I'm working on a load for a 7mm Remington magnum using H-4831sc, 150 grain bullets. I'm at 66 grains with no pressure signs, velocity averaging a sedate 2900 fps. Depending on what source followed I'm either at or four grains over recommended max, to be honest I'm not certain which direction to go from where I'm at. Rifle is a Browning A-Bolt Stainless Stalker, 26" barrel with B.O.S.S. system.
Real World VS Loading manuals
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Hntbambi
Well-Known Member
Well, is your barrel 26" with or without the BOSS? If it's 26" with the BOSS, you have a 24" barrel or so for velocity figures. You will be a tad lower in speed compared to a 26" barreled gun.
There are many factors into what develops pressure. It's not so much the weight as the bearing surface of the bullet that interacts with the rifling that will determine the load. Not all 150 gr bullets will reach max pressure with the same amount of powder.
I have found the data books to be fairly close with my real world findings. The old addage of them being written by lawyers is BS. Without a personal ballistics lab you will not know for sure, so unless you really know your stuff, stick with the books.
There are many factors into what develops pressure. It's not so much the weight as the bearing surface of the bullet that interacts with the rifling that will determine the load. Not all 150 gr bullets will reach max pressure with the same amount of powder.
I have found the data books to be fairly close with my real world findings. The old addage of them being written by lawyers is BS. Without a personal ballistics lab you will not know for sure, so unless you really know your stuff, stick with the books.
boomtube
Well-Known Member
"Depending on what source followed I'm either at or four grains over recommended max, to be honest I'm not certain which direction to go from where I'm at."
Seems to me you're at a rational max. So, what direction do you think you should "go from where" you are, and why so?
Seems to me you're at a rational max. So, what direction do you think you should "go from where" you are, and why so?
johnnyk
Well-Known Member
I would proceed with caution. You should be able to easily get 3050-3100fps from a 150gn bullet. Your powder may be the culprit. Once you run out or switch to another lot you should definately back in on down and start over. JohnnyK.
The barrel is 26" plus the Boss, probably close to 30" all told. My reason for posting is that 2900 fps really seems slow for any cartridge with MAGNUM in its moniker. Heck, I'm getting 2825 with a .308, 150gr. bullets, 22" barrel. That I'm topping out at 2900 with this 7mm using 30% more powder than a 308 to gain 75 fps just does not make any sense to me. I'd like to hit 3000fps, did not anticipate having trouble getting there with the powder I'm using. My primers are not flattened at all, no brass expansion. Actually pressure signs for my load with 66 grains a less than the Federal Premium I've been shooting. ??
Stonewall2
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There are so many varibles when dealing with 7 mm Rem Mag rifles .
Case capacity , chamber -throat differences ,barrel diamensions,bullets all change pressure and the velocity .
See the 7 mm Rem data in the Speer manuals .
Both rifles shot with H-870 powder, ww brass , Fed 215 Primers ,160 Nosler .025 jump to lands.
One older Ruger 77 would not shoot 160 Nosler faster than 2950 but the best 3 shot group was .2 at 100 yards .
Another Ruger M77 with the 160 Nosler and H-870 using 80.5 gr would cronograph at 3075 fps at 32 degrees.
The companys that write the loading manuals have much experiance and equiptment to test the loading data.
Unless you have Pressure Trace strain gauge system and Quickload to meaure pressure in your gun load by the manuals and be very carefull.
What velocity do you get with the Federal factory loads?
Glenn
Case capacity , chamber -throat differences ,barrel diamensions,bullets all change pressure and the velocity .
See the 7 mm Rem data in the Speer manuals .
Both rifles shot with H-870 powder, ww brass , Fed 215 Primers ,160 Nosler .025 jump to lands.
One older Ruger 77 would not shoot 160 Nosler faster than 2950 but the best 3 shot group was .2 at 100 yards .
Another Ruger M77 with the 160 Nosler and H-870 using 80.5 gr would cronograph at 3075 fps at 32 degrees.
The companys that write the loading manuals have much experiance and equiptment to test the loading data.
Unless you have Pressure Trace strain gauge system and Quickload to meaure pressure in your gun load by the manuals and be very carefull.
What velocity do you get with the Federal factory loads?
Glenn
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Fitch
Well-Known Member
Glenn's suggestion to chronograph some factory loads is excellent.
Exactly what bullets are you using? What are the sources you are referencing? Looking at my "library" I see Nosler says 65g is max. Sierra says 63.2g is max. My (2006) Hodgden manual has no listing for H4831SC and 150g bullets.
I pretty much shoot 160g and heavier bullets in my 7mags. Shooting the 160AB in the Ruger 77 MK-II with a 24" barrel I get my best group with 62.5g of IMR4831 @ 2990 fps with an ES of 22 fps. 63.0g gives me 3032 fps but a group twice as big so I go with 62.5.
If you tell me the bullet and COL you are loading to I can model it in QuickLoad and see what I get.
Fitch
Exactly what bullets are you using? What are the sources you are referencing? Looking at my "library" I see Nosler says 65g is max. Sierra says 63.2g is max. My (2006) Hodgden manual has no listing for H4831SC and 150g bullets.
I pretty much shoot 160g and heavier bullets in my 7mags. Shooting the 160AB in the Ruger 77 MK-II with a 24" barrel I get my best group with 62.5g of IMR4831 @ 2990 fps with an ES of 22 fps. 63.0g gives me 3032 fps but a group twice as big so I go with 62.5.
If you tell me the bullet and COL you are loading to I can model it in QuickLoad and see what I get.
Fitch
baldhunter
Well-Known Member
I hate to say this,the 7mag is just getting too old to perform at the levels it did back in 1962.When it was in it's prime,the advertised velocity was a zippy 3260fps with a 150gr bullet from several manufactures.Maybe a little overated at those velocities,but still,way,way higher than what is shown for it today. I usually found that advertised velocities run about 100fps lower out of my rifles so they don't carry much weight with me.But back in those days,it only had one zippy 7mag to compete against,the dreaded Heavyweight Champ of the 7mm Heavyweights,the 7mm Weatherby Magnum.It too was rated at 3260fps with a 154gr Hornady Spire Point,giving it a four grain bullet weight edge.Later came the 7mm Dakota,7mm STW,7mm Ultra Mag and the 7mag got knocked completely out of the line up for the number one contender.So you see today it cannot compete,so it's fed a modest diet that puts it in the 280 class.But heck if I want it to shoot like a 280,I'd get a 280.I never was able to get my two 7mags to shoot at 3260fps with a 150gr bullet,but I was able to get 3180fps with 65.3grs of IMR-4350.It did that back in 1994 when I got my first one,it was 32 and will still do it at 48.So I'm very thankful to have a couple of the "Special Ones" that will,maybe becauseI just take good care of them.My 7mags shoot their tightest when they are getting near their max and I've seen others do the same.But really,the point I'm trying to make,is the 7mag is just as good as it was back in the early days and maybe even better with the powders we have today,but it is at it's best in the hands of people who reload their own.Reloading as you know,must be done safely,for your safety and the others that may be around at the range.So as always,start low and work your way up and watch for pressure signs with each round you fire as you watch your velocity go up.Good Luck and Good Shooting.
J E Custom
Well-Known Member
Very good advice by all !!!!!
Don't worry about the velocity because each rifle will shoot at different velocities.
Load up and watch your groups as you go. some rifles like hot or near max loads
other rifles like the mild loads. But watch for any signs of pressure. And reduce the load by
1 grain to be safe under all conditions.
If you don't like the velocity at max pressure change powders and start low and work up.
All loading manuals are designed to be in a safe range of pressure for most rifles and should
followed with caution when going to max loads.
Most of the manuals have loaded down from the old days because now everyone wants max
velocities. (Look at the old Hornady manuals and compare them with the new ones).
Powder has changed over the years and the manuals have changed with them, so don't
assume that they are no longer correct, because burn rates change from batch to batch.
One last thing, Check your chronagraph against some friends chronagraph just to make
sure it's not giving you false readings/Velocities.
J E CUSTOM
Don't worry about the velocity because each rifle will shoot at different velocities.
Load up and watch your groups as you go. some rifles like hot or near max loads
other rifles like the mild loads. But watch for any signs of pressure. And reduce the load by
1 grain to be safe under all conditions.
If you don't like the velocity at max pressure change powders and start low and work up.
All loading manuals are designed to be in a safe range of pressure for most rifles and should
followed with caution when going to max loads.
Most of the manuals have loaded down from the old days because now everyone wants max
velocities. (Look at the old Hornady manuals and compare them with the new ones).
Powder has changed over the years and the manuals have changed with them, so don't
assume that they are no longer correct, because burn rates change from batch to batch.
One last thing, Check your chronagraph against some friends chronagraph just to make
sure it's not giving you false readings/Velocities.
J E CUSTOM
Fitch
Well-Known Member
What follows is all analysis data, I haven't fired these loads in anything.
H4831SC is one of the slower powders according to QuickLoad. I used a 150g NBT @ 3.29" COL just for fun.
The best Hodgdon powder looks like H1000 with a compressed load (73.5g but back off from that a full 4g to start and run a ladder) pushing the bullet to 3106 fps out of a 26" barrel. I've never compared QuickLoad predictions with the real world for H1000.
IMR7828SSC models as faster than H1000. I get 3121 fps @ 68.8g - back off to 64g and work up from there.
Reloader 25, which tends to be relatively temperature dependent, looks slightly faster (3134 fps @ 71.5g but again, back off at least 4g to start and work up from there) but not enough to justify the temperature issue.
N570 models as fastest @ 3192 but I've no idea how that performs in real life because I've never used it in anything.
All that said, I wouldn't try any of these with out getting a reading on a factory load and verifying the chronograph is working correctly.
Fitch
H4831SC is one of the slower powders according to QuickLoad. I used a 150g NBT @ 3.29" COL just for fun.
The best Hodgdon powder looks like H1000 with a compressed load (73.5g but back off from that a full 4g to start and run a ladder) pushing the bullet to 3106 fps out of a 26" barrel. I've never compared QuickLoad predictions with the real world for H1000.
IMR7828SSC models as faster than H1000. I get 3121 fps @ 68.8g - back off to 64g and work up from there.
Reloader 25, which tends to be relatively temperature dependent, looks slightly faster (3134 fps @ 71.5g but again, back off at least 4g to start and work up from there) but not enough to justify the temperature issue.
N570 models as fastest @ 3192 but I've no idea how that performs in real life because I've never used it in anything.
All that said, I wouldn't try any of these with out getting a reading on a factory load and verifying the chronograph is working correctly.
Fitch
baldhunter
Well-Known Member
How about Reloader-22.I've got good results with it and 140gr bullets @69.5grs=3200fps,not max,but tight groups.Should work well with the 150's too.
Thanks to all that have replied, sorry I haven't been back sooner but sometimes life happens. I have NOT measured the C.O.L, I'm using Remington Core-loks, seated to cannelure. I have checked all cases before and after firing above and on the belt for expansion, none. Primers show nothing either, not one bit of flattening or firing pin cratering. Factory Federal Premium w/160 Nosler Partitions are running 2985 avg. Primers from these are pretty flat and beginning to show a bit of cratering. To be quite honest were my reloads appearing anything like the Fed's I'd have backed off long ago. An old '73 manual shows 69.1 grains of H-4831 to be maxed for a 150 gr bullet. Not saying this would be safe, just throwing it out for reference.
Fitch
Well-Known Member
Modeling it in QuickLoad at 3.29" COL it looks to me like the max is someplace around 67g @ 3040 fps. Working up to that from where you are with one shot per step in half grain increments will give you an opportunity to inspect the brass for pressure signs after each shot and a ladder test at the same time.
Fitch
