Sig Barrel Fitting Questions??? Long - Pistolsmith
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Old 02-20-2002, 07:20 PM   #1
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Join Date: Feb 2002
Posts: 6
I have a question regarding the fitting of barrels on Sig P220’s. Before firing my new P220 for the first time, I inspected the gun’s fit and finish both inside and out then cleaned and lubed the gun. My initial inspection yielded no surprises, a few small tool marks on the underside of the slide but all else looked fine. After firing 50 rounds I removed the slide to clean up some excess oil, and I noticed a couple of nicks and two burrs on the underside of the feed ramp. These marks were not present upon my initial inspection; I proceeded to polished out the small marks and removed any sharp edges from the feed ramp using 600 grit paper, first dry then with oil until I obtained a smooth finish. Obviously these marks were produced by the feed ramp passing over the steel frame insert as the slide and barrel moved into battery, no marks appeared on the frame insert as this item appears to be much harder than the barrel. I reassembled the gun putting a small amount of oil on the underside of the feed ramp, after firing another 50 rounds I removed the slide again and inspected the feed ramp. This time a small horizontal depression appeared on the underside of the ramp, corresponding to an angle on the frame's steel block which the feed ramp passes over on its way to battery. I reassembled the gun without any further alteration to the feed ramp and fired another 50 rounds. Upon inspecting the feed ramp again, I noticed that the newly formed depression had been slightly polished out by the guns cycling. It appears that the feed ramp is a key part of the barrel’s fit on these guns, by ramping up on the frame block the barrel is tilted upward forcing the chamber to lock into the breech, and the muzzle of the barrel to wedge into the front of the slide. The accuracy and tightness of my gun do not appear to have been effected by my deburring and polishing of the feed ramp’s underside, although I’m surprised at the amount of wear this fitting surface has taken in such a short time. I imagine that this wear is somewhat self limiting and the gun will settle in before long. So now for my questions: Did I do any harm to the barrels fitting? What function does the barrel's under lug serve if the feed ramp is utilized to move the barrel into lock-up? What if any aftermarket barrels would seasoned Sig users recommend? How much fitting is required when installing an aftermarket barrel? I know this was a rather long post so thanks for bearing with me.

<font size=-1>[ This Message was edited by: BobPellegrino on 2002-02-20 19:22 ]</font>
 
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Old 02-22-2002, 09:59 AM   #2
 
Join Date: Jan 2002
Posts: 14
Hi Bob,
I too just got a P220. I've put 100 rnds of CCI 230 gr thru it. After reading your post, I disassembled my gun and examined the barrel. On the underside of the feed ramp at either side of the pointy "ears" I have a slight burr, almost need a loupe to see it. But it's nothing that I would deem out of the ordinary. I've also spent alot of time dry firing and the finish is worn off the rear contact surface of the firing pin and the hammer face contact area. Also, on the top of the frame rails at the rear, the finish is scraped on top on each side for a length about 0.5" max. A certain amount of of this is normal as parts seat in. If on a new gun there is a marked grittyness or binding or friction, this is a sign that something needs to be addressed, a burr etc. One thing that I did before I shot my gun was to take the plastic grips off & set them aside, then I took the slide, barrel & recoil spring as well as the frame and throughly washed them with Brake Cleaner. Mineral Spirits or charcoal lighter would suffice as well. This removed the protective cosmoline and any trapped machining tailings. I used light compressed air to blow out the pockets & speed evaporation taking care to protect any springs that might be dislodged. Then I relubed with CLP and Teflon grease on the rails. Mind you, my guns get used and practiced with constantly and they get scratched from speed mag changes etc. so they aren't show pieces, they're life support equipment. So I'm not as concerned as some about cosmetics as I am about performance.
 
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