Low Velocity on First Shot with Subsonics

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parsky1
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Low Velocity on First Shot with Subsonics

Post by parsky1 »

Hi all. I've had a lot of issues with subsonic loads and this gun over the years. I've tried 1680, H4198, Lilgun and now N110. I was hoping N110 would be the ticket. They all produce a first shot that is significantly lower on the first shot than the others. I'm talking 4.5"-12" low. Factory ammo from Sig and Hornady did the same thing. I now have two barrels from the same mfg. and they do the exact same thing. Its a 16" barrel from columbia river arms and a hybrid 46 can. Barrel is free floated on a Mega Arms Upper. Has anyone run into this before? I'm honestly thinking of getting a different brand of barrel (I'll take recommendations from those who shoot subs at 100 yards and get tight groups). I just don't know what else it can be? I'm just at a loss here. This was all single fed from the mag. So I only loaded one round in the mag and then let the bolt slam shut.

7.5gr N110, 2.200" COAL 208gr ELD-M, CCI400, FC brass
808fps 8.5" Low
1004fps
1004fps

Let the gun cool down for 10min...

7.5gr N110, 2.180" COAL 208gr ELD-M, CCI400, FC brass
947fps 4.5" Low
1075fps
1070fps
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dellet
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Re: Low Velocity on First Shot with Subsonics

Post by dellet »

What happens without the suppressor?
300 Blackout, not just for sub-sonics.
parsky1
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Re: Low Velocity on First Shot with Subsonics

Post by parsky1 »

I think I tried that, but don't have it it my notes. I"ll try it again on Saturday. Tomorrow I'm going to try some 110gr Amax with N110 supers and see how those come out of it.

It is beyond me how a suppressor could suck that much energy out of it. It certainly doesn't on my 10.5" 458 socom subsonics. I can get super super tight ES with N110. It didn't group well so I switch to N105 for it. N105 was also much quieter. Anyway I digress...
parsky1
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Re: Low Velocity on First Shot with Subsonics

Post by parsky1 »

Dellet do you use any 16” AR barrels in 300blk for subs?
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dellet
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Re: Low Velocity on First Shot with Subsonics

Post by dellet »

I don't use a 16" barrel very often, My AR rifle is 18".

As far as a drop in velocity first round due to the suppressor, in general you pick up velocity. There me be some anomaly going on where you are losing it, or possibly just not getting it on the first round. 200 fps is a huge difference, but a 3 shot example is almost pointless. So really not enough information.

Something else worth trying would be a magnum primer and see if it evens out.
300 Blackout, not just for sub-sonics.
parsky1
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Posts: 48
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Re: Low Velocity on First Shot with Subsonics

Post by parsky1 »

I’ve tried magnums in the past. Like I said this has done this with every powder I’ve tried. I just didn’t feel like posting all the data. I was sort of hoping N110 might be the savior… obviously not.
parsky1
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Re: Low Velocity on First Shot with Subsonics

Post by parsky1 »

I shot some 110gr vmax supers tonight. They grouped well. Only 50fps difference between first and second. Still more than I expected.
parsky1
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Re: Low Velocity on First Shot with Subsonics

Post by parsky1 »

dellet wrote: Fri Sep 10, 2021 1:18 pm I don't use a 16" barrel very often, My AR rifle is 18".

As far as a drop in velocity first round due to the suppressor, in general you pick up velocity. There me be some anomaly going on where you are losing it, or possibly just not getting it on the first round. 200 fps is a huge difference, but a 3 shot example is almost pointless. So really not enough information.

Something else worth trying would be a magnum primer and see if it evens out.
Shot it again today. Same -200fps cold bore. Supers seem to shoot ok. Maybe it’s the polygonal rifling?
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dellet
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Re: Low Velocity on First Shot with Subsonics

Post by dellet »

parsky1 wrote: Sat Sep 11, 2021 6:46 pm
dellet wrote: Fri Sep 10, 2021 1:18 pm I don't use a 16" barrel very often, My AR rifle is 18".

As far as a drop in velocity first round due to the suppressor, in general you pick up velocity. There me be some anomaly going on where you are losing it, or possibly just not getting it on the first round. 200 fps is a huge difference, but a 3 shot example is almost pointless. So really not enough information.

Something else worth trying would be a magnum primer and see if it evens out.
Shot it again today. Same -200fps cold bore. Supers seem to shoot ok. Maybe it’s the polygonal rifling?
Any comparison with and without the suppressor?
300 Blackout, not just for sub-sonics.
parsky1
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Posts: 48
Joined: Sat Apr 08, 2017 6:11 pm

Re: Low Velocity on First Shot with Subsonics

Post by parsky1 »

Does the same thing with and without suppressor. Gotta be I wonder if this polygonal rifling needs heat to seal better.
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