Which Action for a Custom .338 Lapua AI?

[SaulReichman]

So I am biting the proverbial bullet and getting a .338 Lapua AI built to use as a hunting rifle. I want this rifle to be very traditional in appearance and easy to carry while hunting. Since I cannot afford to buy a Dakota 76, I have decided to build a rifle that meets what I want. I cannot decide between using a Weatherby Mark V or a Montana 1999 action for the build. I am planning on using a hinged floorplate and a straight comb wood stock. I looked at the CZ550 Badlands but really disliked how bulky the 5 round magazine capacity made the rifle compared to the 2 round magazine of the Weatherby. If you guys have any experience working on custom rifles with these two actions, especially in the .338 Lapua AI, your input would be greatly appreciated.

 

[J E Custom]

So I am biting the proverbial bullet and getting a .338 Lapua AI built to use as a hunting rifle. I want this rifle to be very traditional in appearance and easy to carry while hunting. Since I cannot afford to buy a Dakota 76, I have decided to build a rifle that meets what I want. I cannot decide between using a Weatherby Mark V or a Montana 1999 action for the build. I am planning on using a hinged floorplate and a straight comb wood stock. I looked at the CZ550 Badlands but really disliked how bulky the 5 round magazine capacity made the rifle compared to the 2 round magazine of the Weatherby. If you guys have any experience working on custom rifles with these two actions, especially in the .338 Lapua AI, your input would be greatly appreciated.

My preference would be the Mark 5 because of the parts availability and the center feed mag On the 30/378, 338/378, 378, 416 and 460 actions.

Stocks are available also.

With the Mark 5, only the bolt face has to be opened a few thousandths. (The existing extractor can be used and works well.

The Mark 5 is the only action I will use for the 338 Lapua and larger case head cartridges for my custom rifles for many reasons.

Just my opinion

J E CUSTOM

 

[B23]

I have both a 338 Lapua AI and a 30-338 Lapua AI.

My 338 Lap AI is built on a BAT HR action and had no expense spared when I had it built, the thing is an absolute work of art and shoots amazing.

My 30-338 Lap AI was built on a Rem 700. Bolt face was opened up and had a M16 style pined extractor installed. It wears a 28in. (less brake) fluted #6 Lilja barrel and sits in a bedded HS Precision Sendero I stock. I consider it more of a blue collar working mans gun and certainly isn't as fancy and pretty as my 338 and in my hands, it shoots equally well. Maybe in others with a higher skill set could wring more out of the full custom 338 but in my hands they both will shoot in the .3's

Also, on my 30-338 Lap AI I went with a Seekins detachable mag system so I can stretch the OAL out to 3.9 if need be but at present 3.850 with the Berger 230's is touching.

 

[Deleted member 46119]

Mark V for "traditional". J E Custom has it down. One very nice feature as far as I'm concerned is the in bolt safety. I just feel more comfortable with a chambered round.

Stiller Tac-338 but stocks are a little less available or more work.

 

[bigngreen]

The Montana PH action is a tank and frankly dwarfs the Mark V and from the sounds of it would not feel right for you, it holds 5 down of Lapua and is capable of Cheytac size cases which is more than you need thought it will feed longer overall length cases than the Mark V but that makes it a handful of a rifle which I personally like.
The Mark V is a beautiful Lapua action, I've done several and when done right it's a sweet package the one draw back I have seen is they do have a small tenon thread compared to a normal Lapua class action and it does cause extraction issues earlier than an action with a larger tenon.

 

[Deleted member 46119]

The Montana PH action is a tank and frankly dwarfs the Mark V and from the sounds of it would not feel right for you, it holds 5 down of Lapua and is capable of Cheytac size cases which is more than you need thought it will feed longer overall length cases than the Mark V but that makes it a handful of a rifle which I personally like.
The Mark V is a beautiful Lapua action, I've done several and when done right it's a sweet package the one draw back I have seen is they do have a small tenon thread compared to a normal Lapua class action and it does cause extraction issues earlier than an action with a larger tenon.

I want one!
or
A Tac-408. hehehe

IMO Overkill for a 338LM

 

[SaulReichman]

The Montana PH action is a tank and frankly dwarfs the Mark V and from the sounds of it would not feel right for you, it holds 5 down of Lapua and is capable of Cheytac size cases which is more than you need thought it will feed longer overall length cases than the Mark V but that makes it a handful of a rifle which I personally like.
The Mark V is a beautiful Lapua action, I've done several and when done right it's a sweet package the one draw back I have seen is they do have a small tenon thread compared to a normal Lapua class action and it does cause extraction issues earlier than an action with a larger tenon.

Very interesting. I just looked at the Montana PH action and it is certainly a beast. Maybe more fit for a .505 Gibbs (another sweetheart of mine) than the Lapua. I am not sure that I need 5 rounds down and would be happy with 2 if it meant a lighter and narrower gun, which is why I was originally considering the Mark V and model 1999 actions. Then again, I do not really need a .338 Lapua hunting rifle. I do like the fact that there is no way in hell that I could ever break the Montana action. This is also the first time that I have heard about extraction issues with the Mark V, which is something definitely to consider. I was also considering going with a Lapua Improved chambering, which might also be problematic in the Mark V...

 

[bigngreen]

Everything I build on the Lapua is improved and they do work well in the Mark V I've just found that at top pressures under the tenon will get sticky but it's the same with anything with the small tenon and the Lapua, if your run moderate pressure they run like hot butter and will be a trim package. There are a number of other actions, Lone Peak, Bat, Stiller, Defiance and there are more that I can't remember so lots of good stuff!

 

[SaulReichman]

Everything I build on the Lapua is improved and they do work well in the Mark V I've just found that at top pressures under the tenon will get sticky but it's the same with anything with the small tenon and the Lapua, if your run moderate pressure they run like hot butter and will be a trim package. There are a number of other actions, Lone Peak, Bat, Stiller, Defiance and there are more that I can't remember so lots of good stuff!

While I like big tank solid rifles, trim is exactly what I am looking for.

 

[J E Custom]

Very interesting. I just looked at the Montana PH action and it is certainly a beast. Maybe more fit for a .505 Gibbs (another sweetheart of mine) than the Lapua. I am not sure that I need 5 rounds down and would be happy with 2 if it meant a lighter and narrower gun, which is why I was originally considering the Mark V and model 1999 actions. Then again, I do not really need a .338 Lapua hunting rifle. I do like the fact that there is no way in hell that I could ever break the Montana action. This is also the first time that I have heard about extraction issues with the Mark V, which is something definitely to consider. I was also considering going with a Lapua Improved chambering, which might also be problematic in the Mark V...

This is also the first time I have heard of any extraction issues with the Mark 5. I have built many rifles with more powerful cartridges that the 338 Lapua and had zero issues. Some of the cartridges have used up to 145 grains of powder and still no problems.

I also like the fact that with very little effort the magazine can be extended to over 4'' and it is a center feed.

They have a good extractor that can handle the big Weatherby cases that are traditionally are loaded hard. I have also built many 338 Lapua improved rifles using the mark 5 and It would be my preferred action for these cartridges over every other action because of it's strength, looks and the bolt safety. I also like the 60o bolt lift. The only downside is finding a donor rifle at a good price. (The best price I have seen was $500.00 after I sold the stock for $200.00 and they can be up to $1,000.00 + if you don't look hard)

I know that there are larger actions, But the cost of these actions combined with everything you need is quite expensive and not necessary in my opinion for cartridges this size.

Just my opinion

J E CUSTOM

 

[bigngreen]

It's well known if your going to push the 378 in the Mark V you better keep extra extractors because your going to be using a lot of primary extraction to pull cases. Dan Lilja sites the marginal size of the barrel shank and also points out no one builds a custom action for this case head size with 1.062 threads because it's marginal.
Don't get me wrong I love building a Lapua on a Weatherby but the fact is the tenon is on the small side, even Savage uses a larger tenon because of the chamber swell and extraction issue. That said I'm going to build myself another Lapua and I'll probably pick up a GunBroker gun for 600-800 and it'll be sweet, love everything else about it other than the tenon size.

 

[J E Custom]

It's well known if your going to push the 378 in the Mark V you better keep extra extractors because your going to be using a lot of primary extraction to pull cases. Dan Lilja sites the marginal size of the barrel shank and also points out no one builds a custom action for this case head size with 1.062 threads because it's marginal.
Don't get me wrong I love building a Lapua on a Weatherby but the fact is the tenon is on the small side, even Savage uses a larger tenon because of the chamber swell and extraction issue. That said I'm going to build myself another Lapua and I'll probably pick up a GunBroker gun for 600-800 and it'll be sweet, love everything else about it other than the tenon size.

I totally agree that All barrel tenon's could be larger but comparing tenon's of different brands I could not find a savage that had a larger tenon than The mark 5. The Mark 5 tenon is 1.060 and the savage is 1.055. The rem 700 tenon is 1.60 like the Weatherby. the only Weatherby I could find that has a small tenon is the Six lug and it has a .875 dia. And not recommended for big magnum cartridges. The difference is like the large ring Mauser and small ring Mauser, the large shank Savage and the small shank Savage. the 9 lug Mark 5 barrel is as large as all but a few actions.

The reason I have not had any extractor problems is that I don't push any cartridge above SAMMI pressures. With my wildcats, I do other things to hold pressure to SAMMI pressures even though they will hold a lot more powder. I like them to operate in the neighborhood of 62,000 to 63,000
PSI.

Like you I really like the 9 lug Mark 5 For big cartridge builds.

J E CUSTOM

 

[bigngreen]

The large shank Savage is 1.120 also 20tpi so larger at the thread root.

 

[Edd]

BAT told me the reason they put a 1.125" thread on their HR actions is because many of them are used for the 338 Lapua.