Crimped Vs. Uncrimped Handloads (.223)

[Gary L. Griffiths]

A thread on The High Road got me started experimenting with crimped vs. uncrimped .223 loads in the AR platform. Some claim that crimping is unnecessary, that neck tension alone will hold the bullets in place adequately. Others claim crimping is necessary to keep the bullets from seating deeper upon striking the feed ramp, or, conversely, from being pulled forward by momentum as the cartridge slams into the chamber. I thought I would experiment to see what, if any, difference there was between crimped and uncrimped loads.

I loaded up 40 rounds of .223 using twice-fired Federal cases, CCI-400 primers and 26.5 gr. Varget. Half the rounds were loaded with AMSCOR 55-gr. FMJBT bullets with crimping grooves, and half were loaded with 62-gr. SS-109 bullets, also with crimping grooves. Using Dillon dies, both batches of bullets were seated so that the front of the crimping groove on the bullet was just barely visible above the neck of case. Next, half (10) of each batch of cartridges was run through the Dillon crimping die. The end result was 10 rounds each of crimped 55-gr., uncrimped 55-gr., crimped 62-gr., and uncrimped 62-gr.

All cartridges were numbered with a Sharpie prior to measurement. At the range, I measured each cartridge prior to loading. The 55-gr. uncrimped averaged 2.225" with a standard deviation (SD) of 0.003". The 55-gr crimped averaged 2.224" with an SD of 0.007". The 62-gr. uncrimped averaged 2.228" with an SD of 0.003", and the 62-gr. crimped averaged 2.240" with an SD of 0.008".

Next, I loaded the test cartridges into 20-round magazines interspersed with factory (Wolf Gold) cartridges, so that the first round loaded (last to be chambered) was a test cartridge and the last loaded (first to be fired) was a factory cartridge. I then proceeded to empty the magazine by firing the factory cartridge, using a stock Bushmaster Carbon 15, then manually ejecting the test cartridge following it. I did this for all 40 test cartridges, expending 40 factory loads. I re-measured all of the test cartridges with the following results:

The average length of the 55-gr. uncrimped cartridges was 2.225" (exactly the same as before being chambered) with an SD of 0.004". Three of the cartridges increased in length by 0.001", and two decreased in length by 0.001" for a total gain of 0.001". While I was careful in my measurements, I would think that the observed changes may result from measurement error rather than actual changes.

The average length of the 55-gr crimped cartridges was 2.242" (an increase of 0.002") with an SD of 0.007" (exactly the same as the original measurements). Eight of the cartridges lengthened between 0.002" and 0.005" for a total length increase of 0.024". Even accounting for some measurement error, this seems counterintuitive – the crimped cartridges were apparently less secure than the uncrimped!

The average length of the 62-gr. uncrimped cartridges was 2.229" (an increase of 0.001") with an SD of 0.003" (exactly the same as the original measurements). Two of the cartridges lengthened 0.001", and one of them lengthened 0.003" for a total gain of 0.005".

The average length of the 62-gr. crimped cartridges was 2.240" with an SD of 0.008" (exactly the same as the original measurements). Five of the cartridges gained 0.001" in length for a total gain of 0.005".

It seems to me that in .223 being fired from a typical AR platform, there is no significant difference in chambering effects between crimped and uncrimped cartridges. If any difference exists, it seems to weigh in favor of uncrimped cartridges, possibly because crimping may slightly reduce the neck tension elsewhere in the cartridge.

I then fired all 40 cartridges and measured the results. The uncrimped 55-gr. cartridges averaged 2937 fps with an SD of 25 fps, while the crimped cartridges averaged 2939 fps, with an SD of 17 fps. Thus there was no significant difference in velocities between the two. The uncrimped 62-gr. loads averaged 2739 fps with an SD of 31 fps, and the crimped loads averaged 2783 fps with an SD of 14 fps. Crimping with this load (or bullet at any rate) increased the velocity significantly, averaging 44 fps.

Group sizes were 1.30" for the uncrimped 55-gr. bullets, 1.58" for the crimped 55-gr. bullets, 1.13" for the uncrimped 62-gr. bullets, and 1.23" for the crimped 62-gr. bullets, so the uncrimped bullets have a slight to moderate advantage in accuracy. Groups were nothing to brag about, but not bad for a Bushmaster with a lightweight pencil barrel chambered for 5.56mm with 1:9 twist, 1-4X scope set to 4X, and stock (atrocious) trigger.

This test certainly won’t answer the ultimate question of crimped vs. uncrimped bullets in the AR platform, but it reinforces my notion that crimping is unnecessary for reliable feeding, handling, and accuracy.

 

[5whiskey]

Thank you for your effort sir... most notably for posting it here. I have been a religious "must crimp if running through a semi-auto rifle" guy, but it looks as though it honestly makes little difference.. Maybe I need to re-think my regimen.

 

[Bart B.]

Nobody shooting 22 caliber AR platforms in competition winning and setting records crimped in their bullets. Ain't necessary and hurts accuracy.

Sierra Bullets makes 22 caliber match bullets cannelured for crimping but tests them for accuracy uncrimped. They shoot more accurate that way because crimps distorts and unbalances bullets.

As one of the first few people to shoot AR platforms (M16's with match sights and barrels using handloaded ammo) in competiton at the Nationals in 1971, we chuckled a lot discussing the issue of crimping bullets which we all knew was not needed but ne'er the less would be mandated by the ignorant masses later on. After all, isn't all military ball ammo crimped in place for semiauto 22 and 30 caliber military rifles? But they'll ignore the fact that .30 caliber match ammo for those same rifles used in competiton didn't have crimped in bullets and had a lot more recoil and bolt slamming than mouse guns. Arsenals learned decades ago that crimped in bullets shot less accurate than crimped ones, so they quit cutting a cannelure in match bullets and skipped the crimping stage in production lines.

No commercial centerfire rifle match ammo in any caliber has crimped bullets that I know of. If there is one, I'd like to hear about its successes winning and setting records.

 

[steve4102]

I have found similar results when crimping with the seating die. With the Lee Factory Crimp Die just the opposite is true. It helps secure the bullet and it improves accuracy in my rifles.

Most of those that claim crimping with the Lee Factory Crimp die degrades accuracy have never tried it, they only have their untested opinion.

Most of those that claim the LFCD increases accuracy have actually tested the die in their rifles and have actual test data and not just an opinion.

 

[madmo44mag]

I agree that the Lee Factory Crimp Die does improve accuracy in all my 5.56 AR rifles.
Just my nickel 98

 

[1stmar]

I think it's possible the mixed reports on the lfcd are related to distance. Conceivably it's possibly short distance accuracy (100-200 yards) may improve as different factors are more important when velocity is at it's greatest. But over time (distance), these factors change, ballistic coefficient becomes more critical and bullet deformation and balance will weigh heavier. Just my thoughts, not substantiated.

 

[Longshot4]

This has been interesting to hear what intelligent people have found with the 223. I am not at all knowledgeable with the AR platforms although I have found that it is very difficult to use a hammer type bullet puller to remove sutch a small .224 bullet from a case that is not crimped. As has been discussed on other threads. There are ways to increase the grip (friction) a case has on a bullet. As we have found a crimp dose increase the hold on a bullet on other threads. Although for Military specifications it sounds like the crimp is required.

 

[Bart B.]

1stmar, once a bullet is distorted and/or unbalanced as it leaves the muzzle, nothing down range changes that until it's unbalanced/distorted by target impact. They may become more stabilized in flight but they're still unbalanced.

Sometimes, bullets leaving on the upswing of the muzzle axis will shoot more accurate at longer ranges because the slower ones leave at a greater angle that compensates for their greater drop. Faster ones leave sooner when that angles not as much but they drop less. This has been observed for over 100 years.

 

[1stmar]

Bart I'm not saying it changes, just that as velocity decreases and distance increases other factors in accuracy become more influential. Think of putting in golf, if there is a large slope on a short putt I can putt with enough velocity to putt through the break, but as my putt speed slows the break has more effect. If the bullet is deformed it may retain some semblance of accuracy until the velocity declines and bullet wobble has more effect on accuracy. For example if crimping provided more uniform start pressure and velocity, at short distances that may overcome bullet deformation, at longer distances bullet wobble has more effect and velocity drops deteriorating accuracy.

 

[Bart B.]

1stmar, the more a bullet's unbalanced/deformed, the greater the angle it will depart at relative to the muzzle axis. It's the centrifugal force caused by its heavy side that pulls it off the muzzle axis upon exit. Then it takes a normal trajectory to someplace down range near the aiming point.

Dr. Mann proved this in his tests back in 1907 that's well documented in his book "The Bullet's Flight from Powder to Target" first printed in 1909 and reprinted in 1980 with comments by Harry Pope (famous barrel maker back then) he wrote in his copy that was given to his son, Charles, whose pages were reproduced then.

Unbalanced bullets have a greater drag (BC) than balanced ones because they present more surface area to their trajectory axis. Compared to well balanced ones, they'll slow down faster and strike lower at the target than well balanced ones do. This has been proved in modern time of flight tests showing all bullets entering the clocking screens at the same velocity don't have the same time of flight. Perfectly balanced ones have less drag and loose velocity less than those with more drag.

If crimping provides more uniform start pressure and velocity, at any distance, I think the ammo was poorly assembled in the first place.

 

[Jim243]

While I can't say if crimped vs non-crimped is better or not, I do feel that crimping gives me a slightly longer burn time and a more stable bullet travel.

I use a Lee factory crimp die and only use a light crimp on my 223/5.56 reloads. Yes, it will deform the bullet even with a light crimp unless the bullet has a cannelure in it. But the question I always wonder about is how much more deformed is the bullet when forced into the line and groves of the barrel at 3,000 fps and heated up to seal the barrel? Does the slight deformation make any difference or is it a non issue once the cartage is fired??

Even though I crimp, I have found my reloads to be very accurate and give me sub-MOA groups. I do have to qualify that statement since all my shooting is with in 100 yards. What it will do at longer ranges I can not say.

Thanks
Jim

 

[Bart B.]

The question Jim always wonder about is how much more deformed is the bullet when forced into the lands and groves of the barrel at 3,000 fps and heated up to seal the barrel. Does the slight deformation make any difference or is it a non issue once the cartridge is fired?

I don't think so. Especially when the bullet is forced into the rifling, it's moving only a few hundred feet per second; probably less. Any force driving a bullet to 3000 fps in only a few thousandths inch of travel will swage it to the chamber throat diameter deforming it, then it'll be more deformed as its swaged back down to leade dimensions.

Bullets enter the rifling when pressure's enough to put the force needed to get the bullet moving in the case neck. If the force needed to push a 22 caliber bullet forward in the case neck is 25 pounds, pressure in the case needs to be 635 psi to make that happen. By the time the bullet's moved a few thousandths forward and engages the rifling, the pressure's up to a few thousand psi, but way below maximum. Bullets gradually go faster until they're fastest when leaving the muzzle.

Take a look at the pressure/velocity curve in the link below and you'll see very low numbers for both at the point the bullet enters the rifling:

http://ar15barrels.com/gfx/223plot.gif

 

[Jim243]

Interesting chart, by the time it hits 6 inches into the barrel, it is at over 40,000 psi and just under 2,500 fps.

Bart, are you saying there is no change to the shape of the bullet by the time it leaves the barrel??

Jim

 

[Bart B.]

Jim, only microscopic shape changes happen as the bullet enters the rifling as the bullet's moving pretty slow. If gently engraved by the rifling and uniform all the way around the bullet, it will still be perfectly balanced when it leaves the muzzle. This happens when those sub 1/10th MOA groups are shot at short range by the benchresters. It can also happen at 600 yards from 30 calibers when bullets are tested for balance before shooting them, then perfect ones are fired into 10-shot groups ranging from .7 to 1.5 inch (sub 1/8 MOA). And 24 to 30 caliber bullets going into 2 inch (2/5 MOA) groups at 1000 yards.

Barrels with uneven bore, groove and twist numbers tend to distort and unbalance bullets going through them. A perfect bullet tha's an inch into the rifling will be unbalanced by imperfect bores before it leaves the muzzle. Which is why we pay the extra bucks for a barrel maker to lap and measure the rifled bore until it's uniform enough to be perfect.

 

[HJ857]

just for the sake of clarity, it seems to me that the vast number of arguments over crimping is based on the Lee Factory Crimp Die usage.

This test, while a great test, did not use the Lee FCD.

I don't know if one is better or worse than the other but it sure does seem like an apples vs oranges issue. This thread is already going down the same old road and there's no reason for it.

 

[Bart B.]

HJ857, how right you are. But any crimping die yields the same results in the end and only the shape and dimensions of the case mouth and bullet jacket at its crimp vary. Plain, ungrooved or cannelured bullet jackets still get pushed into their lead cores regardless of what's used to do it. And it adds another variable to all bullets' cartridges.

Has anyone ever noticed that the best accuracy with crimped in bullets is not as good as the best accuracy with no crimp at all? Shame on me for even mentioning that.

Nobody got excited about the lack of crimp on 7.62 NATO or .30-06 match bullets twice the weight of .223 Rem bullets that are slammed just as hard into chambers and in magazines. Those bullets stayed in place very well.

When crimped in bullets win all the accuracy and score matches and set records doing it, I will consider crimping. Until then, I've got no interest.

Moderators, please shut this thread down; hard down with a lock on it.

 

[HJ857]

Good lord...

 

[steve4102]

When crimped in bullets win all the accuracy and score matches and set records doing it, I will consider crimping. Until then, I've got no interest.

You have enough interest in crimping to post dozens of comments on the evils of crimping, yet not enough interest to actually test out your own theories?

Give crimping with the LFC the old College try, test it, as the OP did with his taper crimp. Then report back with your actual data and results. I look forward to your results.

 

[Bart B.]

I have enough interest in not crimping[/B[ to post dozens of comments on the evils of crimping. Those with better measuring techniques than I have proved crimping's a bad thing to do if accuracy's important.

Some things are easy to figure out they're not good to do without actually testing to learn for sure. Just like cutting off my leg and not putting on a tourniquet; I've read that it's a bad thing to do so I won't try it to find out for myself.

I decided to learn how to use the right tools reloading ammo with the right techniques without crimping and get better accuracy than anyone's mentioned with crimped in bullets. Others choose not to nor learn how to do that.

 

[steve4102]

I decided to learn how to use the right tools reloading ammo with the right techniques without crimping and get better accuracy than anyone's mentioned with crimped in bullets. Others choose not to nor learn how to do that

If you have never tested the LFCD, how can you with a straight face say you get better accuracy from uncrimped rounds than you do with crimped rounds?

Pick the cartridge, I'll buy the LFCD and have it sent to you. I'll even supply the bullets if it's something I have in stock.

Then when you are all done testing, (with an open mind of course) cumon back and lets talk.