EngrBob

Correct FaRKle!. I was rushing out the door to a meeting and was just trying to indicate to GRA where to measure. In fact, if everyone would measure their BCGs to get these 4 measurements we could have a really good idea of how much variance there is in the industry and some idea of which one we might want to use for a particular build based on the other accessories we might want to have. So if you want to join in, list your BCG brand; measurement A (depth of the BCG body at the front of the gas key); B (depth of the BCG body plus the depth of the gas key); C (distance from shoulder of the underside to the firing pin well); and D distance from the front of the BCG body to the shoulder). By shoulder I am referring to the point where the BCG underside begins to slope back to the firing pin well. See the PDF file a couple of posts ago for a picture.

GRA - see the drawing. BCG Measurements.pdf

I will remeasure with pictures (for AIM) when I get a chance, probably the middle of the week. I don't know about rebranded PSA parts. I do know that Seekins did NOT manufacture these (I asked Seekins). None of the parts has shown up on the Spikes Tactical website as yet; however, they did send me the "non-standard" parts (takedown and pivot pins, bolt catch) and the bolt catch is secured by a roll pin rather than a screw (as is typical with DPMS style setups). My upper and lower were pristine, smooth and without any machining marks or other imperfections and they fit together perfectly, without any gaps, even though the upper and lower were purchased from different suppliers. Combined with the Faxon barrel it appears to be a very accurate weapon, even given the lack of fine trigger control I have with my left hand and the stock trigger that is currently installed. At this point I am happy (except for the trigger situation) as this was my first complete build (having just replaced about 75% of my Mossberg MMR (AR-15). My only question is the AIM BCG because of the binding with the Geissele trigger installed. With the stock trigger; however, it ran like a champ. No unusual extractor/ejector marks on the cases and all of the cases ended up within a few feet of each other so it may be that the lower is a few thousandths of an inch less in the dimension from the bottom of the fire control well and the rim - who knows but I am still investigating (an engineer's curse!).

98 is correct, there is no difference between low and high with regard to triggers, that refers to the rail height (at least I have never seen any indication of there being a difference in triggers in anything I have read or heard). At this point I suspect that it was simply a combination of a BCG that is a little deeper than some others plus the hammer being very stiff on the Geissele trigger due to the hammer spring. Based on some measurements it was hanging up right at the point where the slope changed going down to the firing pin. It may well be that when the Geissele is broken in that it will have sufficient play to allow the BCG to ride over it. At this point, the Geissele runs beautifully in the 15 and I am more accurate with it (the trigger is important to me because I am VERY right handed and VERY left eye dominant so trigger control is very difficult for me using my left hand). I am counting on the MechDef trigger I ordered. If that doesn't work I will need to get a better trigger in the ST-10. I am OK with the old trigger shooting off a bipod like today, but standing is a bit more of a challenge.

Welcome from the border!

OK, back from the range. The new rifle ran like a champ. I put 40 rounds downrange with no failures of any kind. The BCG locked back on empty as it should. The trigger was not particularly kind as it was the old AR-15 rather stiff trigger, but I was able to get the glass sighted in and able to put 3 rounds within 1 inch using some remanufactured ammunition for Freedom Munitions at 100 yards. I also ran the AR-15 now sporting the Geissele G2S, which is a very nice trigger. I can't wait until I get the MechDef trigger I have on order to see if it will work in the ST-10. First impressions are that the Faxon barrel is a very accurate barrel and my guess on the setting for the JP adjustable gas block was about right. Shells were ejected at about 4 o'clock very consistently. Picking up the brass was easy as it was all in the same place. Before leaving I rang the steel at both 200 and 250 yards. By the way I am very pleased with the two Leapers (UTG) 8x scopes I mounted, a 2-16x44 on the 308 and a 1-8x24 on the AR-15. Big smile in place as I separate the brass so I can finish reading the manuals and get started on the reloading bench I have set up. :banana: <thumbsup>

Sounds like a regular week for me. Hope to get to the range tomorrow. With the AR-15 fire control group everything seems to work normally so we will see.

Sorry, saw the post title and thought you were talking about the oval office for the last six years!

Why are you interested in recovery? Go with the flow!

I understand. The folks at AIM; however, appeared to be very concerned that there was an issue. It also may be that the Spike's lower has just a little less depth than the "normal" DPMS 308AR (I guess I should call mine an ST-10) and because of the stiffness of the hammer on the Geissele FCG that it just will not depress sufficiently for the BCG to ride over it. I was going to test with another 308 BCG but my friend's rifle is a piston unit and the BCG is different so we could not swap. With the FCG installed that I took out of the 15 it cycles just as it should, no feel of any obstruction. What can I say. AIM is outside of Cincinnati and I am a Pittsburgh native. They might want to get back at me for years of the Steelers kicking Bengal butts, but then they may be honest folks as are many of us from western PA and Ohio. Apparently they are located very near Faxon and the rumor is that Faxon uses their BCG (hell they may make them) to check their barrels. The BCG goes into battery beautifully and headspaced perfectly so if they tell me that it is within their design spec I think I can live with it, particularly if the drop in from MechDef sits just a bit lower than the Geissele. Based on what I see it may be a while before that gets here but if it works I will have great triggers in both rifles. In any case I do hope to get out Saturday and see if it goes bang. I did put a JP adjustable gas block on it and the gaps in the rail give me perfect access to the adjustment so if it runs I can tune it and will feel a whole lot better no matter what AIM says. Thanks for the advise, really appreciate it. I do hold you and others on this board responsible for the virus that has me ordering reloading equipment and supplies! <thumbsup>

I will. I am also in contact with AIM Surplus and they are checking to see whether the depth (.968" in front of the gas key) and distance (2.25") from the front to where the slope begins are within spec for this manufacturer. The BCG appears to be very well made so that is a good thing, but if it is out of spec and limits my choices on fire control groups, or puts unnecessary stress on other components, I need to exchange for one that is within spec.

No problemwith the bolt catch after I exercised it a bit. Working fine now.

Well, just for the hell of it, I decided to take the stock trigger out of my AR-15 and swap it for the Geissele G2S that I had in the ST-10. Damned if both don't work as they are supposed to! Apparently the Geissele sticks up just a little too high, or is too stiff for the BCG to ride over it on the charging backstroke. Since the stock fire control group has a few hundred rounds under its belt it is a little looser and is OK in the big brother. I have a MechDef trigger on order (was too late to get in on the buy at the beginning of April but it sounded good) so I will try that when it gets here. Thanks all for the suggestions, I certainly appreciate it. :banana: Now I can see if it will go bang! :auto:

I feel his pain - literally!

The difference is that without the hammer installed, my BCG will move back and lock with the bolt catch (I exercised it a few times and it will catch) using the charging handle. You indicate that yours binds without the fire control group installed which, frankly, sounds even worse. Without the hammer installed it operates normally, although without the hammer it obviously does not go bang.

I have a friend that has a 308 build that runs. The next step is trying my BCG in his build and my trying his in mine. In the meantime I sent AIM a message with an explanation of what is happening. While waiting I think I will try to see if I can get the bolt catch working, perhaps try a different spring.

Mine is 0.968" - in front of the gas key.

Just double checked, pulled the hammer and it does pull all the way back. Now I noticed that the bolt catch, special with the Spike's Tactical, will not engage. It doesn't seem to rise enough, but that is another issue (a spring perhaps). It will begin to catch but will not hold.

It is an AIM Surplus BCG. The area in red is 2 1/4" by 9/32". I did test operation without the fire control group and it functions normally, although I did not have the buffer tube on and the buffer installed. I probably should take the hammer out and test it with the tube and buffer in place.

OK, big problem. After soaking the BCG in oil I put everything together to test functions as I got ready to go to the range. The BCG would not retract into a locked back position but stuck about 70% to 80% of the way back. It was not back far enough to clear the rear of the magazine and the only way I could release it was to take the buffer tiube off. As you can see from the picture, there is a mark below the firing pin where the BCG was hanging up on the cocked hammer. I checked my 15 and the hammer doesn't appear to stick up any farther above the rim of the lower than on the 15. The BCG on the 15; however, has a rather large cutout below the firing pin and is sloped such that it gives far more clearance to allow the BCG to get into the locked back position. I checked the trigger installation and it appears to be correct (actually I took it out and reinstalled it to ensure it was correct, and it was). Any suggestions?

Congrats. Let us know how it runs. <thumbsup>

Thanks 392, we go through Deming quite often to visit number 2 son in Mesa. I will stick with consealed carry (have a CHL) because I deal with politicians regularly and don't want to be able to get to my carry piece too easily. >:D

OK, the build is complete and I will hopefully have time to get out to the range this weekend and see if it runs. With glass and bipod but without ammunition it weighs in at 9.0 lbs. I decided to try out Leapers new 8x glass, in this case a 2-16x44 30mm unit with locking zero, flip up objective and eye piece covers. Just fooling with the glass before mounting it is very clear throughout the entire range with no hazing at the edges. The rings were included. I will let you all know how it runs. The only issue seems to be a very stiff bolt catch and a very tight BCG. The BCG goes into a synthetic oil bath tonight. I did decide to put a JP adjustable gas block on the barrel and the adjustment screw lines up perfectly with the hole in the rail so I should be able to tune it at the range without having to take the rail off.

Actually many say that the reason we fare so well in Texas is because our legislature meets for only 140 days every two years. There are many; however, who suggest we would be even better off if they met for 2 days every 140 years. I belong to that second crowd!

I got my set from Brownells, about $60 for the Go and No Go gauges. I passed on the field gauge.