Options for M70 CRF to allow longer COAL?

[ChewMT]

I have started working on load development for my model 70. Rifle is a new model chambered in 300 wm not the express version.

The first issue I have encountered is my short magazine well. After checking headspace on my factory barrel from once fired brass I noticed the barrel has a very long throat. Add to that that I'd like to shoot 215 bergers and you can see my magazine is way too short.

I spent the better part of the day researching solutions to this and this is what I came up with:

1. Wyatt mag extension. Requires machining and looks to have issues with model 70s from what I could find. Not sure if it will work on a CRF m70 either.

2. Put an expess mag well and follower on it. Couldn't find much information on this and would like to know more.

3. Add a dbm, not sure if this would require machining on the action to allow longer COAL or not.

The question. What is my best option? I would prefer not to single round load seeing this is a hunting rifle first and foremost. I want something that is going to be reliable and not cause any headaches down the road.

 

[ChewMT]

Bump

 

[MTHunt]

Am curious about this as well since I have a m70 that I want to re barrel but the shorter mag is proving to be a possible issue.

 

[AZShooter]

Two ideas and one will cost nothing.

1)Why not seat to fit and feed from magazine with the 215s and see how they perform? My experiences with the hybrids has been excellent regardless of jump to lands. You may have read that a short seated bullet will impinge on the powder capacity of the cartridge causing it to loose velocity. IMO you will not loose enough velocity/performance to matter with a deeply seated bullet. For grins measure the powder volume for the current COAL vs the intended longer COAL. Turn the difference into a percentage then divide by 4 to get the approximate velocity change.

2) Call Wyatts and talk to them. I am certain they can tell you which system would work best.
The machining involved in making an extended magazine box fit and altering the bolt stop is not a big deal. Heck I fit a longer box to a SA rem with a dremel tool!

 

[CliffM]

Two ideas and one will cost nothing.

1)Why not seat to fit and feed from magazine with the 215s and see how they perform? My experiences with the hybrids has been excellent regardless of jump to lands. You may have read that a short seated bullet will impinge on the powder capacity of the cartridge causing it to loose velocity. IMO you will not loose enough velocity/performance to matter with a deeply seated bullet. For grins measure the powder volume for the current COAL vs the intended longer COAL. Turn the difference into a percentage then divide by 4 to get the approximate velocity change.

2) Call Wyatts and talk to them. I am certain they can tell you which system would work best.
The machining involved in making an extended magazine box fit and altering the bolt stop is not a big deal. Heck I the fit a longer box to a SA rem with a dremel tool!

Good advice,
when I first started load development for mine in 6.5 cal. the 140 Bergers shot as well .020" into the lands as it did .020" short of max magazine length (3.385"). I have an extended box that I may never need unless the throat length changes to require it.
Cliff

 

[ChewMT]

Thanks for the replies, any idea on what I can expect to pay for the wyatt magazine? Including gunsmith work and components?

I'm tossing around the idea of leaving my rifle as is and getting something else with a longer box if it's that expensive. Not all the areas I hunt require a heavy long range rifle.

 

[Bart B]

Does the magazine have a spacer at the back so case heads stop about 1/8 inch forward of the magazine back metal?

If so, take that spacer out then grind off the bolt stop about 1/8 inch so the bolt will go back further to load rounds. That'll let you seat bullets wo COL is about 1/8 inch longer.

I don't think there will be any significant accuracy difference with any bullet seated so rounds load easy from the factory box magazine. As long as the rounds are pretty straight, you'll be OK accuracy wise.

Detachable magazines typically require a 1/2 MOA or so change in zero across several. They all don't fit the same way and with the history of such mag's on M14NM rifles not using the same zero with match ammo, I think bolt gun detachables will be the same. Or buy several and test each then pick 2 or 3 that enable the same zero.

 

[ChewMT]

Does the magazine have a spacer at the back so case heads stop about 1/8 inch forward of the magazine back metal?

If so, take that spacer out then grind off the bolt stop about 1/8 inch so the bolt will go back further to load rounds. That'll let you seat bullets wo COL is about 1/8 inch longer.

I don't think there will be any significant accuracy difference with any bullet seated so rounds load easy from the factory box magazine. As long as the rounds are pretty straight, you'll be OK accuracy wise.

Detachable magazines typically require a 1/2 MOA or so change in zero across several. They all don't fit the same way and with the history of such mag's on M14NM rifles not using the same zero with match ammo, I think bolt gun detachables will be the same. Or buy several and test each then pick 2 or 3 that enable the same zero.

Thanks that's what I was looking for. I want to avoid gunsmithing if at all possible.

I did some more looking and it looks like I need a different follower, bolt stop and ejector. Is this correct? Does anyone have any experience with this process? Can I just buy a longer factory box too?

 

[Short Case]

The magazine spacer is spot welded in, just us a 1/8 drill bit and drill the spot
welds out and take the spacer out. Next take bolt stop out and trim it down 1/8"
The follower will not need replacing, you should have a 3 3/4" inside of box

 

[ChewMT]

The magazine spacer is spot welded in, just us a 1/8 drill bit and drill the spot
welds out and take the spacer out. Next take bolt stop out and trim it down 1/8"
The follower will not need replacing, you should have a 3 3/4" inside of box

So the follower only corresponds to the individual case head? Still not sure what it is?

What about the ejector?

 

[Short Case]

It might need to be shorten to

 

[AZShooter]

Again why get all worked up to do this? Just load some ammo to fit and feed and see how it shoots that hybrid. IMO that is all you need to do.

 

[ChewMT]

Again why get all worked up to do this? Just load some ammo to fit and feed and see how it shoots that hybrid. IMO that is all you need to do.

Agreed, however I'm going to order a new barrel soon. I don't want to find out that I'm limited in magazine size when it's too late.

 

[Black67]

For a M70 and the Wyatts box, it can be done. I had one installed on my M70 Sharpshooter 7mm STW. For these, they used the Express (Magnum) Classic actions. For this, I had a gunsmith do all of the work. It took some time, as this was the first M70 that he did, as he has done many Rem 700's. I used my old follower for this. He did some other work on the action per Wyatt's page. I have had no feeding problems with it. My brass ejects great too.

For me, I had to change my bottom metal. My rifle had the 2 piece bottom metal (3 bolts) and this modification took out the center anchor point. So, I put in a PGT bottom metal.

These two links are the parts that I ordered from Wyatt. They worked as said.

MBE-8 Magazine Box, WYATT'S OUTDOOR, INC.
Winchester M-70 Ejector, WYATT'S OUTDOOR, INC.