Gunsmithing 338 Lapua receiver

[Hondatech19]

If someone can direct me in the right direction, It would be greatly appreciated as I'm sure this topic has been covered, I'm just not having any luck finding it.

My brother-inlaw and myself are starting our 338 Lapua build. We would like to machine the receiver our self. He does machining/tool and die for a living and is good with CNC and Lathes. We have access to a full machine shop. We are looking to build the 338 off of a rem 700 style action but from what I understand, Remington hasn't quite built their actions beefy enough and I don't want and safety issues or reliability issues. So without duplicating Remingtons action exactly, where could I find specs or even a CAD diagram of a better thought out design that can with hold the pressures of the Lapua. Or what part of Remingtons specs need to be adjusted (beefed up/ lengthened, shaved, etc...)??

Any suggestions for the build would be greatly appreciated (especially on Bolt modifications, extractors, etc, etc...). Our goal is to basically build everything that we can and make it as good as possible. The goal of this rifle is to eventually with lots of practice, get out to 2000yds.. The Lapua is a caliber we have been wanting to add to the collection for quite some time, and now is that time.

 

[ahhshoot]

If I were you, I would take a good hard look at the 700, study all the things people like/dislike about the design, and sit down with your brother in law and write down all the ways you could make it better.

Next, I would visit Bighorn, Surgeon, Defiance, etc etc, and see what they have done, and then study what the pros and cons have been with those ideas.

Then, groom all the ideas down to what you want in the action. Then make a few more after you figure out what you could do better.

The R&D and open mind might pay off in the future, if others want to buy one from you, they seem to be willing to pay top dollar.

I think the first and most important phase, the part where you come up with your own ideas based on what you want, is important to be done first before you are influenced on what others may have done.

Obviously starting with the 700 footprint is the way to go, otherwise you will be fighting for stocks/chassis/mags/triggers, etc, so I would just take a good hard look at that and think about what would make an action better.

Others have longer tenons for more firm and solid/true bond between barrel and action, beefed up tangs, integrated rails/recoil lugs, floating bolt face, all sorts of stuff. Maybe you can't do anything radical but you might be able to improve on a few of these designs which would yiled a very nice platform.

 

[LRI]

Nutshell stuff:


Increase bolt body OD from .700 to .750
Increase bolt lug height from .437 to .45
Leave the 1.0 swept arc of the bolt lugs alone.

Bolt should be around 35 to 37 HRC


Receiver should be at least 42HRC. 44 is better. (5 points of hardness differential to mitigate galling.

If you going to use 15-5 or 17-4 you need to order a very specific grade, otherwise forget it. It'll never harden to those levels.
Don't heat treat at home. You need a shop experienced with these steels in order to get it right. One of the biggest issues with heat treating is contaminates in/on the steel. The material needs to be sterile. Foreign materials get vaporized, that stuff deposits on the fire brick/heating elements and destroys the oven slowly. You end up with hot/cold spots in the furnace and this affects the steel as it can't soak properly. There's more to it way above my paygrade, but this is the gist of it.

CLEAN PARTS ONLY for the furnace!

Alternative materials:

400 series is much easier to work with. Chromoly is the shizzle.

Increase the lug length a bit. Say +.100" should be plenty sufficient.

Bump the port length back a smidge to put a bit more meat at the lower lug abutment. Leave a nice .100" flat between ramp and flat.

At Nesika we did a pile of La poo poos on 1-1/16 x 18 tennons. The trend today is to go larger. Alot are moving towards the 1-3/16 thread pitches. Never seen/heard of a Nesika/Dakota 76 popping a barrel so not sure how much its really needed, but it never hurts.

DONT use a Sako extractor. Go with an M16 or factory M700. Sako's suck if you sneeze a case. It'll try to blind the person(s) behind the gun.


Curious how your B.I.L. is going to cut the clearance ramps in the action for the bolt. Maybe this'll help. If he's CNC savy this'll be pretty easy.

Shaper tool. Grind to suit.

Mount in arbor and chuck it up in a CAT40/CAT50.

Stand your action vertically.

Write a macro using rigid tapping and have G10's in place to incrementally bump the Z offset. Run your tapping cycle, stop, retract, reset, bump the Z, and go again. Bout .0015" to .0025" per wipe.

Another way:

Use the same rigid tapping cycle but ditch the G10's. Mount your 4th axis vertically and make a small incremental move on the 4th for each pass. You avoid the Z offset change/update this way, but it requires a 4th or rotary table.

-Machinable wax is encouraged as it's a great way to proof without destroying a kinky tool. (the shaper geometry is a Mo Fo to grind in order to get the helix right)



Setup your fire control to be cock on open only and make for a shitload of primary extraction. If you get it right you can set it up so that the PE and clearance ramps are essentially one continuous pitch across the length of the receiver. On pulls it in, the other pulls it out.


Controlled round feed actions are the only way to go IMHO. Another M700 clone is just that; another M700 clone. Few attempt the complexities of a CRF action with a 3pos Safety and all the other neat little gadgets that this style is often fitted with. Plus you can build it with a completely enclosed back half (shroud/rear bridge relationship)

This serves as an effective breech block should a case let go. Less stuff to pick from your face...



Good luck and have fun!



C.

 

[338RUM runner]

C. Your info and insight are always a great read, thanks.

 

[gewehr]

Nutshell stuff:


Increase bolt body OD from .700 to .750
Increase bolt lug height from .437 to .45
Leave the 1.0 swept arc of the bolt lugs alone.

Bolt should be around 35 to 37 HRC


Receiver should be at least 42HRC. 44 is better. (5 points of hardness differential to mitigate galling.

If you going to use 15-5 or 17-4 you need to order a very specific grade, otherwise forget it. It'll never harden to those levels.
Don't heat treat at home. You need a shop experienced with these steels in order to get it right. One of the biggest issues with heat treating is contaminates in/on the steel. The material needs to be sterile. Foreign materials get vaporized, that stuff deposits on the fire brick/heating elements and destroys the oven slowly. You end up with hot/cold spots in the furnace and this affects the steel as it can't soak properly. There's more to it way above my paygrade, but this is the gist of it.

CLEAN PARTS ONLY for the furnace!

Alternative materials:

400 series is much easier to work with. Chromoly is the shizzle.

Increase the lug length a bit. Say +.100" should be plenty sufficient.

Bump the port length back a smidge to put a bit more meat at the lower lug abutment. Leave a nice .100" flat between ramp and flat.

At Nesika we did a pile of La poo poos on 1-1/16 x 18 tennons. The trend today is to go larger. Alot are moving towards the 1-3/16 thread pitches. Never seen/heard of a Nesika/Dakota 76 popping a barrel so not sure how much its really needed, but it never hurts.

DONT use a Sako extractor. Go with an M16 or factory M700. Sako's suck if you sneeze a case. It'll try to blind the person(s) behind the gun.


Curious how your B.I.L. is going to cut the clearance ramps in the action for the bolt. Maybe this'll help. If he's CNC savy this'll be pretty easy.

Shaper tool. Grind to suit.

Mount in arbor and chuck it up in a CAT40/CAT50.

Stand your action vertically.

Write a macro using rigid tapping and have G10's in place to incrementally bump the Z offset. Run your tapping cycle, stop, retract, reset, bump the Z, and go again. Bout .0015" to .0025" per wipe.

Another way:

Use the same rigid tapping cycle but ditch the G10's. Mount your 4th axis vertically and make a small incremental move on the 4th for each pass. You avoid the Z offset change/update this way, but it requires a 4th or rotary table.

-Machinable wax is encouraged as it's a great way to proof without destroying a kinky tool. (the shaper geometry is a Mo Fo to grind in order to get the helix right)



Setup your fire control to be cock on open only and make for a shitload of primary extraction. If you get it right you can set it up so that the PE and clearance ramps are essentially one continuous pitch across the length of the receiver. On pulls it in, the other pulls it out.


Controlled round feed actions are the only way to go IMHO. Another M700 clone is just that; another M700 clone. Few attempt the complexities of a CRF action with a 3pos Safety and all the other neat little gadgets that this style is often fitted with. Plus you can build it with a completely enclosed back half (shroud/rear bridge relationship)

This serves as an effective breech block should a case let go. Less stuff to pick from your face...



Good luck and have fun!



C.

That was beyond badass

 

[Hondatech19]

LongRifles - As always, your info and knowledge is greatly appreciated. That was a huge help and cleared up quite abit. We will be sending out the material for heat treatment once its finalized. I haven't talked to my B.I.L about who his shop uses for heat treatment but is there someone that you can recommend?

Were not really looking to do production or anything with what we machine, we just want to have a "one of a kind" rifle. And want to it perform as good and better than its appearance. There is a small group of us that shoot together and are always competiting against each other, this is our new surprise and will be more bragging rights than anything when its built from scratch and performs as well or better.

 

[Hondatech19]

ahhshoot - Thank you for the insite. We have been looking around and doing a lot of research like you mentioned. This site is one place I haven't checked with and I know there are a lot of very intelligent individuals here who also have the experience. I've always found it to be easier and cheaper to learn from others mistakes than to make the same mistake and be told "why didn't you ask, I made the same mistake".