Increasing mag capacity mods

[LeftySixgun]

What all is involved in increasing a magazine capacity by 1 or 2 rounds in a Winchester M70 375 H&H?
Is this actual gunsmith work or just changing out parts like follower, spring, box and bottom metal?

 

[Fish2table]

I’m interested also.

 

[rookhawk]

What all is involved in increasing a magazine capacity by 1 or 2 rounds in a Winchester M70 375 H&H?
Is this actual gunsmith work or just changing out parts like follower, spring, box and bottom metal?

Typically its about throwing away the existing bottom metal. Then buying a suprisingly expensive forged, expanded bottom metal that protrudes a bit further. Then its a matter of changing the inletting of the stock to take a slightly larger bottom metal for a perfect fit. Lastly, its dealing with any potential feed issues, modifying the follower, and replacing the factory follower spring with a stronger one with more "Travel".

Overall, the juice isn't worth the squeeze from my vantage. This is probably over a $1000 job considering the bottom metal is $300-$400 in the white before polishing, fitting, and dealing with the other work involved, plus two way shipping.

 

[AckleyHunter]

This company makes one that looks drop in and claims to use factory spring and follower. I have not used it and can't speak to whether or not it is quality. For a $150, it does not seem like much of a risk.

Increased Capacity Bottom metal for Winchester Model 70 Long Action Rifle- Black

We are a design and full service manufacturing company that specializes in AR-15 parts & AR-10 parts in the firearm industry. Buy your own firearm parts directly or become a dealer to take advantage of exclusive pricing.

kakindustry.com

If you had a ruger I would recommend the one from Alaska Arms. That one is done right.

 

[rookhawk]

This company makes one that looks drop in and claims to use factory spring and follower. I have not used it and can't speak to whether or not it is quality. For a $150, it does not seem like much of a risk.

Increased Capacity Bottom metal for Winchester Model 70 Long Action Rifle- Black

We are a design and full service manufacturing company that specializes in AR-15 parts & AR-10 parts in the firearm industry. Buy your own firearm parts directly or become a dealer to take advantage of exclusive pricing.

kakindustry.com

If you had a ruger I would recommend the one from Alaska Arms. That one is done right.

I don't believe a Win70 in 375HH is a long action? I don't know anything about post-64 Win70s, but pre-64 375HH were a magnum action that was shared with the 300HH.

 

[mdwest]

I don't believe a Win70 in 375HH is a long action? I don't know anything about post-64 Win70s, but pre-64 375HH were a magnum action that was shared with the 300HH.

Post 64's are a bit of a strange hybrid.. The 375 H&H takes the same bottom metal as their "long action" calibers...

I only learned this when ordering a replacement stock for my Win 70 375 H&H from B&C.. I was looking for an option for a "magnum" length action and they had nothing available.. neither did McMillian or anyone else I looked at..

So I called B&C and they told me that internally there are some differences in the 375 H&H action and say a 30-06 or any other "long action" caliber.. but externally the dimensions of the action, mag, bottom metal, etc are the same.. so just order a "long action" stock and my "magnum" M70 would drop right in..

They were right.. the stock arrived a few days later and my barreled action droped right in and fit perfectly..


All of that said.. I completely concur with your assessment of the juice not being worth the squeeze..

I looked at potentially adding an extended mag to mine.. the cost of the new bottom metal, plus the cost of having to finish the bottom metal, etc just wasnt worth the additional 1 shot I was going to get out of the deal... I figure if I cant get the job done with the 3+1 capacity of the factory mag.. I probably need to improve my skills before heading out on the next buff hunt.. or... just let the buff take me and be done with it lol... having 1 more shot probably isnt going to make a whole lot of difference..

 

[AckleyHunter]

I don't believe a Win70 in 375HH is a long action? I don't know anything about post-64 Win70s, but pre-64 375HH were a magnum action that was shared with the 300HH.

Good point. The current production Alaskan 375s are long action. Depends on the OPs rifle.

Model 70 Alaskan | Bolt-Action Rifle | Winchester

Based on the original classic design. Satin finished and checkered Monte Carlo stock. Folding rear sight and hooded front sight. Intregral front and rear bedded recoil lugs.

www.winchesterguns.com

 

[Ontario Hunter]

Doesn't someone make an extended floorplate for an extra round? I thought someone was making and advertising them on the forum.

 

[thoma018]

Alaskan Arms fabricates an extra capacity floorplate but I think only for RUGER rifles.

 

[AckleyHunter]

Doesn't someone make an extended floorplate for an extra round? I thought someone was making and advertising them on the forum.

Yes, appears they are making them for CZ rifles. I saw that post hoping they had them for a mauser actions.

J

Thread 'extended floorplates for various actions'

May 9, 2026

We were getting ready for spring, but had a wet snow last week, so took the day and thought to make a universal floorplate design with programmable depth and either flat bottom or signature elliptical
ParkWest standard floorplate up next unless Sprng arrives....

CZ550 Magnum, std depth

CZ550 Medium, deep, Four 416 Taylors down

the insides

and the infamous Dumoulin standard action, deep, Four 416 Taylor down

• Jefferry404
• Replies: 6
• Forum: Gunsmithing

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[mdwest]

Doesn't someone make an extended floorplate for an extra round? I thought someone was making and advertising them on the forum.

Sunny Hill makes a replacement 3+1 and they also make a 4+1 for a Winchester M70

Sunny Hill Enterprises - 70 Winchester