I want to try VLD bullets but read some about the differences and the history between the target and hunting varities. Since I'm only pushing about 2850 fps should I go with the hunting variety to get the extra .030 BC? I could see with a .243 needing to go with thicker jackets so they don't explode in flight.
Berger posted a short blog early last year essentially admitting that some of their bullet production issues were due to not being able to meet their quality control standards for the thicker target bullet jackets. The post was to say they solved the problem. However, it does kind of imply that on a day in day out basis the hunting bullet quality control may actually be better than the target bullets.
Also not sure how deeply you dug into the issue of bullets exploding, but here is some information from the time when this was a big problem. These are two different posts in another forum by Eric Strecker. My read of it is that you shouldn't have a problem unless you are shooting long rapid strings without letting the barrel cool down.
Warning: This is a long read and is in two parts. If you read it you will see that the thinking about the cause of bullets going poof changed from the initial investigation to the more recent one. And also note that this stuff is from 10 years ago!
"#1 02-13-2007, 12:09 PM
Eric Stecker
Registered User Join Date: May 2006
Posts: 266
Bullet Failure Causes and Solutions Defined
--------------------------------------------------------------------------------
As many of you know we have been working on the bullet failure (blow up) situation for some time. I have been collecting data from numerous shooters over the last 2 ½ years ranging from general observations to controlled experiments. At Berger, we have been working with folks at MIT and with other top minds in metallurgy and ballistics. What I have below is a report on what we have learned.
To briefly review, bullet failure is when the bullet does not hit the target anywhere near the expected impact location. (This is not about the unexpected 8 or the fifth shot out of a bug hole group). This result can be observed as a shot that is driven way off course but does make it to the ground, a shot that appears as a puff of smoke 30 yards or more from the muzzle, and everything in between. The shooter can experience bullet failure with several shots or with one shot out of a string.
The wide range of results and conditions has made it very challenging to sort out the true root cause. The information below is meant to bring the true root causes to the surface. I am not suggesting that these causes exist in every situation; however, they cover the vast majority of bullet failures.
The first two root causes are responsible for the most bullet failures:
Excessive RPM resulting from high velocity and a barrel that has a twist rate much faster than is needed for the bullet used. We are working on determining the general RPM limits for various bullets. This will be a long project, and the data we have now is not enough to publish RPM limits.
Solution: Use twist rates that are the same as or close to (faster) published recommendation. When shooting cartridges that produce higher than normal velocity (high capacity wildcats) consider using twist rates slower than those published since the published twist recommendations are based on velocities achieved by standard cartridges. (How much slower is based on the situation however it will usually be only 1” slower)
Friction that produces heat that exceeds the melting point of lead. This result is observed most often by the puff of “smoke” that will be within the first hundred yards from the muzzle. The “smoke” is in fact molten lead. The puff of molten lead does not always occur during this failure. A core that becomes even slightly plastic will not make it to the target properly.
You have heard me talk about a combination of conditions that produces a failure. I have believed this to be true for a long time but frankly, it has only been recently that we have begun to truly understand what is actually happening. Once we started looking at the possibility of the core melting, all the puzzling information from the various reports began to make sense. This is going to be a lengthy post focused on identifying root causes and their solutions so I will not go into all the various conditions and ranges in which these conditions exist that support these findings.
The report that our bullets would fail while Sierras would not was particularly puzzling. We have known for a while that making the jacket thicker does not make the jacket significantly stronger. As it turns out, we were looking at it from the wrong point of view. We had been looking at a thicker jacket as being a tougher jacket and this just isn’t true, however when you have a thicker jacket you are moving the lead away from the source of the heat (friction between the barrel and the bullet which is mostly in the area of the rifling, not the grooves). Bullets that have thicker jackets are actually thicker in the base and sidewalls near the base, which moves the lead further away from the heat. This increases the amount of friction that the thicker jacketed bullet can realize before the lead core gets hot enough to melt.
Since thicker jackets are difficult to make concentric, we have two solutions. The first is that we are going to work on making thicker jackets for our long-range bullets. This is going to take time, as we will not produce jackets that are greater than .0003 TIR in wall thickness variation. This is harder to do with thicker jackets. The bullets we make now shoot very well and there are several ways that this failure-creating friction can be avoided as it has been by many shooters. Avoiding this condition is the second solution.
Solution for avoiding failure-creating heat using our current bullets: The goal is not to slow the bullet down but rather reduce the heat created by the friction. There are several ways to do this. (Keep in mind that each condition is not absolute and in fact works with other conditions to create failure. Since failures occur occasionally when all the conditions work together to create excessive heat we know that it will not take much to insure that failures are avoided)
First, you can consider your barrel length. It has been found that barrels longer than 28” are capable of produce failure-creating heat. Remember that the bullet is hottest at the muzzle. The more metal the bullet has to travel over, the hotter it gets.
Second, consider using moly, Danzac (tungsten disulfide), or any other dry lubricant as these reduce friction thereby reducing heat. I know moly is a hot button for many shooters however setting all other things aside it works great as a friction (heat) reducer.
Third, consider running a patch with a light amount of Kroil through your barrel prior to shooting. This will lubricate the barrel long enough until the carbon builds up enough to serve the same purpose. The first few shots will be erratic, but failure-creating heat is avoided. Barrels that are squeaky clean produce significant levels of friction if no friction reducers are present before firing. (I am not suggesting that you do not clean your barrel completely but rather pointing out how to avoid failure-creating heat when you start shooting).
Fourth, consider the bore diameter of your barrel (land height not groove depth). Some barrel makers can provide you with different bore diameters. Consider diameters on the larger side of the available options.
Fifth, consider the land configuration in your barrel. Six groove, cut, squared off rifling produces greater friction than a 5C or 5R type barrel. The 5C or 5R type rifling produces more friction than a three-groove barrel. I am not suggesting one is better than another; however, the friction generated by the different rifling designs should not be ignored.
Sixth, consider the cartridge you are using. Cartridges such as the 6X284 or any overbore wildcat are notorious for high velocity and barrel life consumption (rapid erosion). These are some of the main ingredients in failure-creating heat generation.
Please remember that the combination of components used in your rifle is a compromise. I have learned why Berger Bullets fail when others do not. I have decided to share this with you because I am committed to enhancing the experience for the shooter and in my opinion, more information is better even if on the surface this information makes us look bad.
Many shooters avoid failure-creating heat when they use Berger and find that Bergers work best for them. You can look at the information above as a reason not to shoot Berger or you can look at it as detailed instructions on how to make Bergers work for you without the concern of producing failures. If you value the accuracy that Bergers produce, then the above information details areas where you can make an easy compromise now that you have all the facts. If you value the conditions listed above that produce failure-creating heat more than you value the accuracy of Berger Bullets, then your decision is also made easier with these details.
The following root causes are responsible for bullet failures but in smaller numbers:
Human error that produces failure-causing condition. Let’s all admit up front that none of us are perfect. A shooter can create failure-causing condition in the barrel by improper break in, cleaning or storage (crown damage). Failure causing conditions can be created with the load as well. Using the wrong powder, not chamfering necks, excessively tight neck tension damaging the base of the bullet, poor handling practices can also lead to failures. Careful and appropriate firearm handling and loading practices usually avoid these failure causing conditions.
Tight or rough bore that actually tears jacket material away from the bullet. This is an extreme and rare condition that is easily identifiable with a bore scope, by slugging the barrel or by feeling for a spot that is more resistant to cleaning with a tight patch. Barrel makers are quick to resolve this situation.
Poor bullet fabrication such as too low or too high seating pressure. Low seating pressure can create a poor mechanical bond and/or air pockets that further destabilize the bullet. Seating pressure that is too high effects the copper jacket by producing a weakness where the nose can separate from the body. These conditions can be most easily detected by weighing your bullets, as too low or too high seating pressure is mostly the result of an extreme change in the mass of the lead.
Other examples of poor fabrication are any excessive lube on the cores (many bullet makers do not clean their cores before bullets are swaged) or debris between the jacket and the core can produce a weak bond, air pockets and/or significant stability issues through poor balance around the axis. Another poor fabrication condition that is easiest to avoid is lead that contains debris or significant air pockets due to double extrusion. This condition does not exist when a quality source of lead is used. Quality bullet manufacturers of which there are many can avoid all of these fabrication conditions.
There might be some other causes of bullet failures beyond those listed above but they happen is such rare occurrences that they have not been identified and should not weigh heavily on your mind.
It is my sincere hope that you find this information useful toward enhancing your shooting experience.
Regards,
Eric Stecker
Berger Bullets
Eric Stecker
Registered User
Berger bullet failure test
First I want to thank Mid Tompkins for doing so much to make this test possible. Without him it would not have happened. Also I want to thank Sherri Hurd and Michelle Gallagher for their part in putting 950 shots down range using a 6.5X284 in a little over 6 hours. You both earned those sore shoulders.
On January 3rd at Ben Avery Shooting Facility in Phoenix, AZ we (in my opinion) solved the bullet failure issue. We conducted a test during which 220 Berger 6.5mm 140 gr VLD made with regular J4 jackets were fired in two different barrels. After these rounds were fired we shot another 220 rounds of Berger 6.5mm 140 gr VLD made with thicker J4 jackets. The results were interesting to say the least.
Two barrels that had been provided by Krieger were chambered by Mid Tompkins. These barrels were put on two F-Class rifles (Mid's and Bob Mead's). A front rest, rear bag and shooting mat were used in shooting these rifles F-Class style.
Mid and Michelle spent much of the holidays loading the 950 rounds shot during this test. The ammo was loaded in Lapua cases with 49.5 gr of H4350.
Present during the test were Mid Tompkins, Michelle Gallagher, Sherri Hurd, Jeremy Hurd, Bob Jones, Alan Elliot, Walt Berger and I. We made sure that for each shot there were at least two people watching through spotting scopes. All shots were documented.
The goal was to shoot all the rounds in highly abusive conditions and then observe if the bullets would fail. We did not alter the barrels or the load in an attempt to create failures on purpose. These barrels and loads were in every way in the same condition when we started as any combination would be on match day.
The procedure used for this test was to fire 20 rounds with one rifle then quickly switch to the other rifle. We would shoot all 220 (in each barrel) of the regular jacket bullets first then shoot all 220 of the thicker jackets. This course of fire was meant to duplicate match type strings and the rapid firing was to produce the harshest conditions possible for the bullets.
As you can imagine the barrels were very hot to the touch once we got through the first few strings of 20 shots. They would remain hot for the rest of the day.
We started with the .257 barrel first. We were not testing barrels so observations made about the barrels are secondary to the focus of the test. I mention this because I predicted that the .257 bore diameter would produce fewer failures since it was larger than the .256 bore diameter. I was proven wrong.
The .257 bore diameter barrel produced the first bullet failure at shot 106. The .256 bore diameter barrel produced its first bullet failure at shot 151. Even more interesting was the fact that the .257 barrel produced a total of 27 failures (with regular jacket bullets) right up to the last shot. The .256 barrel produced only 12 failures and stopped producing failures when the barrel was cleaned after shot 180. 40 shots were fired after both barrels were cleaned.
Now for the good news. After we finished shooting the bullets made with regular jackets we switched to the thicker jackets. Again both barrels shot 220 each by shooting a string of 20 and then switching to the other rifle. ALL 220 BULLETS MADE WITH THICKER J4 JACKETS (IN BOTH BARRELS) MADE IT TO THE IMPACT BERM.
So that we did not destroy one of Mid's target frames the scopes were adjusted so that we could aim on a target but the bullets would hit the impact area of the next target. At the beginning of the thick jacket shooting we did shoot one 10 shot string on the target. The results were a 12 oclock 6 due to scope adjustment, 8-Xs and 1-10 (string shot by Michelle G.) Accuracy was not the focus of this test but it looked good for ten shots (once we got the scope adjusted).
To verify that something had not changed in the barrel for the thicker bullets we shot another 20 bullets made on the regular jackets in the .257 barrel after the thicker jacket shooting was completed. 9 out of 20 shots fired did not make it to the berm.
Another interesting result was that while we were shooting the thicker jacketed bullets both barrels produced several blown primers. The .257 barrel produced 14 blown primers and the .256 barrel produced 5. There were no blown primers while shooting the regular jacket bullets. We did chronograph five shots using regular bullets at a MV range of 2,996 to 3,024 fps. The chronograph was not working later in the day so we could not check the MV produced when shooting the thicker jacket bullets.
We continued shooting after thoroughly cleaning the .257 barrel using moly coated bullets made with regular jackets. 50 rounds were fired with 14 failures. It is my opinion that the abuse this barrel had experienced does not allow for an appropriate testing of the effectiveness of moly. These bullets were shot mostly out of curiosity. It is certainly clear that moly is not a cure all for bullet failure however I still believe that it helps reduce friction which is the cause of these bullet failures.
It is my conclusion that bullets made with thicker jackets are more capable of sustaining significantly higher levels of abuse before producing a failure. We are gong to do this same test again but this time we will use Bartlein barrels. The purpose again is not to test the barrels but to focus on the results produced by using jackets of different thicknesses.
Even though we are going to conduct another test we are already working on the production of a full line of VLD-THICK bullets in 6.5mm, 6mm, 22 cal and 7mm which will be specifically meant for target competition shooters. I will attempt to attach a detailed report of the specifics of the test.
Regards,
Eric"
