Some makes of Large Frame AR's Takedown and Pivot pins can have a OD diameter of .277 -.291... as well as "odd" lengths.
I "think" Seekins Precision supplies the upper and lowers for GA Precision , however I am not sure which years.
FWIW, I have always wanted a GAP... so please let us know your impressions.
I appreciate the input. I might just buy a .250 as well as .275 and see which one it'll fit, haha.
Having fired AI rifles, and the M110 and the GAP-10 for semi-auto rifles, I'd rank as such:
1) AI series bolt rifles
2) M110
3) GAP-10
In terms of consistency and user-friendliness, it's no competition for the AI series rifles. Yes, it is unfair comparing a Bolt-design gun to gas guns, but I still can't help but to emphasize just how much better and easier the AI rifles are. They are extremely easy to shoot sub 1/2 MOA groups with. It's very impressive.
I haven't had too much exposure with gas guns, but I have shot the M110 extensively in Sniper School and have now zero'd and shot the GAP-10 out to a 1000 yards. I have read many great things about the GAP-10, and it does live upto its hype. However, and this is a personal subjective opinion, I find that the Knights Armament makes slightly better and more consistent gas rifles. The M110 was easier for me to get sub-MOA groups than it was for me with the GAP-10, but not by a great amount. FWIW, the GAP-10 performs flawlessly. It can be obtained for less than 3k for a rifle unlike the KAC SR-25 which will run you at least 5k.
If you would ask me what I'd choose if I had to pick between the SR-25 and the GAP-10, it's a tough decision, but I personally will tell you that I'd save up a bit more money for the KAC's SR-25. I love my GAP-10, but I think I will work on getting an SR-25 in the future.