Reg pressure vs Slug performance

Jump to latest Follow Reply
most important question is what speed you want to achieve with a given projectile..

from there you start working with balancing reg pressure and hammer spring tension .

Preferred higher or lower reg pressure also depends the length of your barrel. With a shorter barrel , let’s say <500 mm I tend to prefer a higher reg pressure in order to achieve shorter valve open time. . With a longer barrel you can aim your tune more towards a more air saving and more quiet report with lower reg setting. You can indeed get differences in your tune of 20 bar as a starting point but getting near same speeds for the same projectile. In the longer barrel the prejectile is longer time inside the barrel hence you have possibility of longer valve open time without “ efficiency and stability problems” when the projectile leaves the barrel. 


succes !
 
Upvote 0
That’s backwards, high reg requires high hammer, unless you want to shoot slower?valve is harder to open, but anyway, I have not seen a quantifiable difference, I have tried many combos and still am trying to beat my bobcat @ 160 bar 30 cal smooth twist @ 100?

With that exact same slug 33.5,25 cal, I have been from 120-170 bar and 950 FPS +or- 10 FPS seems to rule, but that’s my Guns 👍🏻 
 
Upvote 0
Tell us more about the AR you are tuning Drumsnguns?...Find the balance between the two ( reg pressure and hammer spring) for your shooting needs. There is no "magic number" and every AR will be different, even ever so slightly. "slug performance" can vary up to 200+ fps depending on slug choices and caliber. FPE and shot count play a part in the equation here as well. What do you prefer? Where are you currently? Many folks here can guild you to a solution way better that I can, These are questions I ask of myself when I'm tuning.

Balance is key. 
 
Upvote 0
I think I wasn't explaining very clear and forgot to include vitals so:

Impact2/PP/700 mm Superior Heavy with 33.5 gn NSA. I'm using the 57 mm HS and have the Huma Dual TP and FX pin probe. The valve is at around 3.2-3.5 lines out.

I might not have been clear but I was shooting at 140 Bar with the HSTA balance with the reg at Max and had rolled the power wheel down to # 3. That's what I meant by a lighter spring. I got a nice tight spit sound so I know that the valve was shutting pretty quick. And I was shooting at around 985 fps. Good groups at 75-80 yds but not so great at 100. Something like 2" at 100. I had heard from YouTube guys and some others that the slugs preferred high reg settings with the valve closing quicker.

Then without touching the HSTA, I dropped the reg to 125 and used power wheel # 4 for 966 fps and got amazing groups at 105 yds...0.958" to be exact. Best group at this distance for me to date. I'm sure that the HSTA is not perfectly balanced but the target shows that it's probably in the neighborhood so I'll leave it for a while. The weather has been terrible so I'm waiting to get out there again and see if I can replicate the results

Maybe I'm answering my own question? But I wanted to know what the school of thought was on reg. pressure and slugs, if any.

Thanks


 
Upvote 0
I believe that with the 700 mm barrel you get away well with 125 bar reg setting and you experienced just that the slug barrel combo optimum speed was slightly lower than you initial tune. 966 fps is a very nice speed for these nsa and obviously you are at the sweet spot now as the groups you are shooting at 105 yards are well within the mark “ excellent “ !! With a 500mm barrel the tuning outcome would have been different and most likely speeds around 930 fps would do the job there with the higher reg setting ! You know the slugs get a little more time to accelerate and gain speed in a longer barrel . I would say don’t touch your settings with the nsa combo you describe anymore .

succes !


 
Upvote 0
You must log in or register to reply here.
Top Bottom
Back
Home
Forums
Resources
Menu