Saint has one or both problems going on.

The first that the bolt is unlocking too fast and needs to be slowed down with a heaver buffer,
the second is that  the chamber walls are not reamed smooth (reamer chatter) and causing the spent case to over bind at extraction instead.
Note, make sure to clean the chamber with a chamber brush and CLP by hand, then dry patches, before inspecting the chamber.

If you suspect a badly reamed channel, then take a photo and post it.

This is a shite show chamber that has ridges and grooves from a badly reamed chamber.


This is just a upper/chamber in need of a good CLP cleaning, including Chamber brush to scrub the chamber clean by hand as well.

Reloads can be strange ducks,

Hence in 223 or 5.56 nato, your need to work with a powder that will produce the max working pressure you desire (55K in the case of 223, and 62K in the case of the 5.56 nato), but at the same time, burn rate of the powder that will produce an ideal gas port pressure as well.

Hence use powder that burns too fast, and you reduce the working gas port pressure, while use a powder that burns too slow, and this increase the gas port pressure since the max burn dwell is father away from the chamber instead.

Here we have a 63gr bullet, using H335, loaded to Nato pressure of 60K, and the graph for its mas spike dwell, then residual pressure of the gas port pressures at the few locations down bore.   So if we use faster burning powder, and still maintain the 60K working pressure, this will decrease the gas port pressure down bore instead. Slower powder would push the max spit to the farther down bore instead, and increase ga pressure at the gas port instead.


Simply put, we can check the spent primers of the load to make sure that the load is not going over pressure in a specific rifle to start with, the it just a mater of tuning the action (gas port size/recoil spring tension/buffer mass), to get the bolt to unlock at the correct timing, so the bore residual pressure has dropped enough to allow the spent case to be pulled cleanly from the chamber at bolt unlock.

So to sum it up if the spent primers do not show any signs of over pressure, it boils down to either the bolt unlocking too soon with the spent case still to residual bore pressurized to the chamber for a clean pull, or the chamber just too rough and causing the spent case to over adhere to the chamber walls for a clean pull instead.

And the reason that I bring up checking the spent primers, is that the Saint chamber may be tighter cross wall dimensions, may only be chambered 223 (leade cut), and if you try to shoot ammo loaded to Nato working pressure, it going to cause the Nato ammo to over spike in it working pressure in the first place.  The tighter side all chamber decrease blow by at firing forming to increase working pressure, and the shorter leade on the 223 chamber causes higher working pressures as well. So since the Saint rig will run fine with factory nato ammo's, would not suspect it so much as a chamber problem, but more of the reloads in question instead and would check the spent primers to begin with, since the ammo may just be loaded too hot and with a powder burn rate too slow for the rig instead.

Normal for the chamber to have a straight, but burnished finish on a service rig.

Since the rig is ripping off the spent case rims, then check the spring primers for sighs of over pressure, if such is not the problem, then just need to slow the bolt unlock back down (gas port size slightly larger on this rig).

The H series buffers are the standard 1 tungsten disc (H1), all the way up to the H3 that all 3 discs are Tungsten to further increase the buffer weight isntead.



If you don't have a mill to make either new buffers, or just cut new internal tungsten buffer weights, then it does come in hand to have both a standard weight buffer, and a H3 buffer.  This way when it comes time to come up with a H type buffer needed, between the two, has you covered since you can swap internal weights to come up with with the needed H buffer weight type.

Hence you load only a single mag  loaded round to fit it and see if the bolt will lock back on the catch, and working up in the buffer weights one at a time,  to find the buffer that just allows the bolt to lock back, then drop down one buffer weight and your golden for a given rig for that ammo type.

In your case with the upper ripping off the rims with the ammo in question , would dare bank that it would be H3 buffer, or something even heaver needed to get the bolt unlock back in check.

Also, there are adjustable gas block and carrier keys to reduce to the amount of pressure through the gas port if its drilled over sized, but these tends to be more of a hassle with repeat adjustments then just a buffer swap isntead.

And again, check the spent primers, since it may not be the gas system or buffer the problem, but the ammo going over pressure in the rig well past the even nato working pressures to cause the problem in the first place.

Double post,
And sucks that the mod's lost the delete button to delete even our own posts when such double posts happen.

But the queer one (queer as in strange), we still have the admin button, so we can still even ban ourselves is desired.

No worries!!!

With only 40 rounds let of the stuff, just gift it to someone with a bolt action rig to should not have problems with it, since it not going to be worth the rectal itch of having to tweak a rig to just run 40 rounds of such to burn it up, then convert the rig back again.