7mm Mag powder recommendation?


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357SigFan
November 12, 2008, 09:08 PM
I'm going to start loading 7mm Mag for my BAR. I'm planning on using a 150gn Nosler E-Tip, aiming for around 2800 fps. What powder would be good for a BAR? I've got loading data (provided by Nosler) for IMR4064, Viht N165, IMR4320, Viht N160, H4831sc, MagPro, AA3100, IMR7828, IMR4831 and IMR4350.

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Clark
November 12, 2008, 10:16 PM
All those powder will work.
I have been using H4350 and Re22.

NCsmitty
November 12, 2008, 11:48 PM
If you go to the www.hodgdon.com site you'll note that many starting loads of the medium-slow burning powders will get you near 2800fps. I suggest the H4350 or IMR4350 because they give good performance without draining the powder can too fast. Alliant's Rel-19 should prove excellent and I use it a lot. The AA3100 is intriguing too, but I haven't used it myself.
A 2800 fps load should prove to be a nice easy shooting load similar to the 7mm/08.

NCsmitty

357SigFan
November 13, 2008, 12:21 AM
Dumb question; It appears that Hodgton and IMR are at least related at this point. Since H4350 is Hodgton and IMR4350 is IMR, my assumption is that they are NOT the same powder and thus do not share the same load data; Niether my Hornady or Sierra book have data for H4350. Is my assumption correct or off base?

NCsmitty
November 13, 2008, 09:53 AM
357SigFan, you are correct. And that's not a dumb question. They are close but do require different charges. I believe that H4350 is just a tiny bit slower in burn rate. I use H4350 in my 308 Norma Mag, which is nearly identical in case size and capacity to the 7MM Remag. I shoot 165gr Noslers @ 3100+fps. Like I mentioned before, The most current load data is at www.hodgdon.com and gives you many choices. It's your job to choose a load that's accurate with your bullet choice.


NCsmitty

627PCFan
November 13, 2008, 02:00 PM
My input is as follows (based on a Tikka T3)

IMR 4831 for 140-150 grain bullets
H1000 for 168grain bullets and up-

jhrgr
November 13, 2008, 02:10 PM
I use IMR4831 behind a 150gr Nosler

357SigFan
November 13, 2008, 02:30 PM
I may lean towards the H4350 as it's a little lighter on the powder charge (drain the bottle slower), but if another powder would be better, I'm open. Once I've got a good accurate, nice shooting load, I'll lock onto that powder, bullet and primer. I'll probably use Federal GM215M primers unless there's something better out there. My BAR has a BOSS on it, so in theory, i should be able to pick a load and tune the rifle to the load instead of tuning the load to the rifle, although that theory could backfire on me :).

Remo-99
November 13, 2008, 03:44 PM
I may lean towards the H4350 as it's a little lighter on the powder charge (drain the bottle slower), but if another powder would be better, I'm open.

357,
That theory could backfire on you, if you go too low with powder charges. ie down around 70% and under of case volume, as igniton gets a bit eradic, affecting accuracy quite abit.(although there are some powders that are suitable for downloading, like H4895).

The faster H4350 is fairly suitable for lighter bullets(100gr-150gr) in 7mm mag.

Remember also, if your loading for an autoloading rifle, action functioning is also a consideration.

The slower powders such as H1000, H4831sc or similar burn rate powders. Will be more suitable, if you go with heavier 160gr-175gr bullets.

357SigFan
November 13, 2008, 11:36 PM
So maybe I should shoot for 59gr of IMR4350, which according to Nosler, with a Partition, ballistic tip or ballistic silvertip would be 3028fps and 80% density. With the E-Tip, they say to reduce the max charge by 2gr, so my max charge would be 61gr. I think I'll give them a call in the morning and see if, with the E-Tip, can the charge of IMR4350 go down to 57gr, and if so, what would the velocity and load density be. Obviously, if my starting attempt doesn't cycle properly, I'll have to bump it up.

Dumb question, sorta on topic. Nosler says there needs to be a minimum jump to rifling of .050". How do I determine this? Load a dummy round long and chamber it, then reduce its length to allow at least .050, assuming I see rifling marks on the bullet?

357SigFan
November 15, 2008, 01:25 PM
Spoke to someone at Nosler, and they said, yes, I can drop the charge of IMR4350 down to 57gr, it should be about 77% density, and should be pushing about 3000fps.

lindy
November 16, 2008, 12:24 AM
357SIGFAN,, In answer to your dumb question in post #10.
an easy way to determine case overall length to allow for a .050 jump to the lands follows:
1. Insert a wood dowl into the muzzel until it rests on the closed bolt face. mark the dowl at the muzzel (I use a razor blade).
2.open or remove bolt and drop a bullet into the the reciever and press bullet lightly against rifleing with a pencil or other object. re-insert dowl at muzzel against tip of the bullet in the chamber, mark the dowl at the muzzel. 3. measure the distance between the two marks on the dowl, now subtract .050 from this measurement and that will give you a
case over all length with a .050 jump to the lands.

adobewalls
November 16, 2008, 12:38 AM
JRSpicer42 and jhrgr said it all regarding powders and the 7mm Mag. I like IMR 4831; but have used IMR 4350 with 150 and 160 grain bullets and was quite satisfied. You decision to use Federal GM215M primers is sound also. You should be able to find a nice load combination with those components.

One thing to think about, and especially pertinent with a semi-auto, is a rifle will usually have an accuracy node right near max, and then one a few grains less. Going for the lower accuracy node saves a couple grains of powder, wear and tear on the semi-auto action and is virtually insignificant to the upper node at hunting distances.

ants
November 16, 2008, 01:06 AM
Do what Lindy says. A 1/4" dowel is perfect for 7mm and 270.

I'm not familiar with BAR but a pencil may not fit down in the chamber to hold a bullet against the lands. Maybe a 4 or 5 inch piece of dowel will slip into the chamber from the bottom or the ejection port and you can hold it with your finger through the port.

The razor blade marker in a great idea. You can hold it flat against the muzzle to make your mark, and measure the two marks more finely with a your caliber jaws.

Don't try the dummy round, you may jamb the bullet hard into the lands and leave it there when you extract the case.


*** By the way, just to make sure everyone is clear, is this 7mm Remington Mag, or 7mm WSM? ***

Browning offers the latter in certain BAR models.

dirtman
November 16, 2008, 01:29 AM
357, these loads were about 15 years old when i last tested them... this is a 7mm (Rem) 162 grain bullet bt-sp Hornady #2845 and 61 grains of 4831 powder.
in order were 2985, 2959, 2907 fps. bolt rem 700, with this type of various of speed i still had a 1/3 inch group at 100 yards, -20 F not much wind...
.. . great hunting rd. good luck, enjoy...

627PCFan
November 16, 2008, 11:51 AM
If your going to measure your lands do it right. You need the following:


Hornady Lock-N-Load Overall Length Gage Bolt Action
Hornady Lock-N-Load Overall Length Gage Modified Case 7mm Remington Magnum
PTG Bullet Comparator
and a caliper

Keep in mind the measurements you get with this setup will be on a bullet specific basis. You cant use the same measurement for Nosler ballistic tips and then for Accubonds-

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