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Posted: 9/21/2009 4:52:19 PM EST
I apologize if this belongs in the AR pistol section, but my/our swat team has a select fire DPMS Kitty Kat. I've been tasked with getting it running, as it has proven unreliable. I'm uncertain what the exact problem, as I haven't had range time to see what it does. I'm just going over a check list of problem areas I need to look for. All ammunition has been Federal American Eagle for training, and Federal LE/Tactical stuff for duty.

1.) Is the gun clean?

2.) Is the bolt carrier key, installed and staked properly?

3.) What type of buffer is used?

4.) How many rounds has it fired? (Does it just need to be broken in?)

5.) Is the cyclic rate too high?

If members knowledgeable with short barreled M16, would give me some advice on this I would really appreciate it. And for all the smart asses, I can't get rid of it, and barrel replacement and gas port reaming are my LAST option.

Thanks
Link Posted: 9/21/2009 5:52:38 PM EST
perform the short strike test as well(1 round in mag, fire, see if the bcg locks open
Link Posted: 9/21/2009 8:06:52 PM EST
Did you try using new magazines, preferably PMags?

Also, maybe the higher pressure of NATO-spec ammo will give it the extra boost it needs to cycle?
Link Posted: 9/21/2009 8:36:32 PM EST
I would go with an H buffer ,fulton extractor, heavy extractor spring, and d-fender ring regardless . First you need to see the type of jams to determine the problems, but the above could solve other problems.
http://www.fulton-armory.com/D-Fender.htm
Link Posted: 9/21/2009 8:55:55 PM EST
Originally Posted By 1in7:
I would go with an H buffer ,fulton extractor, heavy extractor spring, and d-fender ring regardless . First you need to see the type of jams to determine the problems, but the above could solve other problems.
http://www.fulton-armory.com/D-Fender.htm


Not a lot of dwell time in a short barreled upper. I concur the H buffer, perhaps even an H2, in conjunction with an M16 carrier. Slow that thing down.
Link Posted: 9/21/2009 9:22:27 PM EST
I have used a tungsten and H2 buffer in my 7" SBR, and have yet to experience a failure. I would recommend one of the two (although I have heard of success using a pistol buffer also). All of the shooting with my SBR has been while using an Young Mfg bolt that has not been staked (I know guys I'm getting to it ).

I think the best course of action would be to actually test the firearm and then report your findings. Once this is done we won't have such a broad issue to tackle.

Best of luck and thank you for your service!
Link Posted: 9/21/2009 10:13:17 PM EST
Link Posted: 9/21/2009 10:41:02 PM EST

Originally Posted By Gastonite:
Originally Posted By 1in7:
I would go with an H buffer ,fulton extractor, heavy extractor spring, and d-fender ring regardless . First you need to see the type of jams to determine the problems, but the above could solve other problems.
http://www.fulton-armory.com/D-Fender.htm


Not a lot of dwell time in a short barreled upper. I concur the H buffer, perhaps even an H2, in conjunction with an M16 carrier. Slow that thing down.
Wouldn't a select fire already have a M16 carrier?

Link Posted: 9/22/2009 2:39:47 AM EST
[Last Edit: 9/22/2009 3:49:21 AM EST by ArmedSuspect]
i'm short on time so i'll make this quick.....

why do you have a 7" barrel for SWAT? seriously. the issues associated with a 7" are many and the terminal performance is dismal. for all of the guys that have 7" uppers i'm sure you can make them run but with the demand that is placed on a SWAT weapon it's not nearly reliable enough to depend on.

i'm not concerned about how good the sales man was when he sold it to the department or which officer thought that it would be a good idea. they are/were wrong. the 7" AR is a hobby gun and nothing more. if you handed me a 7" and told me to make entry with it i would switch to my sidearm or reach for the 12ga.

if you guys seriously have a need for a super short barrel i would look into an LWRCi PSD or the 7" PWS Diablo. either way the 5.56 will be seriously anemic from these barrels. LWRC has the PSD in 6.8 . i'll try to find the link for you later today but the ballistic performance of a 7" barrel 5.56 is laughable at best.

i know you don't want to hear this but an 11.5" or 12.5" perform much better and give you excellent CQB ballistics. i'm a fan of the 10.5" but it's a fun factor and not a Tactical need thing.

as former USMC SRT i'm urging you guys to reconsider the need for a 7" barrel.



ETA:

HERE is a thread where some 7" upper owners talk about the piss poor performance. fun? YES. man stopper? NO.

LINK to some guys with more 7" info.

HERE JoeDanger has a 7.5" for SWAT duty. not my first choice but it's working for him.
Link Posted: 9/22/2009 3:34:32 AM EST
[Last Edit: 9/22/2009 3:41:29 AM EST by FailureDrill-P099]
I think all 5 points you make are valid but shooting it is what you need to do to see what the problem is. Also why is it unreliable. What ammo is being used when it malfunctions. The LE tactical bonded is a very dirty round after a few mags have gone threw it because of the exposed soft point. But the American Eagle should be GTG.

I know there is nothing you can do and Its not part of your post but I have to agree with, ArmedSuspect, The biggest issue is the 7 inch barrel. Our Team is using M4 commandos 11.5. The terminal effects for the 7 inch is none existent. Its worth it to bring up this issue with your department. If this is the only one you have, as one of my departments instructors and armorers I would advise on scraping this weapon all together for a more reliable platform all around.

If you cant get rid of it can you buy a new upper for it in 11.5 and keep the M16 lower?
Link Posted: 9/22/2009 4:17:30 AM EST
Originally Posted By badazzar15:
What size is your gas port?


THIS
Link Posted: 9/22/2009 4:54:15 AM EST
Link Posted: 9/23/2009 10:16:08 AM EST
Thanks for you help so far.

ArmedSuspect I agree totally with your assessment, it appears terminal performance of the 5.56 is compromised out of a 14.5 inch barrel (with M855), let alone anything shorter. I'm really interested in moving to the 10.5" to 12.5" barrel length, to keep the entry/PDW qualities. However, the situation, is I'm new to the team, so I'm last in line in seniority, but I made the mistake of telling someone I build my own ar15's and surprise, I get tasked with this. I don't control the purse strings so anything that costs more than a $100, is gonna be a hard sell. As it is, I'm on off days and have better things to do then tinker with this weapon, it has been shelved this long, it can wait a day or two.

As far as ammo goes, duty stuff is Federal tactical loaded with 55gr Nosler Ballistic Tips, so there should be no lead fouling. Also seeing how stingy they are with ammo, not much of that is being shot except to confirm same poa/poi as 55gr fmj.

DPMS, I recorded your information, and I will call when I have narrowed down the main issue. I don't know where you guys aquire buffer tubes, but two carbine stock tubes have turned in the receiver end plates, ruining a portion of the threading. Or is that common to all carbines.

I just hope once this thing is working, I can pass it along. I would like something different for a Patrol/SWAT rifle.

Link Posted: 9/23/2009 3:10:29 PM EST
You have gotten some good suggestions so far. I have used the 7 inch Kitty Kats with no problems. For short-barreled full autos there are several problems that are typical. One is that the pressures are still high as the spent casing is trying to be extracted, and this would show itself by a spent casing staying in the chamber or not being fully ejected. The fix is as stated with an extra power extractor spring and a D-Fender ring or an equivalent o-ring. The next problem is short-stroking. This can be tested as stated by putting one round in a magazine and seeing if the spent casing is extracted, ejected, and the bolt is locked back. The fix for short stroking would be to open the gas port a tad. The most typical problem is bolt carrier bounce, and this will show itself by the weapon stopping firing, and upon inspection you fine that a live round is in the chamber but the hammer is down. The fix for bolt carrier bounce is to put in a heavier buffer such as the Colt "C" buffer. The "H" buffer and even the "H2" buffer may not be heavy enough. AAC and some other companies make special buffers to help with bolt carrier bounce. One way to check to see if it is a problem with the buffer is to put the upper on a full stocked lower and fire it. The full length buffer tube and full length buffer take out the force generated by the bolt carrier coming back forward too fast after firing. If it shoots okay on a full length stocked lower, then you know it is a problem with the buffer. Good luck, and let us know how it turns out. Like I said, I have had a number of Kitty Kats but I always use heavy buffers and never encountered any problems. DPMS obviously knows what the gas port diameter needs to be, so I doubt that is a problem. Some people talk about "timing" with the full auto sear that can be fixed by bending it a little, but I have never had to mess with the full auto sear. I have always solved problems with the short barreled M16's with heavier buffers and sometimes Fat Boy gas tubes but I do not think they make them for 7 inch uppers.

Charles Tatum
Link Posted: 9/24/2009 3:32:16 AM EST
[Last Edit: 9/24/2009 3:36:00 AM EST by MOS2111]
Originally Posted By big_joe555:

I don't know where you guys aquire buffer tubes, but two carbine stock tubes have turned in the receiver end plates, ruining a portion of the threading. Or is that common to all carbines.


Im gonna guess that the castle nut on the receiver extension was not tightened and then "locked" in place by staking the castle nut with a center punch in the grove that faces the end plate in order to prevent rotation...

ETA - Manufactures know what should be done, but that doesn't always mean that it happens for what ever reason (reference THE chart). And an auto sear is like 2$ if your fire control parts dont work - just replace them.
Link Posted: 9/25/2009 4:42:14 AM EST
it has recently come to my attention that PWS offers the Diablo in 6.8. i was unaware of this and didn't include it in my other post. the 6.8 Diablo isn't listed on the web site but i'm told that it's available (not in stock but can be ordered). ADDAX Tactical is also offering the 6.8 Diablo. again it's not listed on the site but i'm sure that a call or an e-mail will get you fixed up.

if a department is dead set on running a super short AR i would ask them to consider the switch to 6.8. it's not like they will be 1000 miles away from a re-supply so ammo selection and availability will not be an issue. the 6.8 is a much better round out of the short barrels.

it's tough to get some people to see the light but there really are better things out there. SWAT isn't a static environment where you get to pick one weapon for one job and be done with it. things are fluid and thus they are always changing. you may intend to go in and root out a homicidal barricaded suspect but what do you do when he bolts from a side window with a gun and heads for a better place. your 7" 5.56 that's intended for across the room shooting just became your precision rifle. you may only get one shot. do you really want to use a rifle where with the best barrel and ammo it's clocking at or under 2300fps at 15" from the muzzle for a 100yd shot? (justified by the circumstances. it happens)

the 5.56 isn't going to function well from these short barrels. again, i'm not bashing the 7" barrels, i just don't think it's a good defensive choice. it's more of a "because i can" range toy and that's fine. sure the bullet will still be able to kill things but it's operating below ideal performance parameters.

YMMV

Link Posted: 10/23/2009 6:06:18 PM EST
UPDATE: 10-23-09 OK, finally I have gotten the Kitty Kat and have gone to the range.

In semi fire mode, the rifle operates as it should, with the bolt carrier locking back on empty USGI 30 round magazines.

The problem begins once the rifle is set to auto fire mode. Depressing the trigger to the rear results in a 2 round burst and the Kitty Kat stops firing even though the trigger is still held fully to the rear. I then release the trigger and press it again, and a single round fire,s and stops, even though once again the trigger is still held all the way to the rear. This continues to alternate, 2 rds, 1 rd, 2 rds, 1 rd, 2 rds etc. I will be trying a Colt M16A1 lower next trip to see if its the trigger mechanism causing the issues. Also the Kitty Kat's lower does say "AUTO" and not "BURST".

Once I figure it out I'll contact DPMS to work out a solution.
Link Posted: 10/23/2009 6:14:09 PM EST
[Last Edit: 10/23/2009 6:14:39 PM EST by chwi548]
Sounds like they put a burst FCG in instead of an auto one.. Look up photos of the two and compare them...

It would not be the first time I have seen DPMS screw up the FCG in an LEO shorty gun.
Link Posted: 10/23/2009 9:40:41 PM EST
Update:, I have confirmed visually, the rifle has a 3rd burst FCG. Will be contacting DPMS for a solution. I want to thank everyone for your help.
Link Posted: 10/24/2009 4:14:19 AM EST
[Last Edit: 10/24/2009 4:17:22 AM EST by strambo]
This continues to alternate, 2 rds, 1 rd, 2 rds, 1 rd, 2 rds etc
SWEET! You got the ultra-secret "mozambique" trigger group. I heard those only went to "sshh...SEAL team Six"
Link Posted: 10/24/2009 5:08:27 AM EST
lol
Link Posted: 10/24/2009 5:20:52 AM EST
There is an agency in their area that shipped a LEO gun that shot fine on auto and wouldn't fire on semi-auto. Again, messed up FCG, and something that shouldn't have left the factory when they knew it was going to an agency that was staking their life on them.

When you contact them, make sure you have your invoice that specifies what you originally ordered. If you ordered FA vs 3-rd, they will possibly tell you that you had ordered 3-rd. I've seen them do that before as well.
Link Posted: 10/24/2009 9:03:24 AM EST
Big Joe: We had the same problems with out DMPS f/a guns purchased a few years ago. One of our Lt's made an illinformed decision when setting up the deal for these crap guns when a local DPMS dealer recommended them. The bores on the 11.5s we received were also non-concentric causing baffle strikes & blown out end caps on our cans. I would never carry a DPMS or an AR with DPMS parts as a duty weapon.
Link Posted: 10/24/2009 10:12:04 AM EST

again i go back to the *good salesman* or *bad purchasing agent* thing. duty weapons should not be subject to a *budget* or *price point*.

on a positive note, it seems like the upper works. not that i would want to keep it but at least it's working.






Link Posted: 10/24/2009 11:13:17 AM EST
[Last Edit: 10/24/2009 11:14:03 AM EST by shadowcop]
Just another reason I don't recommend DPMS for anything serious. Never know wht you will get or how long it will last.
Link Posted: 10/25/2009 2:10:38 PM EST
You don't have a department armourer to access and fix weapon issues and furthermore this task is deligated to an individual officer because "they have experience building an AR"?

Link Posted: 11/5/2009 2:48:28 PM EST
Originally Posted By acidman:
You don't have a department armourer to access and fix weapon issues and furthermore this task is deligated to an individual officer because "they have experience building an AR"?



That's going to be the case with many many many agencies that do not have funds, personnel and resources to be able to have officers maintain various armorer certifications. Not as easy as it sounds.
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