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Discussion Starter · #1 ·
:eek: I have two types of 30-06 barrels and barrel extensions for my 1917A1/1928 Browning. I got a couple barrels from Numrich that were not threaded at the muzzle and have 16 narrow headspace adjustment notches. I also picked up a couple barrels from OOW that were threaded at the muzzle and had 12 wide headspace adjustment notches. I have barrel extensions with fingers to match each type of barrel.
Why are there two different types of barrels and how does one correctly adjust headspace on each?
 

· PhD in Over-Engineering
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The basic headspacing procedure is the same for both. There are just finer adjustments with more notches. The barrels you describe form Numrich sound like original 1917A1. I don't recall the correct number of notches off hand. The barrels with the threaded ends are Argentine, I believe. I think OOW made some new barrels too, with the square notches like the Argentine ones. Might only have made 308 ones. Not sure if those threaded 30-06 are original mfg or new.

Now if you have an original Colt 1928 barrel extension, it has the little spring loaded plunger lock for the barrel, rather than the leaf spring with the 90 degree tip. I have one of those but the gun is not assembled yet. Have not looked at how that is depressed to allow for rotating the barrel when gun is assembled. But there are plenty of guys here with running 28s who can chime in.
 

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Discussion Starter · #3 ·
The narrow notches fit Izzie barrel extensions perfectly.

The barrel extension that came with my MG does not have the plunger. It has a wider tipped leaf spring. I assumed it was original Argentine as the leaf spring, breach block, and breach block pin are all nickel plated. The extra barrel extension I got from OOW is identical to my original one, except no parts were nickel plated.
 

· PhD in Over-Engineering
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The Colt 1928 internals are indeed nickel plated, lock frame excepted. The parts will show a marking of an R in an oval. Most everything got marked. Is the barrel extension in question showing any markings?
 

· Watercooled Addict
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Dan,
The square knotched barrel is a colt barrel designed to be used with the colt barrel extension with the spring loaded plunger.

After ww1 colt implemented changes to its commercial guns that were improvements based on lessons learned in ww1. These were the stepped sideplates with rivets instead of dovetails, a spring to return the feed lever to correct side, a more positive headspace adjustment, a captive recoil spring, and even later, externally threaded waterjacket caps like on a vickers gun. Uncle sam had so many guns in the system they only addressed the issues they were having problems with which was the bottom plate, and left the other things alone.

Sort of like today with the piston upper for the m-16, which colt came up with 40 years ago but uncle said the one we already got is good enough.
 

· PhD in Over-Engineering
Joined
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8,765 Posts
Dan,
The square knotched barrel is a colt barrel designed to be used with the colt barrel extension with the spring loaded plunger.

After ww1 colt implemented changes to its commercial guns that were improvements based on lessons learned in ww1. These were the stepped sideplates with rivets instead of dovetails, a spring to return the feed lever to correct side, a more positive headspace adjustment, a captive recoil spring, and even later, externally threaded waterjacket caps like on a vickers gun. Uncle sam had so many guns in the system they only addressed the issues they were having problems with which was the bottom plate, and left the other things alone.

Sort of like today with the piston upper for the m-16, which colt came up with 40 years ago but uncle said the one we already got is good enough.
Don't forget the shouldered screw for the floating breech lock cam, which Colt also adapted from Marlin-Rockwell. That is what stopped the cracking of bottom plates. Uncle Sam just slapped a reinforcing bracket on the existing guns to solve the problem. Band aid versus cure!
 
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