Browning 7mm Mag Semi Auto - heat/accuracy quesiton

[anorthernhunter]

Hello all 7mm Mag experts ...

I recently was given a Browning 7mm Mag Semi Auto and took it to the range. (I usually shoot a .300 Savage).

I put Nosler Trophy Grade 150 grain ammo through it and after three shots felt the
barrel was very hot - too hot to leave your hand on.

Question 1:

Is this amount of heat normal with "Magnums"? My little .300 Savage takes 6 - 8 shots to generate this amount of heat.

Question 2:

I noticed a significant loss of accuracy if I shot a second group of 3 shots right after the barrel heated up (200 yds 6 inch group). I am ok if this is normal ... I will just have to let more time lapse before putting three more rounds through it while I am sighting it in.

I suspect that given I am using this to hunt the first three shots out of a cold barrel are the only ones that count - if all is normal I am good ... it just means
a long day (in 26 degree weather) allowing the barrel to cool down after every 3 shots.

I was told to check if the barrel free floats and will do that when I get home.

Btw - I gave the barrel a good cleaning and am shooting off of a gun rest so I looked after those variables.

Question 3:

I can get 1.5/2 inch grouping with my .300 Savage at 100 yards (lever action) - what should I expect with this 7mm semi?

Thanks guys!

Northern

[Dick284]

It's a semi, the barrel does not free float! The gas system is attached to the barrel, so there is no way to get an actual free float.
It's also a 2 piece stock, therefore all sorts of things could play into accuracy, but I doubt that is the heart of the issue.

I worked up loads for a buddy with a 300Win Mag BAR a long time back.
To get anything I'd call a group I had to follow this pattern;
shoot, wait 30 seconds
shoot wait 1.5 minutes
shoot.

There is about 1.5 times to 1.8 times the powder in the 7 Rem Mag as compared to your 300 Savage, yes it is way higher intensity cartridge than the 300 Savage, so yes things heat up faster.

Try some less specialized ammo, like a run of the mill soft point loading and see how that groups for you.

[anorthernhunter]

Thanks for the thoughts Dick. I thought the Nosler (being one of "the best") would shoot the best - I will pick up some federal ammo and see.

Sounds like I will shoot and wait to sight it in.

What should I expect - in general - for groups at 100 yards ... 2 - 3 in groups and 4 - 6 in at 200yds?

Northern

[Dick284]

Originally Posted by anorthernhunter

Thanks for the thoughts Dick. I thought the Nosler (being one of "the best") would shoot the best - I will pick up some federal ammo and see.

Sounds like I will shoot and wait to sight it in.

What should I expect - in general - for groups at 100 yards ... 2 - 3 in groups and 4 - 6 in at 200yds?

Northern

Hard to say, since I've never seen you shoot.
The last guy I helped work loads for gets 2" groups, while I can muster a bit over 1" with the same rifle, and load. Tikka T3, 270Win.

K.I.S.S. usually gets you good results.

Please report back, as I'm sure others will be interested in your results.

Tight groups,
Dick

[anorthernhunter]

Hi Dick,

Would you mind shooting me a quick PM - if you don't mind I would like to give you a quick call if that wouldn't bother you for a short live chat.

Northern

[elkhunter11]

Is this amount of heat normal with "Magnums"? My little .300 Savage takes 6 - 8 shots to generate this amount of heat.

It's not at all unusual for a lighter weight barrel on a 7mmremmag.

I thought the Nosler (being one of "the best") would shoot the best - I will pick up some federal ammo and see.

A gun will show you what it likes, and it may not like the most expensive loads. It might shoot much better with a low priced load.

I worked up loads for a buddy with a 300Win Mag BAR a long time back.
To get anything I'd call a group I had to follow this pattern;
shoot, wait 30 seconds
shoot wait 1.5 minutes
shoot.

That kind of defeats the purpose of having a semi automatic.

[timsesink]

This to me really illustrates the inherent issues with a semi-auto for big-game hunting. I'm sure though a deer won't know the difference

[Smokercraft]

I shoot a 7mm Mag Browning A-bolt and with practice and several trips to the range fine tuning some handloads I've got it down to .68" 3-shot group at 100 yards. Granted that's with a good shooting rest.

As for heat, any more than 4-5 shots in succession and the barrel does get pretty warm. In my personal opinion, the 7mm Rem Mag is a great hunting round, just not well suited to a semi.

[anorthernhunter]

I went back to the range today with my 7mm and a box of Hornady 139 gr, Fusion 150 gr and Winchester 175 grain.

I figured out the barrel heating issue ... I had used Nosler Custom 160 gr and they must be hotter loads which heated my barrel ... the Fusions and Winchesters didn't heat it up even close.

My problem is now that the 7mm still doesn't group better than 6 in at 100 yards. Sometimes its 2 within 1 inch then 3 within 7 inches ...I suspect the scope and or scope mounts which I will check.

Interestingly - NONE of the Hornady rounds would fire in my gun ... one got so badly jammed (Browning BAR Semi) that it took 5 minutes to unjam it. Very unusual ... maybe a bad lot from Hornady - will call them Tue. No issues with any other ammo manufacturer.

Frustrating to not have it properly sighted in.

Northern.