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Posted: 12/28/2013 6:11:18 PM EDT
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This thing seems to run very inconsistently. One week I've got it at the range, it's running great just shooting off a bag and getting zeroed. couple of ftf's nothing more. Took it out to the mountains and this thing is FTF on probably 30% of the rounds. Same ammo, same configuration. Do you guys think putting something between the buffer and the back of the bolt will help it run better? I built this thing for a girlfriend and definitely want to see her continue shooting when she moves back to the state. It's light, she's excited to shoot it the way i have rebuilt it, but the damned reliability...I'm sure it'll get her frustrated. I could always make something like the taccom plug. Anything else i can do to get this thing running reliably??
If I can't get this thing to pew pew pew, i'll have to replace the bolt and barrel with something from CMMG. She likes the poly upper since it's so light. incomplete without gun porn 
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ATI/Chiappa have a reputation for the barrel nuts coming loose. The polymer reacts differently to hot and cold compared to aluminum which can effect how rigidly the barrel is mounted on each outing. Leaving the polymer upper in the sun is not a good idea as accuracy will deteriorate. The pressure plug is worth trying as any slop in the required movement of the bolt can affect functioning.
You can also check the hook on the extractor to ensure it is pulling on the rim of spent cases. It may also help to polish the chamber. I use a barrel mop with Flitz on a short cleaning rod attached to a variable speed hand drill to polish the chamber. The ATI/ Chiappa is not readily adaptable to CMMG bolts and the design is closer to the Tactical Solution bolt. |
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Let's try to understand something very important about polymer gun receivers
and strength to weight. The difference between a forged Mil-Spec Upper Receiver, stripped, and the typical stripped polymer AR upper receiver is about 5 ounces in the polymer part's favor. Can you honestly feel the difference between the 5 ounces? Don't be misled, the reason gun manufacturers have migrated to polymer is that it eliminates very costly machine time, forgings and billets. The polymer part is molded "net," which means little to nothing has to be done to it other than assemble it into the gun. Polymer is cheap compared to aluminum or steel and significant cost savings can be had especially in manufacturing high volume runs. Polymer has to be thicker than comparable metal parts in order to attain ordnance strength and, yes, high temperatures do cause POI shifts. Polymer does flex under recoil, which can absorb some shock in a handgun, but in a rifle with little or no recoil, what's the point? Manufacturers want us to buy in to the use of polymer in gun manufacturing because the use of it represents a huge profit margin compared to working metal. There are no broaching machines, no vertical or horizontal mills, no cutters, no grinding, no lathe tools, no lathes, no polishing process or equipment, no drill presses or drill bits, no anti-corrosion process and chemicals, only the mold, mold release agent, electricity and a quick sprue trim - that's the benefit polymer has over metal. All the mumbo jumbo and ranting over light weight and rust proof by the advertisers and gun writers is just that. If you like it, great, buy what you like, but not everything polymer is such a good deal. I'll take metal any day. Ted |
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From everything I have read, I must be one of the lucky ones. I have a Chiappa upper on a New Frontier lower and haven't had any problems what so ever. I did tighten up the barrel nut since it was loose when I bought it. I have used mine in temps ranging from high 90s to low 30s with no change in zero. Like any rimfire AR, using the right ammo makes a difference. Mine loves the CCI AR Tactical ammo, shoots accurate and no malfuntions at all. |
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Read what Ted has to say. The reason for the "plastic" is to save money, period. The marketing people like to come up with all these reasons to say its better but any engineer or anyone who knows how things are made will tell you just how much money they save. Mold it, knock off the flashing and put it together. No long machining, no surface protection (bluing or anodizing) needed. Fast and cheap. Yes, its a bit lighter but on something as small as a gun part its not a giant difference.
We use to over engineer parts. Engines in cars, bridges, etc. But as time pasted people wanted lighter and cheaper. So, the engineers have given you what you want....plastic guns. Just today as I was driving home from the LGS I was thinking of this. They had the little plastic S&W MP-22's on sale for $289. I was thinking of what they would look like in 50 years since more plastic will in time succumb to ozone, oxygen, solvents whatever. Would there come a time when we wouldn't have any more old guns around? I have some guns that are older than 50 years that look like new. No plastic in them however. |
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PLENTY aware of why they use polymer, its advantages and drawbacks (real and imagined lol). My background is ID and MFG, so all this about production costs is pretty much not even needed to be said. Thanks, though.
I'm a cheap ass jew and my girl is all of 110 pounds and not strong. The light weight made it fun for her and saved me 100 bucks in rebuilding on a slickside railed upper. The weight was a difference in her enthusiasm, got her into the shooting sports and carrying daily. Mission accomplished. I'm just being a cheap ass jew again, and wondering if a pressure plug or similar, or perhaps other parts, (other than a new upper) would help it run more reliably. $7 vs $100 means more ammo, and more condoms. 
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| On another note, engineers are responsible, when a polymer receiver blows up, if its a design flaw. They are responsible for peoples safety, when it comes to their products. Just in my opinion. With that being said, I doubt engineers even design polymer uppers or lowers, they would have reinforced problem areas. |
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Make sure the barrel nut is tight (don't over torque it) and try some different ammo. Try some Winchester M22 or CCI Tactical ammo. My upper prefers CCI AR Tactical the best. I have a bunch of Federal Champion HV ammo that shoots great in my Marlin rifles and all my rim-fire pistols but will not work right in my Chiappa upper. Ammo makes a difference in a rim-fire AR, even with other brands of uppers. |
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Quoted:
All the mumbo jumbo and ranting over light weight and rust proof by the advertisers and gun writers is just that. If you like it, great, buy what you like, but not everything polymer is such a good deal. I'll take metal any day. Ted I'd certainly give that $7 plug a try first. Great post Ted! 
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I have the CHiappa upper and I found the issue to be the OEM mags that came with it. It feeds much better with the CMMG block o plastic mags. Even better than the BDM mags. I see you have mags that are different than the Chiappa but i'd still say to try the CMMGs
I never knew about the barrel nut loosening issue. Probably explains why mine was finger tight when I took it apart to add a FF rail I did find that the upper receiver threading for the barrel nut was way off axis. So far that the rail has this much droop over 7" 
I bought a forged upper to swap it all over. I liked this upper so little I bought an "other" lower and decided to hack it up and make a pistol out of it My reliability experiences are the same as yours. No clue why it feeds great some days and not others. Adding a shot of Rem Oil on the bolt every 4 mags seems to help 
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ran much better after inserting a nut and bolt behind the bcg. it didn't like american eagle ammo much at all. had a lot of FTF with them. Federal premium ran better, and i think it's a better load. A buddy is taking it in his shop for a bit, so a probable bump for this when i get more to tell you about.
was awesome to do a 50 round drum dump on steel on the new year :) |
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