Crimping and loading for accuracy

[totalloser]

My experience wasn't a test per se, but the method is relatively scientific for making the conclusion. I found that my best accuracy was with the same powder charge crimped or not crimped. Powder charge did not change, bullet did not change, brass and primer did not change. 26.2 grains win748 pushing a Hornady 55 grain fmjbt with cannelure, #41 primer and mixed mostly military MG fired brass.

2" groups were shot in ideal circumstances at a different time, so that's the weak link in the determination. But I NEVER got 2" out of this rifle before no how. So I *think* it's a good demonstration.

My suspicion is that the crimp helps in my case because I am high volume loading, and the crimp's extra tension helps build a little pressure before releasing the projectile. The reason this helps in my situation is that I am using mixed brass of all sorts, and the pressure curve due to case volume and varying neck tension causes variations in bullet release which changes POI. One other factor is neck hardness. Neck friction will vary significantly depending on how work hardened the brass is. Building to a higher pressure before release theoretically should even this out some. Also, building to a higher pressure is *thought* by some (including me) to help prevent uneven release from the brass.

All other variables are controlled since *every* operation is automated in my process. Trim is automated in station 2 on my press.

Again, I added this process not for accuracy, but to prevent bullet set back.

Using sooper dooper match tolerance data to prove that it works in a sloppy autoloader is not the best argument. Using that logic, we should be neck sizing only which we know will not work. I mean really folks, this is .223 how many .223 are going to be shot in a 1/4 moa match grade bolt action?

[skizzums]

i was suprised to see on that test that crimping reuced velocities and energy, i was under the impression that you were slightly increasing pressure when you crimped

i dont crimp anything that i am not required too(357), if you take accuracy out of the equation, is there any onther benefit to crimping? i know a slight crimp helps a friends kel-tec pf9 feed better, does crimping often feed better? do any have issues wth 223 backing out when in the magazine uncrimped? i just ask because i reaaly just dont understand why people crimp, besides looking a little prettier, but to me it just adds another step with no calculatable advantages, but im no seasoned reloader or benchrester

do you crimp only for accuracy advantage or are there other reasons as well?

[skizzums]

i didnt see the poster right above mine when i started that, but that seems to make some sense to prevent the bullet from being pushed in when loading into the chamber

i would like to see people re-measure oal after chambering w/o crimp, see if its changes in a variety of guns

[steve4102]

Originally Posted by skizzums

i didnt see the poster right above mine when i started that, but that seems to make some sense to prevent the bullet from being pushed in when loading into the chamber

i would like to see people re-measure oal after chambering w/o crimp, see if its changes in a variety of guns

Actually the bullet coming out of the case is more like it.

From the Experts at Sierra.

Neck Tension

When we stop to consider the vigorous (read, downright violent) chambering cycle a loaded round endures in a Service Rifle, it becomes pretty clear it suffers abuse that would never happen in a bolt-action. This is simply the nature of the beast. It needs to be dealt with since there is no way around it.

There are two distinctly different forces that need to be considered: those that force the bullet deeper into the case, and those that pull it out of the case. When the round is stripped from the magazine and launched up the feed ramp, any resistance encountered by the bullet risks having it set back deeper into the case. Due to the abrupt stop the cartridge makes when the shoulder slams to a halt against the chamber, inertia dictates that the bullet will continue to move forward. This is exactly the same principle a kinetic bullet puller operates on, and it works within a chamber as well. Some years ago, we decided to examine this phenomenon more closely. During tests here at Sierra’s range, we chambered a variety of factory Match ammunition in an AR-15 rifle. This ammunition was from one of the most popular brands in use today, loaded with Sierra’s 69 grain MatchKing bullet. To conduct the test, we chambered individual rounds by inserting them into the magazines and manually releasing the bolt. We then repeated the tests by loading two rounds into the magazine, chambering and firing the first, and then extracting and measuring the second round. This eliminated any potential variation caused by the difference between a bolt that had been released from an open position (first round in the magazine) and those subsequent rounds that were chambered by the normal semi-automatic operation of the rifle. Measuring the rounds before chambering and then re-measuring after they were carefully extracted resulted in an average increase of three thousandths (0.003") of forward bullet movement. Some individual rounds showed up to seven thousandths (0.007") movement. Please bear in mind that these results were with factory ammunition, normally having a higher bullet pull than handloaded ammunition.

To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension.

Link.
http://www.exteriorballistics.com/re...sgunreload.cfm

[totalloser]

Wow, I never would have guessed it would be so much! I was more afraid of bullet setback from an accidental double chamber, or a stubbed nose on the way in.

FWIW I think the information regarding NOT crimping does apply nicely to bolt guns though. If I were loading for a bolt gun and wanted accuracy, it would be fire formed brass neck sized only with no crimp and bullet seated to just barely kiss the rifling.

[Bart B.]

If those 69-grain bullets slipped forward from chambering impact, it's my opinion the neck tension (release force in the industry) was too low. It could easily been remedied with smaller case mouth diameters on the cases ready for bullet seating but that must not have been a consideration as some other agenda was the objective.

I've measured 7.62 NATO M852 and M118 match ammo with at least 20 to 30 pounds of bullet release force (MIL SPEC values) after slam-chambered in semiauto fired Garands and they don't shift forward at all. Nor has any of the several commercial .308 Win. match ammo's bullets from 168 to 190 grains in them without any crimp whatsoever. My own handloads for Garands had about 20 pounds of bullet release force for the bullets and they didn't shift at all in chambering.

It's easy to measure bullet release force with all sorts of seating/crimping things done. Compare their forces to the nearest ounce and see what method has the greatest spread in release force.

As I mentioned before, not crimping arsenal match ammo improved its overall accuracy. The asphaltum sealer gripped the bullet hard and consistantly enough that bullets stayed in place and shot the most accurate.

Few people realize that their seated bullets in rimless bottleneck cases have about a .003" spread in their jump to the rifling in spite of fixed/repeatable distances between the seater's contact point on the bullet to the case head. Maybe those with less release force will end up shifting when chambered will all have the same jump distance to the rifling.

[Slamfire]

Amazing, Slamfire has been posting evidence of his incompetence for years and continues to do so even after it's been pointed out many, many times that he grossly overcrimped those bullets.

Follow the Lee Factory Crimper instructions, form a cannulure, and your bullets will look like those.

I know it is hard to read instructions. All those big words and expansive concepts.

[marine6680]

If those 69-grain bullets slipped forward from chambering impact, it's my opinion the neck tension (release force in the industry) was too low. It could easily been remedied with smaller case mouth diameters on the cases ready for bullet seating but that must not have been a consideration as some other agenda was the objective.

Your dismissal of the results so readily shows more agenda/bias than the article.


Seeing as this info comes from Sierra... I don't see why they would have any agenda to push crimping.

Here is the rest of the section about neck tension. (whether it was not included above due to brevity, or other reasons, I can not say)

To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension. The first option, crimping, brings up some other issues that can be troublesome. In general, crimping degrades accuracy. Most match bullets are not cannelured (which also seriously damages accuracy potential), a requirement for correct application of most crimps. Still, there are taper crimp dies available from most of the major manufacturers. Lee offers their “Factory Crimp” die as an alternative, which seems to be one of the better options for those bullets without a cannelure. That having been said, crimping is still, at best, an occasionally necessary evil. Avoid it if at all possible.

The other—and in our opinion, better—option is increased neck tension. This, in turn, leaves us with two more options depending on what type of equipment you’re using. The object of either is simply a tighter grip on the bullet. Using conventional sizing dies, (i.e., those utilizing an expander ball) this is accomplished by reducing the diameter of the ball itself. This can be done by chucking the expander/decapping rod into a drill and turning it down slightly with fine emery cloth or a stone. The goal here is to decrease the diameter two or three thousandths (0.002" to 0.003") under bullet diameter. This is a trial and error process, and must be done slowly. The end result is an expander ball that opens the case neck up somewhat less than the as-issued item. This, in turn, increases the grip of the case neck on the seated bullet.

Basically, crimping isn't prefered but is effective in keeping bullets seated well. Increasing neck tension without crimping is prefered by Sierra when the bullet has no canelature.

[Mike38]

Slamfire opined: ….the idea that crimping improves accuracy is, of course, a creation of corporate advertizing.

If you don’t mind me asking, how do you explain me getting better results with crimped rounds?

Though I said my test was “unscientific” it can’t be disregarded. I loaded 20 identical loads, then crimped half of them. I randomly grabbed the 10 rounds to crimp, to make the test as fair as possible. Then shot four, five round groups. I repeated this three times. 60 rounds total fired. I came up with around 10% better accuracy with the crimped rounds. Granted, 10% isn’t earth shattering, but it’s nothing to discredit.

It works for me and I plan to keep doing it. May not work for you, but that's okay. Yea, it adds some time to the reloading prossess, but not that much. I’m able to make a $400 rifle / scope set up shoot 0.44 inch groups at 100 yards. I’m happy with that.

[4runnerman]

Mike38- I do not doubt your loads,crimped shoot more accurate than un crimped. My point is if you started your load work up again with out crimping,I think you would find a even more accurate load. With proper neck tension there is no need to crimp. There is a reason top shooters in the world do not crimp.
They have discovered there is no need for it and they shoot more accurate.
But as you stated also-If it works for you then that is great. Can't argue with those groups- Good shooting

[totalloser]

Using the bullet glue as a comparison is iffy. How many handloaders are gluing their bullets in? That justification sounds pretty weak. I think I trust a post quoting a manufacturer like Sierra.

As to buying corporate advertising, Lee has some pretty blatant product promotion- irritating, but I have so far found few to be exaggerated, or not by much. And the factory crimp die is a whopping ten bucks. If unhappy with it, it's not like it's a bank buster. Besides, how many munitions processing manufacturers aren't corporate?

I wouldn't push someone to get the FCD, I think it's not necessary, but there are benefits to be had for gas guns. And possibly for any other rifle if using full length sizing. If you have an open station, I would recommend considering getting it and giving it a try. That's what I did since #5 on my press was open. It has not been removed since, but if I had a four station press *I* would not personally bother a second pass just to factory crimp.

Getting torches and pitchforks out against the FCD seems out of proportion.

[Bart B.]

Mike38, depending on how one tests ammo for accuracy and interprets the results, any given load assembly technique can produce the results closest to the objectives set by the reloader. Consider the following.

Two loads are compared shooting five 5-shot groups with each. One load produces groups ranging from 3 to 8 units of measure and the other from 4 to 9. The average of the 3 to 8 unit series is 5 and the 4 to 9 unit series is 6.
If average group size is the determining criteria, then the 3 to 8 series is best.

Plotting the composite of all five groups in each series aligned to their aiming point, the 3 to 8 unit series measures 11 units extreme spread for the 25-shot composite and the 4 to 9 unit series measures 10 units for its 25-shot composite. If the size of the group that all 25 shots produced is the determining criteria, then the 4 to 9 unit series is the winner.

If one calculates the mean radius of all 25 shots in the composite group from that groups' center, either one may have the lowest number, but that one may also have the biggest extreme spread. It's normal for the extreme spread of a many-shot group to be anywhere from 3 to 6 times the mean radius.

I prefer to use the extreme spread of at least 20 shots fired in a group for accuracy measuring. That has at least 80% statistical confidence in representing what all rounds of that load will produce.

Marine6680, I don't think I had any agenda in my comments. I didn't dismiss the results, but instead explained how they could have been changed to zero. Bit I understand why one might think I had one. Thanks for posting the rest of that article and I agree with your comments about Sierra; it tells the rest of the story which in important.

Lee's instructions do not mention the fact that commercial match ammo does not have crimped case mouths on bullets and doesn't mention any accuracy difference between what their FCD produces compared to what that match ammo does. Lee does state that using their FCD will indent non-cannelured bullet jackets and unless one's case necks are turned to exact uniform thicknesses, the amount of indentation won't be uniform across all bullets and probably not uniform all the way around the bullet. This is why Sierra Bullets does not crimp their 22 caliber 77-gr. HPMK cannelured bullet when testing them for accuracy from their reloaded cases shooting them; they know too well than crimping them, even the slightest amount by any means, reduces accuracy.

In 1971, M16's were first allowed in the DCM service rifle matches at the Nationals. The Navy, Army and Marine Corps teams handloaded all their ammo with Sierra 52-gr match bullets. Talking with Army and USMC team members then, I learned they checked their handloads for bullet shift in both chambering and impact from magazine setback in recoil. Sierra Bullets had told us not to crimp those bullets but instead use enough neck tension to keep them in place. I don't know the process the other teams used but the Navy team used new Remington .223 primed cases and beveled their mouths just enough to let bullets seat without scraping off jacket material. The Clerke barrels in them shot about MOA at 300 yards when tested and that's what the other services got with their loads.

[Slamfire]

If you don’t mind me asking, how do you explain me getting better results with crimped rounds?

Though I said my test was “unscientific” it can’t be disregarded. I loaded 20 identical loads, then crimped half of them. I randomly grabbed the 10 rounds to crimp, to make the test as fair as possible. Then shot four, five round groups. I repeated this three times. 60 rounds total fired. I came up with around 10% better accuracy with the crimped rounds. Granted, 10% isn’t earth shattering, but it’s nothing to discredit.

What makes your results definitive?


I would be interested in more information:

Distance

Rifle

Test set up. That is, machine rest, sand bags, elbows...

Type of bullet, powder, cases, weighed charges or not?

Uncrimped group size in inches

Crimped Group size in inches

[marine6680]

I think setting the FCD to just touch the case neck and give a slight squeeze, would not crimp the rounds, but would ensure even case neck tension and a square seating of the bullet... This might be beneficial without deforming the bullet... or it could do nothing.

I have been using some H4198 for my plinking rounds, as it was all I could find at the time. Many claim cycling issues due to the fast burn rate,but I have had none, even at starting loads. Crimping may be why.

I have since located 2lb of H335, 2lb of BLC-2, and a lb of IMR 8208... Figured it would be good to try several types of powder, and if they don't do well, they will all work for plinking loads. (I found a few 8lb jugs of CFE223 for $150 local, but the fiance said no deal on spending the cash right now)


As far as the bullets I got, I only have a 200yd range reasonably close, any farther is too far to drive. So I got some 52gr HPBT from Nosler. Seemed a good choice for 200yds max. (also would like the round to be similar to standard 55gr loads for general practice and fun) Would others agree? (next would be some from Sierra, to see which is liked best)

[HJ857]

i would like to see people re-measure oal after chambering w/o crimp, see if its changes in a variety of guns

I have a feeling that most folks dismiss this idea simply because they chamber and then shoot. If you chamber a round once, movement of the bullet is not something you need to worry about.

However it's a different story if you're repeatedly chambering and unchambering a round, such as in an active carry weapon. Rifle or pistol. Crimped or not.

It's a question that's very valid and one that anyone that carries a weapon should consider.

[HJ857]

As far as the bullets I got, I only have a 200yd range reasonably close, any farther is too far to drive. So I got some 52gr HPBT from Nosler. Seemed a good choice for 200yds max. (also would like the round to be similar to standard 55gr loads for general practice and fun) Would others agree? (next would be some from Sierra, to see which is liked best)

Another bullet to consider strongly is the 53 grain Vmax. Check out it's ballistics. You'll gonna find that it outperforms or matches ALL bullets out to 500 meters in every category, but it has to be run pretty fast to do it.

[skizzums]

okay, i guess i can just grab my ar and stop being lazy and figure out my own opinion on the subject
i was raeding all this too KEEP me from having to think for myself, ill report back later WITH PICS!!!

[William T. Watts]

I'm not going to crimp anything unless it goes in a tubular magazine (Marlin 30/30 or similar rifle), 1911 45 Acp pistol or M-1 Garand. For my needs these simple rules work well for me, if I can shoot 1 MOA most of the time I'm good to go. I know my rifle is capable of shooting MOA, at my age (71) frankly some of the time I'm not up to it, I'm not going to worry about it because I no longer hunt anyway. I do visit the local range and shoot for the heck of it plus it gives me something to do in my spare time!! I will crimp for the above reasons only, that's good enough for me! William

[marine6680]

I seen those, and the A-max as well. Looking at many options.

[Bart B.]

Marine6680, a slight crimp of the case mouth onto the bullet will groove its waist a couple ten-thousandths of an inch; maybe more. There's no easy way to find out if its the same depth all the way around. You could measure it with a micro-optical comparitor to see exactly how deep it is. The thinner the jacket plus the softer the jacket and lead core, the more the bullet's waist will be grooved.

Bullet companies learned back in the 1950's that a .0002" spread in 30 caliber bullet out-of-round measured on its heel (base-body juncture) was enough to cause accuracy problems. So they started making hollow point match bullets which ended up with more uniform and consistant heel diameters (no longer egg-shaped) on their best bullets. Sierra's 30 caliber 168-gr. HPMK was the first one made in calibers larger than 22. Their 22 caliber match bullets were hollow point as were all the custom ones hand made by benchresters at the time.

[skizzums]

http://s998.photobucket.com/user/nwa...31857229637936

i did five chambers to each round, i was suprised to see the factory loads didnt budge, my rifle is very new and nicksthe bullet going up the ramp

i dont own the FCD to test the crimp on a reloaded

results for just one chambering on a no-crimp 2,220-2,195, thats exactly the same as five chambering

im not the one to do the accuracy testing, thats to be left to the professionals, but setback is definetly a reality w/o a crimp, i still am not interested in doing it though

[marine6680]

Eh... I'll test and see what works best for my rifle.

[NWPilgrim]

Not to be too elementary, but practically every reloading manual I have including the ABC's of Reloading, state that crimping rifle bullets with a cannelure will have a slightly detrimental effect on accuracy. Hornady and Barnes don't really discuss it, but Sierra, Nosler, Lyman, Speer and Hodgdon #26 (the old hardback) all recommend not crimping unless needed and then only with cannelured bullets.

They vary a bit on what constitutes "necessary" crimping but if crimping is done it is done to secure the bullet at the expense of accuracy and should not be done on bullets without a crimp. Not one manual except Lee's suggests crimping on rifle bullets without a cannelure, nor that crimping is for any purpose other than securing the bullet in special circumstances.

We harp on beginners to "read the manual" and then we have belabored discussions on a pretty straight forward instruction by all the reloading manuals? This is not just a matter of "only for beginners" because as Bart has pointed out that expert precision competitors do not crimp either.

If you find crimping somehow improves your groups then you should consider that exceptional and unique results that are not typical for the great majority of experts both in precision shooting competition and in the manufacturing of bullets and reloading equipment.

I use Lee dies extensively so I have no beef with Lee. But in this instance I think Lee's advice is off. Maybe he had some promising results with crimping non-cannelured rifle bullets, but that is not what the rest of the shooting industry has found.

[Bart B.]

NWPilgrim, good post.

I don't know of anyone reloading rifle ammo with crimped case mouths onto or into bullets by any means that gets no worse than 1/3 MOA accuracy at 100 yards. By that, I mean the biggest group is no more than 1/3 MOA. And darned few, if any, get no worse than 1/2 MOA.

[steve4102]

Hornady and Barnes don't really discuss it, but Sierra, Nosler, Lyman, Speer and Hodgdon #26 (the old hardback) all recommend not crimping unless needed and then only with cannelured bullets.

Not really. Although Sierra is defiantly not a fan of crimping, they do find it a "Necessary Evil" when loading for semi-autos. Even with non-cannelured bullets.

From Sierra.

To counteract this tendency, the semi-auto shooter is left with basically two options: applying a crimp or increasing neck tension. The first option, crimping, brings up some other issues that can be troublesome. In general, crimping degrades accuracy. Most match bullets are not cannelured (which also seriously damages accuracy potential), a requirement for correct application of most crimps. Still, there are taper crimp dies available from most of the major manufacturers. Lee offers their “Factory Crimp” die as an alternative, which seems to be one of the better options for those bullets without a cannelure. That having been said, crimping is still, at best, an occasionally necessary evil.