View Full Version : Ultimak trouble

06-12-2010, 11:31 AM
Perhaps someone else has had a similar problem and can provide some insight to the cause of the problem. I have a Lancaster AKM that has been 100% reliable until I put an Ultimak mount on the gun. I know there's a lot of Lancaster bashing lately but this one seems to be an older build of better quality. When the gun is fairly cool it's still 100%. But when firing through 30rd mags at a rate of about 1-2 minute each, by the second or third mag I get jams. The gun appears to be short stroking. The gun has about 500 rounds through it. I have thoroughly cleaned the gun including stripping the bolt. I tried remounting the the Ultimak paying careful attention to the manufacturers instrutions, which I did the first time. No change. There is no apparent binding or rubbing of the piston with the Ultimak. Since the gun is fairly new, I'm woundering if I need to just shoot the gun somemore.
I'm new to the forum and the AK system but not new to running other combat weapons.

06-12-2010, 12:16 PM
I tried to determine if it was binding and could not find any hot or cold.
Tried different mags, ammo, etc. no difference.

06-12-2010, 05:42 PM
I have checked and re-checked to varify the clearance as described in the Ultimak instructions. I cannot discern any binding or other obvious issues. Since the Ulimak is the only change to the gas system, and the problem is 2-3 round per mag after the gun gets warming up, it's reasonable to assume the piston is binding some way. I'm wondering what would be the best fix. What about pollishing the inside of the gas tube? Other suggestions?

06-12-2010, 05:50 PM
Have you put the same amount of rounds through it with the stock gas tube to make sure that it actually is the ultimak and not some other aspect of the gun?

06-12-2010, 06:43 PM
Yes, I've put enough rounds through the stock gun to prove it's 100% reliable hot, cold, clear or dirty.

06-12-2010, 09:48 PM
ISince the Ulimak is the only change to the gas system, and the problem is 2-3 round per mag after the gun gets warming up, it's reasonable to assume the piston is binding some way. I'm wondering what would be the best fix. What about pollishing the inside of the gas tube? Other suggestions?

Reasonable assumption. Sure you can't feel any binding when it's hot? With the spring removed it should slide like butter. If it's just a matter of a little polishing then over a few hundred more rounds that might wear it in for you...

Jim Fuller
06-13-2010, 04:56 AM
Try moving the Ultimak forward so it is touching the gas block then retighten the screws in a star pattern. I know Ultimak say to center it but we have found that you will loose gas pressure in the system by creating the extra gap for gas to escape at the gas block.
This may or may not work but it doesn't cost you anything but time to try it.

06-13-2010, 08:59 AM
Just curious about a couple of things, Jim's tube adjustment should be the solution. Does your gas piston have a little wiggle like it should? Did you get a Ultimak without holes?

06-13-2010, 11:10 AM
I tried Jim's tube adjustment with no effect. The piston does have some wiggle and the Ultimak is the B model without holes. I'm going to measure the inside dimentions of the two tubes for comparison to see if that reveals anything significant.

06-13-2010, 11:46 AM
Here are some measurements I made. Perhaps Jim or someone can tell me if they show anything.
The bolt carrier where it enters the gas tube is .625 at the widest part.
The piston is .549
The stock tube measures .707 just inside the forward end and .561 at the narrowest part.
The rear of the stock tube measures .710
The Ultimak measures .741, .574, and .687 respectively.

07-01-2010, 08:39 PM
Giving Ultimak the benefit of the doubt and hoping for some technical insight, I sent emails to the company about the problem I was having. It went as follows:

I am having reliability problems with my Romanian G model AKM with the Ultimak B model installed. The gun has several hundred rounds through it and has been 100% reiable prior to installing the Ultimak. With the rail, when I slow fire or only fire one magazine and allow the gun to cool there are no problems. However when I fire two or three magazines in a row as when doing practice drills, the gun starts short-stroking. Examples of feed problems include: not fully ejecting fired case, and bolt riding over casehead and bullet barely started into chamber. This happens at least three or four times per magazine. I mounted the rail exactly according to the instructions. I also tried mounting the rail all the way forward and far enough back to have a visible gap between the port and the gas tube. nothing seemed to improve reliability when hot. The following measurements are provided for comparision. Perhaps they will help shed some light on the problem.
The bolt carrier measures .625 at the widest point where it enters the rear of the gas tube.
The gas piston measures .549
The stock gas tube measures .707 inside the most forward point
The stock gas tube measures .561 inside at the narrowest point
The stock gas tube measures .710 inside at the rear
The Ultimak measures .741 inside the most forward point
The Ultimak measures .574 inside at the narrowest point
The Ultimak measures .687 inside at the rear
The Ultimak does not appear damaged or defective. Hot or cold, I can't discern any binding between the bolt carrier and the gas tube. I don't see any wear or rub mark on the inside of thr rear gas tube.

07-01-2010, 08:44 PM
Ultimak’s reply:

I’ve fired many thousands of rounds with this system, including rapid fire from 75 round drums, and experienced no such problems—all spent cases eject with the AK’s characteristic authority, even using an UltiMAK mount that’s 1.5 inches shorter than the original “gas” tube. Thousands of customers have had the same experience as mine.

If I were having the problem you describe, probably the last place I would look would be at the “gas tube” (a misnomer, in that the tube plays no role in the cycling of the action other than to ensure the piston finds its way back into the gas chamber that’s pinned to the barrel, where all the work is performed) unless there were obvious and severe binding.

A properly built AK has a lot of excess cycling energy. If yours is short stroking, I’d look at the port diameter (something very difficult to measure unless you have a 45 degree gas block). I’d also look at the barrel length, and whether the gas port was designed for that barrel length. A severely shout-out barrel (rifling disappearing) might could reduce the bullet seal, causing low cycling energy, as it expands. I’d check out my ammo. Improperly loaded or stored ammo, or ammo that has gotten wet at some point, could be producing a severe under-pressure. Measuring velocity with a chrono would give clues to that effect. You didn’t mention caliber, but proper 7.62 x 39 from a 16” barrel should net around 2300 to 2400 fps, give or take, 10 feet from the muzzle, with a 120 grain, .311” bullet.

In trying to identify the problem, I think you’re barking up the wrong tree here, as I have demonstrated;
http://www.ultimak.com/ShortGasTube.htm (http://www.ultimak.com/ShortGasTube.htm)
I have every confidence that I could crank off a full 75 round drum, or two, with the same results, plus we have three-gun competitors, and people taking high intensity training courses using this system, with no issues.

A hot round (one that’s chambered in a hot barrel) produces more pressure than a cold one, typically, as the powder burns faster. That runs counterintuitive with the assumption of an inherent gas under-pressure situation. I’d look at the barrel bore, the bullet diameter (are these reloads with .308 bullets? AKs use .311 bullets, but some load .308s. some .308s will obturate into the rifling grooves and some will not) and look for mechanical problems within the receiver also. You didn’t measure the gas chamber diameter, which is something that would be relevant.

If your AK was built up from a parts kit, there is a large number of possible problems, too numerous to include here. One that’s somewhat common, that could cause the exact set of problems you describe, is an improper camming angle between the hammer and disconnector, creating the need for a lot of pressure to cock the hammer when the trigger is to the rear. That can also cause the dreaded “trigger slap”. We had an AK with that problem. It also had the occasional stoppage, just as you describe, and it is intermittent. When the disconnector/hammer interface was re-worked, both problems disappeared, and that AK has digested over 8K rounds since with 100% reliability, UltiMAK mount installed the whole time.

I know it’s a long shot, but I’d also look at the extractor’s range of motion within the bolt, the ejector, the magazine, and the magazine interface, although two or more problems among those parts would need to exist at the same time to produce the results you describe. I once had a magazine that looked perfectly OK, but it had been stepped on and mashed slightly, such that the follower was binding, resulting in the bolt override problem, but only occasionally. Simple problem, but hard to identify. Disassembling the offending magazine revealed the problem instantly, but only after some frustration at the range. Another mag had a bent feed lip. That results in a classic failure—every other shot fails to feed (one lip feeds OK, but the other doesn’t) but there is no bolt over-ride and no ejection problem. The mag catches, front and back, determine the amount of bolt engagement with the case heads, and the feed angle. There are near endless possibilities.
Please keep us posted.
Best Regards,

Lyle Keeney
UltiMAK, Inc.

07-01-2010, 08:48 PM
My reply:

The rifle in question is near new AKM with 16" barrel. It is unmodified except for the Ultimak. I have checked all the variables you mentioned; dementions in spec, strong rifling, gas port, etc. No hint of trigger slap. I have used the same magazines, 3 or 4 types of factory ammo. Also I chronographed the ammo to verify normal velocity range. The gun ejects the empty cases energeticly with both the stock tube and the Ultimak until the Ultimak heats up. I have stripped the bolt to insure the extractor is working properly.

After several systematic function test with the stock gas tube and Ultimak, the results were exactly the same each time. The gun was 100% with the stock gas tube and not with the Ultimak. You said, "If I were having the problem you describe, probably the last place I would look would be at the gas tube". I understand the gas system but logic should tell you to look at the change that caused the problem to start. Much of what you said in your reply would be reasonable explainations if the rifle was having problems with the stock tube in place. But since the rifle has been and continues to be 100% reliable with the stock tube, it seems reasonable to conlude the reliability problems are related to the Ultimak. I would be happy to try any other suggestions you may have.

Frankly, I was hoping Lyle would have paid more attention to my description of the problem and what I have already tried and less on how his product couldn’t possibly be contributing to the problem.

Jim Fuller
07-02-2010, 03:33 AM
I have to agree with Ultimak I have installed hundreds of them with no issues at all.
Duck 52 if you like send me your gun and I will look at it for free and we will figure out why it doesn't work.
I see no reason for the Ultimak to cause the issues you are having and I'm willing to spend my time to see why. I strongly endorse Ultimak products and want to know why you have an issue where there never was one before.
Your reasoning that "it works with the stock part but not the Ultimak" is valid but many times you need to look further as the true problem may not be so obvious.

Little Teapot
07-02-2010, 06:15 AM
Frankly, I was hoping Lyle would have paid more attention to my description of the problem and what I have already tried and less on how his product couldn’t possibly be contributing to the problem.
I had some issues with an Ultimak and found the seller to be VERY defensive and unfriendly.

He told me exactly what he told you: there is absolutely no way on God's green earth that his product could have any problems.

Gabriel Suarez
07-02-2010, 08:46 AM

Lyle is a good guy. He focused on what he knows betetr...his product. Now I am not Jim Fuller or Mark Graham, but I have some experience with the UM system.

Assuming your gun was 100% before Ultimak and now has issues, I would remove the Ultimak and fire it to see if it returns to 100%. If so, then you have id'd the problem. If you still have the same issues then it has something to do with something other than the Ultimak.

I am not an engineer so measurements look like chicom script to me, but I will tell you of an experience I had with the Ultimak on my 5.45 Suchka. When I put it on, I saw the piston immediately rubbing on the tube. Not good. I added the shim set that Lyle sells and the problem was immediately solved.

I don't know if your barrel is atypical of an AK barrel. If so that may be an issue. other than that...have Fuller, Graham, or Hayden look at it.


Gabriel Suarez
07-02-2010, 09:15 AM
Try a homemade shim set to see what happens.

07-02-2010, 09:55 AM
Jim, thanks for the kind offer. I do think it's time for a professional to take over.
For the record I am not saying Ultimak is a bad product, merely there is a functional incompatibility with my gun.

07-02-2010, 10:09 AM
I never used an Ultimak yet.

But here's a SWAG on the problem, could the gas block be out of alignment just a bit?

With the issue gas tube it may not be a problem but with something afixed the way an Ultimak is?Maybe?:confused:

Jim Fuller
07-02-2010, 04:27 PM
Jim, thanks for the kind offer. I do think it's time for a professional to take over.
For the record I am not saying Ultimak is a bad product, merely there is a functional incompatibility with my gun.

Duck 52
As you said, It is likely a compatibility issue with one or more of the parts on your gun. AK specs vary, a lot. The OD of the barrel in combination with the measurements of the other parts you listed could create a misalignment and something as simple as shims could be the fix. I've put Ultimaks on a lot of 74's with no issues, we even fit them to the Tantals.
Yours can work too.

07-02-2010, 08:41 PM
I'll contact Rifle Dynamics next week for shipping info. Thanks

07-02-2010, 09:31 PM
I had a simlar experience when I mounted an Ultimak to my Tantal. The gas piston would barely brush the inside of the tube with the Ultimak installed. I could tell what my problem was, yours sounds like it may be a little different.

Without the shim set from Ultimak, the piston would rub the top of the tube.

With the shim set from Ultimak, the piston would rub the bottom of the tube.

So.....I scientifically calculated the correct shim height by figuring it needed to be a little less than half the thickness of the shim set from ultimak (too low without, too high with).

I has some stainless 16 Ga wire in the shop, I wrapped the barrel under the "feet" where the Ultimak sits, presto, problem solved. I just wanted to see if it was a clearance issue, or something else. It worked fine after that.

I intended to replace the wire when I made a shim that was the correct height, but that was a year+ ago, and I never got around to it, the wire works fine, and it isn't going anywhere.

It would look like a real hillbilly gunsmith job, but you can't see it under the handguard, so I sprayed it Krylon dark primer grey (to match the park finish) and I left it.

I'm 100% confident that A) Jim can fix your problem.....and B) it will look much better than my solution. The plus to my fix is it takes about 10 minutes and costs about 10 cents.

08-22-2010, 11:57 AM
any word on what eventually happened with this problem? Did it ever get fixed and what was causing it?

08-22-2010, 01:05 PM
I talked to Jim a couple of weeks ago. He said the gas block was tilted slightly and was robbing enough gas from the Ultimak to cause problems when it heats up. Eyeballing it before I shipped it to him I didn't see a problem, but that's just an example why Jim is considered top notch.

08-22-2010, 01:38 PM
Re: Jim Fuller.... More than that- the man stands up for the product he believes in- in a way that is worthy of a title PRO... Without barking and getting defensive, he offers to examine the problem and find the solution. And- when he does- fixes it without the fanfare...
I have Ultimak's on 3 of my many AK's, and none had any issues. Granted- the AK's in question are Fuller, Krebs and Arsenal.


Jim Fuller
08-24-2010, 05:48 AM
Wow Sonny

Thanks for the kind words,

With the Ultimak, the gas block needs to be perfectly alinged or you will have binding issues. The stock Gas tube is more forgiving to that than the Ultimak. We will be testing the gun again this weekend and hopefully it will be fine.