Crimping for accuracy

[Spitpatch]

Crimping a non-cannelured bullet to a degree that would retain the bullet significantly during the ignition process is to the degree that would damage the bullet.

I crimp NO rifle ammunition aside from 30-30's and such going to a tube fed gun, or blackpowder cartridges. (All with a place on the bullet for that crimped mouth to rest without deforming the projectile.)

 

[P7M13]

Uniform neck tension is the key to excellent accuracy

^^^^^^^ that, right there
Uniform neck tension is affected by consistent brass, precise sizing/loading technique, and consistent annealing.
You can feel neck tension when you seat the bullet.
Of course there are other reloading factors that affect accuracy, but when you develop a load which is consistently accurate in your gun, you can then focus on the most critical component - the nut behind the buttstock.
I crimp for my iron sight autoloaders using Lee FCD, and like @Spitpatch, for my 30-30 lever guns (roll). These are plinking rounds where my ability with irons, offhand, is the limiting factor.
If you crimp, you need to pay attention to case length, especially when using a roll-crimp.

If you go to LRH and search crimping, the user Butterbean attests to it contributing to MVs with single digit ES/SD. He is also a very vocal proponent of Hammers.

 

[DizzyJ]

I think it could be done consistently if one separated the step from the seating die and used a dedicated crimp die. Im not worried about bullet damage, I dont see how it could damage the bullet when they often come with cannelures, and monos come with displacement grooves. The Hammers unique drive bands leave a nice rounded surface to roll or taper onto.

Note: its crimping for accuracy. Im not worried about bullet setback.

I found the other place Ive read about this, from Lees FCD page... and my guess is they arent talking about monolithic bullets.

Factory Crimp Die

Collet Style Crimp Die. Incorporates a collet to apply a rifle type crimp to the case. Makes these very difficult to crimp cartridges a delight to reload. Bullets do not need a crimp groove, as the collet is so powerful it will form one. NOTE: This die is not carbide.

leeprecision.com

this might boil down to one of those personal preferences debates like neck vs full length sizing. Just another one of the many rabbit holes I find as I continue to learn reloading.

I would caution buying into Lees marketing claims. Their reloading book of full of promoting their product as well, which in some instances flys in the face of reality.

 

[cameron25]

Hammer bullets are the only ones I've crimped, simply because other people seemed to have better results when crimping them. I actually prefer cutting edge for monos and I don't crimp those or the badlands or the bergers I load

 

[Certaindeaf]

Ive heard or read somewhere to crimp for accuracy. The idea is the amount of crimp can help control pressure, velocity and tune the delay of the bullet to the barrels harmonics more precisely that other methods like seating depth or charge.

Does anyone have any insight or experience with this?

See what benchrest shooters do.
Not one crimps.

 

[Xaevian]

See what benchrest shooters do.
Not one crimps.

Sounds like street gangs, the crimps and the loads. I do the crimps cuz I hike long distances with my gat slung, yo.

Crimpin is pimpin!

 

[Koda]

I like this discussion, its giving me good feedback. I suspect this comes down to a personal preference debate, like others...
Lee does heavily promote their stuff, but many individual handloaders have claimed to crimp for accuracy, including this thread.... its not a Lee thing.

One thing ive not done yet is control my neck tension with bushing dies, maybe that would be the "real" way to control accuracy via neck tension, where crimping is the "easy" way?.
I dunno.

I do know Hammers have a huge following of reloaders, and are getting results. Several of them attest to crimping. Apparently people have crimped for accuracy cup n cores too.

Me? To be determined still. Id rather not add the extra step, but... Since Hammers are not sensitw to seating depth it might be why some of their handloaders are turning to using the crimp to tune accuracy.

 

[Explorer1]

What do the benchrest and F-class shooters do?

For my competition rifles, its no crimp and am very concerned about CONSISTENT neck tension and bullet release. Such as using an ultrasonic cleaner can result in high release tension due to the clean metal interfaces.

 

[Koda]

Can/do competition shooters control precision with increasing neck tension?

 

[Spitpatch]

As to neck tension, @Explorer1 emphasizes correctly that CONSISTENCY is the goal, rather than "more" or "less" neck tension. This is achieved in attention to the steps of the process such as no lube left in the neck, quality dies, matching brass, and in more detailed attention: inside or outside neck turning. (That's not "either-or", you have to figure out where the inconsistency lies, then address it.)

Neck turning is almost mandatory for sharp accuracy in a custom tailored chamber, or when utilizing converted brass from another caliber.

 

[osprey]

Consistent neck tension will do more for accuracy than any crimp and annealing is a big part of this. I crimp very few loads these days.

 

[Koda]

For my competition rifles, its no crimp and am very concerned about CONSISTENT neck tension and bullet release.

so this little nugget of truth just might just be the kingpin in this subject. Would not consistent crimp also be a control on bullet release?
What I think is going on here is crimping for accuracy is something like a simpler way of controlling neck tension thats more specific to hunters.
Lets break down rifle reloading into two categories, hunters and competition shooters. I don't know what level of precision competition shooters need, but I know for hunters anything 1moa or under is ideal, and I suspect that 1moa is less than ideal for competition shooters. (?) Im also guessing that the average hunter is not going to want to neck turn or control neck tension with bushing dies.... so this might be a matter of resolution; maybe crimping brings a 1.5moa group to 1moa, or a 1moa group to .75 moa. Happy hunter has a "tack driver" for big game with just an 1/8th turn of the crimping die. While the competition shooter that "resolution" would not suffice and would need to dig deeper into the methodology of consistent and proper neck tension.

Just hypothesizing here but I thinking crimping for accuracy is a hunter trick, which is why Hammer reloaders are using it since Hammers (supposedly) are not sensitive to seating depth.

 

[NiteQwill]

Can/do competition shooters control precision with increasing neck tension?

Depends. Most competition shooters, myself included, will control the diameter of sized brass with a bushing 0.002 under loaded diameter and then use a mandrel 0.001 under bullet diameter. This would allow adequate spring back and tension on properly prepped brass (cleaned, annealed, etc.).

My discipline of shooting requires me to make first round hits on target, often in an unsupported positions, with targets ranging between 400-1100 yards. I have been practicing the above method for awhile and so far it's working well.

As said before, no one in the competition world crimps their bullets. They would be throwing money away on bullets that are expensive as is (Berger, Hornady Atips, etc.).

 

[gmerkt]

Richard Lee is one of the proponents of routine rifle bullet crimping. One way to look at his ideas is that it's a fail safe to force ammunition to stay in one piece. Hence, his rifle "factory crimp die." Yes, consistent bullet pull is a plus for accuracy. But crushing the case mouth into the shank of the bullet is counterproductive in my own inexpert opinion.

The so-called "factory crimp" has been used by some of the major manufacturers over the years. Like Winchester. But they didn't use it for the sake of accuracy. It was done (1) as a fail safe against bullet set-back, and (2) to compensate for minor variations of case length. New brass at the factory isn't trimmed and it's rarely perfectly consistent in length. The factory crimp crushes slightly over-long case mouths into the bullet sidewall to ensure chambering.

Crimping is primarily for semiautomatics. To avoid setback. I also use a small base resizing die for reliable feeding - but only for semiautomatic.
Some people will say they factory crimp their hunting rifle loads and I approve of a light factory crimp to avoid the remote possibility of setback. But an F-class shooter is concerned about accuracy.

Crimping in precision shooting will possibly scar or deform the shank, reducing accuracy.

The above summarized my thoughts on the subject.

More important is proper neck tension and CONSISTENT tension throughout your cases.

The above, not excessive crimping. Which can be more work, because of potential variations in materials and tools.

 

[Phantom Man]

I watch a lot of Erik Cortina videos and he appears to not be a big advocate of crimping.

 

[MymuttBear]

I think it could be done consistently if one separated the step from the seating die and used a dedicated crimp die. Im not worried about bullet damage, I dont see how it could damage the bullet when they often come with cannelures, and monos come with displacement grooves. The Hammers unique drive bands leave a nice rounded surface to roll or taper onto.

Note: its crimping for accuracy. Im not worried about bullet setback.

I found the other place Ive read about this, from Lees FCD page... and my guess is they arent talking about monolithic bullets.

Factory Crimp Die

Collet Style Crimp Die. Incorporates a collet to apply a rifle type crimp to the case. Makes these very difficult to crimp cartridges a delight to reload. Bullets do not need a crimp groove, as the collet is so powerful it will form one. NOTE: This die is not carbide.

leeprecision.com

this might boil down to one of those personal preferences debates like neck vs full length sizing. Just another one of the many rabbit holes I find as I continue to learn reloading.

Previously for all my reloading, and we are talking years worth, I only used the crimping die that came with the die set and never considered, or thought about the effect it could have on velocity. After reading Lee's blurb about the supposed accuracy gains a factory crimp will give I decided to go down that path.

A couple of weeks ago I put some crimped .41 magnum loads over a chronograph and there was a mean spread of approx 50fps so for what it's worth I think the crimp makes a difference at least in achieving consistent velocities in my revolver.

I don't neck ream any of my cases I simply rely on the sizing button when sizing. Nor do I neck anneal so there is definitely inconsistent neck tension when seating bullets. If a Lee factory crimp die takes that variable out of the equation then IMHO that has to be a good thing.

 

[Explorer1]

Oh, we jumped to handgun loads. Well, that is a different scenario.
In some cases, such as using 2400 in a 44 mag with heavy bullets in revolver, a crimp is desired. But the reasons are to help build pressure (consistency) and keep the bullets from moving forward during recoil and locking up the cylinder.

In summary, no one size fits all.

 

[coop44]

No crimp here, but I do use chicken blood and dark magic.

 

[Phantom Man]

No crimp here, but I do use chicken blood and dark magic.

All reloader do, don't they.

 

[Koda]

Learning to handload with Hammer bullets is like dark magic. No load data and they usually dont align with similar bullets....
That first shot is like, "well lets see what happens here"....