Home Forums Reloading Big Game Rifles Chronograph - the great truth serum

I am well aware that different bullets produce different pressures but it is still not that simple.There are usually several manuals or charts using the exact same bullet.For example the bullet manufacturer and the powder manufactures both use the same bullets.So do other sources that also use sophisticated pressure testing equipment.

Let's say that I have a barrel in .236 Shezam, and Noslererra has one in the same caliber. Let's say the SAAMI limits for this cartridge are 62,000PSI. It is generally assumed that if I reach the same velocities as Noslererra, that I have reached max pressure. This is definitely the most conservative and safest course of action, and probably the way to go.

But....... I'm not sure it is necessarily the truth. If my barrel can be slower at the same pressure limits as Noslererra's, then who is to say that Noslererra didn't get a barrel that will reach pressure limits at a lower velocity than my barrel?

I think the thing is, that unless we have access to pressure testing equipment like Charlie now has, (really looking forward to you posting your results, Charlie) we just don't know. Since we have no real way of knowing what pressures we are getting, the safest things to do are stay below listed book maximum charges, and at or below listed maximum velocities, whichever comes first.

Let the flames begin, but nowhere in this post did I claim to have never violated the safest course of action. <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />

John

It is extremely refreshing, and unusual, to hear anyone use the term "conservative" or "safest course of action" when discussing handloading. RS

Eggggzactly............................ <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

JimF

Like I said earlier, "I go with the manual published by the company who manufactured the bullet". In the case of old vs new manuals, I use the newer manual. I personally haven't come across the big differences you are referring to. Then again, I don't think 100 fps is that big of a difference.

I do not find all this variance in data to be a big issue. Since the velocity spike usually occurs first and I look for that, I just do not have pressure issues when loading.

Hondo,

I had John Ricks pressure test some of my loads. I thought I was safe because I didn't have any pressure signs at all. I was getting 200 fps more than the manual, but I thought that was okay because of the lack of pressure signs. My load tested to 74,000 PSI, and that is with that too soft Norma brass. While it is possible that one identical length barrel may reach the same velocites as another at different pressures, it is not likely, nor a prudent assumption.

Ringman:

If you get the chance, look up the article by John Barnsness (our Mule Deer) titled "Pressure Guessing" in Handloader No 219 (10-02) pp. 46. The first 3 paragraphs give you your answer.

This article is tremendously informative reading and it may give you some perspective on the velocity debates that we have on the forum from time to time. This article coincidentally mentions pressures and velocities for the 7mm STW, (as well as several other cartridges that he tested personally for the article) this may be informative for you as well.

I'm certain that JB had no reason to debunk the velocity capabilities of the 7mm STW, the 300 WM, or any of the other cartridges he mentions. He simply makes the point, that velocity always comes with a price, and that price is pressure. He further, and most importantly, makes the point that pressures are almost impossible for the shooting public (that would be us) to accurately evaluate. I interperet from his writing that he believes the Chrony is the one tool at our disposal that can really quantify what is happening inside that chamber.

This article hopefully will give you some perspective about the wisdom of regularly shooting 65-68K PSI loads, let alone loads of 70K (+) PSI. To assume that such a thing is OK is very foolish.

JimF

JimF
I have started doing some pressure testing. Talk about an eye opener ! <img src="/ubbthreads/images/graemlins/shocked.gif" alt="" /> I am seeing things that I would have never believed. I wont go into the details now, but with the test I've done so far, you can completely forget looking at brass, unless the primer has poped out. 30,000 psi looks the same as 65, 000 psi. One statement I will make that you can take to the bank....... I used to think I knew a little about reloading, but now I'm sure I know nothing. Like I said, I'll not go into the details now, as I am consulting with an attorney friend of mine about the possible backlash of what I am finding. Another thing for sure...what I post will be the exact results of the test, like them or not... <img src="/ubbthreads/images/graemlins/shocked.gif" alt="" />...Many things I held as fact really aint, and when I publish these findings several folks are going to be pissed off, scared, confused, and feel like they have been lied to. <img src="/ubbthreads/images/graemlins/blush.gif" alt="" />
When the Juenke machine became available, the bullet manufacturers lost that ability to say " The bullet aint the problem", now we know sometimes it is... <img src="/ubbthreads/images/graemlins/shocked.gif" alt="" />
I'll start posting results as soon as I get the legalities straight.... <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
Charlie

Charlie- I can't wait to hear the results. I'd also like to thank you for re-testing 'old truths'. I find it refreshing that the same 'ol knowledge is just not being regurgitated for the upcoming generation, but that the knowledge base is being furthered. Beings that I'm new to the game of rifles, I appreciate the time and effort TONS.

Charlie:

That is very exciting. Like your barrel length tests, I'm sure that I'll learn a lot. It could very well be that my cautionary posts Re: the magnum fanciers may be incorrect. If so, I'll gladly eat my serving of crow in exchange for some real knowledge.

As I've posted many times, I have no problem with sombody who wants to push the envelope. I only have a problem with those who suggest that it's a safe practice for others to follow, or those who use unsafe pressure levels to define the capabilities of a cartridge.

JimF

When I start loading for a new cartridge I look up all the data for the bullet I want to use and put them in a chart. By and large, I find there is a lot more variation in maximum charges listed, than in reported velocities.

For instance, several manuals show loads for the .270 Win. with 150-gr. bullets and RL-22. Using the Hornady bullet, Hornady shows 58.7 gr. for 2900 fps; Lyman shows 57.5 gr. for 2852 fps. Using the Nosler Partition, Nosler shows 56.5/2902 and Alliant shows 59.5/2845. All of those are in 24" barrels. In my 22" barrel I get over 2800 fps with 55.0 of my current lot so I stopped there.

When there are big variations I read between the lines -- often you find that one of the companies had a different barrel length, or used a magnum primer instead of standard, or a radically different seating depth or something. And frankly, some companies are just a little more conservative across the board in their methodology.

John

Okay, Charlie. Now I'm REALLY on pins/needles. Please publish your data as soon as you can.

I think one of the problems we face is, there are so many different chambers and barrels out there in any given caliber that data collected in one will have little chance of being remotely close to that collected from another. Even if the barrel/chamber is an SAAMI standard, will the same components produce identical results in every other SAAMI standard setup? I doubt it. What if Pressure Trace or the PBL says the oft-quoted load of 57 or 58 I4350 and 165 grain composite bullet in the 30-06 produces 55KPSI in an SAAMI standard barrel/chamber, does that mean it will produce that in EVERY 30-06 rifle; if not, will it be enough higher to cause potential damage in the future, if fired enough times in even one rifle?

Another thing that will skew the results is how the data is collected. I've seen posts from guys who've tried the Pressure Trace units which mention significantly differing results from the same load combo in the same rifle depending on where the gage was attached.

Like Charlie, the more I learn about this the less I know. I think there's as much black art involved as there is science. Caution and prudence must be our guiding precepts.

Please hurry Charlie. I'll be sitting in the corner with a blanket over my head, quivering and drooling on the floor 'til your results are posted. <img src="/ubbthreads/images/graemlins/frown.gif" alt="" /> <img src="/ubbthreads/images/graemlins/frown.gif" alt="" />

R-WEST

I will admit to using a Chrony as a pressure guage and measuring the belt.One of the things that can mess you up are the powder lots.I know of one lot of H-1000 that behaved like a 4831,much to my grief.

Pressure Experiment Report on HA



Another thread on pressures, etc.



Think I got the links right, now.



John

stubblejumper,

I worked up a load for a friend's 7STW. I setteled on a 140 Nosler with 82 grains of IMR7828 and a Fed 215 primer. The Velocity is 3,450 in 60 - 70 degree weather. It is a reamed out Remington 7 Mag. If this load is "unsafe" how would the owner or I know? We have used it to kill a truck load of game.

Ringman-If you see no sign of pressure and the primer pockets do not loosen with five loadings I wouldn't worry.If you see no other pressure signs the primer pockets expanding is usually the first to indicate that there may be excess pressure.

This

Quote

Pressure Test Thread on Hunt America

just took me to denton's profile at HA. <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

R-WEST

Since we're all sitting around waiting for Charlie to post whatever results he has (please, Charlie), to get back to the intent of the original post about chrono's, likewise, I agree that they're real truth-serums. Don't know how many times I've seen numbers that were a lot lower than expected; rarely higher.

In my experience, most factory ammo (Light Mag and High Energy stuff excepted for the most part) is especially bad in this regard, often times being 10% less than published numbers when fired in the same length barrel as the factory ammo supposedly was. As an example, and I use it because it was so much fun at the time, my brother in law's Savage 110 7RMag in which he fires only R-P 150 Core-Lokt factory ammo, averaged 2,950 for 5 shots from its 24" barrel, about what a well tuned 280 will do, vs factory specs of 3,100 or so. He was so depressed, and naturally I couldn't resist rubbing it in a little <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />, that he's considering a 7 Ultra Mag or some other high-po 7 to replace it. Never mind the fact that he's killed umpteen deer with it, he wants SPEED, darn it.

On the subject of the 7RMag, a recent article by Mule Deer mentions the fact that factory ammo for that caliber keeps getting slower and slower, due to its penchant for weird, unexplained pressure spikes. Everybody's always raved about how "well balanced" the 7RMag is, so, how can that be, and why can't they be explained? I load for 2 of them, so I get very nervous when I hear about such things.

To get back to a question posed by another poster, what does Hondo64d do with his 243 that's near published MAX, per Alliant's data, yet 300 FPS below anticipated speed? If it was me, especially knowing how widely the burn rate for Alliant's (and Accurate, too) lots will vary, I'd try a middling load of another good 243 powder, say IMR 4350, which has a history of consistent lot-to-lot performance, and see where THAT one comes out in relation to what the book says it should. Hondo64d might have a really slow barrel, or, more likely, a strange lot of R19. I know I've seen some unexpected numbers from different lots of R19 over the years.
<img src="/ubbthreads/images/graemlins/confused.gif" alt="" /> <img src="/ubbthreads/images/graemlins/confused.gif" alt="" />

R-WEST

Both of them? Ooops. Sorry! <img src="/ubbthreads/images/graemlins/blush.gif" alt="" /> Let me see if I can fix it. OK. I think it's right this time.



John

I would wonder about the lot of R19 I'm using, but it is doing pretty much as expected in my .250 AI...... There is some visible throat erosion in my son's .243. I'm thinking that's having much bigger effect than I expected. It sure wouldn't hurt to try some other powders, though.....

John

Rwest
Sorry I highjacked the thread. I got carried away.... <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
Charlie