Home Forums Hunting & Shooting Custom Rifles & Wildcats 257 TCU, 25-204, 257 Raptor, 257 Ocelot, etc. AR-15?

For a 257 caliber AR-15, what would you choose and why or, put another way, what are the pro's and con's of the cartridge options listed and similar ones like the 25-45 Sharps without getting into hard to source and work with cases.

I have a 6.8SPC and 300 Black Out so, I'm not really thinking about a 277 Wolverine or 7 Raptor though, Arne makes a really strong case for the 7 Raptor which is pretty easy to source in terms of dies, barrels, etc. However, it is a bit redundant with my 6.8SPC and 300BO.

I am favoring the quarterbore options over something like the 6x223 as I like the bullet options I have a bit better and is a bigger step up from the 223/5.56 premium loads and make the wildcat route more practical and useful. Plus, the extra oomph on a Feral Hog is really helpful.

I'm leaning towards the 223/5.56 case-based options pretty heavily as I don't see enough benefit from a 204R/222 Mag case to be worth the additional effort sourcing cases and similar impacts. I'm also wanting to avoid the 7.62x39, 6.8SPC and, Gendel cases and related magazine and bolt issues.

I have had the 257 TCU recommended to me but, that is one odd poorly documented option. I have been led to believe it is very similar to the 257 Raptor (which is in work) and the 257 Ocelot. I don't get the 25-45 Sharps other than the marketing hype and expect it to go the way of the 376 Steyr and other boutique rounds, comments about neck length, case volume, case shoulder issue and, other similar things also are a factor on this one.

Who has experience with rounds like this? What recommendations or lessons learned do you have? Any strong recommendations for one over the others? I am thinking about an 18" Ranger profile barrel. I'm looking for something effective but not super harsh so, I'm shooting for 2600~2800FPS with common bullets and a 16"~20" barrel.

TIA,
Sid

While I don’t have experience with all of the ones you listed, I do have a lot of experience with all of the various TCU chamberings.

The 257TCU is a cool little round that can launch bullets way faster than you would think. The problem with all of the TCU rounds in magazine fed guns is due to lack of body taper, very sharp shoulder, and relatively short neck, you can very easily run into feeding issues, especially with a gas gun.

I have built a few bolt guns chambered in the various TCU rounds, and I have only had one where I didn’t have to do some tweaking to get them to feed correctly every time. I have all but given up on trying to use AICS pattern mags for them.

That is one of the reasons for the Sharps round. It feeds reliably in ARs.

myself i went 25 Creedmoor i call 257 Creedmoor , necking down 6.5 Creedmoor brass makes things easier to find and use brass

Yep, the 308/7.62x51 class options are pretty good but, I want to stay out of the AR-10 platform due to its overall weight.

Thanks, that suggests the TC Contender advocates of the TCU series probably aren't a good option for autoloader considerations.

Regarding bolt action options, I'm a bit surprised a repeater is a problem. Granted mag-fed issues with high capacity magazines can be tricky if you don't mill out ribs and work on feed lips and similar. With a fixed box magazine though, I would think a blunt squarish case could be set up to feed properly.

The 7 Raptor is doing fine in AR-15's so, that suggests it is likely a better place to start.

The Sharps may be a easy feeder in the AR-15's but, bullet options are a bit restrictive.

I shoot the 22/204 and this works very well in an AR platform according to a friend that used the reamer. He ordered an X caliber barrel in 223, Then the gunsmith ran my 22/204 reamer in. He is very, very happy with the 55g Sierra bthp with 8208 at 3600+ on a 20" barrel.

With the long pointed bullets, you run out of magazine length, and my 22/204 reamer has .020 freebore only. So, bullets in the 25 caliber range that would work well are?

In the 6/204 AR platform, the 60g Sierra would be at the top of the list due to bullet design for shortest OAL to the lands. I have killed many, many coyotes with the 60g Sierra, many. I have just got my 6/204. I shoot Rem 700's, took out the magazine block in the 223 action and it is a marriage made in Heaven for the 22 & 6- 204 platform that outperforms the 223 AI and 6-223 AI platform by a little.

Due to mag constraints, if using the Long VLD bullets, the 223 AI is the champ due to COAL.

Eric on this board has a 25/204 and states that the 257 Kimber velocities are attained with his rifle.

85g Partitons at 3000 fps

100g partitions at 2850, approx

IYou can call JGS and ask for the reamer print for the 22/204 with very little freebore, then change the freebore amount, neck size for 25 caliber.

I've been shooting a 25-204 since 2005, great little round and will duplicate original 250 Sav and 257 Roberts ballistics. The numbers Keith quoted are from a 21" barrel. As far as sourcing brass, I've never had much of a problem finding 204 brass. That said all my 204 wildcats, 22-204, 6mm-204 and 25-204 are in bolt actions.

My current thoughts on the subject, if your going to build on a AR platform use brass that was designed for it, a loss of a little velocity is far less important than putting the first shot where it counts. With the availibility of 6.5 Grendel brass now I might not have even built the 25-204 back in 2005. I'm headed out to a hunt next week and will use a Mini Howa in 6.5 Grendel 90gr Speers and the 25-204 with 85gr NBT's .007 difference in bullet diameter isn't going to be a deal breaker to any animal. I load my 25-204 to 2.41 with 100gr Partitions and wish I could load longer. I think the 204 case is too long for anything other than a 204 and .223(light bullet) application in the AR.

First whitetail(2005) with the 25-204 it handled even this big boy with one shot.

Those small cartridges punch way above their weight class with todays bullets and powder.

My current "fun rifle" is a 7TCU Remington 700. It is responsible for the buck in my avatar. I also have a 6X45 AR that I have killed a pile of does and coyotes with.
If I was building an AR for a 25 caliber, I would just go the easy route and do a 25 based on the .223 case (i.e. the 25-45 Sharps).

Sid, to answer your questions regarding feeding, when using the TCU, you almost always have to mess with the feed lips on the mag to ensure the cartridge pops out of the mag at the right time. Most of the time with non-modified lips, the lack of body taper causes the cartridge to stay in the mag too long (both detachable mags and box mags) and the bullet hits the feed ramp head on. The Remington ADL and BDL mags are the easiest to mess with. Most of the time all you have to do is modify the spacer at the back of the mag box and bend the lips up every so slightly. Others are hard and for AICS type bottom metal and mags, you have to mess around and get the mag height perfect as well.