Bolt Head Overturn

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   While messing about with checking headspace on the T, I noticed that the bolt head overturn is somewhat excessive, I measured it at approx 30 deg. I suspect it’s been this way since the barrel had been replaced by the DCRA armorer and now has approx 1200 rounds thru it. It is certainly the bolt head that’s been on this rifle since 1965.  By the book, it should be replaced.
Sorting thru my spare bolt heads, I found one that appears to be an unissued spare. It’s fully blackened, including the front surface. No markings at all except for the “1” indicating it is a #1 bolt head. It measures 0.632 inches and gives about a 5 deg overturn.  The current bolt head installed measures 0.631 inches, also a #1 bolt head.  This will tighten up headspace a bit.

But, it seems to me that the “damage is done” if there is any damage. I don’t think the loads on the bolt from firing can be taken by the threads. Screwing in the bolt head and aligning it with the body rib shows no gap between the shoulder on the bolt head and front face of the bolt body when a bit of pressure is applied pushing the bolt head back onto the bolt body. 

I may just go ahead and swap out the bolt head, but I wonder if that new bolt head is machined square to the axis of the bolt body like the one I have currently is…

Current installed bolt head:

“New” Spare bolt head:

What do you guys think? 

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britrifles Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February 03 2018 Location: Georgia, USA Status: Offline Points: 8404	Post Options Post Reply Quote britrifles Report Post Thanks(0) Quote Reply Topic: Bolt Head Overturn Posted: December 11 2023 at 6:21am
	While messing about with checking headspace on the T, I noticed that the bolt head overturn is somewhat excessive, I measured it at approx 30 deg. I suspect it’s been this way since the barrel had been replaced by the DCRA armorer and now has approx 1200 rounds thru it. It is certainly the bolt head that’s been on this rifle since 1965. By the book, it should be replaced. Sorting thru my spare bolt heads, I found one that appears to be an unissued spare. It’s fully blackened, including the front surface. No markings at all except for the “1” indicating it is a #1 bolt head. It measures 0.632 inches and gives about a 5 deg overturn. The current bolt head installed measures 0.631 inches, also a #1 bolt head. This will tighten up headspace a bit. But, it seems to me that the “damage is done” if there is any damage. I don’t think the loads on the bolt from firing can be taken by the threads. Screwing in the bolt head and aligning it with the body rib shows no gap between the shoulder on the bolt head and front face of the bolt body when a bit of pressure is applied pushing the bolt head back onto the bolt body. I may just go ahead and swap out the bolt head, but I wonder if that new bolt head is machined square to the axis of the bolt body like the one I have currently is… Current installed bolt head: “New” Spare bolt head: What do you guys think?

Shamu Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 20510	Post Options Post Reply Quote Shamu Report Post Thanks(0) Quote Reply Posted: December 11 2023 at 10:28am
	You've probably tried this but . . . Unscrew the old head about 1/4 turn. Now try a "wiggle" & a "push<>pull" test. If you find any flop in either swap the heads if not keep what you have!
	Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)

britrifles Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: February 03 2018 Location: Georgia, USA Status: Offline Points: 8404	Post Options Post Reply Quote britrifles Report Post Thanks(0) Quote Reply Posted: December 11 2023 at 10:39am
	Yes, I did do this. While there is some movement, it does not seem any excessive or different with different bolt heads. I suspect it’s fine as is. I went ahead and assembled the new bolt head with the other spare bits I have. All of these parts were with the spares my Dad had from the 1960’s. I thought there should have been a proof mark on the bolt head, but there are no marks other than the “1”, not even a manufacturers stamp. My Fulton No. 4 looks about the same as the BSA T, and it came that way right out of Fultons also back in the 1960’s. I suspect I’m worried about nothing here…

Shamu Members Profile Send Private Message Find Members Posts Add to Buddy List Admin Group Logo Designer / Donating Member Joined: April 25 2007 Location: MD, USA. Status: Offline Points: 20510	Post Options Post Reply Quote Shamu Report Post Thanks(0) Quote Reply Posted: December 11 2023 at 11:01am
	I guessed you probably had & compared too. Maybe but at least you'll be back in spec just in case, & its minor surgery.
	Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)