Has your AR Short-Stroked?

Ever heard of a pistol or a rifle “short-stroking?”  No, it has nothing to do with the 1981 hit single “The Stroke” by Billy Squire (what was that all about, anyway?)  Firearms are said to “short-stroke” when the bolt (or slide) does not travel far enough rear-ward to eject the spent case, cock the firing mechanism, and chamber a new round.  Technically, short-stroking can occur with any action (yes, even manual bolt-action rifles – think about it.) but it is most associated with semi-automatic and automatic firearms.  This short Youtube video shows a couple good examples of short-stroking.

So, why my interest in sharing about short-stroking?  I was at the range shooting my gas-impingement AR the other day.  I planned to shoot 40 rounds, in two magazines of 20 rounds per.  First magazine, no problems.  Shot it pretty well for a guy with older eyes.  Second magazine… problems.  The bolt stopped cycling at all (the no-stroke!)  I could manually operate the charging handle to eject the case and chamber a new round, turning my nice AR into a bolt action rifle.  Like most people, since the first magazine had worked and the second did not, I figured “bad mag” or “something broke.”  Let the diagnosing begin.

Ok, specifically with short-stroking, what can go wrong?  Remember, the bolt is not traveling far enough rear-ward to eject the spent case, cock the firing mechanism, and chamber a new round.  Therefore, bolt can be obstructed, something can be slowing the bolt down (too much) as it travels rear-ward, or the bolt isn’t getting enough “push” from gas or the piston.  Why this is happening can be explained by a few hundred things (that’s an exaggeration.  For those of you that know me, I like to stick to the most likely.) However, if you are interested in a lively discussion many of the possibilities, check out this thread from Calguns.

Most of the time, short-stroke problems are caused by insufficient gas to operate the piston or bolt.  Let’s assume we have a gas impingement system and we have two fully functional AR’s (because one is never enough, right?)  Not enough gas could be caused by:

  • Something wrong with the bolt/ bolt carrier (gas rings, gas key, bolt and/ or carrier ports)
  • Something wrong with the gas tube (separated from the gas block, kinked, broken)
  • Something wrong with the gas block (shifted off the port)
  • Something wrong with the gas port (plugged or too small)

As with anything on the internet, you perform any of the actions in this article at your own risk.  I specifically suggest that people who are not qualified to work on firearms bring them to a qualified armorer or gunsmith.

That being said, here’s a quick way to diagnose the issue.

  1. Swap the bolts/ carriers in the ARs.  NOTE – there is some risk here.  It is possible (but not likely with mil-spec ARs that are chambered for the same round (e.g., 5.56)) there may be a head space problem with swapping the bolts.  If you are not sure, SKIP THIS STEP.  Do they both work?  Yes?  Not the bolt/ carrier.  Does one work and not the other?  You’re right,  it’s the bolt/ carrier. Check the key, the rings, and the ports.
  2. Visually inspect the gas tube.  Is it connected to the gas block?  Is it noticeably bent, kinked, or broken?  Is the gas tube pin still securely in the gas block?

    a2_frontSight
    A2-type Front Sight and Gas Block
  3. Check the gas block.  Is it installed permanently (e.g., as in some A2 gas block/ front-sight) or is it a “low profile” block installed with set screws.  If it is not permanently installed, the gas block may have shifted.  In the case of the set screws, this is probable, especially if the barrel was not dimpled and/ or the screws were not set with a thread-locker.  Look for discoloration around the base of the gas block and the barrel.  If you see it, gas is escaping, and that isn’t good.
  4. Check the gas port.  Attach a small piece of rubber tubing to the end of the gas tube in the upper.  Blow through the tube and listen to learn if any air comes out of the gas port in the barrel.  If so, that’s good.  If not, the port is misaligned with the gas block or the port has become obstructed.

My guess is that one of these checks will help you quickly find the issue.

My problem?  I started simple and checked the mags.  You already know that the vast majority of feeding and ejection problems are related to magazines.  Not enough “spring,” too much “spring,” bent feed lips, bad mojo, whatever.  No problems, though.  Both were factory Colt and both were in good shape.  Both worked Ok in my other AR.  Not the mags.  I swapped the bolts/ carriers, no issues.

Moving along to the gas system.  For this AR, I had purchased a complete upper from a manufacturer with a low-profile gas block and a free-float quad rail.  Off with the rail so I could look at the gas block.  Lots of discoloration and it seemed to have moved forward towards the muzzle.  The block was installed with set screws.  No dimples, no thread locker.  In fact, looking more closely and shifting the block a little, the gas block had shifted forward nearly choking off the gas port.  Ah, simple.  Completely remove the set screws and realign the gas block and gas port.  Use thread locker to reinstall set screws.

Time to test fire.  Load and insert a mag with two rounds.  Manually chamber.  Bang.  Good ejection.  Good chamber.  Bang.  Good ejection.  Lock back on empty mag.  Fixed!  Re-install rail.  Get a beverage.

That’s my story on my short-stroke adventure.  If you have any similar issues, this may help you get to the bottom of them.  Or, you can always give me a call.

For a more complete article on short-stroking, check out the article by Foghorn in The Truth About Guns.

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Steel Cased Ammunition

Opinions are in no short supply when the topic is using “steel cased” ammunition.  Steel cased ammunition is exactly what it sounds like: the case is made of steel rather than brass.  Many cartridges manufactured overseas use steel for their cartridges.  Some brand names you may recognize are Wolf, Brown Bear, and many of the imported surplus cartridges.

My personal experience has been that steel cased ammunition “runs dirtier” than brass. Not only is this due to the type of powder, but the fact that steel expands at a slower rate than brass. So, when the cartridge is fired, more gasses and carbon can “leak” around a steel case as the case expands and seals against the chamber wall. This would tend to foul the breech face and, perhaps, other parts of your gun, more than brass cases.

SteelcasedammoOf course, steel-cased ammunition is usually somewhat cheaper than brass-cased. So, a little more cleaning may be worth a lower price per round, right?

Well, maybe. Assuming you do a good field strip cleaning on a regular basis, maybe it’s a good deal. A detail strip may be needed more often if the ammo is running dirtier.

The real question is… will it hurt my gun? My thought is that it probably won’t hurt your barrel or chamber. Some wear may be associated with the extra fouling (at least the fouling I experienced).

The biggest concern I have with steel-cased ammunition is with semi-automatic firearms and the wear on the extractor. The head of the extractor slams around the case lip every time a round is chambered. I know brass is softer than steel so the wear on the extractor would likely be less than if the round was steel-cased. And, based upon my experience, the first part to fail in any semi-auto gun is usually the extractor.

So, for me, it is brass-cased ammunition in my non-Eastern European guns.

Opinions vary. Below is a link and a video giving two other opinions on the use steel-cased ammunition. Very interesting information.  Decide for yourself!

The Blog of Arizona Weaponcraft Solutions… http://azweaponcraftprepper.com/the-truth-about-steel-cased-ammunition/

And a YouTube video doing some metal hardness testing…

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Beware the Bad Guys

FraudOnline auctions are great.  Sometimes there are excellent deals on firearms and accessories.  Most people are honest.  Some are not.  Beware of Fraudsters on the major gun auction sites.  A client almost fell victim fraud recently.  Fortunately, his diligence helped him to avoid losing over $1,000.

Below are a few tips to help avoid being defrauded of your money:

  • Look at the buyer feedback.  Are there lots of entries or just a few?  How are they rated by others?  Be cautious with sellers who have low numbers of feedback and/ or reports of issues.
  • Is the seller an FFL?  If so, you should be able to verify the license (company name, address, phone number)  on the FFL Lookup Page on the website.
  • Before sending payment, send me the buyer and FFL information.  I can verify the FFL and send along my paperwork to help ensure the FFL is aware of the transaction.  This can all happen in a day or less (it’s mostly email these days), so it would have little or no impact on the timing to send payment through the mail.

Finally, if the deal is too good to be true, it probably isn’t!   If you think you have been a victim of fraud, you wouldn’t be the first and won’t be the last.  Contact the online broker.  They usually can help.