This question is for any of you who have carbines with short (less than 16") barrels.

I'm going to have my 16" barrel chopped to 12.5" and have a moderator permanently attached (so my XM177E2 clone is more authentic).  The gas port will also be opened up during this process, but I'm still a bit concerned about function reliability with the short barrel.

Since many of you have carbines with short barrels, have you experienced any function problems (feeding, ejecting, short stroking, etc)?  It would also be great if you could tell me if you have a reworked barrel or an original.

not really.

I have an M4 barrel that was shortened to 11.5. Nothing was done to the gas port.

It works great.

I've had a 7.5 barrel too. From time to time it would have issues. A #60 o-ring around the extractor spring fixed that problem  PDQ.

The barrels have been so short the flash hider is against the front sight(cut down Colt SP1 carbine), factory 10.3 LMT, 10.5 factory Bushy, 11.5 factory Colt, 11.5 cut down Bushy, 14.5 factory Colt and Bushy, all had no problems.
The barrels that I had problems with were aftermarket nonchrome lined all of various makers.
Pat
0-1-25

On lightweight (0.625" diameter) barrels I run a gas port of 0.085" for 11.5" barrels and 0.093" for 10" barrels with no problems.

I also run Wolff extra-strength extractor springs, an extractor "O"-ring and an "H"-weight buffer.

Reliability has been 100%.

Mine was cut to about the same length as you are getting yours cut to and I had hell. The guy that cut it did not open the gas port up. I drilled it out myself to the size UXB posted above for an 11.5" barrel and it works great now. I use standard springs and an original, old school carbine buffer. Since I drilled it out I have not had a single problem with it and have fired 55 to 62 grn through it.

They were not reliable enough for combat

I was issued a 609 from 1983-84 and used it in El Salvador with no issues at all.


Guess I lucked out and got a "good one".

Thanks for the responses.  Sounds like I have nothing to worry about.

The problem with the short barrels occurs with full auto fire.  Colt had enough problems that they finally decided to make no barrels shorter than 11.5 inches, as they found that this was the shortest you could go and still have enough barrel in front of the gas port to cycle the weapon reliably on full auto.  You are going to be doing a 12.5 inch barrel, and that should not be a problem.  Follow the guidelines already mentioned about opening the barrel to .085 inches and you will have no problems.  Aftermarket barrels can be a problem.  Chrome lined is the best way to go.  Remember, as long as you are doing it for semi-auto, you should be fine.

P.S.  uxb - I cannot believe the assortment of carbines you have.  I have been making one of each of the major types and was going to post the pics on this board, but I see you have already done that.  Nice work!!  

Charles Tatum
Alamo Professional Arms

Thanks for the compliment.

I am now in the process of correcting all the little details.

Started with this one.  The 609 will be next.



Oh, and off-topic, but I came "this close" to buying your V-40.

Wait until I put the pics of my new carbine build up.  I think I now have the largest collection of  V40 grenades on the Northern Hemisphere.  I may be able to tighten you up.  For those who do not know what we are talking about, the V40 grenade was used by Spec Ops in Vietnam.  It was a Dutch hand grenade and was the smallest hand grenade made.  It was about one third of the size of the baseball grenade used in Vietnam and still in use today.

Charles Tatum
Alamo Professional Arms  

Quoted: Wait until I put the pics of my new carbine build up.  I think I now have the largest collection of  V40 grenades on the Northern Hemisphere.  I may be able to tighten you up.  For those who do not know what we are talking about, the V40 grenade was used by Spec Ops in Vietnam.  It was a Dutch hand grenade and was the smallest hand grenade made.  It was about one third of the size of the baseball grenade used in Vietnam and still in use today. Charles Tatum Alamo Professional Arms

OT, but do you have anything to suggest the V40 received a designation in US service?  I've seen some online pictures that appear to have "XM5" and some nomenclature on the bottom, but I've never seen anything official.  I'm just a collector of official designations among other things, and you seem the person to ask.

Not familiar with a US Designation.  We used them in El Salvador when I was there in 83-84.

I have two types of V40 grenades - some are pure Dutch and do not have any English writing on the bottom.  The others appear to be for US military and have in yellow paint on the OD grenade in a circular pattern on the bottom:        grenade, hand, frag   V40
                                                                                        LOT-NWM-12-70



Here is a picture of my V40 grenades that shows the Dutch one on the left with no lettering and then the US Army ones with the yellow writing as described above on the bottom of them.  
Therefore, it looks like the designation adopted by the U.S was V40.

Here is another picture of all grenades used in Vietnam by Spec Ops to include the old WWII pineapple grenade, the lemon grenade, the 40 mm blooper grenade, the baseball grenade, and the V40 Dutch grenade.  Underneath the US grenades is a Chicom NVA grenade http://images.andale.com/f2/107/100/6966828/2007/8/15/Collection_of_SOG_Grenades.jpg
Charles Tatum
Alamo Professional Arms

What?  No toe-popper?

All of the V40s we used had no paint markings.