jwhittin

What OAL do you run?

If you move the barrel rearward (not forward) the chamber should sit flat in the frame bed. In rereading your post, you should also check the compensator to make sure bullets are not striking the inside circumference of the compensator. Visually inspect the inside surfaces of all the baffles of the comp. If the bullet is coming in contact you will see wear and possibly lines in the direction of the bullet across the inner surface of one or more baffle. You can probably see most if not 360 degrees by looking through all the ports in the comp. If there are no signs of interference, then it seems like its barrel related. Do you have calipers? If so, measure the diameter of your slide stop where you see the set of wear marks near the middle. This is the location where the barrel lower lugs contact the slide stop. Slide stop diameters are usually 0.200" but could be 0.201". Even wear as little as 0.0005" in the diameter can loosen the fitment and cause issues. Another test is to replace the slide stop with a new one. If the group improves, you know you are on the right track but you still need to check the lower lug barrel contact with the slide stop to make sure its correct as mentioned above (marking the lower lugs and manually racking the assembled gun to see the contact pattern). If you could post a clear picture of the barrel lower lugs and the barrel top lugs, that would be helpful.

There will be some side to side movement, that is normal. The barrel ramps are about 0.365" wide while the frame ramp slot is about 0.370". When the barrel is unlocked and slide to the rear, the barrel chamber should sit flat in the chamber bed of the frame and the feed ramp will be on the base of frame ramp channel, sitting about 1/32" from the edge of the frame ramp. This allows the next round to be chambered. As the slide moves forward feeding the next round into the chamber the lower barrel lugs ride the slide stop pin to cam the barrel up into battery. As long as the barrel moves freely and chamber sits flat in the bed, that's about all you can check in this configuration.

Yes, I forgot about sleeves. I have those exact measurements for a LO build. Simplifying the geometry, the barrel-slide contact area at the muzzle is basically the pivot point so the vertical elongation would only need to be half the difference in diameters (0.0025 in this case) to make contact. That seems reasonable.

Hi Charlie, Thanks for the writeup. I would like to get your thoughts on proper slide ID and barrel OD dimensions for matching up a slide and bull barrel before even starting a project. Seems to me the differences between the slide ID and the barrel OD are critical to obtain a high level of accuracy (at or below 1.5" at 25 yards). Just as a reference, the 1911 spec dimensions for a bushing type barrel is OD=0.580" and the bushing ID = 0.581+0.002 which is a max of 0.003" difference. I've checked some full custom bull barrel guns and they run as little as 0.001" difference in diameters. Checking a couple custom guns with an unassembled slide and barrel lightly held in lockup, there is no discernable horizontal of vertical movement at the muzzle. Slide ID dimensions seem to vary a lot anywhere from 0.699" up to 0.703" or even 0.705" in some cases. What I've seen is that the factor barrels and even the semi-custom barrel manufactures only offer the bull barrels with OD=0.696 (or smaller). That means a minimum diameter difference of 0.003" up to 0.007". Can you even attain an accuracy of 1.5" or less at 25 yards with a 0.003" barrel/slide diameter difference? So if your slide ID is 0.699 or larger, seems like the only option is go with a full custom barrel shop like Bartso. They said they can make the barrel OD per your spec. Are there any other full custom barrel makers? Appreciate your feedback. Joel

magnum primers

What PF does IPSC use? Is it 165? If so, and unless you know your standard deviation is low single digits, you are at risk of failing a PF check. If they use 160 PF then you are ok.

I run 9.6 gn of AA7 under a 124gn 9mm bullet. OAL is 1.170 and I use the same primers, no barrel holes. I have some unburnt powder too but it hasn’t caused a failure. I run 500 to 1000 rounds between light cleaning. could work up a load with magnum rifle primers. I’ve used cci450s without any problems. Didn’t look at the amount of unburnt pwdr and compare.

I was talking about the contact of the slide stop on the barrel lugs. Use a marker on the lugs and manually cycle the slide several times with the gun completely assembled. You should be able to see where the slide stop contacts each lug. Contact should be roughly even on both sides and should also make contact toward the tip on the vertical portion.

Yes, I hadaccuracy issues with my open gun. I check the barrel lug contact and it was a little uneven, the manufacture put in a new slide stop and that fix the issue. The slide stop was worn.

Interesting. I have not seen this before so its a good thing to be aware of. Was the firing pin protruding past the breach face? Is that what caused the discharge? What brand of firing pin has the square tip?

Getting a non-ramped threaded barrel may be you best option. Check ebay. Have to ask a smith if you can make a C/P cut from a standard ramped frame. Good luck

I've done business with them and they are a good company. I have not used their finish services but I hope this helps.

Talk to Jim at http://www.innovativecustomguns.com/ He did front serration on a 1911 slide for me. He did an outstanding job.

+1 for this. Nothing wrong with the SIg AXG Scorpion. That will get you start in Carry Optics. Shoot some matches with what you have and then you will have a better idea of what upgrade might help.