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Posted: 9/29/2004 3:13:19 PM EST
Well, finally got to the range today with my new rifle and its performance was far from steller. I experienced two separate problems numerous times, one of which *I think* I know the solution to. I also have a third question that I'm unsure of.

First off, 90% of the time it is short stroking and not picking up a round. I have been told that venting the gas tube by drilling a hole in the upper butt plate screw will fix this. True or False?

Secondly, I am getting a jam atleast once per 20rd mag in where the round will either be off to the side of the bolt face or have the bullet wedged into the top of the barrel extension. Ammo was PMP 55gr. FJBT and the jam didn't ocure at regular intervals. Barrel and mag both came from another gun in which they had no feeding problems.

Last but not least, isn't the bolt supposted to stay open after the last shot and not return to battery? Mine will close after firing the last round, but when I pull the charging handle it will lock in the rear position.
Link Posted: 9/29/2004 3:18:04 PM EST
[Last Edit: 9/29/2004 3:18:38 PM EST by QuietShootr]
More info is needed. whose parts did you use, and what ammo are you shooting?
Link Posted: 9/29/2004 3:18:34 PM EST

Originally Posted By MrFurious:
Well, finally got to the range today with my new rifle and its performance was far from steller. I experienced two separate problems numerous times, one of which *I think* I know the solution to. I also have a third question that I'm unsure of.

First off, 90% of the time it is short stroking and not picking up a round. I have been told that venting the gas tube by drilling a hole in the upper butt plate screw will fix this. True or False?

Secondly, I am getting a jam atleast once per 20rd mag in where the round will either be off to the side of the bolt face or have the bullet wedged into the top of the barrel extension. Ammo was PMP 55gr. FJBT and the jam didn't ocure at regular intervals. Barrel and mag both came from another gun in which they had no feeding problems.

Last but not least, isn't the bolt supposted to stay open after the last shot and not return to battery? Mine will close after firing the last round, but when I pull the charging handle it will lock in the rear position.



The hole in the stock screw is so the receiver extension will drain if it had been submerged in water. Need more details on bolt, carrier, barrel, gas block, type of stock and buffer and mags.
Link Posted: 9/29/2004 3:33:14 PM EST
[Last Edit: 9/29/2004 3:35:04 PM EST by MrFurious]
DMPS Southpaw Hi-Rider Upper & Bolt
Mega Assembled Complete Lower w/A2 Stock (Carrizo'z)
AR-15 Carrier and parts from M1S (std finish, polished on carrier rails)
Shilen 24" CM Fluted Barrel & Lo-Pro gas block
FF Tube from M1S
20rd mag is from Simmonds Prec. Prod. Inc.

Not sure what parts Clinton uses in his complete lowers, so I can't be more specific there.

http://www.savageshooters.com/images/Misc/AR_RedDot02.jpg
Link Posted: 9/29/2004 3:49:03 PM EST

Originally Posted By MrFurious:
DMPS Southpaw Hi-Rider Upper & Bolt
Mega Assembled Complete Lower w/A2 Stock (Carrizo'z)
AR-15 Carrier and parts from M1S (std finish, polished on carrier rails)
Shilen 24" CM Fluted Barrel & Lo-Pro gas block
FF Tube from M1S
20rd mag is from Simmonds Prec. Prod. Inc.

Not sure what parts Clinton uses in his complete lowers, so I can't be more specific there.

www.savageshooters.com/images/Misc/AR_RedDot02.jpg



Lube your action spring with a light coat of CLP, make sure that you don't have an A2 stock screw in a A1 stock. Be sure your bolts gas rings are sealing well within the bolt. You may have to remove your gas block to see if the port in the barrel is aligning with the gas block. The reason I say this is because after just installing a PRI flip up sight gas block on my wifes DPMS M4 barrel it wouldn't cycle. Upon removing it and checking I noticed that they didn't quite align. When I measured it, it was .071" off. So when reinstalling it I had to keep the gas block that much further forward and tightened the shit out of it. Also using 3pc rings instead of the 1pc Mcfarland rings on her 'enhanced' RRA bolt and carrier worked best. After doing all that and shooting 300 rounds its been 100% reliable.
Link Posted: 9/29/2004 4:14:11 PM EST
Is your PMP ammo the one with a gazelle on the box? I bought 500rds of that $hit and experienced all the same problems you stated. The problem is it's not hot enough to cycle properly.

A long while ago I found some leftover South African surplus 5.56mm which was made by PMP it has staked primers and it cycles perfectly. Problem is you cant find it much anymore. I think IMI is still making 5.56mm for winchester under the box title Q3131A, That ammo is pretty good as well.

Check to see if your gas rings on the bolt are properly set, but it sounds like an ammo issue to me. BTW the bolt is supposed to stay open on the last round.
Link Posted: 9/29/2004 6:16:45 PM EST

Originally Posted By Daubs:
Is your PMP ammo the one with a gazelle on the box? I bought 500rds of that $hit and experienced all the same problems you stated. The problem is it's not hot enough to cycle properly.

A long while ago I found some leftover South African surplus 5.56mm which was made by PMP it has staked primers and it cycles perfectly. Problem is you cant find it much anymore. I think IMI is still making 5.56mm for winchester under the box title Q3131A, That ammo is pretty good as well.

Check to see if your gas rings on the bolt are properly set, but it sounds like an ammo issue to me. BTW the bolt is supposed to stay open on the last round.



Yep, thats the stuff. I was kind of suspecting the ammo as last night when we fired it to check function (5rds) there wasn't a hitch, but it was with some real hot handloads. I'll grab a box of Black Hills tomorrow and see if it eliminates the problem.
Link Posted: 9/29/2004 7:16:32 PM EST
First, try different ammo. Q3131A is my test load, always.

Second... your rifle is short stroking. This can cause the no-lockback-last round failure, and feed jams of all types. This is typically binding, or gas issues. Since you have a custome gas block, I'd start there. Make sure it is aligned with the gas port on the barrel, and that the gas tube is properly installed and pinned. Next, check the bolt carrier. With it removed, does the bolt pull forward and back without much difficulty? Inspect the gas key. It is loose at all? Check the screws on top to make sure.

Binding..... well, I pull the carrier a little more than halfway out of the upper.... then point rifle down at a 45 degree angle. Carrier should slide into place and bolt should lock or almost lock without much extra pressure.

Also, check binding on the buffer tube. When you manually charge it.... is it smooth, or does it bind at all? Pull it all the way back, and slowly "ride" the charging handle all the way up. Does it hang up/bind anywhere along the way? Doing this, does the carrier go all the way forward.... and almost lock, taking only 1 or 2 hits on the forward assist to lock?
Link Posted: 9/29/2004 7:38:42 PM EST
Also check to see if there are black residue behind the gas block were gas tube is inserted. There can be a gas leak if the gas tube is not seal properly around the gas block.

Also check your bolt's gas rings. Make sure the slot on them are not lined up. This will also cause gas leak.

Also make sure your buffer is not binding anywhere in the buffer tube.

Your bolt carrier is not cycling its full length, that's why your mag follower is not locking your bolt carrier back after the last shot. The stuck round is also caused by the same problem. The bolt is not catching the round at its rear instead is trying to push the bullet from its side case. ( check for dents on the casing). This will cause the round not properly line up and may jam it at a steep angle in the barrel extension.

Of course under load ammo can also cause this problem. Since I always buy the cheapest ammo around, I don't expect them to be loaded with max powder. (cost) So I'll actually play with the recoil spring a bit. hinking.gif (a practice frown upon by many) This will insure full length carrier travel but you will feel more recoil and put more stress on your buffer when you switch to more powerful load.

Or you can try a lighter bolt carrier (the more PC version with full slot to the end)
Link Posted: 9/29/2004 7:43:58 PM EST
BTW, the recoil gas is not vented at the buttplate... It is vented from the side of your bolt carrier (the two hole you see from your ejection port on your carrier)
Link Posted: 9/29/2004 7:58:13 PM EST
Sorry it is getting late and I am forgetting things.... Another area generally overlooked is the hammer spring tension. If too strong (due to inproper installation or other) it can also slow down your carrier during the recoil cycle. More promonent when using barely adequate ammo load.

If your hammer spring is sitting above the trigger pin, try to reinstall them below the trigger pin. Becareful however, this can cause light primer strikes and fail ignition.hinking.gif
Link Posted: 9/29/2004 8:25:30 PM EST
Gas rings check out
No binding in buffer tube that I can feel (polished the outter edge of the spring for just that reason)
No residue at gas block
Gas block located correctly
Gas key is tight
No binding on carrier (polished the slide rails prior to assembly for just that reason)

As for the vents on the carrier, mine are ass-backwards being a lefty utilizing a RH carrier. Once I have the bugs out, I'll probably plug the factory holes and mill in new ones the opposite side so all the blow-by isn't blown into the receiver.

Until I can get to the range tomorrow with some different ammo, I'm guessing it was the PMP stuff I was shooting. It was free so I can't complain...other than that funky smell that it has.
Link Posted: 9/30/2004 4:16:18 AM EST

Originally Posted By Walmart_Special:
If your hammer spring is sitting above the trigger pin, try to reinstall them below the trigger pin. Becareful however, this can cause light primer strikes and fail ignition.



I disagree with this, NEVER do this. The hammer springs hold the trigger pin in place..... doing the above will result in your trigger pins walking out.... better to solve the *real* problem than to get it running with a band-aid.... IMHO.
Link Posted: 9/30/2004 8:35:13 AM EST
I ran 1000 rounds of that PMP South African "Gazelle" on the box stuff through my Bushy and didn't have any issues with it.

Seemed to work pretty good.
Link Posted: 9/30/2004 12:27:02 PM EST
[Last Edit: 9/30/2004 12:29:46 PM EST by Daubs]

Originally Posted By MrFurious:
I'll probably plug the factory holes and mill in new ones the opposite side so all the blow-by isn't blown into the receiver.



You should probably weld those holes shut. I'm unsure of the pressure that is produced but it's got to be way past 100 psi. I've used my air compressor set at 120 psi to try to cycle the bolt and no go, so welding should be the best bet at those pressures.


Until I can get to the range tomorrow with some different ammo, I'm guessing it was the PMP stuff I was shooting. It was free so I can't complain...other than that funky smell that it has.


Good thing it was FREE I kept kicking myself for buying that Crap! I have tried Silver Bear and it's Ok but is smells even worse than the PMP and it's loaded a bit light too. Winchester Q3131A is awesome stuff it's hot and it even has flash retardant in the powder since it usually Military over runs.

BTW: Nice looking Rifle


Originally posted by Boog:
I ran 1000 rounds of that PMP South African "Gazelle" on the box stuff through my Bushy and didn't have any issues with it.



That's probably because your rifle is broken in. The buffer spring is probably a bit weaker. Either that or you have good luck I've never had anything but bad luck with PMP "Gazelle" box but I have less than 1000 rds on my rifle.
Link Posted: 9/30/2004 5:18:50 PM EST

Originally Posted By Boog:
I ran 1000 rounds of that PMP South African "Gazelle" on the box stuff through my Bushy and didn't have any issues with it.

Seemed to work pretty good.





FWIW, I too have run a couple thousand of these through my bushy and have had zero problems.
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