Velocity change as suppressor gets hot?

[TAZMAN]

Been doing some load development on my 260 just for fun. 48 grains of RL26 topped off with a 142 SMK yields 2965fps, 2956FPS, 2960fps, then 2921, 2924, 2930. If I let the suppressor cool for a while then the velocity comes back to the 2960 range for approx. 3 shots. Velocity without the suppressor doesn't change like that. I use a SDN-6 can on a 22 inch Hart heavy barrel. My SDN-6 has the ECCO machine conversion so it's a thread on and not a quick detach anymore.

Has anyone had this issue before?

 

[orkan]

Those are some crazy high velocities for that cartridge. The suppressor is causing just enough back pressure to push your cases over the edge. You're losing velocity because your cases are losing cohesiveness.

To be clear, those are crazy high velocities even in a 26" barrel. In a 22... well, suffice it to say you better back off or you're going to learn a hard lesson sometime in the future.


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[TAZMAN]

I appreciate the reply, my 6.5 Creedmoor runs the 140 Berger at 2970 with RL26 and I have 6 firings on the cases with no issues. That is a 26 inch Hawk Hill Barrel though. I use Lapua brass in the 260 and it has probably 11 firings on it. At about 13-15 firings on the brass I sometimes get a small split in the neck with the suppressor on but not with the muzzle brake on. RL26 has been astounding for my 260 and 6.5 Creedmoor but my SAC 6.5PRC pressures up to quick with it and I run H1000 in it.

This is the first time I have run long strings with the suppressor on my 260 so I was a little confused at the loss of velocity after it gets hot.

 

[orkan]

I appreciate the reply, my 6.5 Creedmoor runs the 140 Berger at 2970 with RL26 and I have 6 firings on the cases with no issues.

Yeah, because running a 6.5 creed and a 260rem at 6.5 PRC levels is perfectly normal, right?

You don't want answers. You want validation, and you won't get it from me.

Good luck.


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[TAZMAN]

I don't need anything from you. I had a simple question about the velocity change with a hot suppressor and your answer is flat out incorrect but I let it go because from an engineering perspective the term you used is related to theory of solids and is being used out of scope for function.

I guess I should of posted lower velocities so you weren't offended.

 

[orkan]

I don't need anything from you. I had a simple question about the velocity change with a hot suppressor and your answer is flat out incorrect but I let it go because from an engineering perspective the term you used is related to theory of solids and is being used out of scope for function.

I guess I should of posted lower velocities so you weren't offended.

"wHy iSnT mY vElOcItY cOnSiSteNt?!?!" ... as he runs 150-225fps over the rated velocity of his cartridge in a 4" shorter barrel than standard, which actually equals closer to 250-325FPS over standard!!!, and then wants to argue the fact. lol

"MuH MaJiCaL RLtwemptysix!!!!"

Life truly is stranger than fiction. Guys like this putting their "load data" online is why my phone rings every single day with someone massively irritated because they can't get any real information off the internet anymore. Ask a question, get the real answer, and then get upset. lol

Weird, I can run 40 round strings through my cans without an appreciable deviation in velocity. I must not know what I'm talking about.

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[cohunt]

I havent seen any large drop off of velocity on any of my suppressed loads

 

[TAZMAN]

I switched suppressors to the Huntertown CAN and the issue went away. 16fps spread with 8 shots. I would like it to be single digits in the spread but I can play with the load and a few things to help it. We have some theories on the issue with the SDN-6 but it will take time to prove those out.