I recently picked up a bighorn origin as a backup to my bighorn TL3. I also got one of the Hunts long range recoil lugs for the Origin so that I could use my TL3 barrels on the Origin. I have not shot the Origin yet, but I have installed a barrel on it with the HLR lug and the barrel does not index the same as on my TL3 and seems to have a shorter headspace. I can still chamber brass fired from my TL3 in the same barrel mounted on the Origin, but it is much tighter that when the barrel is mounted on my TL3. Does anyone have any suggestions on how to get these two actions to headspace the same?
- Thread starter mason.ostrom
- Start date
It is likely headspacing fine. The improper index is caused from differing thread starts between the TL3 and Origin. The thread starts are 180 degrees off, which is exactly how far off the index should be.
Sounds like they are pretty close if you can chamber fired brass from the TL3 when the barrel is mounted on the Origin.
To check exact headspace I like to pull the firing pin spring and slowly size brass, measuring as I go with a headpsace gauge, to test to see where the bolt close effort disappears. I might try that to get a more specific number of how far off the two actions are from each other. Another thing you could test is swap the bolt heads to see if any of the difference comes from those rather than the action body and recoil lug.
If they are within a a couple thou of each other then it may not be something to worry about.
To check exact headspace I like to pull the firing pin spring and slowly size brass, measuring as I go with a headpsace gauge, to test to see where the bolt close effort disappears. I might try that to get a more specific number of how far off the two actions are from each other. Another thing you could test is swap the bolt heads to see if any of the difference comes from those rather than the action body and recoil lug.
If they are within a a couple thou of each other then it may not be something to worry about.
Do you have a way to measure the lug to the .0001"?
To be the EXACT headspace, the Origin and the TL3 would have to be within .0001" (very possible) of each other AND the lug would have to be exactly .1500". That's asking a HELL of a lot for the two different products to be absolutely the same AND have a third party product be absolutely perfect as well. You've got to give consideration to what acceptable headspace is and that's determined by go and no-go gauges, not fired brass. It's not impossible, but it's highly unlikely that everything will be that perfect.
If you can chamber fired brass, even though it's tight, the headspace between the two actions is really, really close, but might not be perfectly exact.
Thanks - Ray
To be the EXACT headspace, the Origin and the TL3 would have to be within .0001" (very possible) of each other AND the lug would have to be exactly .1500". That's asking a HELL of a lot for the two different products to be absolutely the same AND have a third party product be absolutely perfect as well. You've got to give consideration to what acceptable headspace is and that's determined by go and no-go gauges, not fired brass. It's not impossible, but it's highly unlikely that everything will be that perfect.
If you can chamber fired brass, even though it's tight, the headspace between the two actions is really, really close, but might not be perfectly exact.
Thanks - Ray
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Thanks everyone for their replies. I did not know (and didn’t even think to look) that the threads for each action start in a different location. I knew the headspace was very close between the two but I did not know how close. Again, thank you everyone for your info!
