I have a 6920 colt lower and wanted to get a 11.5 bushmaster or armalite upper from questar or wolverene .can you go much shorter than 11.5 and still maintain reliability ? i use factory 55 gr ball ammo i see some pictures of 9 " uppers are they practical ?
Shortest reliable ar-15 upper ?
- Thread starter ricka2
- Start date
BISHOP, an american friend of mine has a very reliable 7.5" It is possible to get the AR15 reliable with short barrels but sometimes with a lot of tweaking. Buffer weights, return springs, feed ramps, gas port size, chamber dimensions, gas tube style, extractors, etc, etc. It becomes a great big balancing act sometimes. I think from experience that once you dip below 16" you start having reliability problems. 14.5" and you might see a jam every 100rds, 11.5 and down you start drinking to forget your rifle.
I let my friends have the real short AR's and I enjoy mt 16". Why? It was a discussion a few years back with my buddys that the barrels 14.5" and under were as reiable as my 16" and you know.... we had a test done. One 14.5" had 1 jam in the 100rds fired. The rifle was new and had only 100 rds through it before that. The other 14.5 had about 1 jam every 5th rd. He got mad and had a fit when I suggested a few things. He explained that it was dirty and was the only thing jaming the rifle. He said it had about 500rds through it without cleaning. hmmm. So there I began. I went with G17guy to the range 3 times over the next week and without cleaning shot 500rds. I had 1 jam.
You get less gas pressure operating the action with a short barrel. That pressure acts for a shorter time when you go below 14.5" thus you must start dicking around to get the right ballance with the above items. The 16" is a nice easy way to get the carbine to work. The longer barrel by 1.5" lengthens the durration that gasses act on the bolt carrier and make up for the lower gas pressure.
Parting words: I'm not new at this stuff. Bought my first of many AR15's in the 80's and have a bit of experience with these things, but what the hell, hey you 14.5" and under guys let the flames begin.
Moe
I let my friends have the real short AR's and I enjoy mt 16". Why? It was a discussion a few years back with my buddys that the barrels 14.5" and under were as reiable as my 16" and you know.... we had a test done. One 14.5" had 1 jam in the 100rds fired. The rifle was new and had only 100 rds through it before that. The other 14.5 had about 1 jam every 5th rd. He got mad and had a fit when I suggested a few things. He explained that it was dirty and was the only thing jaming the rifle. He said it had about 500rds through it without cleaning. hmmm. So there I began. I went with G17guy to the range 3 times over the next week and without cleaning shot 500rds. I had 1 jam.
You get less gas pressure operating the action with a short barrel. That pressure acts for a shorter time when you go below 14.5" thus you must start dicking around to get the right ballance with the above items. The 16" is a nice easy way to get the carbine to work. The longer barrel by 1.5" lengthens the durration that gasses act on the bolt carrier and make up for the lower gas pressure.
Parting words: I'm not new at this stuff. Bought my first of many AR15's in the 80's and have a bit of experience with these things, but what the hell, hey you 14.5" and under guys let the flames begin.
Moe
ThePunisher
CGN Regular
- Location
- Belleville/Kingston Ontario
Between 2 14.5" uppers I have fired over 1000 rounds with one FTF (a misfire). I know someone else that has a 11.5 that shoots with me every time I go out...no FTF. I've heard that things get dicey under 11.5", but have not seen any to comment on personally.
I had a jam on round #3 in my 11.5 right after I built it...have not had another in close to 1000 rounds.
The one jam I did have was a #####...wedged the tailend of the cartridge between the bolt lugs and the upper receiver, and it was STUCK!
The one jam I did have was a #####...wedged the tailend of the cartridge between the bolt lugs and the upper receiver, and it was STUCK!
You can get a 7.5" upper with one of those new Krink FH that creates back pressure in aid in cycling. It suppose to solve the problems with under 10.5" barrels. I know guys with 5.5" 223 uppers and they work okay.
Sometimes I wish my 8" 9mm barrel was 223..
Sometimes I wish my 8" 9mm barrel was 223..
You don't need a carbine buffer and tube to run a short upper. You can use a full length tube and buffer. Many do run this set up with an A1 style stock. The short stock allows for compactness, but with he 11.5 inch upper you are pretty short to start with.
I have been running an 11.5 inch for about 4 years now. I haven't fired 1000's of rounds through it at once, but I have put well over that through it since I built it. My gun is deffinately a Franken gun as well. I have bits and pieces from all the major makers. I did built it right step by step. The use of good parts and the right tools, will make it work properly.
I have had stoppages but they were from ####ty rounds (Norinco) and bad mags (badly pinned). I shoot FMJ 55gr stuff now made by Winchester or American Eagle. No problems. Mags are USGI with new springs and green followers. For the 5 round limit that we have to abide by, the high speed followers don't really help out IMHO. In my work mags they rock!
YMMV,
Hoddie.
I have been running an 11.5 inch for about 4 years now. I haven't fired 1000's of rounds through it at once, but I have put well over that through it since I built it. My gun is deffinately a Franken gun as well. I have bits and pieces from all the major makers. I did built it right step by step. The use of good parts and the right tools, will make it work properly.
I have had stoppages but they were from ####ty rounds (Norinco) and bad mags (badly pinned). I shoot FMJ 55gr stuff now made by Winchester or American Eagle. No problems. Mags are USGI with new springs and green followers. For the 5 round limit that we have to abide by, the high speed followers don't really help out IMHO. In my work mags they rock!
YMMV,
Hoddie.
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PaveHammer
CGN frequent flyer
- Location
- Kingston, ON
My Armalite 11.5" runs like a house-on-fire. I've yet to have any problems.
Of course, the first thing I did was fix the gas port. But heaven forbid I say that here.
Of course, the first thing I did was fix the gas port. But heaven forbid I say that here.
My 7.5" .223 works perfectly after I took out pigtail, put back in the regular gas tube and a heavy ejector spring.
I bought mine used so it took some help from the guys on the here but it`s all good now and I did it without drilling out the gas port.
Thanks agin to all who helped with it.
I bought mine used so it took some help from the guys on the here but it`s all good now and I did it without drilling out the gas port.
Thanks agin to all who helped with it.
