation (riffling) then a slight crimp does!
 
#27
Re: How much crimping is too much crimping?

Did you try the non crimped rounds with a few tenths of a grain more powder? Without a crimp your pressure may be lower. shoot them over a chrono and load the non crimped rounds till they reach the same velocity and i think you will be surprised. Any time you change any factor in a load you change the load. you need to work up a non crimped load as they will not be the same
 
#28
Re: How much crimping is too much crimping?

Good day,

A reasonable taper crimp will reduce the neck size by 0.001-2", and leave the same amount of reduction on the bullet bearing surface. This will not affect accuracy of the bullet/powder/depth combination, and may improve it. If you want a consistent crimp, you will need to make sure the brass necks are consistent; which can be one of the reasons to neck-turn your brass.

HTH,
DocB
 
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