Headspace issues

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   I have a numbers matching No4 Mk1 from RTI. It has a great bore and overall good condition. However, it has some pretty excessive headspace. Not quite to the point of case separation on every round but it is pretty evident that the brass is very stretched. I put gauges in and it easily closes on a .074 gauge. I stacked up tape on the gauge and got it to finally fail to close on around .080. Even then it was only about an 1/8” away from closing all the way. I figured out that I probably need about a size 3 bolt head. 
My question is, where to find them. I have scoured the internet and lost a few ebay auctions. The only place I have found them was Southern Cross Militaria in Australia. The had what seemed like boxes of them, but they will not sell to me living in the States. Does anyone have a way to source larger bolt heads or have a treasure trove of them?

Or are there any other fixes? Weld on the rear of the lugs, file to the needed dimension, then re-harden the lugs? I don’t want to condemn the rifle to be a wall hanger quite yet!!!

I would appreciate any help from you very experienced people!!!

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03410341 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: April 17 2025 Location: Idaho Status: Offline Points: 3	Post Options Post Reply Quote 03410341 Report Post Thanks(0) Quote Reply Topic: Headspace issues Posted: April 20 2025 at 5:15pm
	I have a numbers matching No4 Mk1 from RTI. It has a great bore and overall good condition. However, it has some pretty excessive headspace. Not quite to the point of case separation on every round but it is pretty evident that the brass is very stretched. I put gauges in and it easily closes on a .074 gauge. I stacked up tape on the gauge and got it to finally fail to close on around .080. Even then it was only about an 1/8” away from closing all the way. I figured out that I probably need about a size 3 bolt head. My question is, where to find them. I have scoured the internet and lost a few ebay auctions. The only place I have found them was Southern Cross Militaria in Australia. The had what seemed like boxes of them, but they will not sell to me living in the States. Does anyone have a way to source larger bolt heads or have a treasure trove of them? Or are there any other fixes? Weld on the rear of the lugs, file to the needed dimension, then re-harden the lugs? I don’t want to condemn the rifle to be a wall hanger quite yet!!! I would appreciate any help from you very experienced people!!!

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: April 21 2025 at 9:28am
	Just a tip. you may want to measure your bolt head from rear shoulder where it butts up against the bolt body, to the breech face. Many numbered bolt heads have been rep-ground to something other than the "official" length. Don't forget that JUST length isn't the whole story. Bolt head "clocking", equal locking lug engagement, & firing pin protrusion also need to be correct. Secondly find out WHY the excessive length is there. It could indicate a serious problem, or maybe just the wrong bolt head, but its worth a little detective work.
	Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)

03410341 Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: April 17 2025 Location: Idaho Status: Offline Points: 3	Post Options Post Reply Quote 03410341 Report Post Thanks(0) Quote Reply Posted: April 21 2025 at 9:58am
	Shamu, I measured my size 1 bolt heads and got 0.630”. Also I bought a new old stock bolt body and It helped a little but that was prior to my initial post What could cause it?/ how would I check? Rear lug slots in the receiver?

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: April 21 2025 at 11:49am
	I would not consider welding anything to the bolt lugs. This is what keeps the bolt from flying into your face and this will weaken the lugs considerably, plus the surface must be hardened, or it will wear very quickly. It's possible the action body bolt lug recess surfaces have worn. If they are kept clean and lightly greased, headspace should not change even after 10,000 rounds. It's also possible that this bolt required a #3 bolt head when it was built, but no way of knowing that now, someone could have swapped it out to get a #3 bolt head for another rifle. 0.630" is certainly in the range of a #1 bolt head. But, if your rifle currently headspaces at around 0.080", a #3 bolt head "should" bring headspace down to pass the Field gage (IIRC, a #3 bolt head will typically fall within 0.635 - 0.640). The one #3 bolt head I have measures 0.636. Try the new bolt body and check again. Tape will compress easily on the gage giving you a false measurement, try using a feeler gage. You may need to sacrifice a few feeler gages by cutting them into small pieces to fit between the bolt head and hs gage. I've used shim stock before too. But, you really should get it to pass on a 0.074 field gage if your going to shoot the rifle.

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: April 21 2025 at 1:23pm
	What he said ^^^^, don't go grinding or welding in that crucial area! If your original bolts serial number matches the receiver number I'd stick with it as it was hand fitted to that exact receiver. Now you just need to fin a bolt head that clocks & gives you the correct headspace as is, then sort out the firing pin protrusion & locking lug engagements AFTER you've determined what the real actual problem that is, or whether the old girl needs to retire.
	Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)