New guy here I'm hoping I can get a little help on a build I just completed.

I just built my first AR and this past Sunday I took it to the range and the first three fifteen round mags ran beautifully through it. But I got about four rounds into the fourth mag and it started short stroking. It wasn't stripping rounds out of the mag and I'd pull the trigger on an empty chamber.

I'm running an ACE ARFX skeleton stock with an A2 tube. I have a 14.5" Green Mountain GM-M7 barrel in 5.56 NATO with a YHM 9383 low profile block and a pinned/welded YHM Angled Muzzle Brake (I live in Socialist NJ by the way), it's got a Spike's melonited gas tube. I've also got an AIM V2 NiB M16/AR15 BCG. I was thinking I didn't put enough lube on the BCG but I spoke to my gunsmith and he says it's the buffer spring. I'm running a standard rifle buffer (DPMS I believe) and a DPMS standard rifle buffer spring. Here's where I'm confused.

When I pulled the spring out of the Windham Weaponry WW-15 and lay it next to the one in that I put in the Spike's lower it is quite a bit shorter.

The one in the Spike's lower measures 12.75" and has 43 coils, it is also larger in diameter. The one out of the Windham lower measures 12.5" also has 43 coils and is a bit smaller in diameter. I'm assuming both are rifle springs but why is the one I put in the Spike's lower bigger?

My gunsmith is telling me to run a carbine spring with the rifle buffer in the A2 tube. As far as I can tell, this is not correct nor would it work. Isn't the carbine spring a lot shorter? It wouldn't fit in the A2 tube without a spacer inside or if I replace it with an entry tube and a spacer.

I admit, I'm a newb and there is a lot I need to learn, that's why I'm here. Can someone help me figure this out? I've been using Independence 5.56 55 grain in the Windham with no problems and it's the same ammo I'm using in the Spike's I just built.

It sounds like it's short stroking, i'm by no means an expert and i'm sure someone will be along to correct me shortly.

I would not but a carbine spring in a rifle length tube with a rifle buffer.

I did this to prove a point on my SP1 and it caused a lot of issues.

Did you build the upper yourself? I wonder if maybe you gas block has worked itself a little loose? Could be some other things but i'd take a look at that first. Did you try different mags etc also?

Yes, I built both the upper and the lower myself. I brought three mags with me to the range; two Thermold 15 rounders and one Windham Weaponry steel 10 rounder. The two Thermolds would not feed reliably, I had to manually load them via the charging handle every third round, they would then fire the next two rounds then not feed the next. So every third one I had to manually charge. The Windham fed reliably every time. I do have some Magpul Gen 3 mags coming.

The first thing I did when I got home was pulled the handguard off (UTG Pro Super Slim Free Float) and checked the gas block. Screws were still tight and it was still in place, it did not move.

Don't worry, I have no intention of running a Carbine spring because I don't believe it'll work.

Thanks for the help.

I'd try the new mags before you try anything else, especially if you have one that feeds reliably every time. Then we can get into the complex stuff.

OK, they should be here maybe end of the week. They can't get here fast enough. Again, thanks for the help.

Here's a picture of what I built.

Where in NJ are you?. If you are close enough or don't mind the drive, we can go to my range and I'll bring some Pmags with me. I'm going there on Thursday or Friday to test fire my son's Christmas present.

Thank you for fixing my busted link. I couldn't figure out how to get it to show and I was tired and didn't feel like messing with it anymore. Also, love your avatar.



I'm up in Northwest NJ in Sussex County.

I'm down south in Camden County. The offer is still good, just a long drive.

With a new build it is possible something came loose in the gas system, but more than likely you have a lube issue.
I have seen this many times with new weapons breaking in even with weapons that started clean and well lubed.

This is what I thought too; in fact my brother went with me to the range and said the same thing. I've cleaned it up and re-lubed it with some Mobil 1. I'm thinking about either going to the range tonight with it or over the weekend. I did however order a new rifle length buffer spring in case.



This week isn't good for me; I am free this Sunday though. But I'm actually on vacation next week and the week after that. So, maybe then. If the offer is still good.

Yup, I'm off after Christmas but I have to go back Monday the 29th. Maybe we can get together on the 27th or 28th.

PS: keep an eye on your inbox here. If I'm available this Sunday I'll let you know

Will do.

I purposefully saved a week of vacation for the end of the year and combined with the days I already get off for Christmas and New Years it makes for a two week vacation.

I have found spray moly and a coat of grease works well for me for break in.
I can’t help on the spring as I run Tubb’s CS flatwire springs.
A CS spring’s service life is basically good for the life of several weapons
Spikes is one of the better vendors so I doubt a spring from them is likely to be a problem.

I wanted to get a flat wire spring. But figured for my first build I'd stick with a standard mil-spec spring.

Took the rifle to the range today. I swapped the buffer spring out for another standard length spring, lubed the hell out of the BCG and switched over to Gen 3 PMAGs (15/30). Then proceeded to run 100 rounds of 5.56 through it without incident. Ran beautifully. I'm not sure what was causing the short strokes.

I did notice the buffer spring I pulled out of the lower was 1/2" longer but the coil count was the same; 34 coils.