MickB

Step 1: marking the follower

I have a DPMS G2 Recon that I have modified to use in 3 Gun Heavy Metal. Modifications include a Dynamic Resistance muzzle brake, Samson 12.37" Evolution rail, SLR SA7 adjustable gas block, Hiperfire 3G trigger and Magpul STR stock on a Vltor mil-spec buffer tube. Back in early April I bought some Gen3 Magpul P-Mags to use in the rifle. Once the components came together, I tried dialing in the gas system. No matter what I did, I could not get the bolt to lock back on an empty magazine, even with the gas block full open. Checked gas block alignment and it was perfect. Todd at SLR even sent a new gas block to try out. It was with the new gas block that I discovered what the issue was. I happened to have a borrowed Gen2 P-mag with me which locked back fine with the gas block set at 5 clicks from full closed. Switching to the Gen 3 P-mag is when the bolt lock failures occurred again. Manually locking back the bolt with the Gen 3, I would find that the act of removing the mag would cause the bolt to slam shut. Basically what is happening with the Gen 3 mags is that the bolt catch actuation tab on the back of the follower is shorter compared with the Gen 2 mags. This means that there is little to no engagement of the bolt with the bolt catch. I contacted Magpul and explained the situation and they said they would look into it. I also spoke with DPMS and they were only just becoming aware of it. After going back and forth with Magpul with still no resolution, I decided to try my hand at modifying the Gen3 followers myself. What we are doing is making the follower come up higher inside the mag body so that the bolt actuation tab pushes the bolt catch higher. In order to accomplish this, material needs to be removed from the follower directly under the right feed lip. Step 1: First, mark the follower while still inside the mag. Step 2: position follower in your bench vise and use a dremel tool with grinding wheel to remove the material. Step 3: remove the flashing and test bolt catch engagement. As you can see, you don't need to remove much material. Mick

Go with the clamp on SLR gas block in that case.... Mick Running a CF handguard, the side adjustment may not be accessible. Also, I'd prefer the clamp style to set screw. I appreciate the suggestion though. As for the advice on improving upon my current charging handle, I'll see if it's needed after installing the new gas block.

Mark, what are the specs on the load you use for that rifle? Mick

On a 9mm Colt AR15 I once ended up with an empty case crushed behind the hammer that locked up the trigger group... Mick

I asked John where he gets his pants from. if I am remembering correctly, here they are! http://us.loudmouthgolf.com/index.php/men/made-to-order/made-to-order-pants/pole-position-am.html Mick

Nordic is offering 20% off for BE Forum members. This is not a Labour Day special. Check their sub forum here for the deal. Mick

Best AK? Valmet M62 or M76. The M76 can be had in 5.56, but these rifles don't look like traditional AK's. Think Galil type (which is where that design actually came from). For more traditional AK types, the best prebans are the Mitchell Yugoslav AK's, Kassnar Hungarian SA-85's and the Chinese Polytech's. Aside from the Valmets, as Bryan has already pointed out, accuracy is pretty ordinary, typically 3-4 MOA.... Mick

Look at the 308 G2 hunter from DPMS... Mick

DO NOT put Loctite on your shotgun extension. Turn till the extension bottoms out, then loosen a quarter to half turn. This will allow the mag clamp to move the tube relative to the barrel, maintaining POI. Having the extension tight may result in a cocked extension, meaning the clamp will pull the barrel relative to the mag tube, throwing off POI. The problem is the smooth finish on the inside of the clamp and the outside of the extension. You want to increase the friction between these two interfaces, to prevent the extension from spinning under recoil. There are a couple of ways to do this. (1) Wrap some electrical tape around the tube where the clamp will contact it. (2) Put electrical tape on the inside of the clamp where it contacts the extension (much neater this way). Can also do the same thing with a thin coat of epoxy (don't forget to use release agent on the extension!). Mick

Yep, and the US 10rd mags have the same dimples. Just sent some to my brother in Australia. I am assuming you want the bases to use with guns that have large mag wells? If so, why not just screw and glue some delrin extensions onto the bottom of the existing floor plates? Just drill a hole through the middle so you can still depress the floor plate retainer in to disassemble the mags. Heck of a lot cheaper than getting an externsion that doesn't otherwise gain you anything.... Mick

How are these even legal in Australia, with a 10 round mag limit? Mick

Jesse, Could not having a top competitor decide what the fastest times are by walking or (especially) shooting the stages be considered by some as an unfair advantage for that competitor? For example, here in AZ we could use your team mate and our mutual friend. I can only imagine what level of protests we would get at SMM3G if it was even perceived that a top level shooter had the advantage of a "practice run". Example: At SMM3G 2014, one of your Sponsors wanted to take "action" video and pictures of your fellow team mate. Both I and the MD said that this could only be done on a stage that the individual had already shot for score, or we would set up a separate bay for this to be done. This was done specifically to avoid any perception that the competitor had an unfair advantage. People would also complain if the MD had the same "practice run", let alone a highly ranked competitor. The above consideration brings us back to what Tim discussed earlier about waiting for the top score to come in. Mick

I have the VDI barrel and SLR SA7 adjustable gas block. The gas block is installed 0.020" away from the barrel shoulder to align the gas port. With JP LMOS bolt carrier group, TACCOM ULW buffer assembly and TTI reduced power carbine buffer spring, the gas block is locking open on an empty mag at a setting of 5 from fully closed. Mick

4.8gr WSF and precision Delta 124gr FMJ. OAL is 1.150". Mick

In SMM3G IMGA rules, there are power factors for pistol and rifle in the Heavy Divisions.... Mick

Don't forget the Nordic barrel... Mick

Mark, interesting test results. makes a great case for the use of a Ti firing pin in the LMOS carrier. I believe my case was either due to a stuck firing pin, or too long a firing pin, or a combination of the two. I am curious as to what would be the result of the standard firing pin in the JP LMOS carrier and STANDARD buffer spring. Mick This may be (in addition to the long firing pin and soft std rifle primers) the full recipe for your slam fire. By having the cartridge in the chamber already (as opposed to the bolt carrier stripping it from the magazine) your bolt had a running start to the chamber, greatly increasing your chances of a slam fire. i had some uppers to test this morning... Put a standard firing pin in a JP low mass carrier with a JP XP buffer spring, dropped the bolt with the release on a full mag...all good. Locked it in as tight as I could against the rail on the bench and out of 5 trigger pulls, got 2 slam fires. Then, locked down and pointed into the berm, I manually placed a round in the chamber, no magazine, and dropped the bolt...nothing the first time. I tried it 10 times and I got slam fires twice. Went back to the Ti firing pin and the standard buffer spring...I tried for 20 minutes to get a slam fire and I could not. Primers were WSRs by the way.

Interesting you point that out. For the M14/M1A, there are very clear instructions in the box not to put a round in the chamber and drop the bolt due to potential slam fires. I have not seen such a warning for the AR15. However, as has been pointed out above, dropping the bolt on a chambered round and no mag only increases the bolt velocity and serves to increase the chances of a slam fire. Mick

Here is a picture of the fired cases. Slam fired case is on the right. Case on the left is with new, shorter firing pin installed. The slam fired case looks like it was punctured. Mick

Testing the rifle today with the shorter firing pin and different ammunition types gives it a clean bill of health. All ammo had very light primer marks from dropping the bolt. By light, I mean light, as in very normal for an AR pattern rifle. Ammo tested was IMI M193 military (hardest primer), PMC bronze .223, and the same batch of my reloads using CCI400 SRP. I am going to conclude that the slam fire occurred either due to the debris in the firing pin channel, or the firing pin is slightly too long. I will take the suspect firing pin to Accuracy Speaks and see if Derrick can measure it using a proper gauge. Lessons learned. Always fully clean new parts, and when doing live testing, keep the muzzle pointed in a SAFE DIRECTION!!!! Mick

The slam fire I had with this build was with a full weight carrier and standard CCI 400 SR primers. First slam fire I have ever encountered. My models at this point are: Debris in firing pin channel (found a small piece of metal shard). Firing fin protrusion too long. Overly sensitive primer. I'm moving away from the dirty chamber model at this point. Further testing later today. I have replaced the firing pin with the shortest one in my parts box and we will see what happens... Mick

Aero Precision uppers are very well made and priced well. Mick

I measured the slam fired case in my RCBS micrometer gauge. Dead nuts on the zero line, showing as perfect headspace... Mick

Just retested the trigger on the rifle. I could not recreate any hammer follow through, and the trigger passed all safety function checks. I disassembled the BCG. Cotter pin was tough to remove. Yep, it is bent. At first the firing pin wouldn't drop out. A second later, it falls out into my hand, along with the sound of a small "clink" of a VERY small metallic piece of debris. It is possible that this small piece of debris, along with the new, uncleaned chamber, is what caused the slam fire. I also measured the firing pin length and this pin is LONGER than the two spares sitting in my parts box and the Colt firing pin pulled out of my Tac Limited rifle. The firing pin in question has 0.005" more protrusion than the others. Mick