Barrel Fitting on Colt Pre-70 Gov.?

[Rocket 6R]

OK, I may have located my last item, a barrel, for the restoration project on my Colt Pre-70 Gov. model. Once I decide to purchase the item, seller is another member, it will arrive in the mail. Meaning, I don't have the barrel yet, but have seen pictures of it and it looks to be in very good shape. Anyway, my question is does the barrel need to be fitted to my slide? The barrel I wish to purchase is a Colt and appears to come from the Pre-70 era. Remember, this is a restoration and I simply want to be in the ball park of specs as it may have come from factory. I'm not looking for super tight groups. Hell, if I could get 5" groups at 25 yards I would be happy.

*no one seems to know how many different incarnations were made of the Pre-70 barrels. Some have arsenal stamping on them while others do not. Some barrels have different size or depth stamping on the barrel hood. I'm not sure if the above mentioned varies by year of manufacturer or not. To my understanding, the Pre-70 Gov. were made from 1946 to 1969.

I have not been able to match my barrel up detail to detail on any other barrel. The one that I'm thinking about purchasing appears to be correct in every detail except for the depth of the stampings on the hood. My pistol was produced in 1956. I'm not sure if in 1956 that could have made other very slight cosmetic changes to the barrel that year. Meaning, would it be possible to purchase two 1956 pistols and have different looking stampings? I'm not talking about what words or symbols are stamped on the hood, but rather the way it was done.

My barrel:
http://i51.photobucket.com/albums/f382/prsalazar/Picture415.jpg

Barrel I may purchase:
http://i51.photobucket.com/albums/f382/prsalazar/Colt45Autoother.jpg

Thanks, Rocket 6R

[Azrael256]

IIRC, the only real difference in barrels is with the series 80s that have a different OD for the collet bushing.

But to answer your question, yes. It will need to be fitted.

[Rocket 6R]

IIRC, the only real difference in barrels is with the series 80s that have a different OD for the collet bushing.

But to answer your question, yes. It will need to be fitted.

Do you know why it needs to be fitted? I've seen a lot of after-market drop in barrels out there. I'm not putting in an after-market barrel, but simply bring up the question as it pertains to barrel fitting. Does Colt fit their barrels in the Gov. model pistols when they are made?

Thanks, Rocket 6R

[Azrael256]

It needs to be fitted to maximize lug engagement. A gun with a poorly fitted barrel will suffer from accuracy issues (lugs engaging unevenly causing the barrel to point somewhere other than the POA), as well as durability issues. Tuner gave a good example of what happens. Imagine two hammers. If you put the heads together and squeeze real hard, they will eventually deform, but it will take an eternity. Now, try smacking them together with the same amount of force. This is what happens when the barrel is poorly fitted and the barrel slap seats. Obviously the hammers will deform quickly. Now, smack them together off-center. You'll tear the hammers up in a few minutes. This is what happens when the lugs do not engage deeply and evenly.

What you're going for in barrel fitting is the barrel lugs engaging the slide lugs to maximum possible depth, and all three lug pairs taking an equal share of the load. And that's just the top lugs. You still have to make sure the lower lug fits against the frame and slidestop crosspin properly, and the hood has to be fitted to the breechface. Mucking up headspace can cause the gun to kaboom, so all of this has to be done very carefully.

Whenever you see "drop-in," be skeptical. I have seen grip panels that had to be modified and springs that had to be trimmed, and those parts are the only things that don't usually require fitting.

Manufacturers do fit their barrels, but just how they do it varies. Ordnance-spec guns may have been assembled by picking matching parts. You take a whole pile of parts, and start assembling the parts that fit together the best. The variations in X barrel match nicely to the variations in Y slide, which mates up nicely with the variations in Z frame, so you can just slap it together with minimal fitting. It works well enough for an issue weapon. Mid-range barrels will be fitted to a little bit better standard, but you'll find that many barrels don't have full lug engagement. They're almost always perfectly safe and reasonably accurate, but they're not as good as they could be. High-class (and therefore expensive) guns will have deep lug engagement, an even load distribution between the lugs, and will shoot the best. As to specifically what manufacturer does the best fitting, I cannot say since I don't have a whole lot of experience measuring production guns.

[RickB]

I'd be very surprised if the replacement barrel required any fitting, or if there was actually anywhere any fitting could be done. I'm not talking about welding it up and cutting it to fit, I'm talking about the stock barrel being oversize in any meaningful way; it should just drop in.