I have a re-barreled Rem 788 in .22-250 AI. I received the specs for the finish reamer that was used to chamber it today, and I noticed the overall chamber length from bolt face to end of neck is 1.920 inches. That surprised me because the SAAMI spec for .22-250 is 1.912 inches, and fire formed AI brass ends up shorter than that. My Lapua brass seems to vary a lot. I am seeing a range from 1.872 to 1.894. This is with the same number of firings (fire forming plus 2). It doesn't seem like I will ever need to trim brass for this rifle, but I would like it to be more consistent in length. I guess I could trim it all to match the shortest rounds. My fire forming method is loading the virgin brass with a max .22-250 load using Varget with a 55 grain bullet. Has anyone else seen length variation like that in their fire formed brass? And does anyone know why the reamer would create such seemingly excessive chamber length?

You would be surprised at just how long many factory chambers are. . Many are far longer than reloading manual max length specifications.

I would do as you said, trim to the shortest case and then forget about it for use in that rifle.

Why do you care about the variability in neck length? Theoretically it could affect accuracy, but the two AI rifles I have don't see any noticeable affect from sub max variations in case length. A large part of the reason I wanted an AI chambering was to avoid trimming brass, I've let mine be...

David

David, yes it's the potential effect on accuracy that concerns me about the variability in neck length. And it just seems odd that quality brass that was very uniform to begin with ends up with so much neck length variation after fire forming and a couple of reloads. I know that competition shooters strive for absolutely uniformity with every case, in an effort to get the most consistent velocity and accuracy. I'm sure you're right that the effect on accuracy is imperceptible in most rifles.

Neck length adds to the OAL to touch the lands. I have made up for this by short chambering the 22/250 AI, .025 short. You crush the shoulder back with your full length sizing die when you are pepping your cases for fire forming, this makes the necks grow in length.

My reamer also has zero freebore, puts the 55g Nosler BT bullet shank/BT right at the shoulder neck junction, and the 50g BT base of the bullet right at the shoulder neck junction. 60g Sierra's still shoot tiny groups at 3700 fps in the 12T barrel.

Thanks for the info Keith. My chamber has some freebore in it, but I can easily reach the lands with the bullets I'm using which are longer than what you are using (I have an 8 twist barrel so I'm generally shooting bullets around 75 grains). I did not run the new Lapua cases through a sizing die before I fireformed them. All I did is prime, add powder, and seat bullets. So far, through two reloading cycles, I have only neck sized the brass using a Redding competition bushing die without an expander ball.

I have shot a lot of the 60g berger at 3700 in a 12 twist, but none any heavier. I have two eight twist blanks on the shelf, hoping to make a hog rifle out of one of them. I have shot the 55g Speer gold dots and they are very accurate in 700- sps stainless 223.

When guys are designing the reamer, they often forget about how the neck shrinks when they design the amount of freebore in. I am hoping that the speer 75g Gold dot will shoot and perform well on hogs, perhaps 3450-3500 depending on how long I leave the barrel.

That bullet at that speed should be a hammer on hogs. I have a 24 inch barrel, and per load data I should be getting around 3450 with 75 grain bullets, but I haven't verified that with a chronograph yet. I've been on an accuracy kick lately and this rifle has been pretty good. Even fire forming loads go into about a half inch for 5 shots at 100 yards. I haven't experimented a whole lot yet but I bought a bunch of 75 grain Hornady ELD-M bullets hoping to get them to average .5 moa. So far, they don't do quite that well, but they're consistently .6 to .8 at 100, again 5 shots. Nosler Custom Competion 77 grain HPBT's have given me the half inch groups I'm looking for.

The specs. On your reamer are quite a bit different than mine.
Mine has a case length of 1.893” and a trim of 1.883”. Trimmed all to 1.890” after fire forming +1. Have never trimmed again in several rifles.
Probably will never do another 1-12” or 1-14” twist again the 1-8” twist with 80gr VLD’s is my happy spot.
I have run into one unexpected problem though, I had my reamer made before Lapua made 22-250 brass, Lapua is larger at the base than any other brand so after 5-6 firings they get sticky where a die won’t size so I had to switch back to Norma brass that the reamer was made for

I have a chamber length gauge from Brownell's on order so I'm going to try to verify the length, but Manson's spec drawing says 1.920 from bolt face to where the neck transitions to the freebore area (drawing calls it min chamber length). I guess all is well since the bullets I'm using can kiss the lands easily if I want them to (usually I load for at least .010 jump). Most of the load manuals that list .22-250 AI show a cartridge length of 1.892 inches. Which matches up well with your reamer. No idea why Manson makes his so long, if I'm reading it right.