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I am trying to work up a 45-70 load for my guide gun. The load will be carried for defense on an upcomming bowhunt in Alaska.

I am working with H322, H335 and 4198.
Starline Brass
Fed 210 primers
The bullet I have is a Lead 465gr in a style similar to the Hammerheads. It is 1.129"long, sized at .460, .360 meplat, 4lube grooves, 20BN and gas checked. It is similar to the 425 RCBS with a wider meplat and shorter ogive.
I am concerned with chamber pressures. I want to stay within the 40,000cup range. The only load data I have that comes close to 465gr with these powders is in the Hodgdon No.24 manual. I have used their 500gr jacketed data listed as heavy loads ruger and marlins only for my starting point. They list H335/49gr, H322/46gr and H4198/39gr as starters.

So far,
46.0/H322  1703avg 9sd
48.0/H335  1647avg 9sd
38.0/H4198 1619avg 13sd
10shot strings
all loads fell into the same 2"group at 50yds offhand

Assuming similar components and conditions in similar rifles one would generally expect similar velocities at similar pressures(my understanding of the subject). The question is what velocities should I limit myself to in an attempt to stay safe in the guide gun.

edited for grammar and sp., probably still have and oops!

(Edited by RG in Idaho at 6:36 pm on Jan. 21, 2002)
 

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You have to be practical.  1700 with a 465 gr bullet IS ENOUGH.  That should shoot through any bear that walks.  I would say 46 is ok maybe even a little more as the Speer book lists 55 gr H322 as 35000 cup with the 400 gr bullet.  If your load shoots well be satisfied and use it.  Again 1700 with a 465 is plenty.  Remember Harold Johnson the daddy or the 450 Alaskan used Remington and Winchester 405 gr factory loads in a 20 inch 1886 and said they killed well after having bad experiences using a 30-06, 300 Weatherby, and a 348 Winchester.  I would estimate the velocity was not over 1225 from his 20 inch barrel.  What does that tell you.  He did go to the 450 Alaskan later but I've never seen where he ever loaded to max.
 

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RG,
The way I check handload pressures with respect to lever action rifles is by comparing factory ammo case expansion to the case expansion produced by said handload.  The only hitch with the 45-70 is finding a factory load that's known to produce about 40K psi.  Nevertheless, anytime you're getting single digit std devs in velocity for 10 shot strings, you should also be producing very consistent pressures.  Your choice of H322 and H335 are both good for your particular application; however, I feel that IMR 4198 is a bit on the fast side for hurling 465 grain cast.  If I were in your shoes, I'd increase the H335 and H332 powder charges by one grain and perform another chronograph session.  If the chronograph shows less than a 50fps gain for the increased charge (assuming all other conditions including ambient temperature are the same) you're probably near max.  One other thing you might do is put your ammo on ice until you're ready to test fire it for velocity.  Some powders can loose their ambition in the low temperatures of Alaska and I believe H335 could be one of them.

Actually, I have a feeling you may be able to squeeze a little more velocity from H332 with good accuracy and still be well under 40K.  H322 easily drives 400 grain cast past 1800fps and some 22" Marlins with 400 grain cast can exceed 1900fps without straining anything.  

Forty Four
 

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You should be able to go to 1800 to 1850 fps with the powders you mention.  Your shoulder may become the limiting factor before you get that far...
Mark
 

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WHY GO TO ALL THAT TROUBLE,,,,405 GR. REM BULK & 53 GR. OF H322, 1800 FPS , ENOUGH THUMP TO CHANGE THE ATTITUDE OF THE BIGGEST, MEANEST BROWNIE YOU WILL EVER RUN INTO.
 
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