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Old February 7, 2012, 06:16 PM   #1
wyohybrid
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7mm Rem Mag Low Velocities

I've been watching this forum for some time now and found most of the answers I needed.....until now.

I've recently came across an issue with reloading my Rem 700 7mm Rem Mag with a 24" barrel. I was finally able to use a chrony at the range today and was very surprised at the results I got. I am currently working up hunting rounds using 160gr Nosler Partitions with 59.5gr of Viht N165. I am using Win brass trimmed to 2.490" with Win WLRM primers. I am setting the bullet 0.020 off the lands as this has given me the most accuracy with this bullet. I am getting <1" 5 shot groups at 100 yards with a very slow avg velocity of 2674 f/s, well below published speeds for this charge (Nosler #6 lists a middle charge of 59gr at 2846 f/s and max charge of 61gr at 2904 f/s). With any charge beyond 59.5gr of N165, I develop pressure signs with difficult case extraction. I have tried RL22 in the past but found the accuracy to be insufficient with +3" groups. The club owner suggested I use H1000.

Is there any suggestions beyond changing powders to reach acceptable Magnum velocities?
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Old February 7, 2012, 07:40 PM   #2
Brian Pfleuger
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You can pretty well expect to be below published velocities. Most load data is developed using SAAMI minimum chamber dimensions which maximizes pressure. Real guns usually have larger chambers and will develop lower velocity.

Add in the variables of case internal volume, powder lot variance and primer brands and there's really no way to expect that you'll match published data because you happen to have a bullet that weighs the same amount but everything else from the gun to the primer is different.

All that said, I am a believer in achieving the capabilities of a cartridge. If you'd wanted a 7mm-08, you'd have bought one, right? You want a 7mm Mag.

So, try a different powder lot maybe, or a different powder, primer or cases.
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Old February 7, 2012, 08:05 PM   #3
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Are you loading the rounds to the recommended 3.290 ? I know you are seating the bullets just off the lands and if it is longer than recommended it will change the pressures. Some powders become erratic with just a slight change.
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Old February 7, 2012, 09:32 PM   #4
William T. Watts
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If you can hang on to the chrony for another session I would try a box of factory ammunition and compare results with your handloads, you've already stated your rifle has a 24' barrel, the results in your loadbook may have been developed in a 26" barrel.. FWIW the original factory loading developed for the 7mm Remington Mag was an non canister lot of IMR7828, I used the same powder (canister lot) for my 7MM Remington Mag that produced excellent accuracy but have no idea of the velocity developed. William
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Old February 7, 2012, 09:51 PM   #5
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IMR7828 is my go too powder for magnum loads, although I have 42 pounds of WC872 I need to burn though so IMR7828 is taking a back seat to thrift.

Try changing powders AND primers. Try CCI-250s with IMR7828 and see if that works better for you. RL25 and H1000 are also worth a shot.

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Old February 7, 2012, 11:53 PM   #6
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Quote:
All that said, I am a believer in achieving the capabilities of a cartridge. If you'd wanted a 7mm-08, you'd have bought one, right? You want a 7mm Mag.
Exactly....

Will going with a slower powder be the direction I want to take, as the club owner had suggested?
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Old February 8, 2012, 12:35 AM   #7
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Old February 8, 2012, 06:18 AM   #8
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First off is this a new/used rifle? I've had luck in the past shooting IMR-4831
with 160gr Partitions. Load came out of Nosler # 1 manual 59gr to 63gr/IMR-4831 with 160gr Partition @ 2991fps manual velocity was 3011fps.

If you check Nosler manual #6 that load is still list but only change is velocity they lower it to 3008fps and reason for that 1st manual used 25" long barrel Manual #6 used 24" long barrel.

I've also used H-4831 with 175gr bullets in the 7mag. I see you live in Co if your close to the Springs I've got a bunch of powder give you some to try send PM if interested.
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Old February 8, 2012, 08:59 AM   #9
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Every rifle is a law unto itself. Accordingly, some loads will not be even close to published, and so a chronograph is the only way to know.

I used H 4831, but now days would choose a slower denser powder and give it a try.
Like you, I used a 7MM Mag to get magnum velocities with 3100 fps with a 160 grain bullet. If I wanted .280 velocities I would have bought a .280.

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Old February 8, 2012, 09:10 AM   #10
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what was the temperature when you done the testing? it will be quite a bit higher in the summer time as compared to winter.
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Old February 8, 2012, 09:18 AM   #11
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I'd go with QuickLoad's predictions. It's only off on its calculation for your current load by 50 fps. The 7mm Mag is significantly overbore. Consequently, QuickLoad's "weighting factor" default of .5 should probably be more like .4 or maybe less. Adjusting that would decrease predicted pressure and increase predicted velocity. A truly accurate prediction would require your true case capacity though.

Short answer, it appears that a different powder is called for. QL appears to like IMR 7828.
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Old February 8, 2012, 10:24 AM   #12
243winxb
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7mm Remington Magnum Load Data

Quote:
59.5gr of Viht N165. slow avg velocity of 2674 f/s
http://www.lapua.com/view_reload_tab...iteid=products Your result are inline with Lapua reloading data using a Grand Slam 160gr bullet & 24" barrel. Check the note at the bottom of the page. There are trying to say something about starting load producing pressure signs, i think. Different Component=Different Pressure VihtaVuori N165 & IMR 7828 are right next to each other on Hodgdon Burn Rate Chart.

Last edited by 243winxb; February 8, 2012 at 10:32 AM.
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Old February 8, 2012, 11:24 AM   #13
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Ah, yes, I kept looking at N160 data last night when comparing the speeds.

The load you are using is only about mid-way in Vihtavouri's data...

Their online book (http://www.vihtavuori-lapua.com/pdfs...-Data-2006.pdf) shows:

They show 160gr Grand Slam starting at 57.3 @ 2593, max 65.1 @ 2859

and 160 Sierra starting at 54.2@ 2530, max 73.4 @ 3015

The link provided by 243winxb shows:

160gr Grand Slam starting 59.1 @ 2664, max 68.1 @ 2982

They show quite an odd variance in max charge for equal weight bullets. I might expect a few tenths or even a grain difference based on bullet construction but 8 full grains?! Wow.

Hard bolt lift over 59.5gr is odd.
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Last edited by Brian Pfleuger; February 8, 2012 at 11:46 AM.
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Old February 8, 2012, 11:41 AM   #14
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It's odd. He said at 59.5 he is getting hard bolt lift, but QL shows 42k psi at that charge.

His velocity in QL matches up almost identical to what he is getting though.
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Old February 8, 2012, 11:47 AM   #15
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Something is odd for sure. Would be helpful to know case capacity and if the bullet is touching the lands.
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Old February 8, 2012, 12:55 PM   #16
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The OAL measures 3.283" +/- .003" due to bullet tip variances. I begin touching the lands at an OAL of 3.302/3.303" using the same bullets. For consistency, I've started using a Hornady OAL gauge.

The temperature inside the range around 70. http://triggertimegunclub.com/

The rifle was given to me by my father 20 years ago; I have no idea how long he had it previously, but I know he never shot it (he preferred his 308 Norma Mag). The rifle has no more than 500 rounds through it, most of those in the past few months.

I am getting an average of 80.4gr of H2O, filling the cases to the top of the shoulder/bottom of the neck. I am getting an average of 84.9gr of H2O, filling the cases to the top of the neck.

Thank you all for the replies.

Last edited by wyohybrid; February 8, 2012 at 01:12 PM.
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Old February 8, 2012, 02:46 PM   #17
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I handload ~ 60 cartridges, and the 7mmRM is my favorite hunting cartridge.

There are white lies, lies, dam lies, and then there are 7mmRemMag published data.

The 1925 300 H&H case head used in the 1962 7mm Remington Magnum is good for 72 kpsi for an individual rifle with long brass life.

The 7mmRemMag is registered with SAAMI at 61kpsi.

Those two numbers are close for a reason. One causes the other.

It is the published data that is out of bed.

I am currently using H4350 in 7mmRemMag, to get temperature stability.
I work up my own loads.
I get 3350 fps with 150 gr ballistic tips
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Last edited by Clark; February 9, 2012 at 04:37 PM.
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Old February 8, 2012, 05:27 PM   #18
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Different Component=Different Pressure

Bullet construction alone can produce very different pressures, while using bullets of the same weight. Long bearing surface=more pressure. Remember the Barnes X bullet before the grooves were cut into it,they produced very high pressures using standard load data. When the 7mm Rem. Mag was brand new, 1963, the data was all over the place, high , low. The reason for the wide range of data was tight bores in some rifles. Could the chrony be off? How about the scale?
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Old February 11, 2012, 09:15 AM   #19
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I also got "hard lift" with the H4831 sc, 59 grns, and they say it's between 46,400-49,800 CUP. FWIW, Wyohybrid, I load the 160 grn Accubond, (which is a little longer than the Partition) using IMR 7828, my data isn't finished but it's getting closer to MOA at one hundred yds. I have no Chronograph, so I only can speculate, but there is no "Hard lift" at the bolt and the primers are not flattened by any means, but like I said it's not yet where I would say exactly the weight of powder for sure that I'm using, because I'm adjusting it little by little.
Try the H1000, it could be cool with that Partition, as I haven't got that far yet.

Also Clark, what kind of accuracy are you getting from the H4350, with that 150 grn Ballistic -Tip??
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Old February 13, 2012, 10:43 AM   #20
Clark
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I have 4 rifles in 7mmRemMag:
a) $15 Win70 take off barrel on a 1908 Braz Mauser that I rechambered.
b) $33 Rem700 take off barrel on a 1908 Braz Mauser that I rechambered.
c) $185 Lothar Walther barrel blank on a VZ24 that I chambered.
d) $475 used Ruger #1 7mmRM with a limbsaver recoil pad

3 shot groups are 0.8 moa and up at close range.

162 gr Hornady SST are good.
180 gr Berger VLD hunting are good
120 gr Nosler ballistic tip are good.
150 gr Nosler ballistic tip are good.
175 gr Hornady 175 gr spire are good.

Re22 works well
H4831sc works well
H4350 works well.

What does not work well is long range.
I am more like 2.3 moa at 500 yards
But at 600 yards the first bullet gets in the kill zone only 50% of the time.

So in very low wind, a broadside animal would be a 50% chance of a clean kill at 600 yards, 100% at 400 yards.

So if is a really hard stalk, I may take a wang at it at 500 yards, but I need lots more practice and improvement before I shoot at animals at 600 yards.
Attached Images
File Type: jpg 7mmRM VZ24 150 gr BT 10-5-2011.jpg (158.8 KB, 7 views)
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