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| one of us |
I shoot Buffalo 45-70 Magnum loads in mine. The rifle likes them well printing 2" groups at 75 yards. I have hand loaded some loads with the 405 grain Remington flat point and 60.5 grains Reloder 7 and get about the same groups as the Buffalo factory loads. I have seen no problems at all with pressure. These rifles also seem to have very long throats as I can seat bullets very long. Casey | |||
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| <Harald> |
If you look at the warnings regarding the load data for any rifle of the single break action, double or drilling persuasion you find that one is cautioned against high pressure. The danger is not so much of bursting the barrel, its made of the same stuff as bolt action barrels. The problem is that the locking mechanism is not very strong and a steady diet of stout loads will batter it sufficiently to cause it to stretch and get sloppy, which can result in a variety of problems. The load pressure for the .470 NE is 33,600 psi, according to the Hodgdon No. 26 manual, and I would suggest that something in the 28,000 to 35,000 psi range is the prudent limit for the double rifle .45-70 loads. You can still achieve very high performance, especially as suggested by long loading the bullets. | ||
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| <wjb3> |
Shortly after posting this topic I finally received an email reply from Pedersoli regarding the same subject. It reads as follows: "Thank you for your inquiry and for the preference in our guns. Holy garbonzoes, Casey... you are really pushing the envelope with 60.5 grains Re7. That has to be a compressed load. Are you sure you don't mean "50.5?" [This message has been edited by wjb3 (edited 02-22-2002).] | ||
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| one of us |
It is lightly compressed. I seat the bullets out past the maximum OAL. The Remington bullet has two cannelures. I use the one that is closest to the bottom of the bullet. Like I said I have noticed no pressure signs. The Pedersoli double is also chambered in 8X57R which in Europe as I understand it is loaded to 46000 psi. Explain this one. Casey | |||
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| <wjb3> |
Well, I can't expain that one, Casey, but it's nice to now, and a good point. Have you chronographed that 60.5 gr. Re7 load? | ||
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one of us |
CASEY - I'd ask the Pedersoli folks that one! Let us know what you hear. R-WEST | |||
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| one of us |
The explanation is pretty simple: The case head size of the 8x57 is considerably smaller than the 45-70, and therefore produces considerably less rearward thrust at any given pressure. I would imagine an 8x57 at 45,000 psi and a .45-70 at 35,000 psi generate roughly the same amount or rearward thrust. Stated another way, a .45-70 load that generates 45,000 psi is probably generating as much rearward thrust as an 8x57 at well over 55,000 psi. | |||
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| one of us |
Actually I have both of these cartridges and have sectioned them. The cross sectional area differene is 10% at the head. Since pressure is force divided by area that would mean that the thrust force of a 45-70 is 10% greater than a 8X57R if they are loaded to the same pressure. According to my reloading manual my Reloder 7 load is generating approximately 38000 psi. That would equate to about 420000 psi in the 8X57R. I am beginning to think that is why I am not seeing any pressure signs. By the way, 28000 psi is the SAAMI pressure limit for the 45-70. So that is probably why Pedersoli selected that pressure. I think that my rifle shoots accurately becasue I have approximately the same muzzle velocity with the 405 that the factory ammo has with the 300. I am getting on average 2207 fps with the 405 Remington. Casey | |||
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| <wjb3> |
Well I know where the 28,000 cup comes from, but the Speer #13 manual has a third section for reloading the .45-70 titled "bolt-action and modern single-shots only." In that section, average loads are "approach" 35,000. I don't think I have the need (or the shoulder) for those kinds of loads. I'm inclined to be happy with the 28,000 cup section, but when I started this discussion I wasn't sure I could even go that high (their first section is limited to 21,000). I am certain now, thanks to Pedersoli's response, and yours. | ||
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| <Harald> |
The force applied to the breechface or bolt is not, as has been stated by countless pundit since time immemorial, a matter of multiplying the chamber pressure times the head diameter. That would work if the case were in a fluid state, which blessedly is usually not the situation, AND if the pressure were static. The actual force applied is a dynamic and complicated matter of the work done on the bullet and powder as they travel down the bore. The work on the bullet is given by the pressure function and the bore area, so these things are related after a fashion. The closest measure of the breechface / bolt thrust is the recoil you feel. What you feel in your shoulder was first transmitted from the case to the breechface / bolt and then to the stock. Pressure alone doesn't tell the story and with really hard kicking loads you are hammering the action more at the same pressure. The pressure difference for the 8 x 57 mm can be argued by the fact that there is a bit more steel around the other, but probably its just a matter of CIP standards, not burst strength in either case. | ||
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Casey Don't mean to drag this on but a ways up you said you didn't see preasure signs with 60gr of rl-7 with 405 rems. What preasure signs were you looking for? When I started working with warm 45-70 loads in Marlins, Tim Sundles of Buffalo Bore ammo advised me that preasure signs are sticky extraction and stretching brass. He also mentioned that flattening/crattered primers, extractor extrusion, case head expasion and case milking was more in the 60-70000psi range depending on mfg of brass and the number of time they've been shot. (Didn't intend to drop Tim's name but he has been extremely helpful) You might shoot Tim an email (info@buffalobore.com) since he has experience loading for a wide-variety of commercial firearms. RL7 always seemed to be too fast in my 45-70's with anything above 350 gr bullets. I'd highly recommend stepping to slower h322, Benchmark or even h4895 (i'm a little partial to Hodgdon since these are less temp sensitive). You can acheive 1900+fps with any one of these and reduce the presure to much more comfortable levels. One final item... Load to work up to...
Curt David [This message has been edited by cgdavid (edited 02-24-2002).] | |||
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| one of us |
The pressure signs I looked for are all of the above. I did not get any sticky extraction, cratering or flattened primers, case stretching, etc. Nothing. I stand by my load of 60.5 gr Rel 7 and a 405 Rem FP. I would say if you are starting off to reduce that load by 10% and work up to it gradually. Casey | |||
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| <eldeguello> |
I use 60 grains of RL7 in my Ruger No. 1 .45/70 with the Barnes Original 400-grain so-called spitzer type bullet. in my rifle, this given a muzzle velocity of 2270 feet per second. I have never experienced any sticky extraction, or other signs of a pressure level too high for a No.1, but would think twice about shooting this in a break-action rifle!! In addition, it is a very unpleasant load to shoot, so my all-around load is a Lyman .457122 325-grain Gould hollowpoint loaded to 2200 feet per second with 60 grains of 3031. This has substantially less recoil, and is very accurate as well. Would only use the 400 grain Barnes load for big bear or moose. ------------------ | ||
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| One of Us |
I have followed this thread and I do not own a double 45/70 but would like to. But I thought you guy's might be interested in a good read if you have not read it already. "Forty Years With The 45/70" written by Paul A. Matthews. Reagrds PC. I liked it and ------------------ | |||
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one of us |
quote: WHOA, HOLD ON THERE PARDNER! As a pipefitter by trade, I know that the ratio of the increase in area of a circle to the diameter is NOT A LINEAR EQUASION! IT IS A FUNTION OF SQUARE! The formula for area of a circle is: pi X the [radius squared] To simplify I will work with whole numbers. A 2" pipe has a radius of 1". 1x1 = 1x3.14 (Pi) = 3.14. Now, lets double the size to 4". The radius is now 2". 2x2 = 4x3.14 = 12.56! When you double the diameter, you quadruple the area! A diameter increase of 1/2 will more than double the area! If you want to find the % of increase in breech thrust, you must use the formula for area of a circle! Besides would one use the increase in case head diameter, or the increase in bore diameter? After all it is the projectile that the force is working against! Let's explore both situations. Case head increase of 10%, or 1.1. The radius of 1.1 is .55x.55 = .3025x3.141592654 = .950331777 sq. in. Interesting? Let's explore the other theory of bore diameter. .458/.323 = 1.41795, or a 42% increase in surface area. The radius of 1.42 is .71x.71 = .50x 3.141592654 = 1.570/.785 = 2.01 or more than double the surface area! Either way, your formula is flawed! As for pressure signs: This is not valid in this case as all pressure signs will tell you is when you are nearing the PRESSURE LIMIT FOR THE CASE, NOT THE ACTION TYPE! If you are exceeding the design limit of the action type, you will not see any signs until it is too late, as in the action getting "loose"! I think maybe you should rethink your maximum loads for this paticular rifle! ------------------ [This message has been edited by wildcat junkie (edited 02-28-2002).] | |||
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| <wjb3> |
Well, maybe this explains why (as Casey states) the 8X57 is loaded to 46,000 cup. After all, a 42% increase of 28,000 = roughly 40,000. | ||
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