Need help! 240 grain SMK loads won't chamber

[Scollins]

Ok, so I got my 300x221 barrel in today (Randall Rausch made, purchased from a member on AR15.com) and assembled it. I've also loaded up 5 rounds of 240 grain SMKs according to the recipes in my Sierra manual. I've started with 10 grains of H110 under the 240 SMK with an OAL of 2.25". The manual calls for 2.26", but I cut it down just a shade.

Now the problem is these rounds will not chamber in the barrel. They hit the lands well before the bolt closes. The bolt closes on 2.175" properly, so I will have to check a few more OALs in between to see when it starts hitting the lands. Oddly, the Sierra manual says this load isn't for the TC rifles, but for the SSK ARs.

I know that I can safely work up loads that will fit this OAL, I'm just curious as to what others are running for an OAL with the 240 SMK and an AR?

[Scollins]

Well, I managed to get to the range today with 3 different loadings. I went with the 2.175" OAL, as it chambered fine with only the slightest hit of contacting the lands. I think I'll back off the OAL just a touch more to keep it just off the lands.

Anyway, the three recipes are as follows:
All loads featured Keith Davis brass, Remington small rifle primers and Sierra 240 grain Matchkings seated to 2.175" OAL
Pact Model 1 Chrono at 15 feet.
Altitude 400 feet
Temp 74*
Humidity 41%
Barometer 29.99

Load #1
9.0 grains of Hodgdon H110
Avg 933.7
Hi 953.4
Lo 907.5
ES 45.9
SD 19.9
Ad 15.6
1. 952.9
2. 932.5
3. 907.5
4. 922.2
5. 953.4

Load #2
9.5 grains of Hodgdon H110
Avg 1057
Hi 1095
Lo 1017
ES 78
SD 38.6
AD 31.4
1. 1095
2. 1060
3. 1018
4. 1095
5. 1017

Load #3
10.0 grains of Hodgdon H110
Avg 1135
Hi 1161
Lo 1102
ES 59.2
SD 22.5
AD 17.1
1. 1142
2. 1161
3. 1126
4. 1102
5. 1145

I think I'll settle on 9.3 grains of H110 and an OAL of 2.170. I'd like to get around 1,000 FPS on a consistent basis. This keeps me sub sonic in any condition, and has the bullet drop (theoretically) that I'm looking for. Of course, once I get my suppressor back I'll have to see how they work with it attached...:smile:

[jrainw]

I've had my 300/221 from Randall for a year now and use the same loads, I did back down to 200 and 220 grain bullets becuase the 240's would not group at 200+. If you get them to work at long range let me know, I was loading 9.2 grains of H110 to keep me SS with my homemade WCC cases.

Side note, 9.2 seems to get me about the same velocity with 168-240 grain bullets when loaded to the same OAL. (within 50 fps)

Seems kinda strange.