Sierra 125gr OTM bullets

[JohnInNH]

My Sierra manual has a 300 Whisper section for single shot pistol. It listed 19 gr as max for a 125. I believe it is also in some other places, but in my bolt i went a little more, but not much more before it started to show pressure .. I have 20 as my redline.. a few powder companies have posted BLK data which list loads in the 19 gr range IIRC

300 Whisper published data should be a good starting point and in theory a bit conservative.

[Burt]

Thanks for the heads-up! I didn't think to look back there in the pistol section.

[300Blk]

I measured the factory Remington (RM300AAC6) ammunition and the over all lengths were all over the place. Pricey ammo for that type of bad quality control, in my opinion.

The bullets are seated on the ogive, not the tip. So the OAL is mostly dependent on the ogive to bullet tip consistency. These are large radius bullets - so they won't behave like most bullets in this regard.

The main feature of these bullets is the reliability of feeding.

[BradV]

I just loaded a test batch of this bullet using H110 and hopefully I will get to shoot tomorrow sometime over the chrono.

If all turns out nicely I will gladly post up some load data.

Another note for OAL comparisons, like said the bullet is seated on the ogive. For an accurate comparison you need to measure from the ogive as well. A comparator would help you out for checking consistency. http://www.midwayusa.com/product/231904 ... -6-inserts would work for example.

[Burt]

BradV, I hope your handloads turn out well and you can post some good results. I don't know when I will get a chance to get out and shoot again.

300Blk, the bullets I ordered all measure about the same overall length. The loaded ammunition is what was not very uniform in over all length. I have found that one should not go by bullet tips as a way of setting up the seating dies or for overall length, as you stated.

[BradV]

The load I tested was:

125gr SMK OTM
17.5gr H110
CCI400
2.083" COAL Avg of all rounds measured at the tip. I was going close to Hodgdons recommended length here, I may change this next time around.

10 rounds went into a 1.75" group @ 100 Yds. The chrony did not want to pick up the load for some reason though. I shot this one last and I think I was running out of sunlight / didnt adjust the diffusers. It picked up the 110gr V-Max and 155gr A-Max earlier in the day.

Factory Hornady 110gr 300 Whisper - 2200fps avg from my gun. This is about the performance that I am hoping to reach with the 125 SMK, and I don't think I am too far off.

[300Blk]

300Blk, the bullets I ordered all measure about the same overall length. The loaded ammunition is what was not very uniform in over all length. I have found that one should not go by bullet tips as a way of setting up the seating dies or for overall length, as you stated.

It is the distance from the ogive to the tip that effects the OAL of the ammo, not the length of the bullet.

[300Blk]

Hodgdon? They don't have load data for this bullet.

The OAL is supposed to be about 2.230.

[BradV]

The short OAL of the last loading was in hope it was similar in length to others listed near that weight range, but it didnt quite work out as I wanted.

I tried several loadings at the 2.23" that you recommended and found one to be much better than the others, so I have to say thanks for the assistance.

I only had 5 loaded as such:

Sierra OTM 125
18.4gr W296 (Remember to start your loads lower and work up!)
CCI400
2.230" OAL
2135 FPS Av - 16" CMMG Carbine
100 YD

Chrono @ 12 Feet

2125
2134
2142
2178
2091

No pressure signs in the primers, flawless feeding and a lock-back on the last round. I have not shot the factory Remington 125s, so I don't know how they compare using the same bullet.

The target grid is actually 1 1/4".

*CLICK*

[300Blk]

The short OAL of the last loading was in hope it was similar in length to others listed near that weight range, but it didnt quite work out as I wanted.

The other bullets have to be loaded short to feed well with fully loaded magazines. The Sierra 125 was custom designed by me and Sierra to be loaded as long as 5.56mm ammo (2.230 is good, but no longer than 2.245).