After a search on crimping info on this site I thought a poll might come in handy.
I've tried to create questions for various possible scenarios:

Question:
Does crimping affect accuracy?

Choices:
Always Improves
Often Improves
Seldom Improves
Never Improves
Always Worsens
Often Worsens
I abstain (no personal knowledge on this)

Question:
Does crimping stop "set-back" of bullets into the cases from recoil and how critical is this?

Choices:
Yes, and it's critical
Yes, but it's not critical
No, I don't ever get "set-back" from recoil
No, I still get "set-back" in spite of crimping
Abstain (no personal knowledge on this)

Question:
Do you feel a crimp makes for more robust relaible ammo for travelling/hunting?

Choices:
Yes, it's a big improvement
Yes, but it's not that important
No, un-crimped is just as reliable
I abstain (no personal knowledge on this)

Question:
Generally I...

Choices:
Always crimp
Often crimp
Seldom crimp
Never crimp

 

Unanswerable questions for me. Some cals must be crimped, many don't, and shoot as well or better for me.

Hey Stephen, I clicked on the Top Choice in every catagory - because I was thinking about the 357Mag, 44Mag and 444Mar. The Slow Powders typically used for Hunting Loads in the 357Mag and 44Mag really need a firm Roll Crimp to get the Pressure rising quickly so the Powder will burn at it's optimum rate.

If I had been thinking about Bottle Neck Cartridges smaller than "Dangerous Game size Cartridges", then I would have said I do not Crimp, or Abstain from the process as you listed it.
-----

A lot of folks seem to enjoy using the Lee Factory Crimp Die sets and claim greatly improved accuracy. I've never tried any of them, so I can't comment on them accuracy wise. It would seem obvious however, the more the Case Mouth is Stressed with the Lee Factory Crimp Process, the shorter the Case Life will be. On the other hand, the Roll Crimp used on the 357Mag, 44Mag and 444Mar does not seem to be overly Stressful to the Case.

revolver cartridges require crimping as well as the tubular magazine rounds.

I suspect double rifle rounds should be crimped as well.

Bolt action rifle rounds do not require a crimp nor are they "better" if crimped.

Thanks so far folk.

Hot Core, my apologies, but being strictly rifle orientated I actually was'nt even THINKING handgun here; Pretty foolish of me

My real interest here is hunting rifles with magazines, but if folk answer related to other diciplines, please add a suitable explanation/opinion such as Hot Core did.

Even with bolt rifles there is a break-over in caliber and bullet weight that demands crimping while lesser calibers become optional.

Above .338 I crimp everything; below I usually crimp big game rounds for the field only. I never crimp varmint calibers except 223 for my AR-15.

For the big bores the bullets will jump without crimping but I think it helps ignition too. On the mediums I think it just helps with bullet jump or a dropped round inthe heat of it. I don't see a lot of performance variation in the mediums between crimped and uncrimped but I use tight neck tension on everything.

I roll crimp .44 mag, .41 mag and taper crimp .45 ACP, and roll crimp .375 H&H, taper crimp and roll crimp 7 RM. Accuracy is excellent in all calibers.

Since I've been able to obtain Lee Factory Crimp dies, I crimp everything. I use a roll crimp if the bullet cannelure is of the groove type, I use the Lee Factory Crimp if the cannelure is a recessed band. Since my rifles are .375 H&H, 404 Jeffery and 416 Rigby, it eliminates one variable (bullet movement)which does happen from time to time under recoil. Also, I'm too lazy to neck turn all the time and a loose bullet can happen with varying neck thicknesses.

I used to crimp all the time but found that in some combinations of powder, primer and bullet that I could get pressure "spikes".

I don't load anything more powerful than a 375 H&H so I've gone to reducing the size of the expander ball by polishing it and this gives me enough consistent neck tension to hold the bullets in place and removes the chance of damaging the bullet.

I think the key to precision is uniformity. Crimping is another parameter which can add variation. If not necessary like for the brake-top rifles I do not crimp. Of course, for handgun and heavy rifle loads like .375 HH for repeating rifles a crimp is necessary.

quote:

Originally posted by DUK:
I think the key to precision is uniformity. Crimping is another parameter which can add variation.

Hi DUK

I suppose you are correct that another parameter creates another possible variable, but Lee argue that the whole idea of crimping is to bring uniformity where there may not have been? ie A uniform squeeze should iron out slight variances in neck thickness, ovals etc.

quote:

Originally posted by Stephen Palos:

quote:

Originally posted by DUK:
I think the key to precision is uniformity. Crimping is another parameter which can add variation.

Hi DUK

I suppose you are correct that another parameter creates another possible variable, but Lee argue that the whole idea of crimping is to bring uniformity where there may not have been? ie A uniform squeeze should iron out slight variances in neck thickness, ovals etc.

We are comparing from an engineering point of view a positive (by form or rather, crimp) with a non-positive lock (in German: kraftschlüssig, by friction force only).

What has to be uniform is the extraction force, I don't know if the extraction force can be more uniform with friction only (no crimp) or with crimp and friction because you have always both.

I should not matter if you apply a uniform squeeze as long as other variables you mention like neck thickness, roughness and length (!) are completely uniform, too. If not, they should influence variance in the bullet's extraction force.

Maybe someone knows if the benchresters regularily crimp. If they don't, they should have a good reason not to do it.

When I look at the flat noses of the 30/06 Nosler Partitions in the magazin of my bolt action after firing once, I would presume that not even with this caliber a crimp is necessary for tightness.

The 300 grain Barnes TSX I loaded for a friend's 375 H&H were crimped but then, the animals he shot at were quite big so precision was not an issue. The load was however very precise with a pretty heavy crimp.

bench rest shooters wouldn't dream of crimping. crimping is definitely detrimental to accuracy in rifle loads, but if you need to crimp by all means do it as 1/4 or even 3/8" difference in group size is inconsequential for game shooting.

Do not crimp rounds for my double rifles, but the .375 bolt rifle needs to have rounds crimped or those in the magazine set back from recoil.

Regards

If you have a bullet without a crimp ring, does it really do any good to crimp. all you are doing is putting a little more pressure on the bullet. and that is not really [crimping] is it?

Just from a rifle cartridge re-loader point of view, I always rely on roll crimp & neck tension, I have not used any other forced crimping. Steve.

I 'might' have mentioned this before. I went the other way - I don't resize at all. One of the reasons was to eliminate the inconsistency in grip and the other was to eliminate the possibility of run-out. But because my rifle neck area is large, I use a paper cup to seat the bullet, which also happens to be lubed. The lube actually 'glues' the bullet in the neck. If nothing else, it keeps the bore clean. Case life is indefinite and it allows me to headspace on the case mouth. BUT, this is with a 22 hornet. The system works with my 303 Brit but the bullet is not very secure this way so I shall not be using it for this rifle.

Oh, my theory is that the cup keeps the bullet in line with the bore while it clears the somewhat oversize throat area. I have no proof of this but I am able to stabilize heavier and longer bullets in the hornet than usual. (Inculding 55gr BT's). It makes no difference in performance with H4227 but allows a larger powder charge with Lil'Gun, giving higher velocity at 'normal' pressure.

quote:

Originally posted by swampshooter:
bench rest shooters wouldn't dream of crimping. crimping is definitely detrimental to accuracy in rifle loads, but if you need to crimp by all means do it as 1/4 or even 3/8" difference in group size is inconsequential for game shooting.

Agree completely. Also, benchresters have tight-neck chambers and neck turned brass to match which would not be wise in the average hunting rifle. A lot of benchresters also load at the bench so cartridge handling is a non-issue.

I use only the Lee Factory Crimp and all of my rifles except in one case have shown tests like this




I have done this on 3 different occasions that I can recall but these are the only pics I can find right now.

I have a Lee Factory Crimp in every caliber that I reload for and that they are available in. They also help when you load into the lands to hold the bullet. You do not need a cannelure and the trim length does not have to be exactly the same.

What's not to like?

That is very interesting woods. Especially for someone like me who does not want to crimp. I notice the velocity was identical. Did you by any chance record the ES and SD? Is there any chance that there was a difference in runout? Do you get the same results with different powders?

quote:

Originally posted by 303Guy:
That is very interesting woods. Especially for someone like me who does not want to crimp. I notice the velocity was identical. Did you by any chance record the ES and SD? Is there any chance that there was a difference in runout? Do you get the same results with different powders?

I will look back through my spreadsheet and see if I can find the tests but it seems that I came to the conclusion that velocity increased by an average of about 10 fps and group size decreased by an average of 1/8".

Here's one on 14-May-06 shooting 300 win mag
CRIMPED - 168 gr TSX / IMR4831 / 75 gr / 1 1/2" / 3213, 3225, 3208 = avg of 3215
NO CRIMP - 168 gr TSX / IMR4831 / 75 gr / 1 1/2" / 3204, 3210, 3210 = avg of 3208

and a retest on the following week, same gun same loads
CRIMPED - 168 gr TSX / IMR4831 / 75 gr / 1 3/8" / 3209, 3215, 3210, 3208 = avg of 3211
NO CRIMP - 168 gr TSX / IMR4831 / 75 gr / 1 1/2" / 3204, 3211, 3210, 3198 = avg of 3206

And on 10-Jan-07 with a 30-06
CRIMPED - 200 gr Accubond / RL22 / 61 gr / 1 1/8" / 2668, 2668, 2640 = avg of 2659
NO CRIMP - 200 gr Accubond / RL22/ 61 gr / 1 1/2" / 2648, 2626, 2655 = avg of 2643

and a retest the following week on 17-Jan-07
CRIMPED - 200 gr Accubond / RL22 / 61 gr / 1" / 2658, 2623, 2628, 2677 = avg of 2647
NO CRIMP - 200 gr Accubond / RL22 / 61 gr / 1 5/8" / 2633, 2644, 2668, 2638 = avg of 2646

I know I did a test on a 270 and another 30-06 but I can't find it right now. My record keeping is not perfect but it is getting better.

Thank you for that. So the differences are small but measurable. (The difference in accuracy might seem small but is actually 10%).

I knew the velocity difference to be small with 'regular' powder but it makes a huge difference with Lil'Gun. But then, so does seating the bullet 0.6mm deaper!

I never crimp a jacketed bullet that does not have a crimping groove. To do so could cause the jacket to separate from the core and cause problems in your barrel...

quote:

Originally posted by homebrewer:
I never crimp a jacketed bullet that does not have a crimping groove. To do so could cause the jacket to separate from the core and cause problems in your barrel...

I don't believe that to be true at all. Cannelures are much deeper into the jacket of a bullet than a crimp could ever drive the mouth of the case into it. Also, bullets are groove diameter and are severely grooved and gouged by the lands, just as a guess probably 1,000 times more than a crimp.

To just make a statement like that as fact with no evidence or instances where it has happened is ridiculous.

I use the Lee Factory Crimp Dies for .243 & .270Win & have seen a noticeable increase in accuracy.
I've used it with 130gr Hornady SST's in the .270 where I have to seat the bullet out from the cannelure for accuracy & had no problems.

I use the Lee Factory Crimp dies on about everything with good success, but there is quite a debate on this subject. Didn't AR doe some tests on crimping and had the results published somewhere on the site?

Yup! http://www.accuratereloading.com/crimping.html

I crimp everything that Lee makes the FCD for, even some they don't after modifying one they do make so it works.

Thanks for all the response folks!

It seems that, like many things in reloading, what works for one guy is a failure for the next. So each has to determine what works for him