View Full Version : Cannelure and Accuracy
Does a cannelure affect accuracy in any way, when you don't apply a crimp?
I usually don't crimp rifle bullets in a bolt gun, unless it's a magnum type round. But if one has some BTHP bullets, with cannelures, would there be a decline in accuracy compared to another BTHP without the cannelure?
Coal Dragger
05-29-13, 02:43
I've never noticed any difference in practical accuracy between a cannelured bullet and one without a cannelure. I've loaded plenty if 77gr Matchkings with and without and they all shoot the same for me.
You might see a difference in a bench rest rifle but short of that I wouldn't sweat it too much.
ICANHITHIMMAN
05-29-13, 06:38
I would not crimp any of my bolt gun rounds, its just not needed. I don't think you will see any degradation in accuracy, bullets with a canalur typically are not high end accuracy driven projectiles.
Canellures do effect accuracy. It was one of the reasons sierra did not want to add a canellure to the matchking for mk262 mod1. The canellure they did use is almost non existant.
The debate over crimping, and whether it degrades or enhances accuracy will go on forever. Some claim crimping causes accuracy to be enhanced, while others state it degrades it. If you have good neck tension I would not worry about crimping.
Nosler and Sierra's cannalures on their 77s, as jstone noted, are practically not there at all. The right amount of neck tension is key... if you get that with or without a crimp, you'll be fine.
As far as NOT crimping into a cannalured bullet. The in itself won't hurt anything.
The debate over crimping, and whether it degrades or enhances accuracy will go on forever. Some claim crimping causes accuracy to be enhanced, while others state it degrades it. If you have good neck tension I would not worry about crimping.
From my short bus understanding (jstone and markm know way more than me), crimping has benefits in bullet retention due to rough handling and has some benefits with feeding in auto-loaders. For benchrest/bolt gun accuracy, there is no "rough" handling so it isn't needed. For rounds that are bouncing around in a mag in the bed of a truck, it helps to keep things where they are. For feeding, the crimp should just be enough to slightly round the edge of the case neck so you don't have any notchy edges from sizing (or powder expansion for pistol rounds).
Whether crimping is more accurate or not is probably subjective, but use depends on application. If you shoot a canalured/crimped SMK through a scoped bolt gun from the bench, you will likely achieve better accuracy than a non-canalured/non-crimped SMK from an AR with an Aimpoint that been banged on a rock. Is it the projectile/loading prep or the platform/application? I guess it depends on how you define accuracy and what your expectations are.
If you're reading on crimping from materials provided by any die manufacturer, the uniform claim to nearly everything they sell is always to make your round more accurate. This seems to make no difference who the manufacturer is, the claim is always the same. So grain of salt is mandatory.
There's so many factors in play. I believe a guy who gets good results with crimping just as much as a guy who's killin it with no crimp.
You're brass, resizing equipment, process, etc... all play a part in what neck tension you get. There's NO hard rule one way or another.
ICANHITHIMMAN
05-29-13, 14:15
Lets note that crimp and neck tension are not the same thing.
crimping helps to increase muzzle velocity but not always accuracy. The crimp will increase starting pressure and could lead to a more consistent powder burn, in a bullet with a cannelure.
Lets note that crimp and neck tension are not the same thing.
True. Neck tension is there before a crimp is introduced into the equation.
crimping helps to increase muzzle velocity but not always accuracy. The crimp will increase starting pressure and could lead to a more consistent powder burn, in a bullet with a cannelure.
I tried testing this in my younger years, and could find NO difference.
I had a cheapo chrono. But at that time, there was no difference in No crimp, taper crimp, and Factory crimp on 55 gr 223.
It might be something I try again this summer when we're stuck on the square range.
You guys are right about there being a lot of variables. I'd never thought about the cannelure much, and when I saw a good deal on some hunting bullets, with the cannelure, it got me to thinking.
Thanks for the responses!
Coal Dragger
05-29-13, 14:41
I can report that a heavy crimp applied to some rounds is very helpful for consistent accuracy, ignition, and feeding. Namely in your big bore sporting rounds where recoil will bang around the rounds and act as a bullet puller. This also applies in big bore revolvers, I once tried getting away with a light roll crimp on some .454 Casull ammo I loaded, not only did I not get good accuracy checking only 3 shots into the cylinder showed the remaining 2 rounds were walking out of the cases and I was getting inconsistent ignition. Probably would have tied up the cylinder if I kept shooting.
Lets note that crimp and neck tension are not the same thing.
crimping helps to increase muzzle velocity but not always accuracy. The crimp will increase starting pressure and could lead to a more consistent powder burn, in a bullet with a cannelure.
Neck tension and crimping are definately different. I rely on neck tension for everything accept revolver and tube fed firearms. I would also use a crimp if I had a big magnum.
I think a good crimp can help with consistent ignition, but I have not seen an increase in velocity. I have never trusted the chronos I have had so there may have been an increase in velocity.
The thing about crimping and canellures is you will get different responses from nearly every loader you ask. I have loaded batches of 223 with and without a crimp. Using bullets with and without a canellure. All rounds were fired on the same day. There was no real difference that I could see.
I would also use a crimp if I had a big magnum.
We don't on the 300 WM. But they all have beefy barrels and brakes. Never a problem with those.
The one sucker that might need it... but we never checked.. is the 338 WM that Pappabear has. No brake... not fun to shoot. Next time he brings that beast out, I'll take note.
I tried testing this in my younger years, and could find NO difference.
I had a cheapo chrono. But at that time, there was no difference in No crimp, taper crimp, and Factory crimp on 55 gr 223.
It might be something I try again this summer when we're stuck on the square range.
I tested the "crimp/no crimp" just this past weekend & I didn't see any difference in velocity either.
We don't on the 300 WM. But they all have beefy barrels and brakes. Never a problem with those.
The one sucker that might need it... but we never checked.. is the 338 WM that Pappabear has. No brake... not fun to shoot. Next time he brings that beast out, I'll take note.
Any opinions if I should crimp loads for my Mark V 300 WBY? I'm assuming so?? I haven't even begun to dabble in that yet but it would be good to why/why not a head of time.
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Any opinions if I should crimp loads for my Mark V 300 WBY? I'm assuming so?? I haven't even begun to dabble in that yet but it would be good to why/why not a head of time.
No experience... but I recently saw an article in handloader about the WBY cartriges. I could scan a pdf of it to you if you want.... it's at home, but it might have good info.
No experience... but I recently saw an article in handloader about the WBY cartriges. I could scan a pdf of it to you if you want.... it's at home, but it might have good info.
That would be great if you could. You had mentioned that in a post to me awhile back. I had tried looking it up but it appeared that, without a subscription, I could only view a preview of the article.
Thanks, I appreciate it.
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PM me an email address. I'll try to remember to get it tonight and scan it at work tomorrow.
PM me an email address. I'll try to remember to get it tonight and scan it at work tomorrow.
Will do. I'll try to get the PM thing to work on Tapatalk, otherwise it'll be after work this aft.
Thanks again
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We don't on the 300 WM. But they all have beefy barrels and brakes. Never a problem with those.
The one sucker that might need it... but we never checked.. is the 338 WM that Pappabear has. No brake... not fun to shoot. Next time he brings that beast out, I'll take note.
The magnum area is a week spot of loading for me. So I am rather in experienced with magnum cartridges. The biggest round I load is 30-06, and it does not get a crimp ever. It is also a semi auto, and I have never had any problems.
The magnum area is a week spot of loading for me. So I am rather in experienced with magnum cartridges.
Oh it's real fun. :rolleyes:
I mean.... Who doesn't love a cartridge where you get 90 rounds per pound of powder?? :p (especially in this market)
Coal Dragger
05-30-13, 16:17
The worst offenders for bullet tip damage, or bullet set back, or bullet pull (depending on how well the magazine is designed) are the big bore magnums in sporting weight rifles.
A well designed box magazine for a big bore sporting rifle, or even a light weight that is going to kick a lot, will have a recoil shoulder stamped, molded, or machined into the magazine. This shoulder will contact the shoulder of the case and prevent too much forward movement of the loaded round(s) under recoil. This is good because you don't end up damaging the bullets if they are soft points and also you don't have them driven back deeper into the case risking chamber pressure spikes.
The downside of a magazine that controls fore and aft movement is that at a certain point of peak recoil and recoil velocity with some calibers using heavy bullets, that kick hard and fast, you can get bullet pull instead. Some of your slower burning magnum rifle powders like to be packed in pretty tight for consistent ignition and accuracy. So you will need a crimp. I've never seen this problem with an average .300 Winchester or .300 Weatherby in a standard weight rifle, but it might be possible with a real light weight, particularly in .300 Winchester because the neck is kind of short and doesn't have a lot of potential for neck tension. Once you start playing with bullets of 250gr and up at magnum velocities and recoil levels in sporting weight rifles without brakes, I would be applying a crimp.
Then you have the factory sporting rifles that just have a magazine with no provision at all to control fore and aft cartridge movement under recoil. In most calibers this shouldn't be a big deal other than damaging the tips of soft point hunting ammo. The heavier magnums once again are going to be a pain in the ass and will need a crimp since the whole loaded round will be slamming into the front of the magazine under recoil hard enough to potentially push the bullet back into the case.
A lot of reloading manuals will give a good indication of what calibers are going to be sell served with a firm crimp for the above stated reasons.
I have an H.S. Precision Lightweight in 300 WSM, which weighs 5.5 pounds, without the scope. If you want some real fun I'll let you shoot it. When we chronographed some loads, I had my son shoot it. He wasn't pleased.
I crimp the bullets, which don't have a cannelure, to about a medium level I guess. I haven't noticed any issues with bullet set back.
Coal Dragger
05-30-13, 22:19
I have an H.S. Precision Lightweight in 300 WSM, which weighs 5.5 pounds, without the scope. If you want some real fun I'll let you shoot it. When we chronographed some loads, I had my son shoot it. He wasn't pleased.
I crimp the bullets, which don't have a cannelure, to about a medium level I guess. I haven't noticed any issues with bullet set back.
Yeah I'd be crimping too with a little lightning rod like that. I imagine long practice sessions must be very pleasant.... ha ha ha.
That's the kind of rifle you hope to sight in with as few rounds as possible.
When I work up loads for it I have to use my Shooter's Ridge rifle rest. Of course you then need to shoot a few without it, for a true field zero, once you have found a load you like. Then I try not to forget the thickest PAST pad they make! :(
Coal Dragger
05-31-13, 01:37
I'll bet sighting in from prone must be a real treat, especially if you're like me and tend to creep the stock from prone. I've done that once or twice with my standard weight Cooper M52 in .280AI and been rewarded with a little love tap from the scope, which is disconcerting enough. Can't imagine a rifle and scope combo that weighs 3 pounds less would be nearly as forgiving. As it is I'm glad that Swarovski equips their scopes with a nice rubber bumper on the ocular lens housing. ;)
I have an H.S. Precision Lightweight in 300 WSM, which weighs 5.5 pounds, without the scope. If you want some real fun I'll let you shoot it.
You couldn't PAY ME to shoot that. The lightweight 300 WSM that Pappabear had was the most miserable gun in the world to shoot. :(
ICANHITHIMMAN
05-31-13, 10:01
That would be great if you could. You had mentioned that in a post to me awhile back. I had tried looking it up but it appeared that, without a subscription, I could only view a preview of the article.
Thanks, I appreciate it.
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Its not needed, wby factory rifles are known for having a lot of free bore also seating a bullet deeper REDUCES pressure .
ICANHITHIMMAN
05-31-13, 10:11
also you don't have them driven back deeper into the case risking chamber pressure spikes.
As a general rule the deeper you seat your bullet the lower the pressure will be, however if you seat the bullets so deep that you have pushed the bullet threw the neck all bets are off.
http://www.barnesbullets.com/resources/newsletters/september-2007-barnes-bullet-n/
The pressure seems to fluctuate between highs and lows as distance from the lands becomes larger. For example, as the distance moved to 0.100,” pressure increased with some of the cartridges, particularly the .300 WSM and the .30-06 Springfield. Some of the cartridges had pressure increases with either the ball or extruded powders but not both. This was true with the .300 RUM and the .300 Win. Mag.
As can be seen in the chart below, pressure change was not a constant for this experiment and results were highly surprising for several of the cartridges. Keep in mind, this was not an average of tests, but the result of a single test per cartridge.
We tried to work up loads that would be within the 96% range of the SAAMI maximum pressure rating for each cartridge. This proved to be somewhat tenuous, as the pressures would drop off differently for each cartridge.
*Note: beginning on the left with shot No. 1, distance is closest to the lands, and ends with shot No. 5 on the right, which was seated at the greatest distance from the lands. This applies to all charts.
Figure 1: Pressure Change Versus Changing Distance Off The Lands
VELOCITY CHANGE
When we began this experiment, we expected velocity to drop off as the pressure decreased. This seemed a valid, objective view following a law of physics that says forcing an object in one direction results in an equal force being exerted in the opposite direction.
Notice that velocity for both powders fluctuates, almost mirroring the pressure curves seen in the above chart. If pressure increases, velocity usually follows suit. Thus if the pressure drops, so does the velocity. However, this was not always seen in our tests because of the randomness of primer ignition and powder burning rate. We note here that when testing bullets for our regular production, we may fire a thousand rounds to ensure the bullet performs optimally, and this effect of reduced pressure and higher velocity has been seen quite often during these tests.
As the distance increases and the pressure drops, velocity drop may be minimal or non-existent. The randomness of primer ignition and powder burning rates is one of the few things we cannot account for. While shooting enough test groups to determine the overall average would be interesting to try, the average reloader would not be able to duplicate our tests.
As seen with the .300 Weatherby Magnum, the pressure drops from 64,900 psi to 63,100 psi — a change of 1,800 psi. Yet the velocity drops from 3128 fps to 3114 fps, a change of only 14 fps. Another example of this is the 308 Winchester loaded with the ball powder. Here the pressure drops from a high of 64,800 psi to 62,700 psi, a change of 2,100 psi. The velocity drops from 2639 fps to 2637 fps, or only 2 fps.
Figure 2: Velocity Change Versus To Change Of Distance Off The Lands
ACCURACY CHANGE
We wanted to find out how accuracy would be affected by changing the distance off the lands. For optimum accuracy, our standard is normally 0.050” off the lands for the best accuracy. The test did show how each rifled barrel reacted to the change.
As we documented our accuracy, it became apparent that when bullets were seated close to the lands, accuracy was good. With some cartridges, we noticed that accuracy would fluctuate as we moved the bullet away from the lands. As the bullets were moved farther from the lands, some cartridges became less accurate. Surprisingly, as the bullets were moved even farther away, the accuracy would improve again.
Figure 3: Accuracy Change Versus Change of Distance Off The Lands
In the overall perspective, we can say that generally pressure will decrease as the bullet is moved farther from the lands. Generally, we can say that velocity will decrease as pressure decreases the farther the bullet is seated from the lands. And generally, we can say that accuracy is depending on bullet placement from the lands dependent on the rifle the bullet is fired from.
In comparing overall accuracy between ball and extruded powders, the table below lists the average accuracy for the five groups over the full spectrum of distances the bullets were seated off the lands. As seen by the results, the differences between the powders are negligible.
Type/Cartridge
308
Win
30-06
Springfield 300
WSM 300
Win Mag 300
Wby Mag 300
RUM
Ball Powder
0.5
0.7
0.5
1.0
0.8
0.7
Extruded Powder
0.6
0.6
0.7
0.9
0.6
0.8
http://www.hornady.com/ballistics-resource/internal
Damn it! I forgot to get that Article.
I'll put a note in my stuff right now. :rolleyes:
Damn it! I forgot to get that Article.
I'll put a note in my stuff right now. :rolleyes:
:D
No problem. I'm in no hurry.
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Its not needed, wby factory rifles are know for having a lot of free bore also seating a bullet deeper REDUCES pressure .
Thanks
I thought seating them deeper increases the pressure... or is that only in certain situations?
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Coal Dragger
05-31-13, 15:58
Seating a bullet deeper within "normal" specs should reduce or have few affects on pressure. Having the bullet hammered deep into the case on the other hand can be bad and increase pressure. Bullet pull that leaves the loaded round too long and jammed into the rifling will result in even more pressure.
Gotcha, thanks. In the case of pistol loads though, it's more likely to increase the pressure because there is a greater chance of the bullet contacting or compressing the powder. Correct??
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Coal Dragger
05-31-13, 16:11
You couldn't PAY ME to shoot that. The lightweight 300 WSM that Pappabear had was the most miserable gun in the world to shoot. :(
While I was in college I worked for a large retailer of firearms and outdoor gear, and in the store we had a 100 yard rifle tube. Every deer season those of us who actively shot on the range or were known to be decent shooters, would get tasked with sighting in customer rifles in the tube. Getting assigned to this duty, and shooting hundreds of different rifles and scope combinations, and calibers helped me develop a true hatred of lightweight magnum caliber rifles. This was before the advent of the Caldwell Lead-Sled, so we just got to use a PAST pad and hope for the best.
I was also able to witness en-mass the odd notions that many of my fellow hunters have on what constitutes a good deer rifle, some of the combinations of rifle type, caliber choice, optics, and mounts would have been pretty amusing; if I were not expected to make them work right and shoot acceptably. :suicide2:
Coal Dragger
05-31-13, 16:22
Gotcha, thanks. In the case of pistol loads though, it's more likely to increase the pressure because there is a greater chance of the bullet contacting or compressing the powder. Correct??
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Potentially. Some powders don't mind being compressed even in a pistol, many of the loads I generate for .454 Casull are heavily compressed using H-110 as powder. I'm talking about loads so compressed that if you forget to full length resize the case, the powder will push the bullet back out after seating. I crimp in a separate step from seating and this has happened to me a few times working with new brass.
In a rifle, unless it recoils so hard that the bullet is being driven deep into the case, I wouldn't worry about over pressure too much. If you're shooting a .375H&H or some other big rifle made for flattening large bitty-scratchey-stompy animals and you're getting bullets driven into the case your magazine is not controlling fore-aft movement and it is a bad design. Plus you should be crimping the hell out of those calibers anyway because even in a good magazine that controls movement, you'll more likely than not get bullet pull from the combination of big recoil, and heavy bullets that want to resist that rearward inertia.
In more run of the mill hunting rifles etc. accuracy might go to hell if you get mild bullet set back, and soft point ammo might be damaged a bit but I don't think you'll have safety issues.
Good info, thanks. The rifle in question is a Weatherby Mark V Deluxe 300WBY. The cost of factory ammo is pretty high so I'm getting ready to start reloading for it. Just want to make sure I've got my shit straight.
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Coal Dragger
05-31-13, 17:02
Good info, thanks. The rifle in question is a Weatherby Mark V Deluxe 300WBY. The cost of factory ammo is pretty high so I'm getting ready to start reloading for it. Just want to make sure I've got my shit straight.
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I wouldn't sweat it with that outfit. You'll have a 9.5lb rig with glass, mounts, and sling. I'm sure it has some recoil but probably not enough to worry about affecting ammo in the magazine. You can certainly test it though. Just load two rounds of uncrimped ammo and shoot one of them, then top it off and shoot again checking the round left in the magazine. If you see bullet pull or bullet set back after 3-5 repetitions then apply a crimp. Otherwise get to shooting.
Awesome, I appreciate the help CD, Thanks
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ICANHITHIMMAN
05-31-13, 17:16
Thanks
I thought seating them deeper increases the pressure... or is that only in certain situations?
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The only situation that comes to mind is if you push the bullet threw the neck and I can only guess at the result.
This should help you out, I typed out a long this earlier but it said "needs approval by moderator" and it never showed up.
http://www.barnesbullets.com/resources/newsletters/september-2007-barnes-bullet-n/
http://www.hornady.com/ballistics-resource/internal
ICANHITHIMMAN
05-31-13, 17:19
Do you have dies? I got a set of RCBS that came with some other shit if you want. I have typed out two responses to your question and both said they need moderator approval so I'm done.
Do you have dies? I got a set of RCBS that came with some other shit if you want. I have typed out two responses to your question and both said they need moderator approval so I'm done.
Here I thought you were ignoring me. :D
I do have dies but I appreciate the offer.
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Bullet setback is something most people dont understand. It has nothing to do with the powder. It is the volume of case that can cause over pressure due to setback.
Pistol cartridges are affected by set back due to the lack of volume. I have seen bullets shot that were setback so bad there was virtually no neck tension at all.
As I stated previously I have very little experience with magnum cartridges, but they have a larger volume. So they should be less likely to cause over pressure due to set back.
In rifle cartridges the big problem is when bullets move forward putting them closer to the lands. Two rounds with the same load one very short oal and one with a long oal. The one with the longer oal will have the higher pressure.
If you go to tos in the ar15 ammo section on page 2 a member posted a thread about set back. Check it out. The further the bullet was set back the lower the velocity with no pressure signs.
I have not seen any evidence that set back in rifles causes pressure to jump. Everything I have read actually shows the exact opposite. I think people worry about set back because of pistol rounds and expect rifle rounds to act the same way. Bottom line is they do not.
:D
No problem. I'm in no hurry.
That sucker is sittin on the counter now. I'll scan it on Monday for sure.
That sucker is sittin on the counter now. I'll scan it on Monday for sure.
:D
No problem. I'm still in no hurry.
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