heavy 7mm rem mag duplex loading/ front ignition loading smokeless powder

[e55komp]

hi, im new here and i would love to get your input on this subject, im thinking about shooting a heavy 170/180 gr bullet out of my 30in 7 rem mag barrel and maximum velocity, i would like to do this by using a very slow burning powder(h870) and put a very small charge of kicker powder to help the priming process,. i would love to hear what kind of advice you would have for me since people in the know have directed me to you for your experiance in this subject, thank you in advance.

[calvon]

Conventional wisdom says no to duplex loadings. Not just "no", but "HELL NO!"

You have no way to know what pressure you're getting. Consult one or more loading manuals, and in particular, since you're using H 870 begin with Hodgdon's manual.

You will do well to end up with a load, something under published max loads, that gives you best accuracy and moderate recoil. If you're looking for hunting loads, remember that a well-placed shot from something like a .30-30 is a better killer than a poorly placed shot from some super magnum.

[parkergunshop]

Never, never use a duplex load with smokeless powder period.  Duplex loading is what P. O. Ackley used to blow up  Jap 6.5 rifle actions with when single loading would not give enough pressure to do the job.

Use Federal Magnum Primers to get the extra kick.

With H870 in the 7 M/M Remington case, 79 grains is at or near  the compressed load level, and it is the maximum load in the Hogdon manual.

79 grains is the load I used in a Remington 700 in 7 M/M Mag with the 145 grain Speer for a velocity of 3191 Feet Per Second, My velocity testing , this is about 100 FPS faster than the Hodgon loading data has for this load, the pressure per their test was 51,700  CUP.
This load shot 1/2 inch groups at 100 yds for three shots, this was with less than 20 rounds through a new Remington barrel. the barreled action was glass bedded into a walnut stock with the barrel free floated except fot the first two inches.    This was with the rife owner watching me shoot left handed and I am right handed, the roll over comb prevented me from shooting his left hand Remington right handed.

Hogdon did not list the barrel length for their load data, the Remington 700 Action above had a 24 inch barrel.  With maximum loads, bullet seating and case capacity is critical,

I tend to load a round with the bullet seated long to seat the bullet into the lands, then set the bullet seater to the chambered round's bullet , this gives better accuracy and allows the use of a little more powder for full case powder loadings.  This is the way you load for a benchrest rilfe to get maximum accuracy.   H870 is so slow that it allows full density loading in many chamberings, but be careful.

This means that you have to change the seater for each and every rifle you load for in many cases for that chambering.

[parkergunshop]

e55Komp,

One more note.  Loading manuals are good starting points for loads, but each rifle seems to be different when dealing with accurate maximum loads. and I find loads that approach maximum to be more accurate in many cases.

For example:

I use H450 in my .338 Winchester Mag, Shaw Barrel, 1914 (P14) Enfield Action, bullet seated out to touch the lands when chambered.

For the 200 grain Speer Bullet, I started with 75 grains of H450 and went up a grain at a time looking at the accuracy and for signs of excessive pressure.

The Hogdon manual lists 79 grains of H450 as their maximum load velocity of 2942 with a pressure of only 47,500 CUP.

I stopped my load at xx grains of H450 with no pressure signs for a velocity of 2881, note I used x grains more powder and got over 50 FPS less velocity.
The barrel used by Hogdon must have had a tight chamber, sometimes pressure test barrels are at the minimum from a tolerance standpoint.

Two back to back loads of xx grains shot into .322 and .348 inch for 3 shots at 100 yards.  So I stopped there happy shooter.  No pressure signs either.

[e55komp]

thanks to all the replied, i have read the loading manuals i am very aware of the ( dont do it ) mentality, i have heard from a wise man that the person running this forum happens to be an individual who has dabbed in this before and i just wanted to get his input more for curiosity sake and if something concrete comes out of it maybe give it a shot. i would love to see 3200 fps with a 180gr but without a 1gr fast powder kicker i just dont see it happening.

[Veral]

  I've played with it quite estensively and wrote a fairly length piece about it on this forum.  Look it up and read it over. 

  I've forgotten about the entirity of what I wrote now, but don't recall recommending it as a method to make heavier loads but as a method to use up surplus slow powders which wouldn't give decent velocity if used alone, or that wouldn't burn clean.    A kicker worked up slowly turned the trick for me with several cartridges.

  As for getting an extra 100 fps from your already too fast ammo, I'm not interested either, and wouldn't have your gun on a hunt if I had any other suitable option, and I can be suited with some fairly anemic rifles, by gun rag standards.

  Some 25 years ago I worked up some really hot cast bullet loads for my 30-06, which were nice and accurate.  Something over 3000 fps as I recall.  I got my chance to use the load on a deer in a small box canyon, and my ears rang for a week after.    No super whaming report for me anymore.  I've killeds hundreds of head of big game with loads that don't destroy my hearing or demand hearing protection.   At 70  I'm far too old to change my opinions on that matter!  But help your self if you like to see the bullet hit a few seconds before smoke begins to come out the barrel, go for it!  We still have THAT much freedom!


  You see, I butcher all the game my wife and I kill and am quite particular about not ruining more meat than necessary.   I talked to a hunter here a couple years ago who didin't understand why his 338 Win mag ruined ALL the meat on the front half of his trophy bull moose!     He was over gunned and probably incapable of shooting that beast many times and not starting a flinch.