Started this upper with the 10.5 inch barrel and A1 upper. Would carbine triangle handguards be right or is that only the slick side upper? Also the flat delta ring or later model? Any where to find a repo modulator cheaper than arsports? I have the stock. Might SBR this eventually.

What rollmark is that on your lower?

Local manufacturer that went out of business. Dirty Martin Arms Halstead, Ks.

Post Rock Guns in Jetmore, KS bought out his stock.

10.5 inch triangles would be correct for early CAR15, known as Model 607.   They had both slick-sides (non-fa) and Forward assist uppers as in 1965...... there was a transition.  So either can, could be correct.

Hey thanks! I was born in 65 so that's what I'm shooting for...

Is this non castle nut just weird or was it ever used? Only the one hole.

10.5 barrels were never used.

10" on 607s and 177E1s, then 11.5 on E2s

Absolutely right.

That's a pre-M4 lock ring AKA castle nut.   Was standard on Colt carbines until the M-4 came out.  

I dont believe that one is colt, the colt ones Ive seen had two holes that go all the way through. I have two just like that one, single hole that doesn't go all the way through.

You are correct, I miss read the question, I thought the OP was asking why it's different from a modern castle ring/nut.  holes vs slots.  That's what happens when I try to read without my spectacles.

Thank you, I learned something new and more history. It always amazes me what you gain in knowledge in comments that get posted and aren't thought of anything special. It's like finding all the bit of wisdom dropped on the shop floor by just working/apprenticing/volunteering beside skilled people.  In different area of subject matter, the same effect happens.  I learned more shuffling speaker cabinets and doing basic maintenance(random tidbit trivial casually mentioned)/storm repairs in a shop with the  gurus then I did in college courses on the subject with professionals where I had a 4.0 average. You tend to learn more information than you do in a class. With it usually being information that classes will miss or fail to cover. So while you may not see multiple thanks, know there are people(some ashamed to admit their ignorance ...) who you are helping.

Just like it was for the eventually locked "retro deals" thread that was locked since we can't have nice things. Without it, I most likely would have never learned about the  XM231. The facts of it didn't have a rear sight assembly and would have wondered what that odd threaded  hand guard was for. Simple conversation and listing of the sales were filled with educational opportunities. However the amount of knowledge just dropped on the floor from simple discussion was amazing. Add in suddenly knowing a new name with terms/designs to research and the world opens up. So I was sad to see that thread ended, because while it had good deals that were educational to the newer beginners on what things cost compared to full/upper retail websites, the amount of educational value was very high. Now I have a new retro rifle I want, the Bradley for the full accessory collection would be nice, but the rifle will have to do.

I've always loved how this board is more education driven with less smart ass answers than the general tech discussion. Something about the retro-crowds that all have some level of being teachers in their base make up. They're more interested in helping than showing they're out of work comedians.

I was. Thanks!

I guessed it was just a cheaper way to make them.