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Old November 18, 2017, 11:32 AM   #1
tpcollins
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Question about bolt action top load magazines

Recently I bought a 450 Bushmaster that a guy converts from a Savage .308 action. This dang thing is nearly the best shooting rifle I have.

The magazine only holds 2 cartridges but that's fine, the issue is loading them. It is very difficult to push the cases down past the "side lips" or whatever ever they're called.

When I look down from the top, the front of these lips look closer together than at the rear. Seems to me if they were parallel and the front was as wide as the rear, the cartridges should load much easier.

Yeah or nay? Thanks.
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Old November 18, 2017, 12:31 PM   #2
T. O'Heir
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That a Savage with an internal mag? Isn't easy to widen 'em, but it can be done. Don't even think about using a rotary tool to do it.
The .450 is based on the .284 Win(has a rebated rim). It's case body diameter(called the base diameter) is 20 thou bigger than the .308. That might be the issue.
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Old November 18, 2017, 12:45 PM   #3
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I've been researching online and found a feed lip tool used to tweak/widen/straighten these retainers. Might be what I need to do.
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Old November 18, 2017, 01:19 PM   #4
tpcollins
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Quote:
That a Savage with an internal mag? Isn't easy to widen 'em, but it can be done. Don't even think about using a rotary tool to do it.
The .450 is based on the .284 Win(has a rebated rim). It's case body diameter(called the base diameter) is 20 thou bigger than the .308. That might be the issue.
Not sure where you're getting your info. My reloading book shows the back of a .308 at .532" and .492" just in front of the neck.

My 450 Bushmaster cartridge measures .498" at the rear and .478" at the front, it it swells to about .507" (swells from the bullet inside) where it sits at the end on the feed lips.

The feed lips measure .424" at the rear and .397" at the front where that .507" sits. When I push the top cartridge forward into the chamber, the front of the bottom cartridge tips down, hits the magazine wall, and will not feed up into the chamber. That's .110" difference at the front of the feed lip - another problem.

I emailed to builder and I'm waiting to hear back.
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Last edited by tpcollins; November 19, 2017 at 09:55 AM.
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Old November 18, 2017, 06:06 PM   #5
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I have no experience with that caliber, but do have 3 Ruger Americans in other calibers. I know that Ruger had to design a completely different magazine for the 450 Bushmaster, they couldn't make the 308 size magazine work with that round..
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Old November 18, 2017, 09:26 PM   #6
FrankenMauser
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$0.50 feed lip tool:

Cut some round stock (or square, or hex...).
Slot it with a hacksaw or cutoff wheel. (Where ever and at whatever angle you want.)
Shape as desired, if the stock shape causes interference.




Mine are all out in the garage right now, and would get murdered by condensation if I brought them inside for a photo, so I went with a quick CAD rendering.
I use O-1 drill rod, since I keep a fair amount on hand. But many other steel alloys would work just as well - or better.
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File Type: png lip_flange_tool.png (27.5 KB, 231 views)
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Old November 18, 2017, 09:53 PM   #7
std7mag
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Really??? Again with the rebated rim foolishness??

Westley Richards proved the design in 1909. And the 425 was rebated more than the 284 Win.

It's a miracle the bench rest shooters get the 6.5-284 to work.

To answer the OP yes the lips on the feed need opened up.
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Old November 19, 2017, 10:02 AM   #8
tpcollins
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Thanks FrankenMauser - a feed lip tool should work - bought or handmade. I'm still waiting to here back from the original builder.

It sort of got passed over in my post but there's a secondary issue with the first cartridge that gets loaded. The top cartridge loads into the chamber just find when racked, but the first loaded cartridge tips downward and will not feed.

I think it could be a combination of the magazine spring being it's weakest with only one cartridge loaded plus the front of the feed lips being so much narrower than the cartridge it just naturally wants to tip the front end of the cartridge down.

If I shoot twice, I will have to manipulate that last cartridge with my finger before racking the bolt forward for now.
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Old November 19, 2017, 01:43 PM   #9
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That sounds like a multi-faceted problem.
Likely feed lips and follower shape. The spring could also be a factor.
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Old November 20, 2017, 08:02 AM   #10
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"My reloading book shows the back of a .308 at .532" and .492" just in front of the neck."
You'd better look at that page again. The base of a .308 is .473" and the shoulder is .454". The measurements you state are close to the numbers for a 300 Win mag.
My guess is the " guy converts from a Savage .308 action." failed to properly open the feed lips of the action and needs to have a do-over.
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Old November 20, 2017, 04:50 PM   #11
tpcollins
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Quote:
You'd better look at that page again. The base of a .308 is .473" and the shoulder is .454". The measurements you state are close to the numbers for a 300 Win mag.
My guess is the " guy converts from a Savage .308 action." failed to properly open the feed lips of the action and needs to have a do-over.
My bad - my Nosler reloading handbook has a dozen labeled .308 - you're dimensions are correct. This is from a Savage .308 Winchester action with a custom 450BM barrel. I'll be able to get thru to Novemebr 30th and then I'll have it fixed.
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Old November 21, 2017, 11:45 AM   #12
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You might consider if the magazine feeds right or not.

If it does, then opening it up may change that.

Savages are not the best feeding creatures but they tend to shoot pretty good.
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Old November 21, 2017, 05:59 PM   #13
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TOHeir is correct, the case of the 450 Bushmaster is bigger than the 308 win and is likely what is causing your issues.

Sadly it's things like this that reveal to us why we got such a good deal on a rifle.

It shouldn't be insurmountable though, you will have to work out the mag issues through trial.

Good luck, my next AR build will likely be 450 Bushmaster.
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Old November 21, 2017, 08:38 PM   #14
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It's darned hard to combine single feed with top load in a fixed magazine.
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