300 AAC load frustration

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6724

New member
I have a brand new D-Tech 16" 300 AAC upper that i am trying to develop a super sonic load for. i want to use a speer 125gr tnt because i have had good luck with them on coyotes. i have loaded with h-110 from 16 to 19 gr in 1 gr increments, nothing was particularly good. best was 17gr at about 1.75 inches. i had a few sierra 125gr spitzers that i loaded with 19.5gr and 20.0gr of 1680. 20gr of 1680 had 4 shots in less than 3/4 inches, but a flyer high and right that opened the group to about 1.5" 19.5 gr was the same, 4 in one good group and 1 flyer high and right. the flyers were on shots 2 and 3.

next i tried some 150gr round nose speer bullets, it was an odd lot of old bullets so i figured i might as well give them a try. with 14.0gr of h-110 i got a 1/2" wide group about 2.5" tall, so i moved up to 15.0gr. with 15gr i got two pairs of bullets touching but the pairs were about an inch apart, but the 5th shot was high and left of the pairs.

so i went back to my original 17gr of h-110 with a 125gr speer and got a 4 shot group a little over an inch but again with a flyer to open it up. then i tried the 125gr speer with 20gr of 1680 and had 3/4" group going until the 5th shot which went high and right again.

maybe after a bunch of groups and increasing crosswind i was not shooting my best, so i got out the cooper 17AH to check myself, and promptly shot 2 5 shot groups under 1" i had 3 in one hole and then pulled the 4th shot, total group was still only about 7/8".

i see most people claiming great accuracy with h-110 and 125 or 130gr bullets with the same loads that i am trying. but i dont see people stating seating depths. i seated them out pretty far, with less than bullet diameter into the case. the chamber is more set up for a longer bullet like a 220gr so i imagine there is a large jump to the rifling.

all loads cycled without issue, and none showed any pressure signs. the barrel is a 1-8 twist with a pistol length gas system.

suggestions?
 
The 125gr TNT with 17grs of Lilgun has shot half MOA in mine from day one with some decent FPS for super Sonic's and I like the TNT's very well.. H4198 has also worked very well with Sub Sonic loads and 220gr Sierra's... Both are loaded to Max mag length for P mag's..
 
might try to pick up some lil'gun. in the mean time, i am messing around with 1680 and seating depth. i seated the 20gr of 1680 deeper and got the group down to 1.25". next i will try 19.5gr of 1680. the groups are not bad, but i really am not happy with over 1".

but i have done a bunch of looking on the internet and though some people are claiming excellent accuracy, there are many others posting pictures of targets and specs and the grouping is NOT great. many statements are of groups at 50 yards. some are showing groups of a couple inches!
 
I use Hornady SST's or Nosler 125's, with H110 rem 7 1/2 primers and suggest trimming cases to 1.360" and a COAL in the 2.090" to 2.1" range, I have found the most accurate loads are right below max, work up to the max safely, I have found that increasing the charge of 110 at a certain point only produces more pressure signs and the extream spread goes nuts, ( probably would produce vertical stringing ) the fastest most consitant loads I have shot are in the 2250fps range for a 125gn.
 
For a 300... bullet length seems to be one of the most critical factor, a lot of standard flat based bullets, will fall way short...the loads stated above makes sense, also the lead free barnes, add weight by length, a lot use them for super sonic,, but pricey.



X
 
thanks for the specifics.

i tried some subsonic yesterday, function was perfect, velocities right at 1000fps, accuracy of 3/4" or less .... at 50 yards. shot one group at 100yds, strung vertically to about 5.5 inches. i have never seen something group well at 50 and then do that at 100. no indication of stability issues. more testing to come.

220gr sierra hpbt 1-8 twist.
 
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