Preparations before a build

[ssc]

The not cycling thread got me thinking. Before I begin a build, I spend at least an hour inspecting, measuring, test fitting and cleaning. Let’s keep this thread for lowers only. I am curious as what everyone does before building a stripped lower. I will outline my procedures.

I am no expert, but have built, repaired, stripped, rebuilt and replaced many parts. My guess is that I have been involved in over 50 builds from a stripped lower and many more from rebuilding etc.

The first thing I do is a visual inspection. I have seen grip screw recesses that wasn’t threaded. Had one that had plugs in the threads. Seen lowers that we’re not drilled for the bolt catch roll pin. Had four lowers from the same manufacture that were all out of spec regarding the distance between the front lugs. Etc.

If all looks good, I start test fitting. I have a set of all generation pmags and D&H and okay mags. They all need to fit and fall out. If so I install the mag catch and adjust and recheck. I test fit at least 3 uppers and check for fit and test fit both the pivot and take down pins. Then I test fit the bolt catch. Had a few that were out of spec and wouldn’t fit in the frame.

I always inspect the bolt catch plunger recess by installing two different plungers backwards. This is very important. If short drilled, I can remove the plunger via the nipple with needle nose pliers. Having had a short tapered recess that the plunger got wedged in and was a real bitch to extract, I consider this essential. Then I test fit the trigger pins and safety as well as the grip. Usually I have to work the grip off and on and remove some material while verifying the depth of the safety spring. Then check fit the remaining springs and detents.

Next comes the receiver etc. check fit the stock, spring, detent, castle nut and QD plate. Had a few plates and extensions that were defective. Then test install the receiver to the frame and check interface with the buffer detent. If all checks OK, I start my build.

That’s my preparation before I start to build a lower. What preparations does everyone else utilize?

Cheers, Steve

[DG23]

What preparations does everyone else utilize?

Cheers, Steve

I make sure the parts do not say Anderson or PSA on them. If not - I am much more likely to 'not' have problems.

[lysander]

If I have to do the final dimensional and quality checks on a lower, I better be paid for it.

I like to buy quality, and like DG23 said, and then not have to worry . . .

[Five_Point_Five_Six]

The not cycling thread got me thinking. Before I begin a build, I spend at least an hour inspecting, measuring, test fitting and cleaning. Let’s keep this thread for lowers only. I am curious as what everyone does before building a stripped lower. I will outline my procedures.

I am no expert, but have built, repaired, stripped, rebuilt and replaced many parts. My guess is that I have been involved in over 50 builds from a stripped lower and many more from rebuilding etc.

The first thing I do is a visual inspection. I have seen grip screw recesses that wasn’t threaded. Had one that had plugs in the threads. Seen lowers that we’re not drilled for the bolt catch roll pin. Had four lowers from the same manufacture that were all out of spec regarding the distance between the front lugs. Etc.

If all looks good, I start test fitting. I have a set of all generation pmags and D&H and okay mags. They all need to fit and fall out. If so I install the mag catch and adjust and recheck. I test fit at least 3 uppers and check for fit and test fit both the pivot and take down pins. Then I test fit the bolt catch. Had a few that were out of spec and wouldn’t fit in the frame.

I always inspect the bolt catch plunger recess by installing two different plungers backwards. This is very important. If short drilled, I can remove the plunger via the nipple with needle nose pliers. Having had a short tapered recess that the plunger got wedged in and was a real bitch to extract, I consider this essential. Then I test fit the trigger pins and safety as well as the grip. Usually I have to work the grip off and on and remove some material while verifying the depth of the safety spring. Then check fit the remaining springs and detents.

Next comes the receiver etc. check fit the stock, spring, detent, castle nut and QD plate. Had a few plates and extensions that were defective. Then test install the receiver to the frame and check interface with the buffer detent. If all checks OK, I start my build.

That’s my preparation before I start to build a lower. What preparations does everyone else utilize?

Cheers, Steve

If I felt any of that was necessary I'd never bother assembling a lower.

[rpoL98]

on AR-15's, if not already tapped, I tap the hole for the take-down pin detent & spring for 4-40 set screw. it's a very common mod. Some AR-15 lowers come with that mod.



ETA: had incorrect screw size of 2-56, now corrected to 4-40. thanks to @M90A1 (below) for catching this flub of major proportions.

[ssc]

If I have to do the final dimensional and quality checks on a lower, I better be paid for it.

I like to buy quality, and like DG23 said, and then not have to worry . . .

Thanks for the responses. They are bit different from what I anticipated. If I am understanding, folks don't inspect anything before the build? My process can take up to an hour or as little as 15 minutes. I absolutely agree on buying quality. I do buy what I consider quality stripped and complete lowers as as well as parts.

This includes Sionics, SOLGW, BCM, FCD, Colt and a few others. However, on one occasion I bought a complete lower from a gun store. It is what is considered top tier. Therefore I didn't check it over. It was out of spec and improperly built. I guess I prefer to do an inspection before the build to ensure all is good. Otherwise, I would have to strip the lower etc if I found a problem. That, to me, would be aggravating if it was towards the end of the build.

I have personally seen top tier products that were out of spec. I believe we have seen numerous people post about various issues. Perhaps the one I have seen is a lower that wasn't drilled for the bolt catch roll pin, or improper grip screw and short bolt catch plunger hole and tapered.

Hence, my reasons for an inspection as set out above. Frankly, even top tier companies can put out lemons, so that is why I do a preventative inspection. Thanks, For the response.

Cheers, Steve

[Hammer_Man]

on AR-15's, if not already tapped, I tap the hole for the take-down pin detent & spring for 2-56 set screw. it's a very common mod. Some AR-15 lowers come with that mod.

I kind of like your idea, I might have to try it out on my next build.

The only prep work I do before assembling is to wipe it down with a lint free cloth and some degreaser if needed. Zev, SOLGW, and Aero have never given me fitment issues.

[rpoL98]

on AR-15's, if not already tapped, I tap the hole for the take-down pin detent & spring for 4-40 set screw. it's a very common mod. Some AR-15 lowers come with that mod. (corrected, was 2-56 which was wrong)

if you do this mod, you need to shorten the detent spring by about the length of the set screw. The set screws I use are 1/8" long, so I shorten the spring by that amount using a Dremel cut-off wheel. I just eyeball guesstimate on how much to cut off with the whiz-wheel, and then also use the side of the whiz-wheel to put a flat surface on the newly-cut end of the spring, "dressing" the end of the spring.

[rpoL98]

all of my lowers from Aero, Spikes Tactical, and PSA have been completely in-spec, uneventful. Yes, PSA. no surprises during the builds. including AR-10 builds on Aero M5 lowers.

[Sidneyious]

I make sure the parts do not say Anderson or PSA on them. If not - I am much more likely to 'not' have problems.

Yes, this, Ive only 3 lowers right now but 1 lower was built and then striped at least 5 times at this point and everything ive done works just fine.
Its a spikes lower if that makes any diff.

I robbed parts from it a few times to finish my adm and aero lower and back, only issue I had was when originally building the spikes lower I mushroomed the bolt catch roll pin and one of these days I will get around to replacing it and the bolt catch.
Its a strike industries enhanced that works with the norgon clones well but the ****ing wobble they both have(other is on the aero) im afraid my a5 green sprinco will snap the ****ers when the bolt stops.