what's this on this bolt face?

[swadiver]

I have a Savage short action with a Criterion barrel in .223. the bolt originally had a .308 bolt head. i replaced it with a Savage factory .223 bolt head. (seen here)

trying to figure out what these concentric circles forming on the bolt face mean.

I assembled and headspaced the bolt with a go gauge and then the scotch tape over the go gauge as a no go gauge as i have done with other builds with pre fit barrels. no sign of headspace issues in difficulty in chambering rounds or excessive brass stretch, etc. as of late, the rifle has been shooting a bit erratically.

any ideas as to the cause of these etched circles?

 

[Larryh128]

That would be the cutter that made the hole.

 

[swadiver]

That would be the cutter that made the hole.

thanks could be right. but i don't remember them being there when the bolt was new, but i could have missed it

 

[ab_bentley]

That's great quality control from savage.

Adam

 

[gunsandgunsmithing]

From an accuracy perspective, I'd be more concerned with the marks on the front of the lugs. If the barrel and bolt are touching, accuracy is not it's best. Strange things can happen as it heats up, too.

 

[Preacher]

I sure doubt that shooting it caused the circles, as mentioned before, it's the cutter thats the culprit...
Like also mentioned, the marks on the outside edges need tended to......

 

[swadiver]

From an accuracy perspective, I'd be more concerned with the marks on the front of the lugs. If the barrel and bolt are touching, accuracy is not it's best. Strange things can happen as it heats up, too.

i wondered about that. thanks much. that could explain the erratic accuracy. i guess i need to disassembly and re head space?

 

[GrocMax]

From an accuracy perspective, I'd be more concerned with the marks on the front of the lugs. If the barrel and bolt are touching, accuracy is not it's best. Strange things can happen as it heats up, too.

Not uncommon for prefit barrel mfgs to cut chambers too deep. It happens far more often than people talk about.

 

[GrocMax]

i wondered about that. thanks much. that could explain the erratic accuracy. i guess i need to disassembly and re head space?

Root cause is likely the chamber was cut too deep. If you have a go gauge, measure the distance of go gauge protrusion from the chamber to barrel, then measure the distance from bolt face to front surface of bolt head, you want some clearance to avoid contact and allow gas to escape in case of head rupture, .010" works, some people prefer tighter. If too deep fix is to turn the appropriate amount off the breech.

If the measurements show you have good clearance, you may have got some chunks of trash caught between the bolt face and barrel, but that bolt head looks like a classic too deep chamber.

 

[gunsandgunsmithing]

Root cause is likely the chamber was cut too deep. If you have a go gauge, measure the distance of go gauge protrusion from the chamber to barrel, then measure the distance from bolt face to front surface of bolt head, you want some clearance to avoid contact and allow gas to escape in case of head rupture, .010" works, some people prefer tighter.

...or if a new or short piece of brass is used to set the hs.

 

[CJ6]

I think you need to clean the chamber real good. It looks like you may have some grit between the bolt head and barrel causing the marks on the front of the lugs.

 

[Riesel]

Are you having a great deal of resistance closing the bolt? If so............... Since you don't have an actual no go gauge I believe I would review that measurement. If your going with the "tape method" measure a piece of masking tape, more like .003, and use it.
Those circles inside the bolt on the bolt face are just bad workmanship. Was this bolt head brand new or has it been worked over by some one with one of those .308 bolt face cutters and not enough chip cleaning?

 

[Dusty Stevens]

Typical savage machining and tolerance stacking on the boltface clearance. I think youre seeing the marks in the boltface because its dirty now. You need to check that boltface clearance with some silly putty or plastigauge then have a machinist adjust accordingly

 

[billlarson]

From an accuracy perspective, I'd be more concerned with the marks on the front of the lugs. If the barrel and bolt are touching, accuracy is not it's best. Strange things can happen as it heats up, too.

+2

 

[swadiver]

thanks for the reply's. in reference to the other lines scored on the lugs of of the bolt, it's possible i caused them when i first assembled and head spaced the barrel/bolt. the problem was that when i installed the .223 bolt head in the bolt and tested it in the receiver without the barrel in place, the bolt lift had become pretty hard. don't know why. so, when i started the head space process, i screwed the barrel down too far and then operated the bolt a few times. the already hard bolt lift threw me off. in short, i screwed up. at this point i don't think the lugs are still rubbing up against the barrel breech face, but not 100% sure. i am going to do some cleaning and testing, but it may have to go to the 'Smith. we shall see

 

[Dgd6mm]

Do this before you decide to send it to a Smith.

Root cause is likely the chamber was cut too deep. If you have a go gauge, measure the distance of go gauge protrusion from the chamber to barrel, then measure the distance from bolt face to front surface of bolt head, you want some clearance to avoid contact and allow gas to escape in case of head rupture, .010" works, some people prefer tighter. If too deep fix is to turn the appropriate amount off the breech.

If the measurements show you have good clearance, you may have got some chunks of trash caught between the bolt face and barrel, but that bolt head looks like a classic too deep chamber.

 

[swadiver]

Do this before you decide to send it to a Smith.

ok thanks seems like a good idea

 

[calgarycanada]

Can slight touch of bolt head with barrel breech cause accuracy issues? My savage has same issue. It's not hard to manipulate so touch is minor.
I took it to smith, he closed the bolt on empty chamber and was able to move bolt back and forth slightly so he said it's fine because savages have anti rattle twist washer between bolt body and bolt head which pushes bolt head forward but as long as there is back and forth play when bolt closed on empty chamber, it's ok. He explained it as bolt head only touches on empty chamber but it won't touch with case in chamber as that'll compress the washer and push bolt head back away from barrel.

 

[Riesel]

The bolt head is pinned to the bolt body so it really doesn't have any back and forth motion per se. The washer is really for the benefit of the baffle. I'm likely to disagree with your smith, just not a good thing if bolt face kisses breechface. Just my opinion.

 

[Ggmac]

+1^ . If the bolt is cocked it should have no movement foward