Home Forums Hunting & Shooting Ask The Gunwriters A Question of Pressure

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Other forums keep beating the drum about watching for pressure signs. Any new load development should "start low and work up". Good advice in any high pressure cartridge, but what about lower pressure cartridges? A 300 Win Mag operates at around 65,000 PSI but a Marlin lever gun operates at 44,000 with most cartridges. Are both guns going to demonstrate the same signs as they approach maximum respective pressures? The Marlin will show flat or blown primers, case sticking, brass flow etc. at only 50,000 PSI or so and the 300 WM doesn't always show this at pressures in excess of 70,000 PSI?

If I "start low and work up" with my 30-30 or 35 Remington, watching for pressure signs, exactly WHAT am I looking for? 70,000 PSI would be a one time thing for my Marlin or Winchester rifle and maybe for me as well.

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You're not likely to get pressure signs as you near the max for your lever guns. Best advice I'd give is to start low and work up from a reputable manual, then use chronograph/velocity as a metric in establishing your working maximums.

The best way is to monitor case stretch. This is the method Mic McPherson advocates and I agree with him. Basically, if you are stretching the case you are overloaded.

Velocity compared to pressure checked data with actual pressures, using the same components.The only way other than that to gauge pressure accurately in a Marlin or Winchester levergun is to use strain equipment.

I have two friends that have strain equipment for there 45-70's and as one told me,PRE/CHE and all the rest,are probably better than doing nothing but very inaccurate compared to actual pressure testing.Guessing is for fools loading lever actions designed for sub 45,000 PSI ratings and watching for pressure signs before it is to late with components designed for 65K+..

George Weber of Hodgdons Powder tested Winchester 45-70 brass(The thinnest of 45-70 brass) to 70K and it just fell out of there SAAMI barrel.

All of the components are up to the task,the actions aren't!

Jayco

With a lever action, I don't think you will see excess pressure signs, those in the 70,000 PSI range, until you actually reach those pressures. You might not even see them then.

A cartridge in a lever action will not react to 70,000 PSI any different than in a bolt action, although there might be some case and action stretching.

The difference is, the rifle itself might react differently to 70,000 PSI, for example, come apart.

All of this is in addition to the fact that you will never be able to estimate 70,000 PSI, or 50,000 PSI, or anything in between. Or above or below.

Only pressure testing equipment will tell you for sure, and pressure tested loads for lever actions, those loads found in loading manuals, were probably not tested in lever actions, but in guns specially made for pressure testing.

The most accurate indication of pressure in any home handloading is a chronograph, combined with pressure-tested data.

YEP!

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Thank you, Gentlemen.

That's just what I suspected, looking for pressure signs is dangerous at best. The chronograph and/or pressure equipment is the only way.

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Here is an example of primers in the 45-70 shot in a test from the Saami 28K to almost 70K...Reading primers..I don't think so!




Jayco

Mule Deer
Just what are looking for using the chronograph? Is it a big spike in velocity when working up in small amount of increase in powder.

At times when I look at Hodgden load data using the same brand and weight of bullet, it can be 5% more and/or less than load data from the bullet mfg. load. I have found that when you have a heavy bolt lift, it is time to back off. But what are the indicators on a lever gun? I have never found primers to be a very reliable signs of pressure.

Once upon a time, I loaded up a series of cartridges ranging from starter loads to full loads. I fired them all, extracted the primers, and lined them up from least flattened to most flattened. There was no obvious correlation between flatness and powder charge. So I agree: In the normal operating range, primer flatness is not much of a pressure indicator.

I agree with JB on using a chronograph, with one exception. That is, sometimes when you add powder the MV does not go up. I've seen that in my own 308 with (IIRC) 2520 powder. So my statement is that you have to watch to see that you're getting reasonable increases in MV as you're adding powder. With that exception, your MV is a good indicator of pressure. As Dutch once summed it up for us, speed is a pressure sign. If you are getting above book MV you are almost surely getting above spec pressure as well.

"But what are the indicators on a lever gun? I have never found primers to be a very reliable signs of pressure."

Actually, there are no indicators on a lever gun. By the time you see indicators, even if you do, you have gone way too far.

Indicators are not reliable on bolt guns, either, but 70K would be safer in a bolt gun than would 70K in a lever gun.

There can be indicators on a bolt gun, but not necessarily. Hard bolt lift could be one, but even then, you would have no way of predicting how much too much you have.

There has been a lot said about using a chronograph, but when I started loading, back in the early 60s, only the very rich had ballistic labs had chronographs.

I relied on loading manuals. Even if I reached a top load listed in a manual, I never went past that, even if I didn't get indications of excess pressure, such as flattened primers and hard bolt lift.

Flattened primers, case head expansion, and hard bolt lift were the indicators advocated by many gun writers at the time, but now it has been proven than those indicators are not reliable, and in some cases, it is not even feasable to think about using them as indicators.

A very good reason for not relying on these indicaters is that even 70 or 80K might not show signs of excess pressures.

During this time, I did observe a few people who loaded that did get these signs, such as blown primers. When I observed them, I did so from a safe distance.

To rely solely on a chronograph, a re-loader would have to have a very good understanding of powder burn rates, and also of the type of powder best suited for the bullet and cartridge being used.

A chronograph would not be of much use if you were trying to bet 2700 FPS from a .30-06 using a 180 grain bullet and Bullseye powder, and at a reasonable and safe pressure level.

The first sign when your way over is the action locking up if you don't blow it before that.I know more than one person who used the wrong 7 as in #7 rather than RL-7 and it locked up tighter than a .........but never blew..Took it to a smith to get it fixed and the estimated pressure was 81,000....Not very heart warming when a diet of less than 20 rounds at 62,000 PSI loads left the Marlin'95 action mangled and Freedom Arms had there hands in on that controlled testing.

Point being..If your running 50K or over for very long in a Marlin levergun,your doing unseen harm to the weakest link,the action.The Winchester '86 can handle 50K with it's double locking bolts and better design.

Jayco

I'd also agree that velocity is probably the cheapest indicator of relative pressure that us novices can obtain. There are no free rides in the velocity realm. Get above book velcities, and one is probably not in a suggested pressure realm.

1minute

Definitely true, but with some leverguns the data is all over the place..For people using most manuals that follow SAAMI pressures,the Modern 45-70 is still rated at 28K with all the Trapdoors still around.The modern 45-70 can easily handle alot more pressure so came the 450 Marlin at 43,500 PSI,which is now history out of the catalog.

Hodgdons gives pressures to 40K CUP with there components and on another note..45-70 brass differs in volume more than most calibers.......

1-.450 Marlin Brass/73.5 grains of water(2.7 grains less than Remington 45-70 Brass!!!)
2-.45-70 Remington Brass/76.2 grains of water(1.3 grains less than Starline Brass)
3-.45-70 Starline Brass/77.5 grains of water(2.8 grains less than Winchester Brass)
4-.45-70 Winchester Brass/80.3 grains of water.(4.1 grains "More" than Remington Brass.)

Jayco

On the contrary. Always look for pressure signs. Just don't use the absence of pressure signs in your 30-30 as an excuse to go beyond pressure tested load data published by reputable sources. You should never see pressure signs in the 30-30, but if you do, stop shooting immediately and determine the cause(s).

Logcutter: From memory, I think it's the August 2008 Handloader rag that has an extensive discussion and tables listing powders, loads, bullets, and pressures focused solely on the 45-70 and mostly the modern Marlin 1895. Far more extensive than one sees in any reloading manual. If one is interested.... A friend just acquired a copy with a phone call to Handloader and a $10 fee.

From the replies it seems that one gets into high pressure it maybe to late for you and/or the gun. I am most concerned about M-99 308 and 358. The SAMMI on 308 Win is 62000 PSI and the 358 Win is 52000 CUP. Looking Hodgden data some of the 308 are listed in CUP not PSI.

But I still wonder when I look at Hodgden load data using the same brand and weight of bullet @ max gr of powder, it can be 5% more and/or less than load data from the bullet manufacture load data with the same components. Are both safe, I have used the higher one most for the time. I can count on one hand the times I have ever got the velocities are shown any load date. Most data is taken from 24" or 26" barrels. All my guns are 22" barrels. I do not use much factory ammo, none that I have check came close to listed velocity.

I have talked to Hodgden about some max. loads that are listed less than SAMMI max pressure. They have said that increasing powder should be okey - work up very slow. But that is not assuring when the only way one know you have reached high pressure is the EMT�s haul you a** off, and or you are holding a stick of wood.

How about loading to 80-90% of the manual max.? It will probably shoot better and be easier on your gun also. If you want faster -get a bigger gun.

There is another worry to loading a levergun beyond it's limits.Recoil induced tube ignition using hard or hard cast bullets and it has happened more than once.

It's just not worth pushing a levergun...



Jayco