308 subsonics

[Dannywayoflife]

Does anyone have any experience of building 308 subsonic ammo? I have been fancying building some for my dta

I have prepped some cases, Ie I've opened the flash holes to give more consistent ignition. And I have a box of the 200 grain lapua fmj subsonic bullets. I plan on using trail boss powder as it seems to give a really good case fill from what I've read. I can't seem to find a safe start point though. Could anyone point me in the direction of a safe published start load?

Also I'm sure I've read about packing down the powder with tissue paper to help with constant ignition, some say do it some say don't. What's the pros and cons of both?

Thanks

Danny

[DOGGER2UK]

If you plan on using a sound moderator do not pack tissue paper into the case...you risk an explosion.

[phaedra1106]

Absolutely no need to open the flash holes or pack the cases, read the sticky posted by Dromia in the library here,

http://www.full-bore.co.uk/viewtopic.php?f=36&t=810

For .308 I use 4.9gr of Viht N310 and a 123gr cast boolit, works perfectly at around 980fps from a 26" barrel.

8gr of TrailBoss with a 162gr cast boolit gave 1020fps from the same barrel.

Using my 16" .300AAC Blackout I use 3.4gr of N310 with the 123gr cast and get a very accurate load at just over 1000fps.

Make sure you shoot test groups without the moderator first to check for any signs of keyholing, last thing you want is them clipping your moderator.

[dromia]

The last thing you want in a bottleneck case loaded with a fast pistol powder are wads or fillers.

Never seen a need to open up flash holes, especially with fast pistol powders which ignite readily and consistently. If you have opened up flash holes make sure the cases are permanently marked as such so that the don't end up being used in full power loads at later date either by you or an inheritor of the cases.

I'm not a fan of jacketed bullets in subsonic rifle loads as the high start pressure needed means that the pressure window between getting the bullet to exit the barrel and staying sub sonic is quiet narrow compared to cast boolits.

[dromia]

BTW cast boolit loads at these low velocities are not transferable to jacked bullet loads, again because of the high start pressure required for condoms.

[Sandgroper]

Published data from Hodgdon (http://www.hodgdonreloading.com/) which worked very well for me;

168 gn A-Max with 8 gn of titegroup (or clays if you have it). Just load it as you would any other 308 round and off you go!

[hitchphil]

Never seen a need to open up flash holes, especially with fast pistol powders which ignite readily and consistently. If you have opened up flash holes make sure the cases are permanently marked as such so that the don't end up being used in full power loads at later date either by you or an inheritor of the cases.

I'm not a fan of jacketed bullets in subsonic rifle loads as the high start pressure needed means that the pressure window between getting the bullet to exit the barrel and staying sub sonic is quiet narrow compared to cast boolits.

Dromia - would you expect Berdan (2 hole) cases to ignite in an acceptable way too? as I am looking to develop a cheap lower energy target training round using a cast bullet, RG case to come in under 2000 J & 900m/s to fit the range cert limit.

The latter info is valuable thanks, we intend to stick to a lead round with a copper gas check - do you see using or even not using? a gas check causing any effects like this?

[dromia]

Berdan primed round should be fine so long as they are not altered.

The reason given for enlarging the primer pockets on reduced loads with fast pistol powders is to avoid the shoulder moving back over time, I have never had this problem yet and if it happens then I would re fireform with a stouter load.

What actual velocities are you looking for, in imperial please as I don't do metric.

[Dannywayoflife]

Thanks for the replies men. I may in the future experiment with a heavy cast bullet. With the 1in8" twist the rifle was made for the heavier bullets. I would like to use the trail boss powder as it looks a lot bigger than others so case fill should be better.

[dromia]

Case fill is irrelevant with these powders in relation to consistent ignition.

It is unlikely that you will get case overflow with double charges with these powders.

So it is back to the old fashioned, look in every case to check for a double or no powder load.