Crimping for accuracy

[Koda]

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?

Read More

 

[Local Loader]

I've personally seen no difference myself, but I'm placing my max range at 300yd out for my loads. I'm sure of you're going 500yd or more than your see a difference or possibly if you're using a slower burn powder to give it more time to ignite and build more pressure sooner or trying too get a higher pressure faster with a faster burn powder(typically for short barrels). (Feel free to correct me if I'm wrong)

 

[Koda]

I've personally seen no difference myself, but I'm placing my max range at 300yd out for my loads. I'm sure of you're going 500yd or more than your see a difference or possibly if you're using a slower burn powder to give it more time to ignite and build more pressure sooner or trying too get a higher pressure faster with a faster burn powder(typically for short barrels). (Feel free to correct me if I'm wrong)

I left out my load specifics because I'm curious how this works in general for all calibers. But I am working on a new rifle out to 500yds and did pick a slower burn powder to match a longer bbl and lighter/faster bullet choice.

Anyways, I would think if crimping makes a difference it would show up in group size at the typical 100yds?

 

[arrowshooter]

I was using a light crimp when I first starting loading for my -06, but when i tried a medium crimp the groups shrunk and average of .25". I was/still am using H4350 and was at the top of the chart for this load, so I assumed that the extra crimp gave it the oomph it needed. This was with my old Win model 54 so the barrel has a bit of wear and needed the help.

 

[Koda]

I was using a light crimp when I first starting loading for my -06, but when i tried a medium crimp the groups shrunk and average of .25". I was/still am using H4350 and was at the top of the chart for this load, so I assumed that the extra crimp gave it the oomph it needed. This was with my old Win model 54 so the barrel has a bit of wear and needed the help.

this is what Ive heard, some even find an accuracy node will open back up as they crimp more. Ive read to start load dev with a very light crimp because the first crimp can jump pressure but after that 1/8 turn per crimp adjustment are tiny increases in pressure. Be careful adding a crimp after load dev at the top of the chart...

 

[quneur]

My thoughts for what its worth.

There shouldn't be a consistent formula for all calibers. A good test would be find a test distance for each caliber (ex, for .308, 25 yards accuracy will be much different than 300 yards.) You will also have to test kinetic energy to determine the distance (ex, kinetic energy for 300 win mag will be different than .22LR. Pick a distance where gravitational, windage, etc. effects won't play a significant part, eg. perhaps, ratio of Energy/Muzzle Energy.)

Then take 10 shots heavy crimped and 10 shots light crimped for 10 calibers with the same shooter and optics.

 

[orygun]

I try to be consistent and use a medium/light crimp. I do it when seating the bullet. The only other thing I tried was a heavier crimp and found that when doing it when seating the bullet I screwed up the cases...
I then decided if I wanted a heavier crimp it would need to be done as a separate step.
It makes sense to me to have a bit of a crimp to keep the bullet from moving due to the primer "pop". But I'm lazy and if I'm getting good groups with the way I mentioned, I stop load development and go shooting.
The furthest I've shot on paper was 400 yards, and that's prone with a sling. It wasn't the ammo or the rifle that I was worried about, it was the shooter!

All of the above is rifle ammo. Loading for a handgun, especially a Magnum revolver, I crimp heavy.

 

[DizzyJ]

What do the benchrest and F-class shooters do?

 

[Xmark1]

What do the benchrest and F-class shooters do?

I am one of those people, and I do not crimp.

 

[Koda]

I feel like nows a good time to divulge a little more detail about my project.
I would love to learn what an F Class shooter would do to fine tune the precision of an Absolute Hammer all copper monolithic hollowpoint?

.284 Cal-140g Absolute Hammer - Hammer Bullets

We tested this 140g Absolute Hammer in my personal 280ai with a 22" barrel. My previous load was with the 143g Hammer Hunter at a velocity of 3126 fps. The 140g Absolute Hammer load settled in at 3387 fps. This is exceptional from a short barreled rifle. Absolute Hammers do not line up with...

hammerbullets.com

 

[Xmark1]

My .02

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.

For precision - I full length size the first load, each load thereafter is neck sized only. No crimp.

Crimping in precision shooting will possibly scar or deform the shank, reducing accuracy.
I anneal after each firing using tempilaq to assure consistent neck tension.

Another important point is jump. You can effect pressure buildup in the cartridge by varying your jump. Jump also varies widely with caliber. I jump ~.015 in my 308 but use over .100 in my 338LM. Jump drastically affects accuracy!

I looked at the link you provided and the MV of 3,387fps for a projectile weight of 140 seems too fast for accuracy. I'm sure it will hammer anything it hits at that speed. Biased on their price I would submit for your consideration that this is not the projectile for a newbie reloader.

I shoot long distance. Heavy projectiles (High BC) at relative slow speed always produce better accuracy, providing you have the correct twist. Think of the stress you put on your barrel using a hot load, it's gonna flex like a wet noodle and the harmonic nodes will be inconsistent, from one shot to the next.
Now might be a good time to mention barrel temperature - it does change POI.

Whenever I post here, the naysayers chime in. But I have the targets, signed by witnesses to prove what I say.
If you want to cloverleaf multiple shots at, say, 300 yards, or sub-MOA @ 1,000.

We have now entered into the arena of ballistics and the long-winded speech I just gave is but the tip of the iceberg.

 

[NiteQwill]

Crimping does not improve accuracy... In fact, the possibility of deforming the jacket of the bullet will inherently lower BC and ballistic performance.

No F Class, BR, or PRS shooter crimps their loads.

Proper tension at the neck is controlled by bushing, mandrels, etc.

If you're shooting a semi auto and need reliability ( aka no bullet setback ), you can crimp. But even serious gas gunners (PRS, service rifle, etc) do not crimp their loads.

 

[Koda]

Hammer bullet technology does not line up with conventional handload data, their Absolute Hammer projectiles typically get up to about 400fps faster than their conventional cup and core equivelent without overpressure. Hammers are not sensitiv to seating depth.
For those reasons, i dont think competition shooting reloading techniques will apply here.

I have read somewhere that people have used a crimp to control group size even with traditional bullets but I cant find it. Ive read some Hammer users are using crimping with sucess, so i cant say at this time I agree it wouldnt work.

Maybe what I will do is test some side by side and compare velocities. Im not certain if I want to crimp if Im satisfied with my group size and velocity but am curious how its done since Hammers are not sensitive to seating depth if I need to fine tune group size.

 

[Xmark1]

Disregard for seating depth is beyond the realm of my understanding.

Sometimes MV is limited because of the spin rate at barrel exit. Some jacketed projectiles simply explode when they exit the barrel due to centripetal forces at high MV. I can see how a copper solid can be pushed faster.

I will be interested in you test results.

 

[DizzyJ]

My thoughts on crimping (I don't do it for rifle rounds) is that it's too hard to do it consistently to get best results.

As mentioned, neck tension is generally enough to keep a bullet from moving in most common caliber rifles for precision shooting.

I know a guy who did a study on crimp and it's effects. My worry is that it would be difficult to apply the same consistent crimp on the cartridge and May in fact damage the bullet.

 

[DizzyJ]

I am one of those people, and I do not crimp.

It was my assumption they (you) don't crimp when trying to create the most consistent, accurate ammunition.

 

[Koda]

My thoughts on crimping (I don't do it for rifle rounds) is that it's too hard to do it consistently to get best results.

As mentioned, neck tension is generally enough to keep a bullet from moving in most common caliber rifles for precision shooting.

I know a guy who did a study on crimp and it's effects. My worry is that it would be difficult to apply the same consistent crimp on the cartridge and May in fact damage the bullet.

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.

 

[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.

Do a test and let us know.
20 rounds each.

 

[ron]

I have done the 'Test' several times. Two identical loads one with a crimp, from the separate stage
Lee die and one no crimp. Every time the no crimp is considerably more accurate. I use full length
standard RCBS dies. 223/556, 30/06 and 308 fired in semi auto gas guns in Highpower competition
out to 600 yards. Never had an issue with bullets pushing back. Uniform neck tension is the key
to excellent accuracy. For the 223 brass manufacture makes a big difference. Winchester brass
produces a much tighter group than LC brass. My plinking 223 loads I do not crimp either.

 

[Member 5605]

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

Deep rabbit hole