quote:

Originally posted by SlamFire:

quote:

Originally posted by B L O'Connor:
Thanks, Ray, excessive pressure certainly is the problem, but we are looking for the cause of the blown primers in a sub-"starting load" charge of Varget.

We may now have identified the problem: he had unknowingly used SR Mag. primers rather than SR primers. The issue is, as you say, likely human error.

Apporeciate the thoughts.

Something else, a primer is not a primer is a primer. They are as individual as any other product. They are made within tolerances. Since I don't have a pressure gauge, and don't make primer cake, I don't have data on how primers vary, and how their variance affects the pressure curve.

Understand, primer cake is a mixture, hand stirred by humans. The components in primer cake vary in purity, have plus or minus percentages, and since it is a mix, will have homogeneity issues.

I am aware primers have different flame temperatures, different dwells, different amount of mass ejected, and there is probably more, which I don't know about. All of these are controlled parameters which tells me, they have an effect on the ignition and combustion of gunpowder. And therefore, have an affect on the pressure curve.

No one should any expectations that changing primer lots, or brands, will not change the pressure curve.

One other point, and this is actually very important, humans don't think in exponential terms, you think in linear terms. You think, 1,2,3,4. You don't think 1, 2, 4, 16. Therefore when encountering a pressure curve, which the slope is exponential, linear thinkers have no conception about the magnitude little changes will have on the pressure curve.

That's well put and I agree. And as others have pointed out, "subcalibers" are a phenomenon unto themselves. Methods and component changes that may be relatively safe in larger calibers may not be safe in cartridges like the .17 and .20 caliber cartridges.

And my guess is that, if standard Small Rifle primers turn out to be just fine, then the use of Small Rifle Magnum Primers in their place may illustrate your "geometric" point as well as the fickleness of the "subcalibers."

Thanks again. I don't know about others, but I'm learning a lot. Or think I am!

On the bigger stuff, you can mix and match components and mostly keep out of trouble. But the sub small bores like yours, any variable component is compounded. Crap I just read that you already said that. Anyway, good luck; carry on.

quote:

Originally posted by dpcd:
On the bigger stuff, you can mix and match components and mostly keep out of trouble. But the sub small bores like yours, any variable component is compounded. Crap I just read that you already said that. Anyway, good luck; carry on.

Heh! Well, you did tell me first:

quote:

These sub small bore cartridges are very sensitive to changes of any kind. Expansion ratio is high.

Slamfire's explanation made sense to me as well, as did the suggestions of several other folks.

My working hypothesis is that the SR Mag primer with that sub-starting load of Varget detonated. I've heard that if you don't use enough powder you can get a detonation, and maybe we simulated that with Mag primer and a slightly sub-starting load charge. It would fit with the notion that sub caliber are, er, particularly "touchy" about changes in components

In any event, we should know for sure tomorrow and I'll report what happens.

"starting loads" is a manufactured word by gun experts and it mean nada damn thing..Ive seen many guns maxed out with starting loads, and all but explode with book max loads..Rifles are an inity unto them selves, if you start with a starting load and its even a little hot work up your max going the other way or down not up, it indicates you have a tight or perhaps a bench rest chamber with 0 tolerance, other times you get to max and your under grained two to as much as 8 grs with some powders specifically H414 in certain guns for reasons not specific to this thread..Start low and work up or down is the final..

In my mind I thought the first post had this covered, but guess not, I ramble a lot..

quote:

Originally posted by Atkinson:
"starting loads" is a manufactured word by gun experts and it mean nada damn thing..Ive seen many guns maxed out with starting loads, and all but explode with book max loads..Rifles are an inity unto them selves, if you start with a starting load and its even a little hot work up your max going the other way or down not up, it indicates you have a tight or perhaps a bench rest chamber with 0 tolerance, other times you get to max and your under grained two to as much as 8 grs with some powders specifically H414 in certain guns for reasons not specific to this thread..Start low and work up or down is the final..

In my mind I thought the first post had this covered, but guess not, I ramble a lot..

You do just fine Ray. I for one love reading your posts and regard you as a living legend and vibrant part of history (And I was flattered as all get-out when you thought I was Brad! ).

These bare-bones observations are what we face. Same Rifle, same day:

26 gr. bullet. 27.0 grs Varg. Hornady Brass. Primer SR-Mag. Blown primer.
26 gr. bullet. 27.0 grs Varg. Nosler Brass. Primer SR. Intact primer
39 gr. bullet. 27.5 grs Varg. Hornady Brass. Primer SR. Intact primer.

I'm betting the Small Rifle Mag primer detonated the powder.

But we'll see. Keep your fingers crossed for us!

I'll report later today after our range session.

"In theory, theory and practice are the same. In practice, they are not." — attributed (rightly or wrongly) to Yogi Berra.

Those of you who are still following this thread will know that my most recent best guess as to the cause of my friends .204 blowing primers with sub-starting loads of Varget was that he'd mistakenly substituted Small Rifle Magnum primers for Small Rifle primers (recommended: 27.5 gr. Varget, used 27.0 Varget) to drive a 26 grain Barns bullet.

By doing so, I reckoned, he'd caused the powder to detonate rather than burn.

Well, today we tested that hypothesis, and the hypothesis was falsified.

Using standard CC1 400 primers, the 27 grains of Varget load blew its primer. Being a courageous sort (he is a former marine), he shot a series of 5 loads with 28 grains of Varget, with all of us shielding ourselves from the rifle at each trigger pull.

Four of those rounds were fine, the fifth blew its primer. (If pure experimentation and rifle integrity and our personal well-being had not been factors, we'd have tried 28.5 grains of Varget on the theory that if 28 grains caused fewer primer blow-out than 27 grains, perhaps 28.5 grains would not blow any primer . . . but safety, prudence and the lack of an imperative [as in "Really! How important is it to track down this problem?"] reared their lovely heads and we did not.)

This supports Lamar's suggestion (and Wingnut's concurrence) that the problem did not lie with the primer. It may lie, as Lamar suggests, with an enlarged flash-hole (and/or as Wingnut suggested) soft brass.

And Ray (our portal to god knows how much personal experience) suggested:

quote:

"starting loads" is a manufactured word by gun experts and it mean nada damn thing..Ive seen many guns maxed out with starting loads, and all but explode with book max loads.

.And dpcd and Kevin Gullette have both pointed out that "sub-caliber cartridges are pretty much a world unto themselves." Expertise galore.

That's where we are, and while my friend is mulling things over, I think he's going to abandon the combination of Varget and a Barnes 26 grain bullet. With my encouragement.

As Winston Churchill said wrt the USSR during WW-2:

quote:

It is a riddle, wrapped in a mystery, inside an enigma...

So that's where we are right now. If anything relevent pops up, I'll post an update.

Thanks to all who have offered their opinions and spent their time thinking about this.

One thing that might also help with getting an idea as to what is going on would be some chronograph data for the bullets.

Give you an idea if it’s the case not handling pressure well, or if you just plain are way high on pressure. If the velocities are just plain high then it’s bad lot of powder, or bad data.

I’m inclined to say bad data as both rifles seem to be showing pressure signs from those primer photos, and you used different lots of powder.

quote:

Originally posted by crbutler:
One thing that might also help with getting an idea as to what is going on would be some chronograph data for the bullets.

Give you an idea if it’s the case not handling pressure well, or if you just plain are way high on pressure. If the velocities are just plain high then it’s bad lot of powder, or bad data.

I’m inclined to say bad data as both rifles seem to be showing pressure signs from those primer photos, and you used different lots of powder.

Thanks for the suggestion. Both those cartridges were fired in the same rifle (his) and the Varget came from the same lot (his).

Stupid me, I didn't think to set up my chronograph for this test. I can certainly do that and probably will. FWIW, the 39 grain Sierra and 27.5 grains of Varget shot in my FCV rifle (one number different, at least for the action) was right at 3800 fps (the FCV has a 26 in barrel).

The photograph of the case heads accentuates the severity of the cratering of the intact primer. In real life, it's there, but not the most severe I've seen or, IMO, as prominent as it appears in the photo.

Savage rifles are given to a mismatch in size between firing pin holes and firing pin diameters (both are within tolerances, but if you have a hole whose diameter that is at the large end of it's range and a firing pin whose diameter is at the low point of it's range, you will get cratering in even mild loads).

I had a more severe problem with cratering in my rifle, and after I pierced several primers I had a bushing fitted and the pin turned. Problem solved.

I've recommended he have the hole bushed and the pin turned and I just this minute learned that he's all for having that done.

I like the idea of chronographing our loads going forward. And you have caused my self esteem to crater by pointing out what should have been perfectly obvious to me. I know you care about my self-esteem . . . . Just call me Homer!

too bad you didn't have the chrono setup it could have given you something.
I have seen the numbers go zooming right up, and I have seen them tumble down when your breaking cases.

quote:

Originally posted by Lamar:
too bad you didn't have the chrono setup it could have given you something.
I have seen the numbers go zooming right up, and I have seen them tumble down when your breaking cases.

Totally, completely and humbly agree. And I feel even dumber than I normally do.

But I promise you . . . I will do so in the future. I Hope HOPE that will be this weekend. Co-ordination must happen . . . (notice the passive voice )

No you are certainly not dumb.
One more thing in case it hasn't been mentioned; if the Barnes bullet is a solid copper one, maybe it has more engraving resistance than a lead core one.

quote:

Originally posted by dpcd:
No you are certainly not dumb.
One more thing in case it hasn't been mentioned; if the Barnes bullet is a solid copper one, maybe it has more engraving resistance than a lead core one.

Good suggestion. Hadn't consided that. So I cut a bullet in half and confirmed that it has a jacket and a core.

Turns out that was a needless waste of a good bullet . (Somewhere, the ground squirrel whose name was on that bullet is rejoicing!)

All I had to do was to consult the Barnes website, where I found this:

quote:

The Varmint Grenade® is based on a lead-free projectile design developed for military applications. The hollow point, flat base bullet features a copper-tin composite core surrounded by a thin, tapered jacket with a scored nose. The Varmint Grenade is highly frangible, expending its energy early, seldom showing exit wounds on larger predators such as bobcats and coyotes.

Good idea, but the bullets are not monometal.

Appreciate the idea. I should have thought of that.