Set back and rechamber question

[cdhknives]

I may have outsmarted myself but I bet someone out there has tried this.

The 22-250 I built last year was my 3rd rifle barrel to fit, so I am still on the steep end of the learning curve. It has turned out to be a really fun rifle and I ahve spent a LOT of time tuning loads, getting to half MOA with a couple. BUT, I am starting to see significant lengthening of the loads to still touch the lands...throat erosion.

It is on a Rem 788 action, so a separate recoil lug design. Reading all the chatter about this being a short throat life cartridge and setting back/rechambering being popular in some circles, I thought I would try and machine the threads to allow one small setback. I cut a very small ledge for the recoil lug, just enough to center it and hold it in place as the barrel is torqued. The lug essentially covers the thread relief groove, if you can visualize that. Now I should be able to cut back one or two thread lengths by only adding length to ledge the lug slips over and cutting back and refacing the end of the barrel. Call it around 1/8" total deepening of the chamber. That should leave plenty of threads to simply screw the barrel back on after reaming the chamber the same amount.

Will that allow enough deepening of the chamber to clean up normal approx 1000 round throat erosion on a Medium Varmint profile Douglas SS barrel that has bever been shot to more than 'warm to the touch' heat???

 

[pontiac428]

How much has your COL or ogive length grown? That's a starting point. For 22/250 at a1000 I would expect.100-.120 of throat erosion, but it depends. It's a great cartridge for people who own lathes. Small price to pay for reaching towards mach 4.

 

[55fairlane]

Tagged for interest. I have a couple 22-250's

 

[cdhknives]

How much has your COL or ogive length grown? That's a starting point. For 22/250 at a1000 I would expect.100-.120 of throat erosion, but it depends. It's a great cartridge for people who own lathes. Small price to pay for reaching towards mach 4.

Hard to tell, I seem to have lost my notes from the first few loads and I was determined to throw 69-75 grain VLD bullets then. 1:8 twist. For whatever reason the old standby 55 grain Nosler BT and 52 grain Berger JHP are the most accurate, so I burned several hundred rounds trying to tell this barrel what it likes. Long story short I am now having to load to 2.537" for 69 Nosler CC and 52 Berger JHP has about .150 in the neck. Mag max is 2.405" and I can't get there with any pointy bullet and still be reasonably close to the lands. Accuracy is still good so my main goal for setting it back is to see if I can get the berger 52 JHP at mag length. Single shot is fine at the range but I have a trip planned this fall in Wyoming and hope to have time for varmint shooting...

 

[pontiac428]

Yeah, it makes sense that you're having better luck with the 52-55 gr. pills. 8 twist can be a stretch for the heavies like the 75 gr, and the VLDs have less bearing surface than spitzers. I've had schittluck with 75 VLDs in .223 8 twist myself. I love VLDs in the barrels I can run them in, but they do load long. The .22-250 as a variminter or a predator caliber was really intended for lighter, faster bullets. Who cares if you have a boat tail when you're hitting 4000 fps? At those speeds, BC is overrated... at least inside of 500 yards, and better than that if the wind is calm.

At 1000 rounds, I'd definitely do the set back. Barrel life is something for people who don't own lathes to whine about. For us, setbacks and re-crowns are things we can do while having our morning coffee.

One thing you can do is notch and blend your feed ramp to allow an extra .125 of COL. I do it on everything that needs it. Mag boxes are what they are, but BDLs give a lot more room than those trendy AICS magwells. Here's a pic (not my gun, this Army vet doesn't grease his junk, nor does he do camouflage):