Posted: 8/20/2007 8:45:05 PM EDT
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I'm been lurking around the forums for a while trying to gather as much information as I can. Though I have an idea of what could be affecting my XM-15's performance. I would like to have a expert take a look at it. So I'm looking for an AR-15 expert or Gunsmith with an excellent reputation in western Washington to take a look at my rifle. Some of its symptoms are: It doesn't always hold the bolt open when empty (with Magpul P-Mags). Held loosely, it won’t feed a round. I have noticed a small gas leak at the front sight base as well. The rifle fires fine when held tight. It will fire all 30 rounds as fast as I can pull the trigger. I discovered the short stroking symptoms when I tried to bump fire it. I have only ever achieved 2-3 round bumps, mostly because it wouldn't feed the next round. At first I thought it was just my loads, I had loaded some weaker loads to punch paper, but I also tried hotter loads with the same result. Then I've tried holding it loose at the shoulder and noticed that my rifle won’t feed the next round. I've also ran into the same problem holding it with one hand. Personally I'm not sure if this is something Bushmaster developed to counter bump firing, or if my gas system is not properly setup. My friend who has the exact same rifle (twins) has experienced the same problems. I just think that the rifle should cycle under almost all circumstances. |
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Is this a fairly new rifle? How many rounds through it? I'm not qualified to diagnose this and I don't even shoot that much but I'm thinking other than the gas system could it be that the buffer spring just isn't broke-in yet? Also, what ammo are you using? Just hand loads? Have you tried this with some XM193 or Q3131A? Some loads are hotter than others. ETA: Take out the carrier and inspect the gas key to make sure it is tight and staked on properly. |
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Yes the rifle is still fairly new. I bought it in December last year. It has only seen maybe 1500 rounds. From my understanding of your posts it sounds like that my rifle should be able to "bump fire"(not that I want to do it all the time) and cycle when held loosely, and that this isn't some factory setting designed to counter these shooting styles. Is there an in-depth article somewhere on the gas key setup and torque specs? |
I'll see if I can dig up the thread. In the meantime, take out your bolt carrier, look at the carrier key (gooseneck tube on top of the carrier). Try to wiggle it with your fingers. does it move? Try to hand turn the screws holding it to the carrier. do they turn AT ALL? There should be a dent or score mark on the screws holding them in place, preventing them from turning. Take a close look at your gas tube inside the upper. does it have any big visible scratches, dents, zombies, or tigersharks? |
Those carriers look familiar. 
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Well everything is put back together. I will take it out tomorrow and see how things work and try some oh what was mentioned. As with my initial purpose of posting here, can you recommend someone that wouldn't mind getting together to diagnose my rifle. I can supply food and ammo. Or if there is a gun smith that you would recommend taking it to to have a look at. As for when held loosly, it will fire a round and not chamber the next. Or when bump firing it will fire 2 shots and not chamber the 3 and the bolt will close. Maybe 30-50% of the time the bolt wont lock open on an empty mag. If the weather is decent I will bring the video camera and take video of it and post it. |
Ya know... LCR is comin' up, bring the rifle and you'll have a couple dozen AR experts that will probably be willing to help. Don't forget the beer. They always forget the beer.  ETA: Welcome to the board  AND To answer your question; "What is LCR" Go HERE and HERE |
One of the two top posts. LCR pig roast etc. Linky |
I've seen the farm that the event happened at.|
Funny thing is I'm related to a EPD member. So I got the inside details. The ammo I'm using is 55g FMj lead core with 22.4g of Hogden H355 powder. This charge according to the Hornady book with a 24" barrel 1 in 12" twist produces 3000fps. This ammo was all handloaded by myself. Not one failure to date. I have also tried some H322 powder with 40-60g Vmax with the same results. I haven't yet tryed anything hotter than what the book reccomended. Even though the bottle of power suggests loads up to 2g more. Maybe I will try some a little later. I've also tryed some Old Remington UMC ammo. |
What Kind of Carrier is in your rifle? Im wondering if he has a exposed firing pin. Remember when they did that to make it so you couldnt remove the disconnector to try to create a slam fire. If its exposed the firing pin flange "hooks onto the hammer"
Keep in mind am also a little drunk right now..... I didn't read that these other weirdo gun nuts posted. But if alls else fails listen to grumpy... he knows his shit.. I need more Patron The thing is red because it would be the LAST THING I EVER RECCOMEND!!! However it is an option. just say goodbye to your rifle for a while |
I've shot H335 and 55gr before, have to look at home but it seems to me that is a very light load.  I have shot hand loads in 6 different AR's for the last six months and never had a malfunction of any kind, but then I have never loaded down 4 grs off max either. Buy a box or two of Hornady ammo and see what it does. |
| FIrst thing I would do before tearing into anything on the rifle is to buy a couple of boxes of factory ammo and try it. IF you are still having a problem then you can tear into your rifle. Never try only one type of ammo, and declare that something is wrong with the rifle. No offense intended but I'm willing to bet it is an ammo problem not a rifle problem. |
| Does Remington UMC count as a underpowered load? I have tried it before, but never in the sole purpose of testing it. I have another hundred round of it laying around. I will take it up with me today. If you look in the Hornady book. 22.4g of H335 is the highest load before the Red or Hot load. So I don't imagine it is too under powered. If I only had a Chronograph I could see where they sit. Maybe I'll pick one up this weekend. I'll also Bring a Magpul P-Mag, C Products and factory Bushmaster mag. I will try and video tape it all and post it. |
Thats not the 45gr hollow point stuff in the yellow box is it? 
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This out of a DPMS AR15 with 24" Bull Barrel.
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The UMC is in a Green and White box. It used to be in a yellow box about 20 years ago. It is a 55g FMJ. Its basically pinking ammo that you buy at Walmart for 8$/20 nowadays. The Hornaday 7thEdition handbook of Cartridge Reloading states that for H335 23.2 is the maximum load and should be used with caution. Having that said, I think it is their way of not getting sued for letting people over charge rounds by publishing them a little less hot than they can go. One of those better safe than sorry. Hodgdon's website says: 55 GR. SPR SP 55 H335 .224" 2.200" 23.0 3018 40,800 CUP 25.3 3203 49,300 CUP Hodgdon's Bottle says: .223 Rem. 25.3gr 55gr. Spr. SP Win. Win. SR 2.200" 3203 fps About the onlt thing I'm willing to believe will be how my tests go today. |
The test is the best thing only if you use ammo you know is good, not 20 year old plinking ammo. Buy some GOOD ammo and you will know for sure. ETA: As I told you in the IM I sent reloading for a Semi Auto is much different than for a bolt gun. |
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Video The video looks more "succesful" than the testing really went. At this point I will presume it is the ammo, untill I can rule it out. The weapon ran fine when fired properly as seen in the latter part of the video. Though while bumpfiring I ran into something I that haven't happened before. A round would feed but the sear didn't reset. I also didn't run into many gouged shells from the bolt this time, it only happened once. I did mostly 10 rd mags, being successful in a few 6-8rb bumps to finish off the mag. 2-3 rd bumps were the norm fallowed by either a round not loading, or a round loading but the trigger not resetting. Something that concered me was that after a little while of trying to bump, the charging hadle became tougher to pull as the bolt rotated. The gun was well lubed with CLP. I added more CLP while bumping becuase the bolt was having a harder time unlocking. All and all, I don't feel that I came any closer to ideniflying a problem. I will need to try differnt ammo and test it next saturday to see if ammo is the culprite and then develope a load my rifle likes. Let me know what you guyes think. |
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I think that first and foremost, you need to find someone with an AR that works, and swap carriers. If the problems go away, that gives you a better starting point. Diagnose starting in the reciever first. Did you punch off the front sight base? I hope not, but if you did, it could be making things worse. IM me. |
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You describe several problems after your new testing. Sounds like a switch in ammo "mostly" cured the cycling problem? If you're still having short strokes and misfeeds then something is still wrong. Many folks encounter hammer follow when bumping. It happens more often with match triggers. You can tell if that happened by ejecting the live round and checking the primer for a light dimple from the firing pin. A couple of ways to cure this problem is to use a stock FCG and by changing your technique. Sticky CH extraction typically indicates a hot, dirty chamber. Have you tried using a chamber brush when cleaning the rifle? |