Help with my evil black rifle :-)

[tllstaco]

I recently bought my first evil black rifle. It has a SI Defense 308 upper and lower with a DPMS bolt, barrel, and other parts. It's shoots real good, except.......

I'm having a little problem that I hope someone can help me with. The first 10-12 rounds fire just fine. But after the rifle heats up, the bolt stops going all the way forward after it has chambered a round. As a result, the firing pin doesn't strike the primer hard enough for the round to go off. I can manually force the bolt forward (with very little force) and the rifle fires just fine. Any suggestions on what I can do?

[dicion]

I recently bought my first evil black rifle. It has a SI Defense 308 upper and lower with a DPMS bolt, barrel, and other parts. It's shoots real good, except.......

I'm having a little problem that I hope someone can help me with. The first 10-12 rounds fire just fine. But after the rifle heats up, the bolt stops going all the way forward after it has chambered a round. As a result, the firing pin doesn't strike the primer hard enough for the round to go off. I can manually force the bolt forward (with very little force) and the rifle fires just fine. Any suggestions on what I can do?

A multitude of things can cause this. Short stroking, too weak of a buffer spring, underpowered ammunition (which would cause the short stroking)

Try this. Once it stops feeding normally, Try and use the charging handle instead, and pull it all the way back and release, does it feed properly?
If so, your rifle might be short stroking, eg, the bolt is not being pushed back far enough to get the full power of the spring on return to battery, but it is being pushed back enough to feed another round.
First thing I'd try on this is different ammunition, see if there's a brand recommended by your upper manufacturer.
If you can't get it to work with any ammunition, there's some other things to try, but ammo's the easiest, and should be tried first.

If it still doesn't feed, your problem lies elsewhere, and your buffer spring might could use an upgrade.

Although unlikely, the upper, or bcg, or something might just barely be in spec, and the heat and accumulation of junk after a dozen rounds causes it to not be in perfect spec anymore, causing non-normal rubbing or a tight fit anywhere. Are there any wear marks on your bolt, or the area surrounding the chamber that looks abnormal?

Also, Just like the .223/5.56 differences, 7.62x51 and .308 are similar, but not the exact same.
See here: http://www.303british.com/id36.html" onclick="window.open(this.href);return false;
Find out what your barrel actually is chambered for, and see if you're trying to use the other.
Generally, swapping the two does not make as much as a difference as .223/5.56, but it can make a difference on power. 7.62 nato rounds generally are more powerful then civilian .308, although there are civilian .308 that are more powerful then nato 7.62.... confusing, I know But back to answer #1, try different ammo

[tllstaco]

Try this. Once it stops feeding normally, Try and use the charging handle instead, and pull it all the way back and release, does it feed properly?
If it still doesn't feed, your problem lies elsewhere, and your buffer spring might could use an upgrade.

Although unlikely, the upper, or bcg, or something might just barely be in spec, and the heat and accumulation of junk after a dozen rounds causes it to not be in perfect spec anymore, causing non-normal rubbing or a tight fit anywhere. Are there any wear marks on your bolt, or the area surrounding the chamber that looks abnormal?

At the range this morning, pulling the charging handle initially chambered a round just fine. The lower receiver lists the caliber as 308/7.62. I've used a couple of different brands of ammo in it with the same results.

After your email, I field stripped the rifle and cleaned it. I oiled it heavily and put it back together. It's now working just fine when using the charging handle to cycle the bolt.

Please pardon my terms, but I'm just learning. At the back of the bolt, the diameter is small. There is a larger area that has rings on it that reminds me of piston rings in an engine. Inside the bolt carrier, there is a slightly raised area. It was very snug when the larger area of the bolt with the rings met the raised area. In fact, it took some force to pull out the bolt once pushed in. I oiled the area with the rings very generously and the bolt moved much better.

Do you have a suggestion on some good reading on AR type rifles? I need to learn!

[dicion]

Try this. Once it stops feeding normally, Try and use the charging handle instead, and pull it all the way back and release, does it feed properly?
If it still doesn't feed, your problem lies elsewhere, and your buffer spring might could use an upgrade.

Although unlikely, the upper, or bcg, or something might just barely be in spec, and the heat and accumulation of junk after a dozen rounds causes it to not be in perfect spec anymore, causing non-normal rubbing or a tight fit anywhere. Are there any wear marks on your bolt, or the area surrounding the chamber that looks abnormal?

At the range this morning, pulling the charging handle initially chambered a round just fine. The lower receiver lists the caliber as 308/7.62. I've used a couple of different brands of ammo in it with the same results.

After your email, I field stripped the rifle and cleaned it. I oiled it heavily and put it back together. It's now working just fine when using the charging handle to cycle the bolt.

Please pardon my terms, but I'm just learning. At the back of the bolt, the diameter is small. There is a larger area that has rings on it that reminds me of piston rings in an engine. Inside the bolt carrier, there is a slightly raised area. It was very snug when the larger area of the bolt with the rings met the raised area. In fact, it took some force to pull out the bolt once pushed in. I oiled the area with the rings very generously and the bolt moved much better.

Do you have a suggestion on some good reading on AR type rifles? I need to learn!

The only single source I know that has all this information I've found is is the AR15.com & M4carbine.net forums. It's quite a lot of reading though, I basically read through all the major stickies for a few months before even purchasing my first AR. That's how I learned everything I know ;)

[tllstaco]

The only single source I know that has all this information I've found is is the AR15.com & M4carbine.net forums. It's quite a lot of reading though, I basically read through all the major stickies for a few months before even purchasing my first AR. That's how I learned everything I know ;)

I started reading at AR15.com. Nice source of information.

One more question for you. I had a former Marine buddy of mine say that you should make sure everything on your rifle is oiled very well. How much oil do you use on your bolt and associated pieces?

[flintknapper]

If its a new weapon......"give it a little more wink" (it needs to break in).

You will find that the AR needs to be two things: Clean and well lubricated. If you can do these two things you will love it, if not....get an AK.

You can speed up the break-in process by removing the magazine, checking the chamber to see that it is empty, then just hand cycle the bolt and carrier while you sit in front of the TV. Pull it back and let it go forward gently (do not release it)!

No need to actually fire it!

[tllstaco]

If its a new weapon......"give it a little more wink" (it needs to break in).

You will find that the AR needs to be two things: Clean and well lubricated. If you can do these two things you will love it, if not....get an AK.

You can speed up the break-in process by removing the magazine, checking the chamber to see that it is empty, then just hand cycle the bolt and carrier while you sit in front of the TV. Pull it back and let it go forward gently (do not release it)!

No need to actually fire it!

Thanks for the advice. I cleaned things up and lubricated them real well. Think my problem today was I didn't have it lubricated enough. Have been cycling the bolt and carrier off and on today, will do it some more. So far I have 140 rounds through the rifle. I actually find taking apart my guns kinda relaxing......

[dicion]

Despite what some people may say, an AR does not need to be run 'soaking wet'.

I have had no reliability issues with mine at all, and I use a rag to wipe down the bolt, and other parts after I clean them to leave a light coating. That's about it.
I Use CLP Breakfree almost exclusively on mine, with a little copper solvent to clean the feed ramps.
That being said, yes, it does need to be cleaned and lubricated. Don't expect it to run forever without it

If you need 50 gallons of lube to make your AR cycle, you're doing something wrong

[tllstaco]

Despite what some people may say, an AR does not need to be run 'soaking wet'.

I have had no reliability issues with mine at all, and I use a rag to wipe down the bolt, and other parts after I clean them to leave a light coating. That's about it.
I Use CLP Breakfree almost exclusively on mine, with a little copper solvent to clean the feed ramps.

If you need 50 gallons of lube to make your AR cycle, you're doing something wrong

You mean I shouldn't have put the whole quart of 10w-30 on it????

Thanks for all of your help.

[TDDude]

You will find that the AR needs to be two things: Clean and well lubricated. If you can do these two things you will love it, if not....get an AK.

I have an old pre-ban Colt A2 and a new home-made thing with parts from all around. They both shoot great but if they don't have enough lube, things get hinky as soon as things warm up. After 50 rounds, they both basically shut down when there's not enough lube.

I keep a thin film of Milspec grease on the bolt rails and I can shoot all day.

[TDDude]

I finally was able to go out with my CMMG .22 conversion kit and man, was it fun!!

But, along the lines of this thread, before I installed it, I put a couple drops of oil on the rails that are part of the bolt. It was shipped dry and of course I knew it wouldn't work without some lube.

(For those that don't know, the conversion bolt itself is a completly self contained unit and doesn't move inside the rifle like the full size bolt does. The smaller .22 bolt moves within the kit that is placed inside the upper. It has it's own built in buffer spring & rails and the internal AR main buffer spring isn't used at all except maybe to keep everything in place and snug. That may be an obvious observation to the gray hairs out there but until I had one in my hand, I never really knew how it worked.)

Well, after about 20 rounds, it stopped working. I could still see the drops of oil I applied at home but it wasn't enough. I pulled out my small tub of Mil-spec grease, applied a very thin line along both sides of the tiny rails, reinstalled and proceeded to shoot 250 rounds with nairy a hiccup. Perhaps after it gets broken in, it may need less lube but for now I'm keeping it wet.

Anyway, the moral of the story is: Lube, Lube, Lube.

The hardest part is loading that silly mag. It's listed as a 30 rounder but the most I could get in was 20 or so. The spring is too stiff and those cartridges too small. I'm sure there's some sort of speed loader out there but I haven't seen it yet.

[asleepatthereel]

Dont use too much oil on the rings. They will get gummed up quick, and give you problems. When I clean my Bushies, I put a little oil on a Q-Tip, and lightly go over the rings, and other areas that are subject to spent gasses. Too much will collect carbon and eventually cause all kinds of failures.

TDDude, Keep your barrel free of lead buildup near the chamber when you use the conversion kit. .22LR bullets tend to foul up the rifling down there. Some folks have said that they just put the .223 bolt back in and fire a few FMJs through it to clean out the fouling, but I dont subscribe to that theory myself. To my way of thinking, if you are shooting a jacketed bullet through fouled rifling, not only are you increasing the pressure in the barrel, you are taking a chance on the lead fouling up the gas hole and tube as well. Just my .02.

[tllstaco]

I wanted to give you and update and get some more advice.

This past weekend, I took my rifle out to the range and ran into the same issue. The first 20 rounds fired just fine and then the bolt would no longer close completely. The individual I bought it from didn't have any ideas so I wrote the manufacturer of the upper receiver as previously suggested. Their advice was:

"From the way it sounds, you may have a headspace problem with your bolt and barrel or your gas tube is out of alignment to one side or another. These may affect the bolt operation when cycling. I would recommend checking these first. "

I took the rifle apart today, took the bolt apart and cleaned everything. Out of curiosity, I took the bolt carrier (without the bolt) and pushed it forward like it was cycling. It was binding and then would release and move completely forward as it should. After doing this a couple of times, I noticed that the gas tube was moving everytime the binding occured. Upon further examination, the gas tube appears to be bent or is not aligned as it should be which is causing a momentary binding.

My question.....what do I need to do to get the gas tube aligned? I tried to get a picture, but my camera didn't do a good job.

Thanks for your patience...

[tllstaco]

Are your gas keys staked in place so that they don't move, or are they loose?

Edit: These two things:

They are staked in place. When I was cleaning it last night, it did not move.