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Posted: 6/29/2010 12:41:04 PM EDT
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I have a .308 bolt gun with a 1:11 twist and a supressor. I'd like to work up a subsonic load for fun. I've done some searching and it looks like this is a frequent topic but a little difficult to achieve good results. I don't need to drive tacks, its more for just plinking 100-200 yard large targets. What I'd rather not do is: 1) get a bullet stuck in my barrel 2) ruin my suppressor 3) blow up my face. Anyone have advice on where to start with components and charges? |
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I too have a .308 and an AAC- Cyclone, I have not yet loaded any subs, but the general consencious is about 10.4 grains of TRAIL BOSS (the fluffy one) gets it done. The important thing is to start a little higher and work down till the crack goes away. See hodgdon's website for real data. |
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There are a couple of things you need to be mindful about when working up subsonic loads. First, you probably want to use magnum primers. Second, you probably want to clean up the flash hole and enlarge it just a bit. I don't recall exactly the drill size we used but I will find that out an edit this to include. Third, you want to make yourself a reloading tool. This tool will be used to measure (estimate) case fill volume. It is simple. It is simply a 1/4" piece of WOODEN dowel rod about 6 to 8 inches long. To make it, clean a piece of brass. (If the brass still has the previously fired primer in it - so much the better. If the case is new without a primer or has been deprimered, you will eventually need to plug the flash hole so powder does not leak out.) Now, take your piece of clean, empty brass and insert the dowel rod in the mouth (mark the end of the rod you are going to insert in the case) until the end of the rod touches the inside head of the case. Mark the point on the rod where the rod and the mouth of the case intersect. This is your "0% Full" mark. Remove the rod and fill the case with powder (any powder will do but it is better if you use the same powder you will be using for your loads) to the point where you consider the case to be FULL making allowance for the bullet seating. At this point you should not worry about the charge weight of powder - you are just filling up the volume of the case. BE MINDFUL OF POWDER AND PRIMER COMBINATIONS IF YOU HAVE A LIVE PRIMER IN THE CASE. With the case "full" of powder, reinsert the wooden rod in the case using the same end as you used before and again mark the end of case mouth - rod intersection. This is your "100% Full" mark. Remove the rod from the case. Empty the powder from the case. Now your wooden rod should have three marks 1) the end that goes in the case, 2) the 0% Full mark, and 3) the 100% Full mark. Measure the distance between the 0 mark and 100 mark and divide equally into 2, 4, or 10 evenly divided segments marking the rod accordingly. Now when ever you have a partial powder charge in the case you can measure just how full is the case. If you have 2 segments, you can accurately measure 0%, 50% and 100% full and estimate the rest. If you have 4 segments, you can accurately measure 0%, 25%, 50%, 75% and 100% and estimate the rest. If you have 10 segments you can measure 0%, 10%, 20%, 30% .... up to 100%. Why did we just make this tool? Forth, whatever powder you use, you do not want to have a case fill volume less than 20%. If you do, you may get a flash over of powder ignition which will give you a huge pressure surge which will make your #3 concern a reality. This is why we like trailboss because it is "fluffy". Fifth, you will want to have a chronograph to work up your loads. Start fast and work slower until you get subsonic speeds. I know it is a pain in the butt but it is what you should do to verify how the round and your gun interact. For our .308 subsonic loads we use Winchester, Remington and Lapua brass with 9.5 gr. Trailboss powder, and 170 gr. Hornaday round nose lead tip bullet. The bullet shape makes it easier to punch it out the back of the barrel when you get one stuck. Disclaimer: Your results may vary. I make no representation that this load will work for you or anyone. If you want to work up a subsonic load, you should experiment starting with more powder and work your way down in 0.1 gr increments until you achieve subsonic speeds. It is difficult to achieve and sustain consistent subsonic speeds in all conditions. |
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Quoted:
I have a .308 bolt gun with a 1:11 twist and a supressor. I'd like to work up a subsonic load for fun. I've done some searching and it looks like this is a frequent topic but a little difficult to achieve good results. I don't need to drive tacks, its more for just plinking 100-200 yard large targets. What I'd rather not do is: 1) get a bullet stuck in my barrel 2) ruin my suppressor 3) blow up my face. Anyone have advice on where to start with components and charges? research trail boss. fill your case to just below the bottom of the bullet. that is your 100 % load then drop 20% and work up your load as normal. |
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While the subject is here, I'm looking for bullet selection help. Bullet selection can be a bit more tricky in the pesky 1:12 Remington's and I don't want to end up with a bunch of bullets I can't use.
Right now I'm looking at Remington Core-lokt 170 gr 30-30 (.308) bullets found here at Midway What about the similar Remington 180 gr. pointed soft-point for the same price? Hornady 180 gr Interlock roundnose I know the 220 gr is a longshot for 1:12 but anybody try the Hornady 220 gr in a 1:12 Reminton? ETA Sierra Pro-hunter 180 gr? |
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Quoted:
8gr clays with a 168 HPBT works good for me. Published load in Hodgdon manual In a 1:12 twist? I've read other reports of that load slightly keyholing in a 1:12 remmy. I'm sure the 170 gr CLRN would work because it is a shorter bullet but if it won't it would save me the hassle if somebody could tell me now. 
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