300 BLK Problems and testing

[garandman]

Ran a velocity test:




Powder: CFE BLK
Load 1 - 178 gr Hornady Match... Min - 1,416 Max - 2,385 SD - 328 ES - 969
Load 2 - 180 gr Hornady SST ...Min - 916 Max - 2,305 SD - 602 ES - 1,389

Came home and checked my powder charge weights. Threw 10 charges and got a low 9.5 gr and a high of 10.7 gr. Fixed that and got consistent 9.5 gr powder throws.

Re-Ran Load 2 today with consistent powder charges (9.5gr CFE BLK) COAL: 2.220" (just fit an AR mag)

Results:

Min - 801 Max - 2,331 SD - 487 ES - 1,530 fps

I'm baffled. MagnetoSpeed has always run well. Just last week with 6.5 CM, it gave single digit SD's.

Running a Sig MCX 8.5" barrel and Omega 9(k) suppressor.

Any ideas?

 

[P1ZombieKiller]

have you ever shot the Magneto over the suppressor before? did it preform different?

 

[garandman]

have you ever shot the Magneto over the suppressor before? did it preform different?

Yes. In 6.5 CM and 224 Valkyrie. No, its always performed well.

Right now, I'm guessing its my bullet / powder combo.

Seems AA1680 and Lil-gun both performed well. But with heavier bullets. With 2.260" COAL.

I've just never seen these kind of WILD velocity swings.

 

[P1ZombieKiller]

well. I would venture to say that those aren't REAL numbers.

I have switched from LiL Gun to AA1680 for both my subs and my supers in 300 BO.
and I am loading a bunch for a buddy right now using H110 (he is just shooting 147 FMJ).

 

[Sniper338]

I have an 8.5 inch 300blk upper, run a TBAC suppressor... i couldnt get subsonic to work at all. Gave up. Never used it since, but stuck it away to just develop a full power load for. It was all over the place... best I could get was 205 amax? Subsonic that hit the target, but accuracy sucked still.

Im convinced a rifle barrel is needed for subsonic 300blk. Never played with it sny further yet.

 

[DukeDuke]

Am I reading this right, 2300+ fps with 178 Hornady's?

 

[garandman]

Am I reading this right, 2300+ fps with 178 Hornady's?

Yeah. With 9.5 gr CLE BLK.

 

[P1ZombieKiller]

Am I reading this right, 2300+ fps with 178 Hornady's?

that's why its clear there was an error. I get 2100 fps shooting 150's with 22.5 grins of AA1680

 

[P1ZombieKiller]

I have an 8.5 inch 300blk upper, run a TBAC suppressor... i couldnt get subsonic to work at all. Gave up. Never used it since, but stuck it away to just develop a full power load for. It was all over the place... best I could get was 205 amax? Subsonic that hit the target, but accuracy sucked still.

Im convinced a rifle barrel is needed for subsonic 300blk. Never played with it sny further yet.

I think accuracy is relative. I dont expect my hunting rifles to shoot like my benchrest rifles. I also dont expect my subsonic rifles to shoot as good as my hunting rifles. I do however expect EVERY rifle I have to perform good.
Subsonic accuracy is a different expectation. I only have 1 AR platform, and it has the 10.5" barrel. This pistol shoots very well (as my expectations are set accordingly).

 

[X-Caveman]

well. I would venture to say that those are REAL numbers.

I have switched from LiL Gun to AA1680 for both my subs and my supers in 300 BO.
and I am loading a bunch for a buddy right now using H110 (he is just shooting 147 FMJ).

H110 for supers (125gr & 110gr) and AA1680 for subs (208 A-Max) here. Run magneto over a can pretty regularly without incident.

 

[garandman]

that's why its clear there was an error. I get 2100 fps shooting 150's with 22.5 grins of AA1680

That would mean it runs perfectly 100% of the time with supers, but errors out near 100% with subs....???

I'm getting no super sonic crack.

 

[XTR]

What triggers a MS? I can't believe it's magnetic or lead bullets wouldn't trigger it. (I have one but I honestly don't know)

Just thinking the logic through, if it's a shock wave sensor then subs have a different input to the bayo. Did you try turning your sensitivity up (or down) as the case may be.

 

[garandman]

What triggers a MS? I can't believe it's magnetic or lead bullets wouldn't trigger it. (I have one but I honestly don't know)

Just thinking the logic through, if it's a shock wave sensor then subs have a different input to the bayo. Did you try turning your sensitivity up (or down) as the case may be.

Sensativity set on 6.

 

[Hoser]

Ran a velocity test:




Powder: CFE BLK
Load 1 - 178 gr Hornady Match... Min - 1,416 Max - 2,385 SD - 328 ES - 969
Load 2 - 180 gr Hornady SST ...Min - 916 Max - 2,305 SD - 602 ES - 1,389

Came home and checked my powder charge weights. Threw 10 charges and got a low 9.5 gr and a high of 10.7 gr. Fixed that and got consistent 9.5 gr powder throws.

Re-Ran Load 2 today with consistent powder charges (9.5gr CFE BLK) COAL: 2.220" (just fit an AR mag)

Results:

Min - 801 Max - 2,331 SD - 487 ES - 1,530 fps

I'm baffled. MagnetoSpeed has always run well. Just last week with 6.5 CM, it gave single digit SD's.

Running a Sig MCX 8.5" barrel and Omega 9(k) suppressor.

Any ideas?

Almost 2400 fps from a 178 out of an 8.5 inch barrel?

That is an indication problem. At that velocity you should be popping primers or blowing out cases. Try turning the sensitivity down a little bit. Something is triggering it.

Using 10.3 gns of 1680 I get a very accurate and quiet load going just under 1,000 fps with an ES of 30 out of a 9 inch SBR. When I got to 10.9 gns I started to see some pressure signs and about 1100 fps.

 

[garandman]

Almost 2400 fps from a 178 out of an 8.5 inch barrel?

That is an indication problem. At that velocity you should be popping primers or blowing out cases. Try turning the sensitivity down a little bit. Something is triggering it.

Using 10.3 gns of 1680 I get a very accurate and quiet load going just under 1,000 fps with an ES of 30 out of a 9 inch SBR. When I got to 10.9 gns I started to see some pressure signs and about 1100 fps.

I agree. Sumpthin' ain't right. Sensativity of 6 has worked on everything from 223 to 338 Norma Mag.

Thanks for the load data. Trying to find some 1680.

For now, changing to 11.2 gr CFE BLK under a 208 gr Hormady A-max. 0.4 gr under Hornady's published data. Will test tomorrow.

 

[Oso]

Overall, I found that H110 performed better than CFE Black for supersonic and subsonic. I am reliably running 195gr bullets with H110 out of 8.5" barrel.

 

[carlsbad]

You can look at the brass. If the ES is real you'll see a lot of variation in pressure signs. If all your brass looks identical, then the ES isn't real.

If it is real, then I'd check your neck clearance. 300 SBO brass can vary a lot so you may not have a god fit in the neck.

 

[skiutah02]

Disclaimer: I am a newbie to the 300 BO and subsonic game, but I am a neurotic reloader/tester, but I feel that I can add to the conversation here. I do love my Magnetospeed and use it in my testing regimen often in combination with my Labradar. In my experience with some of my large diameter match barrels, if the magnetospeed is too far removed from the bore and the bullet passes too high over the sensors, but close enough to trigger a reading, it can behave in the manner described in the OP (wild fluctuations in readings). I agree with those who suggest the sensitivity, but in some cases the only way to get a reliable reading is to get the magnetospeed's "deck" closer to the bore. Sometimes a tired battery in the MS can be at fault. I'm guessing that your can might be playing a role in your observations.

I cannot believe that you have a 178/180 getting to those higher speeds or see that wide a range in velocities with even the nearly 2 grain spread of powder. With about a 1-grain spread with AA1680 and the 210 I see just about 100 fps. With RL7 and the 155 SMK, my >2-gr spread is less than 150 fps. I do have some CFE BLK to try myself but have been using AA1680 with 210 SMK or RL 7 with 155s. I have a 7" barrel with a relatively cheap AR_Stoner barrel from Midway. I've been playing around with this cartridge during lockdown and trying my hand at a build.

With AA1680 and the 210, I've been able to get full cycling, lockback and about 1010 fps. With RL7 and the 155, I can get full cycling, lockback and about 1070 fps. If I try the 155 at lower velocity, I start to lose cycling/lockback. Accuracy is decent, but I've been shooting at 50 yds and standing, so I am the limiting factor.

My issue has been with too many failure-to-fires which I am tracking down the culprit...

I'll be curious what solves your problem. Good luck, Drew

 

[Hohn]

Shoot the loads at a bit longer distance. There's no way an ES of 1000 fps doesn't show up at 100y.

If you aren't seeing HUGE differences in vertical, than you know it's your MS that is not legit.

 

[garandman]

Disclaimer: I am a newbie to the 300 BO and subsonic game, but I am a neurotic reloader/tester, but I feel that I can add to the conversation here. I do love my Magnetospeed and use it in my testing regimen often in combination with my Labradar. In my experience with some of my large diameter match barrels, if the magnetospeed is too far removed from the bore and the bullet passes too high over the sensors, but close enough to trigger a reading, it can behave in the manner described in the OP (wild fluctuations in readings).

I'll be curious what solves your problem. Good luck, Drew

I'm pretty sure the deck height is good. At least this height works well for 338 Norma / 6.5 Cm / 224 Valkyrie.

Battery might be the issue. And maybe sensativity.

But I agree.... I don't see ANY possible way these readings are accurate, with 1.1 grain of powder variance. AND I got the wild fluctuatons AFTER I corrected the powder problem.

Thanx again. The search goes on. Will be trying a different load today.