Blowing out primer at below recommended start load 300WM

[steve4102]

In the chart posted before by our Moderator UncleNick, start with a load developing 61,000 psi with about .135" jump to the rifling, not against the lands as the chart shows. This is the basis for my comment you've disagreed with.

You can "Start" wherever you wish, if .135 jump gets you what you want out of this graph, by all means go for it.

As this thread is about the OP and his VLD touching the Lands with .000 jump, that is where I choose to "Start" using this graph.

Carry on.

[Unclenick]

Windfall,

Several points:

1. The .300 Win Mag has more difference in capacity between different brands of cases than any other cartridge I am aware of. QuickLOAD even lists different case brands as if they were different cartridges because of that large difference (the only cartridge for which it does this). The spread is something like 7.5 grains difference in water overflow capacity between brands, ranging from 88 grains to 95.5 grains. This is one cartridge where you want to follow published load data, including choice of case brand and primer brand.

Even though your Norma cases should be on the high end of that range, I would measure it. Manufacturers have been known to change designs without telling anybody. Weigh a fired case with an intact primer. Fill it with water level with the case mouth (no meniscus) and weigh it again. Take the difference in the two weights. You should have around 95.5 grains of water if the case is 2.620" long. For any other length, adjust your result to that length by subtracting your length from that length and multiplying the difference in inches by 18.8 grains per inch (this is for .308" diameter), then adding the result to what you measured. If your case is longer than 2.620", then the result will be a negative number which will reduce the result when you add it.

2. Federal primers seem to have cups on the soft side of the range. You might try a CCI primer and the problem may just go away.

3. On that plot I've previously posted: it comes from Dr. Lloyd Brownell's study done in the mid-60's. Note that the bullet is round nose. The shape of that curve will vary with bullet shape. With kind permission from Jim Ristow, the following is an example of actual pressure measurements showing just 0.030" seating depth difference causing a 20% difference in peak pressure with a more pointy bullet shape.



Dr. Brownell's theory was that the pressure differences with different bullet distances off the lands is due to the amount of gas that bypasses the bullet while it is jumping into the throat. The further the jump, the more time gas has to do the bypassing. This is not a large volume of gas, but it does cause a short stall in the pressure rise. Add to this that a moving bullet engraves deeper when it hits the lands, then goes on to get moving again sooner and expand the combustion volume more by the time the pressure peak is reached. That results in lower pressure.

The sharper the bullet nose shape, the further it has to travel to complete obturating the bore, which is an important reason for the affect of bullet shape.

4. How big a step you need to make in seating depth to get a change in pressure or accuracy also varies with how sharp the ogive is. I'd suggest reading Berger's own recommended procedure for finding an accuracy sweet spot for their long VLD shapes.

5. Finally, you want to check your gun for other variables that could cause pressure issues. Do you have a fast barrel? Velocity is not a great pressure indicator because of chamber and seating depth variation, but if you've got a bullet going 200 fps faster than the manual lists (after allowing for any difference in barrel length), you are running at higher peak pressure.

If you've got copper fouling build-up near the throat, that can cause higher pressure. Carbon build-up in the front of the chamber ahead of the throat can sometime form a ring that causes it. You can slug your barrel to feel for build-up constrictions and to check that its groove diameter is not unusually tight.


steve4102,

That first plot is mine, which fine to use. I don't know about the second one. Since you said it was from a manual, I had to remove it because a manual is copyrighted material and you have to get permission from the owner of the copyright in order to post copyrighted material on this board. Since you don't know where you got it, you apparently don't have that. Please read the board policy on posting copyrighted material. Thanks.

[windfall]

Thank you. This is very useful

[windfall]

This is a video of my setup. As you can see I did not have trouble shooting BTLRs at charges all the way up to 70.5 grs. Then suddenly after switching to VLDs and changing the R22 lot numbers, I started blowing out primers. After feedback from Berger, it's appearing like I the VLDs are requiring a further distance from the lands... https://www.youtube.com/watch?v=4DdP71va6sw

[F. Guffey]

windfall, I do not know which posting (forum), I do remember someone suggesting some bullets are load specific. There are times two bullets can both weigh 150 grains, and, that is were the similarities end.

F. Guffey

[Unclenick]

Windfall,

backing off the lands may do it for you if the behavior of your load is analogous to that of the 6 mm in the RSI image I put up.

One other thing, though: It's normal for rifle starting loads to be 10% below a maximum listed load, which would be 64.0 grains for the 71.1 grain maximum load you listed. It should be about 83.5% case fill in the new Norma brass when your bullet is at 3.340" COL, and 82.3% case fill with the 3.406" COL you mentioned. Normally, with stick powder, as long as you stay above 70% case fill, you don't have pressure spike issues, and often 60% is still OK. I checked Alliant's manual, and they specify 10% reduction from their maximums in general, and I see no exception for RL22. So, in your shoes, that's where I would actually have started.

For whatever reason, the Berger minimum is only 5% below maximum in their data. Using the same lot of powder they have, QuickLOAD suggests this would bring just under 15% pressure reduction. Not quite enough to make up the 20% change shown in the RSI plot, if that's what your gun is doing, too. Standard manufacturing tolerance for the canister grade powder sold for handloading is ±3% in burn rate. If I vary the burn rate of RL22 that much in QuickLOAD, I get an 11% difference in pressure. So that 5% load reduction barely covers what might be expected for different powder lots, allowing only about 4% for difference in seating depth left over. That makes the 5% reduction in charge weight inadequate in my view. Adding that the powder maker recommends a 10% reduction, that's what I would have used in starting your load workup: 64 grains, worked back up in 1.4 grain steps (2% of maximum) while watching for pressure signs like the popped primers. Once I knew the limit, I would go looking for maximum accuracy loads in smaller steps below that number.

In your case, since you've already fired the 67.5 grain loads and know they are warm for your components, QuickLOAD suggests a 20% pressure reduction from maximum would happen at 66.0 grains, so I would go there next to see if the primer issue didn't stop.

Note that as you reduce charge, you increase the empty space in the case that has to be pressurized to starting pressure by the primer. That lower load is another reason to look at a magnum primer, though you want to drop all the way down to 64.0 grains if you change primers and work back up. The extra pressurizing gas produced is what makes a magnum primer magnum. Even even in non-magnum cases, when the percent case fill gets lower, magnum primers can sometimes improve ignition consistency. (See this article.)

[windfall]

"There are times two bullets can both weigh 150 grains, and, that is were the similarities end."

I am in complete agreement since, as I learned from Berger this week, the characteristics of the VLDs are significantly different from the LRBTHP. In one of the many emails from them they say,

"the VLD bullet has a bearing surface length of .540”. The LRBTHP bullet has a bearing surface length of .438”, making it shorter, with less resistance to overcome than the VLD design has to work with. This would mean that due to the higher resistance, of the VLD design, you would not be able to use as much powder, and you would get into pressure issues faster with the VLD, as compared to the LRBTHP."


Both are 210 gr.

[windfall]

In the spirit of contributing the handloading community I wanted to close this thread by passing on some knowledge and also let you know the actions I will be taking to remedy the situation.

Bottom line: My custom barrel has been bored at or slightly shorter than SAAMI specs causing too much pressure when seating the VLD bullet very close to the lands.

From Alliant "Ask the Pros"
"Bullets seated to touching the lands can cause the pressures to go up. This is because the bullet hits resistance immediately when it begins to move. The target shooters often times take this approach with certain bullets, particularly with some of the low drag bullets (Berger as an example). ... In hunting rifles, touching the lands is not recommended nor is it a benefit."


Walt Berger personally reviewed my rifle's custom bored chamber print and responded:
1) "the VLD bullet has a bearing surface length of .540”. The LRBTHP bullet has a bearing surface length of .438”, making it shorter, with less resistance to overcome than the VLD design has to work with. This would mean that due to the higher resistance, of the VLD design, you would not be able to use as much powder, and you would get into pressure issues faster with the VLD, as compared to the LRBTHP."

2) "if you continue to use the current chamber configuration, as shown by the print. You could still use the VLD bullet, but you most likely will need to alter the load to keep a handle on the pressures."

Hard to get more of an expert opinion than Walt Berger.

It just so happens the gunsmith who did the work on my rifle is known to Walt. Walt says he knows him "personally and considers him to be an honest, straighforward guy and thinks very highly of him as a precision gunsmith". The gunsmith has kindly offered to let me send the rifle back to him so he can throat my rifle's barrel and lengthen the freebore to get the pressure down has offered to do this for free. My gunsmith is Mike Bryant at http://www.bryantcustom.com/

[steve4102]

The gunsmith has kindly offered to let me send the rifle back to him so he can throat my rifle's barrel and lengthen the freebore to get the pressure down

Wouldn't seating the bullet deeper accomplish the same thing if you want to give the bullet more jump?

[Unclenick]

Steve,

It would, except he'd have less powder space, for sure, and with some long bullets you just can't seat them deeply enough for a standard chamber without part of the ogive being below level with the case mouth, leaving a gap between the mouth and the bullet. The 80 grain Sierra MatchKING in the .223 cartridge is a common example. One normally uses a longer-than-SAAMI-maximum COL with these long bullets for that reason.


Windfall,

I have to say from your last post that some of the confusion seems to be that you were trying to use load data for the LRBTHP design with the VLD bullet. That wasn't clear to me initially. My assumption was, since you cite Berger's load data, that the data was bullet specific. Was that not the case? If not, and Berger didn't say so clearly, then the fault is with Berger's data.

It has long been known by handloaders that not copying a published load's components exactly can change pressure. In particular, there are more solids around these days, which raise pressure noticeably over their cup and core constructed counterparts because they are not only harder to engrave, but they are less dense, so they are longer. But even among cup and core bullets you get different dimensions (as you found out) and different jacket thicknesses and alloys, so going by bullet weight alone is no guarantee the same load specifications will work. This is why we work all loads up from a starting load level while watching for pressure signs.

I'll respectfully disagree with Berger's explanation for why seating in the throat raises pressure. That's the static vs. kinetic (or sliding) coefficient of friction difference explanation. It has been around for at least as long as I've been reloading. The fault with it is shown in the plot of Brownell's data. If static engraving force were responsible for the rise in pressure, then pressure would stay moderate until the bullet was actually in contact with the lands, at which point it would jump up abruptly. Instead, you see actual data shows a continuous increase in pressure as the bullet nears the lands and not a sharp transition or jump when the bullet contacts the lands. That makes Brownell's gas bypass explanation a better fit.

The bearing surface length affects how long it takes for the bullet to become fully engraved, with a longer bearing surface letting start pressure get higher before it's fully engraved by the rifling. Once engraved (actually swaged) into the rifled bore, anywhere in the first two or three inches of bullet travel past the throat, the dominant friction term is due to the pressure differential between tip and tail of the bullet upsetting the bullet outward against the bore. That's why copper fouling is normally most heavily accumulated in this area. This bulging pressure is primarily determined by accelerating force and the height of the bullet mass column above the base. It is then distributed over whatever area of contact there is, and thus the total amount of friction it causes does not change with bearing surface. Greater contact area just distributes that same force and resulting friction out over whatever area there is. Only the friction due to spring-out of the jacket against the bore after swaging will vary with bearing surface length. It does not become dominant until after the pressure peak, if at all (depends dropping muzzle pressure).

[steve4102]

Originally Posted by Unclenick

Steve,

It would, except he'd have less powder space, for sure, and with some long bullets you just can't seat them deeply enough for a standard chamber without part of the ogive being below level with the case mouth, leaving a gap between the mouth and the bullet.

True, but the OP never gave any indication that he was up against the lands and the bullet could not be seated any deeper without seating past the Ogive. If I understand his posts and technique, he measured to the lands and started there. I have no idea if he has room to seat deeper or not, hence my question to him.

[Metal god]

I don't know were he is on seating depth either but I'd bet he could seat 10 to 20 thou deeper with out issue and it is what I'd try first ( if it can be done )before sending the barrel in for work .

The other thing to think about is a few more hundred rounds and the throat will be longer do to erosion and he will gain that many more rounds of barrel life . How ever if thats the only bullet he plans to shoot you might as well have the chamber/throat/lands set perfect for the bullet . I would think any other bullets after the new work is down will have to be jumped to the lands .

[windfall]

Unclenick,
Correct, Berger's load data is the same for the 210 VLD and the 210 LRBTHP. It sure seems like this is an example where the book is wrong or at least requires some clarification.

Thanks for the additional explanation. I've only been hand loading for the last year so it's still quite new to me.

[windfall]

Yes, I have been starting out gently touching the lands and then measuring my bullet seating based on this. Well, this all seems quite backassed now that I have read so many responses to my threads on this topic at hand. But, I'm figuring this out completely on my own and started out with the ABCs of Handloading and by watching youtube videos. It appearing I should be starting at .015 off the lands and moving forward very slowly. I need to buy a chronograph to verify velocities to help me decide how far to move forward to reach the book listed velocities.

I'd be interested to hear your recommendation, if you have one, on how far back to start with a Berger VLD.

So no, there is no room to move the bullet forward from where Im at and I think this is the point Walt Berger picked up on.

[windfall]

Right, as I stated above I am up against the lands and cant move forward any more.

Due to the stated high velocities of the VLDs with R22 and because I see in my NBRSA magazines that top competitors are using this combination, I am planning on *only* using setup, if I can get it to work after having more headspace made available by Mike Bryant

[old roper]

Windfall, Wouldn't it been lot easier getting holed of your gunsmith and talking to him first?

I seen same post here on Br site and I think Mike post over their or at least use to. I had LR 6.5x284 build with tight neck all work done by Mike and I know during the planning I send him some dummy rds for throating.

[windfall]

Actually, I've learned quite a lot this week. This rifle was the first serious investment I've made in a precision rifle so I don't know the proper procedures for everything. I'm just new. I received my first hunting rifle from my grandfather when I was 13 and got my first hunting license when I was 16. I've owned 20 some odd firearms over the last 34 years.

[Metal god]

Sorry I was not more clear . I was saying I bet you could seat the bullet deeper into the case not the lands . seating deeper into the lands would cause more pressure problems . If you can seat the bullet deeper into the case . It would give the gases some room to blow past the bullet before it hits the lands .

Do you have room on the bullet to seat it deeper into the case and not pass the Ojive with the mouth of the neck ?

Seating the bullet deeper into the case and therefore reducing case volume can at times be a problem when loading max charges because there is no room left in the case for the bullet . I would think the fact your at or below minimum load/charge , Seating the bullet deeper into the case should not effect your ability to load that same charge .

Can you shoot a pic of a loaded round or a dummy round with the bullet seated to the OAL you are having problems with ? Maybe even a pic with a comparator on it

[steve4102]

Sorry I was not more clear . I was saying I bet you could seat the bullet deeper into the case not the lands . seating deeper into the lands would cause more pressure problems . If you can seat the bullet deeper into the case . It would give the gases some room to blow past the bullet before it hits the lands .

Do you have room on the bullet to seat it deeper into the case and not pass the Ojive with the mouth of the neck ?

^^^This^^^

[HUBEL458]

Ok,using same bullet, same starting load, same gun, same case, slow powder..
With slow powders you have minimum amounts that should be used, so as
to not have to much airspace, leading to the SEE problems.

The most important factor that changing seating debth, with starting or slightly
less than manual listed starting loads, in changing the pressure, is not
the bullet jump changing pressure but the change in total available volume
under the bullet. Backing bullet up lowers volumn so that there is less tendency for SEE and peak pressures reduce. Changing bullets changes volume,
changing the airspace.

In example, why try to make RE22 work, go to RE25 and use more.
More will get speed you want and case will be fuller, so that SEE goes away.Ed

[steve4102]

Originally Posted by HUBEL458

The most important factor that changing seating debth, with starting or slightly
less than manual listed starting loads, in changing the pressure, is not
the bullet jump changing pressure but the change in total available volume
under the bullet. Backing bullet up lowers volumn so that there is less tendency for SEE and peak pressures reduce. Changing bullets changes volume,
changing the airspace.

See posts # 39 and #52 for pressure related to seating depth. Shorter OAL = Less Pressure.

[HUBEL458]

MOST Cases are designed to work at certain volumns, between 90%
and full compressed loads depending what the powder will stand.

IF WE LOAD LESS THAN 90% WITH A CERTAIN POWDER
AND HAVE TO BACK THE BULLET UP SO NO CHANCE OF SEE,
WE IN ESSENCE MADE THE CARTRIDGE SMALLER.....

WE made volume smaller to get back to around the 90%.
This is not the way to load, it is wrong to build a load combo
around the powder, good results mean we start with the case
and bullet, and fit right powder to that case,
IE, in example use more of a slower powder.
We have about 30 different rifle powder speeds to use.Ed

[Unclenick]

Note: I moved Skizzums question and answers to it into its own thread.

[oldcspsarge]

The condition of the inside of the barrel is also a key to the pressure signs when they reveal themselves in ANY rifle/caliber.

Clean the inside of the bore with a powder solvent. Cotton patch and brass brush..never a stainless brush.

Then use a copper solvent.

Next use Holland's Witches Brew and get the rest of the copper out.
(sold by MidwayUSA )

I'll bet you will be amazed with what you see...that you missed.

With VLD bullets in particular, due to the additional contact surface with the lands & groves, copper fouling increases drag that spikes pressure.