Reloading for 7mm Remington Mag


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parker51
April 1, 2010, 03:17 AM
This is the first time I have reloaded a belted cartridge and just want to make sure I am measuring the OAL correctly for this round. I am planning to start off with Nosler Ballistic Silvertip 140gr, Ballistic Tip 140gr and Ballistic Tip 129gr bullets. I am using a Remington 700 and came up with the following OAL cartridge lengths:

Silvertip 140gr = 3.326 to the lands, O.A.L. of this round 3.316
Ballistic Tip 140gr = 3.390 to the lands, O.A.L. of this round 3.380
Ballistic Tip 120gr = 3.355 to the lands, O.A.L. of this round 3.345

The Speer manual calls for a maximum cartridge length of 3.290. Should I back mine back to this length or use the actual measurement for this gun? What is the minimum amount of the bullet that needs to be inserted in the case? 1/4? 1/3? The 120gr bullets are only going to have about 1/3 of the bullet inside the brass if I use the 3.345 measurement.

Brass cut to length of 2.490.

I did find some of this brass was cut to 2.480, would this still be safe to shoot?

I haven't decided on a powder yet, but suggestions for these lighter loads would be appreciated.

Thanks in advance!

Chuck

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NuJudge
April 1, 2010, 06:36 AM
There are several cartridge lengths you need to pay attention to:
-the overall length to the bullet tip
-the length where the bullet strikes the lands of the rifling
-the length beyond which the cartridge will not fit in the magazine.

Has this rifle been shot a lot, eroding the leade and allowing bullets to be seated so much further out? Will the longer cartridges fit down into the magazine?

Intrusion of the bullet into the cartridge case reduces powder capacity, which is bad for velocity. If your rifle lets you load longer than the books say, you might want to try it.

Cases a bit shorter than standard are not a problem. A casting of your chamber using cerrosafe will probably show that brass a bit longer than the standard will not be a problem.

I've used 4831 in the past, but will probably use mostly RL22 in the future.

azar
April 1, 2010, 10:29 AM
The Speer manual calls for a maximum cartridge length of 3.290. Should I back mine back to this length or use the actual measurement for this gun?
3.290" is the SAAMI max length, which my understanding means it's a standard that everyone who chambers the cartridge should meet at a minimum. Going longer is fine as long as your magazine & leade will allow it.

What is the minimum amount of the bullet that needs to be inserted in the case?
Unless the gun is going to be used in a benchrest competition where the bullets are fed one at a time into the chamber, then one calibers worth of bullet (excluding the boat tail) is a good general rule. This allows the full length of the neck to grip the bullet.

I haven't decided on a powder yet, but suggestions for these lighter loads would be appreciated.
I have yet to shoot bullets that light in my 7mm Rem. Mag so I can't help you there.

howlnmad
April 1, 2010, 12:38 PM
I launch Nosler BallistiçTips in both 120 and 140 grn and Rem 140 grn corelokt in my model 700 . IMR-4350 does a fantastic job..

parker51
April 2, 2010, 02:16 AM
Thanks for the help! Today I tried the Nosler/Winchester Silvertip 140gr using 58gr of IMR-4350. I used the O.A.L of 3.316 for this round and I was able to get 3 5-shot 1 1/2" groups at 100 yds. I will probably bump this up to 58 1/2 to 59 to see if this pulls the groups in a little tighter. Since I posted this I read in the Speer reloading manual that anything under 145grs should not be used for hunting whitetail as the velocity is so high that these lighter weight bullets tend to explode on impact with muscle tissue so you don't get good penetration with these bullets. I don't believe these bullets were being made when the Speer manual was published but if this still holds true I may have to rethink my loads for this gun. Thanks again for all the help.

Chuck

NCsmitty
April 2, 2010, 10:03 AM
I read in the Speer reloading manual that anything under 145grs should not be used for hunting whitetail as the velocity is so high that these lighter weight bullets tend to explode

If you plan on hunting deer with the lighter bullets, then you need to be concerned a bit about the jacket thickness and bullet construction.
The 7mm Remag is a magnum in every sense of the word, and capable of driving most standard 120gr bullets beyond their intended design velocity. Close shots at big game can rupture the bullet jacket, and it can act like a varmint bullet and lacking penetration, destroy a bunch of meat and perhaps not kill DRT.
Selecting a good 140+gr for hunting will still give you a flat shooting round and most bullets in that weight will expand and kill reliably.
IMO, you should use .020 off the lands, as the ogive of the bullet can vary the .010 that you are using now, due to manufacturing tolerances.
Good shooting.



NCsmitty

parker51
April 2, 2010, 01:49 PM
If you plan on hunting deer with the lighter bullets, then you need to be concerned a bit about the jacket thickness and bullet construction.
The 7mm Remag is a magnum in every sense of the word, and capable of driving most standard 120gr bullets beyond their intended design velocity. Close shots at big game can rupture the bullet jacket, and it can act like a varmint bullet and lacking penetration, destroy a bunch of meat and perhaps not kill DRT.

I had no intention of using the 120gr for deer hunting, just the 140's. After reading what they said in the Speer manual I was concerned the 140gr might fall into the same category as the 120 gr. bullets. I still think I will look at a heavier bullet (150 to 160 gr.) should I decide to use this gun for hunting whitetail.

Selecting a good 140+gr for hunting will still give you a flat shooting round and most bullets in that weight will expand and kill reliably.
IMO, you should use .020 off the lands, as the ogive of the bullet can vary the .010 that you are using now, due to manufacturing tolerances.


Good point! I have been using .010 in my hunting rifles without any problems, but it would only take one problem to make me wish I had used .020 so I will take your advice. I use .030 for my Swiss K-31's but that is primarily so I can use these rounds in several guns. Thanks!

Chuck

627PCFan
April 3, 2010, 10:05 AM
I run 140BT's pushed by 68gr on IMR4831. Tried H4831 but didnt do anything special. If you get the 120s to shoot well, let me know. The twist rate is at the opposite end of the spectrum for that weight bullet.

smokey262
April 3, 2010, 11:59 AM
Nosler says that 3000 fps is the suggested maximum impact velocity for all Ballistic Tip hunting bullets.

The 120gr BT has the same jacket as the 140gr BT, but is shorter, thus the jacket is comparitively thicker than on the 140gr

Either of these would be fine for whitetail deer as long as you don't shoot them too close at a high impact velocity

howlnmad
April 3, 2010, 12:19 PM
I have shot several whitetails with all three of the loads I posted. shot placement has a lot to do with everything as well. My friend prefers a shoulder shot:scrutiny:, I hate to waste that meat. I prefer just behind the shoulder. And each deer had the same results...small entry hole, exploded heart and a slightly larger exit hole. You gotta use whats right and comfortable to you. I can't say what results the Speer bullets will have because I won't use them.

ForneyRider
April 4, 2010, 01:35 PM
I use R22 for the most part with 7mm Mag. R19, R22 and H4831SC are very popular with 7mm Mag. IMR 4064, 4350 and 4831 are popular as well.

The Nosler 120gr have been great for me. I am about 2gr down from max in Nosler data. I load mine to mag length.

Bullets/Powder I tried:
Nosler 120gr - R19, R22
Sierra Pro Hunter 120gr - did well with min load of IMR 4064 and 4350
Hornady 139gr SST - R22
Hornady 162gr Interlock - R25, R22 - accuracy was mediocre with R25, so going with R22 here as well.
Sierra 168 Match King - R25

Got very good accuracy with 120gr Sierra and min. charge of IMR 4064. IMR 4064 and 4350 min loads did better than Varget and R19 for my goal of accurate 3000fps load of the 120gr Sierra.

I tried R25 with the 168gr SMK with not much accuracy or velocity.

I use Winchester/Remington brass and CCI 200 (LR) primers. I got better accuracy with the CCI 200 than 5 other primers I tested with. I think you have to include experimentation of primers to get best accuracy.

I have been working with 7mm Mag, work from min to max in .5gr increments. Some load data can have 6-7gr difference between min and max. Norma data is pretty consistent 2-3 gr difference between min and max, but they don't list pressures.

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