Jp chamber is TIGHT

[Shadowrider]

So is this a major problem for my barrel and accuracy or should I just leave it alone and deal with pulling on the CH hard once in a while?

It could be a major problem for your barrel. Accuracy? Not so much.

You really need a few thousandths clearance between to bullet and lands. You want the bullet to get going BEFORE hitting the lands because the pressure is higher if your start the bullet touching. Kind of like trying to break a concrete block with your hand. Put your hand on it and push, it ain't breaking. Then rear back and try it karate style, it will break with far less muscle force on your part.

You don't have to have a long jump, .010" is my minimum and I'd like to have .020.

Edited November 17, 2010 by Shadowrider

[finch6013]

Is this adjusted by using different ammo or rolling my own to fit my barrel?

I dont reload because its not cost effective for me at the moment so that is why I have been shooting xm193. Maybe a .223 load would be shorter.

[Shadowrider]

The Wylde chamber as I understand it is a "compromise" between a SAMMI spec chamber and a NATO spec chamber which has a much longer throat. In theory you would probably be able to run NATO spec ammo in it without problem. I believe the whole idea was to be able to run the heavier weight bullets (which are longer). But you aren't with the XM193, as that is a 55 grain round. I'd call JP and see what they say. Sounds like to me they cut that chamber a tad short. You should be able to run a 68 grain load without issue IMO. 77's and 80's may not, but 55's should have plenty of clearance.

Edit: Now that I read the whole thread, do like others said and check your rounds first. That gage from JP is probably the way to go, though I got the dillon and found that I need to check my trim length a bit closer that I have been. Also check your overall length of those rounds and make sure they are the proper length to the XM193 spec. If they gage good and the OAL is good, your chamber is the problem.

Edited November 17, 2010 by Shadowrider

[jaredr]

Try this, take your remaining rounds from your XM193 batch and case gauge them. See if they all gauge.

The reason I say this is that I just got back from a Rifle Instructor Recert class and we had all kinds of scary tales about the Federal .223, some was the XM193, and others. Rounds not chambering, rounds keyholing, a couple of squibs, etc.

This is from LE ammo that was bought about a year ago and in storage now. Same stuff on the market now....

As fast as they were making ammo to keep up with demand, QC had to suffer at times......that is just the human factor.

QC your ammo and see if you find any turds, then shoot the rest and see if you have any more problems. If you do, then it may be a chamber issue....

Just something to try before you get the dremel out......

Good luck,

DougC

FWIW, i've had the same experience with xm193 this year - mostly primers popping from overpressure rounds and tieing up the gun (lodging in the fire control group or in one memorable case bhind one of the lugs on the barrel extension, where it was virtually invisible!). Had one instructor who indicated that after a series of these problems non-stop in an LE class, he'd returned the remainder of a case of the product to federal, and had been told later on that it had tested out in excess of 65k psi, tho i'm not sure how this information made it back to him.

Pat Sweeney recently posted that these problems may be due to using 5.56 ammo in a .223 chamber, and can be remedied by using one of ned christenson's reamers to clear out the throat. that may be so, but at the class I attended, I two of the folks having these problems were using a colt 6920 (5.56 chamber) and a noveske (which has some proprietary variant of the sammi 5.56 chamber according the the noveske website - i don't know the details of how it differs from 5.56)

FWIW......I have found that the Dillon case gauge is acutally tighter than the JP Gauge that I got. If it will fit in my Dillon gauge it will run in anything.......

DougC

funny - I have a wilson gauge that appears to be a bit tighter than my Dillon. some cartridges that won't gauge in the wilson will gauge just fine in my dillon gauge. i just take everything that gauges in the dillon but NOT in the wilson gauge and keep it for practice ammo, ammo which passes the wilson gauge is good for classes/matches.

Edited November 17, 2010 by jaredr

[AlamoShooter]

Lots of information and Voodoo too. The pressure spike from having the bullet touch the lands would be, could be a big problem IF. you were loading hot rod rounds to over 3,300 fps or heavy bullets to max powder.

The light bullet with some room left in the case is ..not as..bad.

The set -up you have from JP is the best way to get the best accuracy and still be able to shoot 'cheep' factory bullets.

Don't worry. , just keep an eye on the brass, save some at least every fourth time to range and compare the looks. One Voodoo trick is to put the spent brass in a case gauge , I bet it will fit with your barrel near new. = what that means in Voodoo Terms is that the chamber pressure is not so high as to stretch the brass past the point of not returning.

A piece of brass out of a sloppy worn barrel will not fit back in a case gauge.

my one year old Fire Bird gun will still keep the bass so that it fits in the case guage after I have shot it.

The thing that you are worried about is the same reason I would spend 50% $ more cash to get a JP barrel. shoot some off a rest at targets over 500 yards and you will find the love for that barrel.

Lots of good books can confirm this for you on barrel /chamber set-up.

I just want to learn how to get close to my bench rest results at a 3gun match. = I just lack the skill

[finch6013]

I think I am going to talk to JP one more time and see what they say. I might just end up sending the upper in just to be sure everything is how they like it.

[Fullauto_Shooter]

I think I am going to talk to JP one more time and see what they say. I might just end up sending the upper in just to be sure everything is how they like it.

The peace of mind I got from having them check out my upper was priceless. Now I "KNOW" it's within spec and as intended.