Thread: Remington 700 Sako and M16 extractor conversions

This thread is following on from the thread started by Kiwi Greg in buy, sell, swap that then got shifted to his commercial section. In it he claimed that M16 extractor conversions on Remington 700’s for the Lapua magnum case were safer than the Sako extractor conversions. I asked him to clarify this, which he hasn’t done. So here are the pros and cons in our opinion based on having fitted and used both systems for some years now.

As can be seen from KG's links most if not all of these Sako extractor failures due to complete case head failure have been in benchrest or standard head size cartridges. There have been no instances with the Lapua magnum case that we are aware of. Case head diameter has nothing to do with it. If you are stupid enough to overload a Lapua magnum case to the point you get complete case head failure, which will be in excess of 90,000psi, the extractor issue will be the least of your problems! With a catastrophic action failure in a Remington you will almost certainly have copped other parts of the action or barrel, potentially even the bolt itself. The Lapua Mag brass has such a reinforced web of extremely hard brass that it is not necessarily the weakest link in the chain any more as with ordinary brass. That is why you cannot use conventional pressure signs as indicators when working up loads with this brass. And if you really think the tiny roll pin that retains the M16 extractor is going to resist this sort of pressure I think you’re fooling yourself, especially when the much longer length of the M16 gives the escaping gas more leverage on this pin anyway. There may be some argument that the M16 extractor retaining pin will withstand the much lower case head failure pressure of the PPC and similar comparatively weak brass, which is where this very rare Sako extractor issue first arose.

Tikka has used this exact same Sako extractor system for years, and there’s been no wail of terror from T3 users!

Action strength wise verses the extra bolt thrust due to the larger diameter case head, the main issue with either of these conversions is the way the lower locking lug is undercut reducing its shear strength. The standard M16 extractor requires an even deeper cut than the Sako extractor, reducing lug shear strength even more. This would be more of an issue with the extra bolt thrust from the extreme pressures involved with a Lapua Magnum case head failure. Recently narrower width and depth Sako and M16 extractors have become available that reduce the amount this locking lug is undercut, making this less of an issue.

Another disadvantage of the M16 extractor is that it needs more barrel counterbore clearance to hop over the case rim, about 40 thou or 1mm. This means the counterbore needs to be 90 thou or over 2mm bigger than the bolt nose diameter. One of the often quoted strengths of the 700 action is the 3 rings of steel around the case head - the bolt nose, the barrel counterbore, and the front receiver ring itself. But all of these are pointless if you have to run extra clearance between the bolt nose and the counterbore, negating the other 2 rings of steel. This is more of an issue with the Lapua magnum head size, as after you open the bolt face up, you end up with a very thin rim remaining around the bolt nose. With the extra clearance required with the M16 conversion, there is even less support for this rim, and a flying piece of this wouldn’t be much fun either.

We have come up with a system we’ve been using for our Sako and M16 extractor installations that solves all these extractor captivation issues, but the standard gunsmith barrel installation certainly won’t go to this extra effort and expense.

As with most things, if you exercise common sense and reasonable caution in your reloading, you’ll be quite safe with all these conversions. Just don’t go chasing some of the silly over the top velocities posted on the web at times. Stick to load info from reputable sources you can trust and you won’t get into trouble!

Just get a proper action made for it in the first place. . . ?

I think the issue is that some people believe that loading manuals are ''playing it safe'' and that hard brass is safe beyond the stated values as they don’t exhibit pressure signs.

For one reason or another squeezing an extra 100fps out of an already fast rifle at unsafe pressures appears to make sense to them? However I can see no tangible gain in obtaining that extra 100fps at the cost of brass life and having an unsafe rifle.

Stick to the safe loads and it won’t be an issue. And unless you have pressure measuring equipment, a loading manual is about all we have to go on...anything else is just a stab in the dark.

kj

Originally Posted by Greg Duley

This thread is following on from the thread started by Kiwi Greg in buy, sell, swap that then got shifted to his commercial section. In it he claimed that M16 extractor conversions on Remington 700’s for the Lapua magnum case were safer than the Sako extractor conversions. I asked him to clarify this, which he hasn’t done. So here are the pros and cons in our opinion based on having fitted and used both systems for some years now.

As can be seen from KG's links most if not all of these Sako extractor failures due to complete case head failure have been in benchrest or standard head size cartridges. There have been no instances with the Lapua magnum case that we are aware of. Case head diameter has nothing to do with it. If you are stupid enough to overload a Lapua magnum case to the point you get complete case head failure, which will be in excess of 90,000psi, the extractor issue will be the least of your problems! With a catastrophic action failure in a Remington you will almost certainly have copped other parts of the action or barrel, potentially even the bolt itself. The Lapua Mag brass has such a reinforced web of extremely hard brass that it is not necessarily the weakest link in the chain any more as with ordinary brass. That is why you cannot use conventional pressure signs as indicators when working up loads with this brass. And if you really think the tiny roll pin that retains the M16 extractor is going to resist this sort of pressure I think you’re fooling yourself, especially when the much longer length of the M16 gives the escaping gas more leverage on this pin anyway. There may be some argument that the M16 extractor retaining pin will withstand the much lower case head failure pressure of the PPC and similar comparatively weak brass, which is where this very rare Sako extractor issue first arose.

Tikka has used this exact same Sako extractor system for years, and there’s been no wail of terror from T3 users!

Action strength wise verses the extra bolt thrust due to the larger diameter case head, the main issue with either of these conversions is the way the lower locking lug is undercut reducing its shear strength. The standard M16 extractor requires an even deeper cut than the Sako extractor, reducing lug shear strength even more. This would be more of an issue with the extra bolt thrust from the extreme pressures involved with a Lapua Magnum case head failure. Recently narrower width and depth Sako and M16 extractors have become available that reduce the amount this locking lug is undercut, making this less of an issue.

Another disadvantage of the M16 extractor is that it needs more barrel counterbore clearance to hop over the case rim, about 40 thou or 1mm. This means the counterbore needs to be 90 thou or over 2mm bigger than the bolt nose diameter. One of the often quoted strengths of the 700 action is the 3 rings of steel around the case head - the bolt nose, the barrel counterbore, and the front receiver ring itself. But all of these are pointless if you have to run extra clearance between the bolt nose and the counterbore, negating the other 2 rings of steel. This is more of an issue with the Lapua magnum head size, as after you open the bolt face up, you end up with a very thin rim remaining around the bolt nose. With the extra clearance required with the M16 conversion, there is even less support for this rim, and a flying piece of this wouldn’t be much fun either.

We have come up with a system we’ve been using for our Sako and M16 extractor installations that solves all these extractor captivation issues, but the standard gunsmith barrel installation certainly won’t go to this extra effort and expense.

As with most things, if you exercise common sense and reasonable caution in your reloading, you’ll be quite safe with all these conversions. Just don’t go chasing some of the silly over the top velocities posted on the web at times. Stick to load info from reputable sources you can trust and you won’t get into trouble!

Great write up and info Mr Duley , good to see you are keeping the amateurs smiths on the right track

Well said Greg

When i have done the sako extractor on ones i have done with rebarrel an just fitting the extractor to standard barrel, to keep the 3 rings you speek of i mill a small bit to allow the extractor to hop over the case an still have minimal clearance over the nose

Originally Posted by kimjon

I think the issue is that some people believe that loading manuals are ''playing it safe'' and that hard brass is safe beyond the stated values as they don’t exhibit pressure signs.

For one reason or another squeezing an extra 100fps out of an already fast rifle at unsafe pressures appears to make sense to them? However I can see no tangible gain in obtaining that extra 100fps at the cost of brass life and having an unsafe rifle.

Stick to the safe loads and it won’t be an issue. And unless you have pressure measuring equipment, a loading manual is about all we have to go on...anything else is just a stab in the dark.

kj

So if the manual says for instance 46grmax of whatever for 2900fps and I only get 2600fps am I being reckless in going over max?

Originally Posted by tui_man2

Well said Greg

When i have done the sako extractor on ones i have done with rebarrel an just fitting the extractor to standard barrel, to keep the 3 rings you speek of i mill a small bit to allow the extractor to hop over the case an still have minimal clearance over the nose

You got it Abe! And it captivates the extractor in the battery position as well. Even more important with the M16.


Tussock, what about on Tikkas? They have a Sako extractor?

Originally Posted by veitnamcam

So if the manual says for instance 46grmax of whatever for 2900fps and I only get 2600fps am I being reckless in going over max?

Hell no, you load to the same velocity, then you'll be getting the same pressure as the loading manual load. I wrote an extensive reloading series on this back a few issues. You may take more or less powder to equal the same velocity and pressure, depending on your individual rifle's chamber and barrel specs. The velocity is your best guide to pressure if you don't have pressure testing equipment. Just be sure you're comparing like with like, eg same barrel length - minor chamber dimension variations don't matter.

Originally Posted by Greg Duley

Hell no, you load to the same velocity, then you'll be getting the same pressure as the loading manual load. I wrote an extensive reloading series on this back a few issues. You may take more or less powder to equal the same velocity and pressure, depending on your individual rifle's chamber and barrel specs. The velocity is your best guide to pressure if you don't have pressure testing equipment. Just be sure you're comparing like with like, eg same barrel length - minor chamber dimension variations don't matter.

Just the answer I was looking for.....................there are those that will not go over book max even if their hand load is well below factory ammo velocity's and the rest of us.

Originally Posted by veitnamcam
So if the manual says for instance 46grmax of whatever for 2900fps and I only get 2600fps am I being reckless in going over max?


That's a good question and one that neither of us can answer without the correct tools to measure the pressure, in this case your guess is as good as mine.

Some barrels are tight and produce high pressure-low velocity. Others are loose and produce high velocity-less pressure for the same load. Just look at what a difference seating death can do to pressure by simply altering it by 10thou.

I'm sure you already know this but pressure increases dramatically with those last few grains powder, it’s not a linier equation that you can extrapolate from tables more an uncontrolled spike that happens when you go past a point of no return. Sure the manuals will be conservative, they have to be in order to avoid people from killing themselves, but if you want to push it to the limit it’s a fine line and it’s going to come at a cost (minor - brass, barrel wear or major - a catastrophic failure?).

Knowing what that limit is without a way of measuring the pressure makes it simply a guess a best doesn't it?

kj

Yep but as Greg Duley said if your getting the same velocity(in the same length barrel) then you must be achieving the same pressure.

Originally Posted by veitnamcam

Yep but as Greg Duley said if your getting the same velocity(in the same length barrel) then you must be achieving the same pressure.

Correct, For example, I shot a remmy 7-08 SPS today, ADI 2208 for 140 BTips, books say about 42gn for 2820-2850fps

At 42gn I was only getting 2680fps out of this rifle, so worked up to 44gn for 2800fps with no pressure signs, will try 44.5, 45 next time. I'm picking 45gn will be about a safe working max, 3gn over the Nosler book.

Originally Posted by veitnamcam

Yep but as Greg Duley said if your getting the same velocity(in the same length barrel) then you must be achieving the same pressure.

I see where you're coming from....But hang on a minute- thinking about the physics, that may not be a perfect rule:

If a barrel is "tighter" or "rougher" it will place more friction on the projectile trying to pass down it.
As a result, more pressure will be required behind that projectile to create the same speed.

-So I wouldn't think pressure vs. speed is a straightforward relationship. Sure, there will be a correlation. But I'm not sure it'd be a safe assumption to make at the upper end of the range???

Given the book maxes are lower (if like me you believe they fudge their numbers for fear of liabilty) than real life maxes, using velocity is near enough. You might be slightly higher but not enough to go blowing up guns in my experience.

Originally Posted by James

I see where you're coming from....But hang on a minute- thinking about the physics, that may not be a perfect rule:

If a barrel is "tighter" or "rougher" it will place more friction on the projectile trying to pass down it.
As a result, more pressure will be required behind that projectile to create the same speed.

-So I wouldn't think pressure vs. speed is a straightforward relationship. Sure, there will be a correlation. But I'm not sure it'd be a safe assumption to make at the upper end of the range???

True but then how tight/rough/smooth was the test barrel? how accurate is your crony? how accurate was thiers? how well calibrated was their pressure test gear? and you can guarantee you are using different components to the test data so its a moot point really.
Let common sense prevail (even if its not that common)