Berry's 220gr Subsonic load workup using SR4756

[Matt/TX]

My Gun is Rem700 bolt 1:7 twist. I have been working up a "quiet" and cheap sub load using Berry's 220gr plated with IMR SR4756 powder & CCI 400. I am wondering if anyone has a Quickload run for this combination they could post. Thus far I have used 6grs up to 7.5grs in 0.2gr increments with little pressure indications. All have stayed subsonic but I am worried about increasing further without having a reference point. I have found that Red Dot yields too slow speeds at the point it is giving good accuracy/pressure results with 220gr bullets. Therefore I am trying a moderately slower powder that should still burn up well before the muzzle exit... theoretically giving a quiet load. All test loads have been really quiet thus far especially compared to a known load I shoot using H110 @ 9.2grs. Any help here greatly appreciated.
thx
Matt

[Regaj]

Alas, Quickload doesn't have SR-4756 in its database. Probably because that powder was discontinued in late 2014. My "One Book/One Caliber" compilation of 300 Blackout load data also doesn't have any reference to that powder, probably, again, because the powder was discontinued shortly after the cartridge was birthed.

None of which makes any difference, of course, if you have a bunch of that powder sitting on the shelf. But most load data for the 300 Blackout uses somewhat slower powders.

If you have another powder you're interested in, let us know.

Welcome to the forum!

[Matt/TX]

Thanks for looking. I have photos of the primers if any one cares to look whether they see pressure signs - [email protected]
At 7.5grs I am getting good results but do not have a chrono to know how close to supersonic I am. I hate to pass on this powder because seems to be doing well - just not comfortable going more than 7.5grs.

Also I have Int Clays and Herco and they seem to be in the slower burn than Red Dot range and fast enough to burn before muzzle zone. Does anyone have a quickload reference for those and I will work those up and report back?

FYI I have previously used 6.7gr SR4756 with 160gr Hornady FTX and 165gr Sierra SBT with great results. They were definitely just as quiet as 5.5 gr Red Dot loads. All loads here were subsonic.

[dellet]

Not familiar with 4756, but.....

In a pinch 357 magnum or 32-20 data will be very close, but a 200 grain bullet may not be listed. Both 45 acp and colt can give an indication and will have 200 grain plus data.

I would search for 4756+300 whisper data,

Looking thru older manuals it was hard to find much data but there was a bit.

[golfindia]

4756 was my favorite 10mm powder! Wish they still made it......

[Regaj]

Well, here's a rough snapshot of what Herco looks like. Berry's Bullets are also not in the Quickload database, but their website shows the 220 gr. .308 bullet (SKU #21019) as 1.350" in length. Using Nosler's 220 gr. Semi-Spitzer as a starting analog, but then modifying the bullet length to match Berry's number, and using Berry's suggested COAL of 2.150"... looks like 5.5 grains of Herco gets you just over 1050 fps - the area I assume you're targeting. Pressure is quite mild, at 32,000 psi.

That's with a 16.5" barrel; and assuming case capacity of 25.1 gr. of water (reasonable for most .300Blk headstamps).




To give you an idea of the powders most typically used, here is Nosler's load data for their 220 gr. projectiles. Keep us posted of how you make out.

[Matt/TX]

Ok went out this morning and shot some rounds with Herco and one with International Clays. Cold and wet here in southeast Texas - for me anyway - low 40's. Very quiet loads especially in the lighter charges - but as one would expect more powder = more noise. My Herco is an old can (Hercules brand before Alliant bought them) so I am little suspect of it - powder smells fine no sour odor at all. Once again for reference all loads shot this morning are noticeably quieter than 9.2gr H110 load of same bullet. My notes were based upon my reaction to the report upon firing and inspection of spent cases. Never reached supersonic crack.
COL = 2.08" CCI400 220gr Berry Plated
5.5gr Herco - very mild, no pressure signs - subsonic baby whisper
5.7gr Herco - very mild, no pressure signs - subsonic baby whisper
5.9gr Herco - strong, no pressure signs - subsonic
6.0gr Herco - strong, very slight firing pin indent ridging - subsonic
6.2gr Herco - strong, very slight firing pin indent ridging - subsonic
6.4gr Herco - stout, slight firing pin indent ridging - subsonic
6.5gr Herco - mild, slight firing pin indent ridging and beginning to flatten - subsonic, bullet maybe was tumbler as it ricocheted weird

5.7gr Int Clays - strong, slight firing pin indent ridging - subsonic
Changed to COL 2.12
5.9gr Int Clays - mild, slight primer flattening - subsonic still very quiet but decided to stop, too many unknowns

[dellet]

something here might be helpful

viewtopic.php?f=141&t=91549&hilit=bolt+action+subsonic

[Matt/TX]

Dellet - yeah I read that earlier but no luck anytime soon finding any of those powders . My future definitely involves me getting some Unique or BE-86. I also just noticed that HERCO has been remade and is now cleaner and meters better.