AR Sponsor
Posted: 3/1/2010 8:42:13 PM EDT
|
Hey guys,
I took my new LRB lower / Del-Ton upper AR out to the range today. She was short stroking every three or four rounds. The ammo and mags are not suspect as they function in my colt carbine with no issues. No fte's only ftf's. I believe this to be a short stroking issue as she wouldn't lock open when one round was chambered and fired. The rings look good, the gaps were staggered. Someone suggested I was not running wet enough or that I needed to take fine steel wool to the bcg as it is brand new... any thoughts? 20" rifle length upper 1/9 twist, LRB lower (that I assembled), A2 Stock (cause I live in NY), using 55grn Remington UMC Ammo Thanks! |
|
Quoted:
Are you using the correct buffer and spring? Is the gas key tight and properly staked? If it doesn't lock the bolt back on the last round fired it's most likely short stroken. I am guessing it is the correct buffer and spring it was purchased as a complete assembly... I compared it to my pre-ban carbine spring and the A2 spring is longer and buffer is larger. I checked the staking, I believe it needs to be staked properly, but the allen screws are not loose. |
| sounds like a gas problem..not enough power during recoil to go back far enough to have enough momentum to re chamber and then not locking back.Ive seen gaps with gas key to carrier that you could barely fit a piece of papaer under and the screws were not loose.Screw off the key and use red locktite between carrier and key for a seal..dont get any on the gas port in the carrier or under the keys port.Then the srew threads and re tourque them and properly stake them.First I would try your Colts carbine carrier in the new upper to make sure first. |
|
ok, relax. some guns have tight tolorences. shoot it, clean it, shoot 5.56 ammo (not .223) again... it may just need broken in.
however, after doing this, if there are still issues, id say you either have burrs over your gas port or it was drilled too small and the company should take care of either. fwiw My friend just got a delton 16" carbine and it short strokes a little (no problems but ejects at 5oclock with .223 which is odd for a 16" carbine. |
| I bought a 20" inch rifle kit from del-ton and i also had the short stroking problem, i ended up sending it back and found out it was issues with the gas block (A2) and they got it back to me in a little over a week. She shoots great now, and Del-ton customer service was great. You seem to know alot more about AR-15 then me though so maybe you can fix it, but i am newbie and i didn't feel like making it worse. |
|
If it the FSB and the gas block is not lined up with the barrel hole, I would defintely send it back. I assume the FSB is pinned on, thus it is drilled through the barrel for the taper pins. It may also be possible to enlarge the gas block hole or slighlty elongate the top portion of the barrel hole to get better alignment for hte gas to pass through. However, this still means that you would have an out of spec barrel and/or FSB. There is no easy fix for this as the barrel has been drilled already.
Be careful with the red locktite. Even a small amount on the gas key and the carrier can leach into hte bolts when tightened as the interface is minimal between the two parts. If this the problem, a few rounds should depsoit enough carbon to seal it up. If the gap is that big, then you might see carban tracks from under the gas key. If you remove the gas key and it look at the interface between it nad the carrier, you should be able to tell if there is carbon deposited in such a manner as to vcause concern for proper sealing. IMHO, I would not use the red locktite, as you will prety much permanently affix the parts to gether and any repairs would require heating the parts potentially damaging any temper. Another good test would be to put your Delton BCG into your Colt, etc and see if that works too. This would give you some redundancy to verify or rule out the BCG. Another option would be to swap recoil spings and buffers around to isolate those parts. I have seem a few black recoil springs on DPMS cause short stroking. Not sure why other than too stiff, but putting in a new non black spring made the difference. You might also want to look at your brass. See if theer are any marks on it that would indicate a burrin the chamber that causes the brass to hang up ans therefore absorb some recoil energy that would otherwise be used for cycling. You might also want to check to make sure the bolt is not requiring extra force to rotating into place and lock/unlock. You could do this your Colt bolt as a reference too and see if they are similar. In the same vain, also verify that hte BCG is passing thru the upper smoothly and that there is no grease or burr s,owing it down. As mentioned, grease inthe receiver extension/recoil spring or hte upper is not a good thing. During cycling, the hammer is also cocked. You might make sure there is no debris, etc under the trigger, disconnector nad hammer that would cause hte hammer to ride on the BCG and create extra friction to slow the bolt. THere is alot of info here, hope this helps. If you have any questions, send an email. |
|
Quoted:
I bought a 20" inch rifle kit from del-ton and i also had the short stroking problem, i ended up sending it back and found out it was issues with the gas block (A2) and they got it back to me in a little over a week. She shoots great now, and Del-ton customer service was great. You seem to know alot more about AR-15 then me though so maybe you can fix it, but i am newbie and i didn't feel like making it worse. I'm hoping I don't have to send it back. It has been back once, cause they sent me an A2 instead of a flat top. they definitely have great service... As far as knowing more about the AR, I just pretend  , but thank you for thinking that 
|
|
Quoted:
If it the FSB and the gas block is not lined up with the barrel hole, I would defintely send it back. I assume the FSB is pinned on, thus it is drilled through the barrel for the taper pins. It may also be possible to enlarge the gas block hole or slighlty elongate the top portion of the barrel hole to get better alignment for hte gas to pass through. However, this still means that you would have an out of spec barrel and/or FSB. There is no easy fix for this as the barrel has been drilled already. Be careful with the red locktite. Even a small amount on the gas key and the carrier can leach into hte bolts when tightened as the interface is minimal between the two parts. If this the problem, a few rounds should depsoit enough carbon to seal it up. If the gap is that big, then you might see carban tracks from under the gas key. If you remove the gas key and it look at the interface between it nad the carrier, you should be able to tell if there is carbon deposited in such a manner as to vcause concern for proper sealing. IMHO, I would not use the red locktite, as you will prety much permanently affix the parts to gether and any repairs would require heating the parts potentially damaging any temper. Another good test would be to put your Delton BCG into your Colt, etc and see if that works too. This would give you some redundancy to verify or rule out the BCG. Another option would be to swap recoil spings and buffers around to isolate those parts. I have seem a few black recoil springs on DPMS cause short stroking. Not sure why other than too stiff, but putting in a new non black spring made the difference. You might also want to look at your brass. See if theer are any marks on it that would indicate a burrin the chamber that causes the brass to hang up ans therefore absorb some recoil energy that would otherwise be used for cycling. You might also want to check to make sure the bolt is not requiring extra force to rotating into place and lock/unlock. You could do this your Colt bolt as a reference too and see if they are similar. In the same vain, also verify that hte BCG is passing thru the upper smoothly and that there is no grease or burr s,owing it down. As mentioned, grease inthe receiver extension/recoil spring or hte upper is not a good thing. During cycling, the hammer is also cocked. You might make sure there is no debris, etc under the trigger, disconnector nad hammer that would cause hte hammer to ride on the BCG and create extra friction to slow the bolt. THere is alot of info here, hope this helps. If you have any questions, send an email. Thanks for your reply, a lot of good info, I will have to try Quoted:
You might also want to check to make sure the bolt is not requiring extra force to rotating into place and lock/unlock. You could do this your Colt bolt as a reference too and see if they are similar. In the same vain, also verify that hte BCG is passing thru the upper smoothly and that there is no grease or burr s,owing it down. As mentioned, grease inthe receiver extension/recoil spring or hte upper is not a good thing. The bolt on the Del-Ton does seem to take a little more to rotate than the Colt... Would more CLP be helpful? |
|
Clarification on bolt resistance with Colt. I assume the Colt has had many rounds in it, thus I would expect it to move and rotate easier than a new BCG.. That bolt is likely a little more slick than a new one having been shot and honed smooth. THis may be a better test and give you some comparison in results that will help your understanding of the resistance. It is a touch thing and you will learn it.
Manipulating the bolt by hand with the upper off the lower (ie no sproing tension/force from recoil spring) you should be able to get the bolt to open and close without much force. There should be little, if any, resistance when done on an empty chamber - if pointing the muzzle down, the weight of the carrier on the Colt bolt will likely rotate the bolt and close it so the carrier slides forward all the way. The new bolt may require a slight push with your thuumb or finger. This is very slight. If you have to force it, something is binding in the BCG or with the bolt and the locking piece on the barrel. To verify if the bolt to carrier fit is the suspect, remove the bolt from the carrier and manipulate it with your fingers to see if it hangs up when locking into the locking piece on the barrel. What you will see is that you line up the slots on the bolt with the fingers on the locking piece. The bolt will slide forward to the back face of the chamber and it then be free to rotate the width of one slot/finger so that the fingers on the bolt and the locking piece are one behind the other to keep the bolt from coming out. Normal operation with carrier rotates the bolt closed like this and then opens again. This is done with the cam pin (rectangle thing on the right side of the gas key on the top of hte carrier) and the half moon slot cut in to hte upper receiver. If you play with it you will see how it works. Lube on the bolt and carrier. Motor oil will work, but CLP is porobably fine. I would also be concerned with the motor oil detergents and cleansers gumming up leaving you with a cleaning mess. A little goes a long way. Won't hurt anything, but just messy. Instead of CLP you might try some synthetic lube or light oil as I find it slicker than CLP. I realize some people like CLP, but I have not found it to protect as well as others. I use Millitec which fuses itself into hte metal with use. I have also used rem oil with teflon with good results. |
AR Sponsor