Specifically, a heavy match barrel. I have seen a friends DSA with my conversion kit shoot excellent groups compared to his high-speed 10/22. Is there a chance this could hurt the accurracy of the 5.56 ammo when it goes through the same barrel?

I'm not speaking from experience, but the only problem I can forsee is the possibility of lead build-up in the rifling if you're shooting solid lead .22 rounds.  Otherwise, the AR is built for a much higher pressure, higher velocity round, so I wouldn't think there would be any problems.

Again, I am not a doctor, or even a gunsmith...  hacko.gif

Quoted: I'm not speaking from experience, but the only problem I can forsee is the possibility of lead build-up in the rifling if you're shooting solid lead .22 rounds.  Otherwise, the AR is built for a much higher pressure, higher velocity round, so I wouldn't think there would be any problems. Again, I am not a doctor, or even a gunsmith...

+1

You are talking about shooting a lead round... just make sure you clean it well after your done.
If you go crazy and shoot a few 1000 rounds with out proper cleanig you should deffinetly look at your gas port... most of the loose stuff will blow right out of the gas tube, but if it is built up and packed in there you should clean it out before using .223 ammo!

Thanks, all.
Part of what I was concerned about was the conversion kits 'fake' 5.56 cartridge section doing damage to the chamber and initial rifling. I'm assuming the barrel material is of a higher quality than the kit material.
Thanks again!

The chamber adapter doesn't touch the rifling/throat so it can't hurt that.  I suppose theoretically the steel on steel contact of the adapter to the chamber could wear, but the adapter shouldn't be moving so it can't wear much.    

The fouling from the .22s would be a far bigger concern than wear.  I suppose if you got it leaded up enough the buildup could raise pressures if you fired a .223 without cleaning and hurt something, but that's unlikely.  Firing a .223 without cleaning wouldn't be a good idea anyway since the bullet would tend to press the lead fouling into the surface of the barrel.  

If it was a high-$$ custom barrel I probably wouldn't risk it.  If it's an off-the-shelf barrel I wouldn't worry about it.  Just be sure to clean it good before switching back.

I have read that the .22 conversions should not be used in the 1 in 7 twist barrels due to excessive leading.  The 1 in 9 twist are less likely to have heavy leading but if you can find an old 1 in 12 barrel it would be better (SP1 or old M-16).  I think I have seen that dedicated .22 uppers are a 1 in 14 twist.  
I have used my Colt conversion in my AR15.COM RRA LEGP with the 1 in 9 with no problems but only running about 100 rounds before cleaning.

Accuracy is usually reported to be better in 1/12 barrels than the faster ones. but I can't think of any reason for a 1/7 to lead measureably more than an 1/9 or 1/12.  I haven't tried my Ciener in my 1/7, but it doesn't seem to lead any more in my 1/8 than in the 1/9.  The normal twist for .22LR is 1/16 and as far as I know all of the dedicated uppers use that.

I've shot a few hundred rounds through my .223 upper with a ciener kit.  (Probably around 1000)
With regular cleaning in between sessions.  

Recently I removed the gas block and inspected the gas port and noticed no residue what so ever, but every application is differant.



Also, the chamber conversion should not damage the chamber at all.  Chances are that they are all made to better tolerance  than brass that gets cycled through your .223 anyway.



Happy shooting.