As stated previously I have only done a little reloading. The match ammo I reloaded was a little cheaper than factory but no real difference in accuracy so I just bought factory ammo.

BUT, I have toyed with the idea of trying a subsonic load in my 6.8 speedmaster. Unfortunately, no factory subsonic is available yet ( though a company in America are "considering it" ) so I might have to try reloading it.

My questions ( and forgive me if silly due to my inexperience ) -

If I were to take factory match ammo ( 115 grain bthp at 2580 fps ) remove the bullet and powder, take away a percentage of the powder and reassemble the round - would there be any problems ? Reduce the charge by a certain percentage, increasing the amount removed gradually to try different batches etc ?

It it as simple as less charge, less velocity with same weight bullet ? Will reducing the charge have any implications on pressures ? Is it better to try a heavier bullet ? What is the heaviest .270 ( .277 ) bullet available ? 170 grains was heaviest I could find.

Any advice / suggestions appreciated.

I have never done it with factory ammo. However I did run different loads to find the best for my rifle. I just got a reload manual after advice from streetfighter. Then loaded 10 rounds of ammo with the lowest powder amount and worked up till about 10% under the maximum powder. Then shot them all to test what grouped best. Then I made 3 batches of the best and tested 50 rounds of each to see what was best. Then made loads of them I suppose you could pull factory and reload it but what powder is in them or are you going to dump the powder and replace it ?

Problem is no manual or online ( that I can find ) resource lists a load for 6.8 which is subsonic.

CORBON are doing a subsonic load but its not available yet apparently.

I was proposing to use the existing powder but just reduce it a tiny amount per batch and compare accuracy / velocity / noise.

Be careful underloading - it's not as straight forward as reducing the powder...



More info: http://members.shaw.ca/cronhelm/DevelopSubsonic.html



 

I know nothing about 6.8 so this might be useless


http://www.ar15.com/content/page.html?id=217





scroll right down for some subsonic loads

 

Your search-fu is weak (I've always wanted to say that)
scroll down to 'subsonic loads' http://www.ar15.com/content/page.html?id=217

Bollocks - beaten to it by Individual!

Like target-hunter said underloading is not as straight forward as reducing the powder. It can be unsafe to download below a certain powder level. I'm sure there is a better explanation, however this is how it was explained to me. If you download below the lowest recommended load there is a possibility of the round exploding. I don't know how true this is but one of the reloaders at my local club explained it as when the round lies flat the powder only fills half of the space of the inside of the round. When the primer detonates it flashes the entire surface of the powder in 1 go causing unsafe pressure. As I said I'm not sure how true this is but I have never loaded under the minimum stated in my reload manual.

PS.. Im sure someone will correct me

That will because you've done relatively F'all reloading and your reloads were not tuned to your rifle as well as they could be.  

Guilty as charged !! Maybe one day I will give it another bash.

Yes, I heard about the powder at bottom of case thing - and a some guys loading an inert filler to counteract it.

Thanks for the link - will check it out.

As to the power - I know its low - in fact the ft/lbs quoted by Corbon for theirs was EXTREMELY low.

Novice reloader+Subsonic=

Loading below the lowest load in the table is a recipe for disaster, don't do it. find a powder big on volume, low in energy that's how the manufacturers do it. As an example I was shooting a borrowed swedish Mauser in 6,5x55 with the owners own reloads and kept getting smoke in my face from blown primers.*  About 60 % of the primers failed to contain the pressure so I asked what it was I was shooting. A load approx 25 % under the lowest recommended.
*Thank God for Norma brass.....
Soren

Well, Trail Boss looks good in respect of being high volume and low energy.

Be very carerfull when you develop a reduced charge load, worst case scenario is a chamber detonation as your powder flashes over.....buy buy gun potentially.

ETA

I should know, I have been there while making some sub loads for .223. It took an hour or so to dissassemble the gun (AR15) I now have the only belted .223 magnum brass in existance. It bent the extractor and fused the brass case to it. I will post some photos later.