7mm Bad Group

[sprocket]

The gun is a BSA Monarch 7mm rem mag made in England

I can't find out what barrel twist this gun is but think it's a 1:16

On the barrel it says 7MM MAG 2.50" 19.5 TONS PER SQ IN.

I hand loaded with Nosler Accubond 168 gr. used 62 gr. IMR4350 Powder and CCI 250 mag primers

Did a full resize and case length trim to 2.500

Set the bullet depth to (recommended 3.290 max)

Since my COAL is 3.60 with bullet touching lands thats almost 5/16" jump, seems a lot to me

I have a Caldwell Lead Sled and this load shot terrible (4" @100)

I had some Hornady factory CustomLite 139 gr. that did near 1" at 100

I can lengthen my bullet out to 3.400 and will clear in magazine and eject

What do you think is wrong and which should I change

I'm after the heaver grain bullet for Elk here but also would like to kill one out to at least 500

Thanks sprocket

 

[tazzman]

sprocket,
If I were you, I would verify the twist using a cleaning rod with a tight fitting jag and patch.
If it is indeed a 1-16", you will not be able to stabilize the heavier bullets. It is not a question of weight, but of bullet length. A normal twist for the heavier bullet starts at 1-9".
Keep us informed.

Phil Fortin aka tazzman

 

[Riesel]

Can't tell where you hail from. My be best to just start over.

 

[gotcha]

According to Hornady manual 57.6 gr. IMR 4350 for a 162 gr bullet is Max load. Back off your powder chg. by at LEAST 10% and work up slowly then experiment with seating depth before you hurt your gun, yourself or an innocent bystander.

 

[sprocket]

sprocket,
If I were you, I would verify the twist using a cleaning rod with a tight fitting jag and patch.
If it is indeed a 1-16", you will not be able to stabilize the heavier bullets. It is not a question of weight, but of bullet length. A normal twist for the heavier bullet starts at 1-9".
Keep us informed.

Phil Fortin aka tazzman

Phil, your right on
I found a poop sheet for the BSA rifles and this one is a 1 in 10 twist with 5 grooves

 

[AckleymanII]

160g Accubond or 160g partition will work well in the 10 twist, my load is 70-71g of Retumbo with a fed 215(3130 fps).

61g of IMR 4350 is a max load for my rifle, and the slower powders may work better, trial and error.

Not to worry, I killed two bulls with a 140g old style ballistic tip in the 7 mag and they were dead when they hit the ground with a load of 65.5g of IMR 4350, 9 1/2 primer. Switch to the 140g tipped triple shock if it will make you feel better.

 

[shoot4fun]

Berger Bullets has two bullets in their hunting line that are built to stabilize fully in 1 in 10 twist barrels.
I suggest checking out the 28503 140 VLD Hunting and the 28570 168 Classic Hunter.
I have found them pretty easy to tune even well off the lands.

 

[Shaggy357]

Did you set your sizing die so the brass just fit your chamber? Excessive shoulder movement in the 7mm Mag is not conducive to good accuracy. If you have already confirmed your COAL with that bullet is 3.6", I would be keeping that bullet out to narrow that jump as much as possible, as your magazine allows. Less bullet depth in the neck = (usually) less pressure and more capacity for powder in the case. (depends on your powder and primer). My Parker Hale likes the 175 with a near max load of Rel 22. My bullet is seated so it just fits the magazine. If my load does 1", I am wondering what is wrong.

Sounds like all the bases are covered. You already confirmed barrel twist. Set dies to size brass for your gun. Confirm powder charge. Seat bullet to fit your gun/magazine, not the book.....a good start....

Steve

 

[sprocket]

Thanks everyone for the help

I picked up a box of Hornady 28452 and some H1000 while in Boise

I now need to load up some of each and give them a try
I'm a little more savvy now thinks to your help

I will report back after I try them

Did you set your sizing die so the brass just fit your chamber? Excessive shoulder movement in the 7mm Mag is not conducive to good accuracy. If you have already confirmed your COAL with that bullet is 3.6", I would be keeping that bullet out to narrow that jump as much as possible, as your magazine allows. Less bullet depth in the neck = (usually) less pressure and more capacity for powder in the case. (depends on your powder and primer). My Parker Hale likes the 175 with a near max load of Rel 22. My bullet is seated so it just fits the magazine. If my load does 1", I am wondering what is wrong.

Sounds like all the bases are covered. You already confirmed barrel twist. Set dies to size brass for your gun. Confirm powder charge. Seat bullet to fit your gun/magazine, not the book.....a good start....

Steve

 

[284winner]

Try shooting some 140s. If they group well, obviously the rate of twist is too slow for the 168s. Some of the heavier 160s with flat base design are easier to stabilize as well from slower barrels. I have a 12 twist 7-08 that shoots the 160 partition very well. Will not shoot the 168 Berger very good tho. The cleaning rod measurement works too if you really want to measure the true twist in the barrel.

 

[CJ6]

The gun is a BSA Monarch 7mm rem mag made in England


Set the bullet depth to (recommended 3.290 max)

Where did this recommendation come from?

 

[Martin52]

sprocket,
you might find this interesting, if the barrel is original you probably have a 10T LH.

https://books.google.com.au/books?id=tuVUMLRE47UC&pg=PA218&lpg=PA218&dq=BSA+monarch+7mm+mag&source=bl&ots=tJHvw0lcCE&sig=4S5ormf1Qzm-nIs9tJZ6uGeGLzo&hl=en&sa=X&ved=0ahUKEwjVwNDzv4_NAhWSNpQKHdUrA9wQ6AEIKzAF#v=onepage&q=BSA monarch 7mm mag&f=false

Check per tazzman's advice.