308 blown primers question
- Thread starter steves86ta
- Start date
When i first got started with this deal. I was only shooting the match BTHP's (168)gn and i loaded up and did seating depth tests. with that bullet and BLC-2 it liked a .016 jump. But i havent done a seating depth test yet
Need to figure out this velocity thing/charge weight thing and then go after that too
shoot4fun
Gold $$ Contributor
Another couple things to check would be case length (make sure FL sized brass isn't longer than your chamber) and seating depth. How does your seating depth compare with the SAAMI COAL?
IIRC, bullet seating deeper into the case actually causes pressure rise where seating out longer tends to reduce pressure.
All the brass is trimmed to 2.005"
Seating depth is much 'longer' than saami. I pulled them all and didnt write down the length. But they are longer than magazine length.
Random thought. Howa's may be prone to spitting primers out the back of the case when fired on a hot load.
I have a friend with a Howa 6.5 X 06 AI he's trying for +3000 fps with 140 grainers it keeps wrecking Norma brass by enlarging the pocket. I won't get near him when he is shooting. And have told him to download and change brass.... like I said, maybe it's a Howa/Chowa thing.
I have a friend with a Howa 6.5 X 06 AI he's trying for +3000 fps with 140 grainers it keeps wrecking Norma brass by enlarging the pocket. I won't get near him when he is shooting. And have told him to download and change brass.... like I said, maybe it's a Howa/Chowa thing.
You state the brass is prepped (neck tension) and you "jammed" the bolt closed. Is there a chance that the bullet is still in the lands at that point, making your .02" jump actually less then .02" maybe even 0.
Something has to give, either the bullet is pushed into the neck or or the rifling, your assuming neck, correct?
Yes - i didn't even think about it. Im only running .002 neck tension but yes, i'm assuming its pushing into the case and not the lands.
Will say it IS moving into the neck, but by how much vs how much into the lands i couldn't tell you.
Ned Ludd
Silver $$ Contributor
Externally, there is nothing about the brass that would suggest extreme over pressure. There is certainly an ejector mark on the case with the popped primer, but it's not extreme and unsupported brass will do that.
I would suggest starting at the very beginning, then try to identify the cause in a stepwise fashion. Although doing this can be painful, sometimes it is the only way to identify the cuplrit. As a part of that process, I would recommend you buy a set of these if you don't already have them:
These are used to assess the diameter/tension/interference fit of the primer pockets in a simple and easy yes/no manner. This way, you can determine whether the primer pockets of your brass may already have started to expand close to "unacceptable" territory before you even started loading the brass with this current recipe.
Next, you need to start taking and recording some critical measurements, if you haven't done so already. The taking and recording of accurate measurements is sometimes the only way one can readily troubleshoot problems such as this, and it's generally just a good practice. For example, measure the case diameter at the datum line just above the extractor groove (circled in red on the following .308 Win Cartridge/Chamber diagram from SAAMI). Doing this before/after firing can provide some idea of how much case expansion is taking place in your chamber.
In addition, taking and recording base-to-shoulder (BTS) measurements can also be critical. It is sometimes possible for the case shoulder is bumped back excessively during the re-sizing process (i.e. > .002" or so). When the firing pin hits the primer cup, it drives the case forward until the case shoulder "bottoms out" in the chamber. If the case BTS dimension is too small (i.e. the shoulder has been bumped back too far), this can create an excessive gap between the base of the case and the bolt face as the firing process proceeds, allowing primers to "pop out", even in cases where the pressure may not be over MAX. It may not seem like a tiny gap of only a few thousandths could cause this to happen, but I can assure you it does. For this reason, it is not uncommon to observe popped primers when fire-forming virgin brass, which is usually much shorter (BTS) straight out of the box than it will be after the first firing/re-sizing cycle. Seating bullets long to prevent this tiny gap from opening up may help with virgin brass, but it's not really where you want to be with fire-formed brass, where optimal bullet seating depth is absolutely necessary for good precision. Make sure you are sizing your case back at the shoulder by no more than .001" to .002" during the re-sizing process.
As has been noted by others, bullet seating depth is another critical measurement that needs to be taken and recorded. The deeper the bullet is seated into the case, the greater the pressure from a given charge weight. Conversely, bullets seated into the lands can create an extra pressure spike at the start of the firing process as the bullet is forced to engrave into the rifling starting from a jammed/stopped position already into the rifling. This has to do with difference between coefficients of static versus kinetic friction and the engravement process. Because they have a little room to get moving before engravement starts, jumped bullets tend to have a lesser pressure spike during intiation of the firing process.
Neck tension/interference fit would be another place I might start looking in your shoes. If you're really using a 0.333" bushing, that seems extremely tight for Lapua necks. I re-sized various different Lot #s of Lapua LRP brass for years with a 0.336" bushing to yield approximately .002" neck tension. If you're actually using a 0.333 bushing, it could be a contributing factor if the neck tension is in the .005" range, or above.
IMO - it is almost impossible for anyone merely reading this thread to correctly and accurately diagnose the exact cause of your blown primers. We can throw out a bunch of possibilities, but we simply don't have enough information to reliably troubleshoot everything, which unfortunately still puts the burden on your shoulders. Taking and recording good measurements is a good place for you to start, if you haven't been doing so already. Good measurements provide a wealth of information that can be used to compare "before/after" in almost any circumstance.
I can think of a couple more things you might consider. If you have another powder in the appropriate burn rate range such as Varget/H4895/IMR 4064/RL15/etc., you might consider working up a load with one of those to see if you can develop similar velocity without popping primers. In other words, could it be an issue with the powder you're using? Although I am familiar with what they are, I have no direct experience with the Staball powders and so cannot offer any insight. But it may be worth looking into.
Finally, the last thing I would strongly suggest would be to obtain small rifle primer (Palma) .308 Win brass from either Peterson or Alpha Munitions (Lapua has halted production of their .308 Win SRP brass due to the Ukraine conflict). Small rifle primer .308 Win brass is far more appropriate for the loads we tend to use in F-TR, as it can withstand pressures that would render LRP brass pockets unusable in a single firing. In other words, you get more for your money with SRP brass because it lasts longer. Using SRP brass may not be the solution for blown primers, which is another issue entirely, but it will be of benefit for shooting F-TR in the long run.
I would suggest starting at the very beginning, then try to identify the cause in a stepwise fashion. Although doing this can be painful, sometimes it is the only way to identify the cuplrit. As a part of that process, I would recommend you buy a set of these if you don't already have them:
Small and Large Primer Pocket Swage Gage ® Set
Swage Gage Small Primer Pocket Gauge
ballistictools.com
These are used to assess the diameter/tension/interference fit of the primer pockets in a simple and easy yes/no manner. This way, you can determine whether the primer pockets of your brass may already have started to expand close to "unacceptable" territory before you even started loading the brass with this current recipe.
Next, you need to start taking and recording some critical measurements, if you haven't done so already. The taking and recording of accurate measurements is sometimes the only way one can readily troubleshoot problems such as this, and it's generally just a good practice. For example, measure the case diameter at the datum line just above the extractor groove (circled in red on the following .308 Win Cartridge/Chamber diagram from SAAMI). Doing this before/after firing can provide some idea of how much case expansion is taking place in your chamber.
In addition, taking and recording base-to-shoulder (BTS) measurements can also be critical. It is sometimes possible for the case shoulder is bumped back excessively during the re-sizing process (i.e. > .002" or so). When the firing pin hits the primer cup, it drives the case forward until the case shoulder "bottoms out" in the chamber. If the case BTS dimension is too small (i.e. the shoulder has been bumped back too far), this can create an excessive gap between the base of the case and the bolt face as the firing process proceeds, allowing primers to "pop out", even in cases where the pressure may not be over MAX. It may not seem like a tiny gap of only a few thousandths could cause this to happen, but I can assure you it does. For this reason, it is not uncommon to observe popped primers when fire-forming virgin brass, which is usually much shorter (BTS) straight out of the box than it will be after the first firing/re-sizing cycle. Seating bullets long to prevent this tiny gap from opening up may help with virgin brass, but it's not really where you want to be with fire-formed brass, where optimal bullet seating depth is absolutely necessary for good precision. Make sure you are sizing your case back at the shoulder by no more than .001" to .002" during the re-sizing process.
As has been noted by others, bullet seating depth is another critical measurement that needs to be taken and recorded. The deeper the bullet is seated into the case, the greater the pressure from a given charge weight. Conversely, bullets seated into the lands can create an extra pressure spike at the start of the firing process as the bullet is forced to engrave into the rifling starting from a jammed/stopped position already into the rifling. This has to do with difference between coefficients of static versus kinetic friction and the engravement process. Because they have a little room to get moving before engravement starts, jumped bullets tend to have a lesser pressure spike during intiation of the firing process.
Neck tension/interference fit would be another place I might start looking in your shoes. If you're really using a 0.333" bushing, that seems extremely tight for Lapua necks. I re-sized various different Lot #s of Lapua LRP brass for years with a 0.336" bushing to yield approximately .002" neck tension. If you're actually using a 0.333 bushing, it could be a contributing factor if the neck tension is in the .005" range, or above.
IMO - it is almost impossible for anyone merely reading this thread to correctly and accurately diagnose the exact cause of your blown primers. We can throw out a bunch of possibilities, but we simply don't have enough information to reliably troubleshoot everything, which unfortunately still puts the burden on your shoulders. Taking and recording good measurements is a good place for you to start, if you haven't been doing so already. Good measurements provide a wealth of information that can be used to compare "before/after" in almost any circumstance.
I can think of a couple more things you might consider. If you have another powder in the appropriate burn rate range such as Varget/H4895/IMR 4064/RL15/etc., you might consider working up a load with one of those to see if you can develop similar velocity without popping primers. In other words, could it be an issue with the powder you're using? Although I am familiar with what they are, I have no direct experience with the Staball powders and so cannot offer any insight. But it may be worth looking into.
Finally, the last thing I would strongly suggest would be to obtain small rifle primer (Palma) .308 Win brass from either Peterson or Alpha Munitions (Lapua has halted production of their .308 Win SRP brass due to the Ukraine conflict). Small rifle primer .308 Win brass is far more appropriate for the loads we tend to use in F-TR, as it can withstand pressures that would render LRP brass pockets unusable in a single firing. In other words, you get more for your money with SRP brass because it lasts longer. Using SRP brass may not be the solution for blown primers, which is another issue entirely, but it will be of benefit for shooting F-TR in the long run.
Thank you for all of the info - will definitely work on some of these measurements.
I will dig the blown ones out of the trash and measure them
I will look into the SRP brass as well.
Again Thank you!
I always had more pressure signs with brass primer cups. They would pierce easier. Wish you could check head hardness. Might be soft heads and brass primer cups. Doug
Following what Ned said. It would be interesting to hear how other powders perform. I have heard, but not personally experienced, that some of the newer double based spherical powders (AKA Cfe 223) will go from just fine to NOT FINE very quickly. Not making any assumptions or accusations, but it might be good information if an extruded powder gets you there without issues and this new kid on the block does not.
Yeah I agree. Originally i was looking for Varget, but this was what was available.
I had really good luck with BLC-2 with the 168 HPBT's. But my SD and ES were way lower with the staball.
I will keep my eyes open for somehting like Varget
Ned Ludd
Silver $$ Contributor
Hodgdon has had Varget in stock continously for several months now, either in 1 lb, 8 lb, or both. They currently have 1 pounders in stock. There is a limit of five per month period, but hey, it's Varget...even one pound is better than none. 
shop.hodgdon.com
Hodgdon VARGET®
Buy VARGET Smokeless Propellant by Hodgdon, powder specifically designed for 223 Remington and similar calibers. Hodgdon, the brand that's true.
shop.hodgdon.com
So As an update to this thread incase anyone else comes across this.
I went back out today with fresh rounds, a very clean rifle and the chronograph
i started at 42.4gn of staball and worked up from there.
Had the same problem around 44.4-44.6gn's Popped 3 more primers stopped shooting.
Got home and figured id dig into this more. Called the president of the Long Rang club i shoot at.
We bounced some ideas off of eachother. While we were looking at the data on Hodgdon's reloading center. He did some more googling and found an article with a picture from a book at Shot Show 2023 about StaBall Match powder. The caption on the picture lists the MAX at 44.5gn @ 2595 fps with a 168 SIR HPBT.
At 44.2 with my magnetospeed and the ELD-M's I am at average 2588 with a max of 2594 (for the 3 i shot)
At 44.4 i was at 2606 for the one that didn't pop a primer and 4568 for the one that did.
Here's the link to the article. I think the Reloading Data Center has the wrong data in it. My velocities are right in line with what they have listed.
www.thefirearmblog.com
I went back out today with fresh rounds, a very clean rifle and the chronograph
i started at 42.4gn of staball and worked up from there.
Had the same problem around 44.4-44.6gn's Popped 3 more primers stopped shooting.
Got home and figured id dig into this more. Called the president of the Long Rang club i shoot at.
We bounced some ideas off of eachother. While we were looking at the data on Hodgdon's reloading center. He did some more googling and found an article with a picture from a book at Shot Show 2023 about StaBall Match powder. The caption on the picture lists the MAX at 44.5gn @ 2595 fps with a 168 SIR HPBT.
At 44.2 with my magnetospeed and the ELD-M's I am at average 2588 with a max of 2594 (for the 3 i shot)
At 44.4 i was at 2606 for the one that didn't pop a primer and 4568 for the one that did.
Here's the link to the article. I think the Reloading Data Center has the wrong data in it. My velocities are right in line with what they have listed.
[SHOT 2023] New Winchester StaBALL Powders For 2023
The Winchester StaBALL family has two new members, StaBALL Match with a Varget-like burn rate, and StaBALL HD which is a Retumbo-class powder.
www.thefirearmblog.com
Ned Ludd
Silver $$ Contributor
FWIW - Years ago, I ran into an issue with a Hornady "Superformance" powder 178 BTHP commercial load. It was apparently generating a significant pressure spike and an early shot during the first string shooting it blew a primer and actually cracked the bolt face of a DTA SRS rifle. I wasn't the only person at the time to observe similar excessive pressure issues with that specific commercial load and obviously, I never used it again. The general thought at the time was that because Hornady was touting the loads with special blend "Superformance" powder as being able to generate as much as 200 fps greater velocity than the same load with a conventional powder, it was probably a pressure curve issue. Obviously, the extra velocity came at a cost.
In your case, something is obviously wrong because the apparent velocity/pressure you are generating from a 24" barrel with a 168 gr bullet should not be grossly excessive, yet the pressure signs suggest it is. Other reloading manuals (Berger and Speer) list maximum velocities for a 168 gr BTHP with various commonly-used .308 Win powders to be in the mid 2600s to well over 2700 fps for a 24" barrel. So you have something going on with the pressure/velocity for sure, but you already knew that empirically. Testing another powder such as Varget would probably be enough to tell you whether the issue lies with the Staball powder, or somewhere else. Obviously, if you work up a load to a reasonable velocity/pressure with 168s over Varget and the pressure issue disappears, you have your answer. On the other hand, if the primer issue remained with a powder like Varget, you might want to get the rifle checked out.
In your case, something is obviously wrong because the apparent velocity/pressure you are generating from a 24" barrel with a 168 gr bullet should not be grossly excessive, yet the pressure signs suggest it is. Other reloading manuals (Berger and Speer) list maximum velocities for a 168 gr BTHP with various commonly-used .308 Win powders to be in the mid 2600s to well over 2700 fps for a 24" barrel. So you have something going on with the pressure/velocity for sure, but you already knew that empirically. Testing another powder such as Varget would probably be enough to tell you whether the issue lies with the Staball powder, or somewhere else. Obviously, if you work up a load to a reasonable velocity/pressure with 168s over Varget and the pressure issue disappears, you have your answer. On the other hand, if the primer issue remained with a powder like Varget, you might want to get the rifle checked out.
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From what era ?
There was some weak runs a few years back.
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