What are the consequences of running barrel hood length too short?

[RacerDad46]

Hello guys.  I was hoping you all could answer a question for me.  I recently bought an Apex semi-drop in barrel for my M&P pistol.  Unfortunately, during fitting, I cut the barrel hood length too short and now the only thing making contact with the breech face of the slide is the actual base of the cartridge instead of the back of the barrel hood when the gun is in full battery.  There is zero headspace between the shell casing and the breech face.  However, I function tested the gun and it shoots well, still accurate even, and also has been feeding reliably after 200 rounds through it.  

 

My fear is that with only the base of the bullet contacting the breech face every time the gun slams shut into battery that I am doing long term harm to it by running it this way.  Will I eventually put a dent the shape of a circle in the guns breech face?  Am I doing other harm to the gun by running it this way?  I have no problem just buying a new barrel and starting over the right way if this will harm my gun long term.  But if not, then I may run this barrel for a few matches until I feel I got my money's worth before buying a new barrel.

 

Here is a picture of how much gap there is between the breech face and the back of the barrel hood...

http://i68.tinypic.com/34j7r5c.jpg[/IMG]

Edited January 21, 2019 by RacerDad46
included picture

[jcc7x7]

Many people leave a .001 space between the breach face and the hood.

[Hi-Power Jack]

7 hours ago, RacerDad46 said:

 

Here is a picture of how much gap there is between the breech face and the back of the barrel hood...

http://i68.tinypic.com/34j7r5c.jpg[/IMG]

 

You wouldn't believe where I went when I clicked on your http.     

 

Very pretty young ladies.     

 

But, no breech face or barrel hood.     

[Steve RA]

I'd run it for awhile and see if you can spot any problems before doing anything.

[zzt]

I'm not certain exactly how an M&P locks up, so take this with a grain of salt.  I once did an experiment on a 1911 barrel.  I had read all the arguments for and against a tight fit.  Bullseye shooters (not all) want the back of the hood to hit the breach pace when locking up.  Others (competition shooters) say that is stupid, because any little bit of crud could keep the gun from going into battery.  Then I remembered military 1911s where you could throw them together from across the room.  So I decided to experiment.

 

I fit a Kart Easy-Fit 1911 45 bushing barrel the way is is supposed to be fit, but touching the breach face.  I shot it for bullseye and from a rest.  Then I took .001" off the rear of the hood and shot it again.  No difference.  THen, because Kart recommends .003" clearance on the sides of the hood, I open it up to that.  No difference.  I hadn't expected any, because the bottom lugs position the barrel.

 

Next I started taking a couple thou off the rear of the hood and shooting it.  Again.  Again.  By the time I got to .013" short with absolutely no difference in accuracy I quit.

 

You are not going to 'wear out' your breech face, because the front of the case does not hit the front of the chamber.  If it really bugs you, have the hood TIG welded up and refit.  That's exactly what I did with the now too short Kart barrel. 

Edited January 21, 2019 by zzt

[jwhittin]

I will add that for 1911/2011s there must be some small space to allow the barrel to move up and down into battery.  I assume the same is true for the M&P.  If the  hood is too long it will cause reliability issues. Sounds like you are not having any problems so I wouldn't worry about it.   

[RacerDad46]

Thanks for the reply and suggestions guys. I feel a little bit more at ease running it this way for a short while. I hate to just chuck this new out barrel out the window. 

[Absocold]

The hood's function is to align the the slide recesses with the barrels upper lugs. If the hood is too long the barrel can't engage the slide and if the hood is too short it will make for a rough engagement which can lead to poor accuracy and lug peening.

 

I won't bother getting into proper dimensions and clearances. That's a long discussion for another day. If accuracy is fine, shoot it. But keep checking the lugs for damage on a regular basis. If you never get any, great. If you start to see some...