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115 Dtac 6 creed pressure help

CBeck

CBeck

Sinister Precision
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Full Member
Minuteman
Jun 4, 2013
757
458
NW Georgia
#1
I have been having a hell of a time trying to work up a load without having pressure signs. They are shooting great but so far the only load not showing pressure is running 2880. While that velocity isn't the end of the world, I expected a little bit more after reading through the posts in the 6 creed thread in the other reloading forum. The rifle has a 26" 1:7.5 and I am using H4350, alpha srp 6.5 brass necked down, and CCI 41 primers. I initially tried them loaded at the lands and after finding pressure I backed them off .02 and that didn't really help with the pressure but shot really well. The brass is trimmed and the neck clearance is plenty. Is there something I am missing that could cause pressure at this low of a charge? Factory Hornady 108's are running 3050 and I loaded some 108's up to over 42 grains in Hornady brass and hit 3150 but went with 41.4 to stay at 3050.
IMG_4888.jpeg

38.2 had no pressure signs at all but pressure starts at 38.6 with a faint ejector swipe and slightly heavier than normal lift at the top of the extraction.
IMG_4889.jpeg
IMG_4891.jpeg


I don't have to have a shit ton of velocity and if 2880 is it I can live with that but if there is something causing the pressure that I can fix I want to fix it. Thanks in advance.
 
#4
qodeBebop said:
Kreiger. Ejector swipe and a little heavy at the top of the bolt lift
Click to expand...

if your not happy with that speed you may want to try a slower powder like 4831sc....or RL-16 might get a little more velocity...RL-26 if you can get enough in the case if not you might have to run 105s.

i just put a 28" bartlein on my prone gun because im bored and was going to run 115s again but change my mind after i seen what the 105 hybrids do.
 
#5
I'm just about done running close to 1000 115 DTAC's through my RPR. I ran 38.0 of H4350 (around 2800 fps) and then about 300 or so ago bumped up to 41.0 (around 3000 fps) Accuracy and velocity consistancy seem better at that higher load. Never seen any signs of pressure at either charge. Loaded in both Hornady and Starline brass with CCI and Federal match primers. Current seating is about .015 off the lands.

250 yard target from last weeks match. One of my better groups....
20190702_141623.jpg

My best round was a 244 out of a possible 250 and I know it can shoot better. Learned the point at which my barrel heats too much.
 
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#6
Carlos Danger said:
I'm just about done running close to 1000 115 DTAC's through my RPR. I ran 38.0 of H4350 (around 2800 fps) and then about 300 or so ago bumped up to 41.0 (around 3000 fps) Accuracy and velocity consistancy seem better at that higher load. Never seen any signs of pressure at either charge. Loaded in both Hornady and Starline brass with CCI and Federal match primers. Current seating is about .015 off the lands.

250 yard target from last weeks match. One of my better groups....
View attachment 7107267
My best round was a 244 out of a possible 250 and I know it can shoot better. Learned the point at which my barrel heats too much.
Click to expand...

41gr of H4350 with 115 DTAC should be around 66k PSI give or take with seating length and chamber depth.

OP, try another powder. H4350 is pretty fast for 6CM, especially with 110/115 class bullets. RL26 has the ideal bulk density for this cartridge and projectile to make velocity. Pretty much anything slower than 4831SC under the Hodgdon brand is too bulky. The options I would look at first are H4831SC, RL26, RL16, and RL19.
 
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#9
I hope this doesn’t come across wrong as I am not trying to be an ass, but why are you fighting the DTACS? There is nothing wrong with your Hornady load run it and be happy. Or run the DTACS at just under 2900 and be happy with bug holes. FWIW Chase accuracy not velocity. At 2880 your barrel will last a long time for a 6mm.
 
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#10
CavReconScout said:
I hope this doesn’t come across wrong as I am not trying to be an ass, but why are you fighting the DTACS? There is nothing wrong with your Hornady load run it and be happy. Or run the DTACS at just under 2900 and be happy with bug holes. FWIW Chase accuracy not velocity. At 2880 your barrel will last a long time for a 6mm.
Click to expand...
I have 1000 dtac’s and only had 200 of the 108’s. I said I would be happy if the velocity is what it is I was just curious if there was something that could be causing the pressure that I haven’t checked and not necessarily the powder. They aren’t jammed, there is enough neck clearance, and the charges I tried didn’t seem outrageous based on the loads listed in the 6creed thread with the same powder and bullet. If I have a 6creed that identifies as a dasher it’s not the end of the world and I will accept it for what it is. I’m not against trying a different powder because I’d like something that fills the case up a little better.
 
#11
That’s certainly reasonable. Your loads are way under the max given by Hogdon. I am running 40grs of H4350 at 3004fps with the DTACS and it’s a hammer. I might go to the lower node tho as it has been 90-100 degrees here for the last couple matches. I also tried Re26 and gave it up after fighting carbon rings. I still have a bunch and will give you some to try if you are in the sourthern Wisc/ northern IL area. How many rds do you have on your barrel? What type of action?
 
#13
qodeBebop said:
I have 1000 dtac’s and only had 200 of the 108’s. I said I would be happy if the velocity is what it is I was just curious if there was something that could be causing the pressure that I haven’t checked and not necessarily the powder. They aren’t jammed, there is enough neck clearance, and the charges I tried didn’t seem outrageous based on the loads listed in the 6creed thread with the same powder and bullet. If I have a 6creed that identifies as a dasher it’s not the end of the world and I will accept it for what it is. I’m not against trying a different powder because I’d like something that fills the case up a little better.
Click to expand...


did you by chance get a .236 bore?
 
#14
CavReconScout said:
That’s certainly reasonable. Your loads are way under the max given by Hogdon. I am running 40grs of H4350 at 3004fps with the DTACS and it’s a hammer. I might go to the lower node tho as it has been 90-100 degrees here for the last couple matches. I also tried Re26 and gave it up after fighting carbon rings. I still have a bunch and will give you some to try if you are in the sourthern Wisc/ northern IL area. How many rds do you have on your barrel? What type of action?
Click to expand...
The fact that I am under Hodgdon’s max is one of the reasons it’s left me scratching my head. This is my first 6mm. I’m at less than 200 rounds on the barrel. It’s an impact action. I have a buddy locally that has some 4831sc so I’ll see what it does. What brass are you using? I have a pile of the alpha 6.5 brass but I thought about trying some Hornady that I have but didn’t think it would make any difference.
 
#16
I am using lapua brass which I think is similar in case capacity to your Alpha. The Hornady I believe has more capacity at least the stuff I checked did. Not sure about lot or if they have changed anything. FWIW I have a 6mm Creedmoor match chamber my OAL is 2.790 .020 off the lands.
 
#17
The alpha has a little less internal capacity I believe.

I shot 5 24” hawk hill barrels in 6cm with 115s and never had an issue hitting 3025-3050...I bet the Kreiger is a tight bore.
 
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#18
47guy said:
The alpha has a little less internal capacity I believe.

I shot 5 24” hawk hill barrels in 6cm with 115s and never had an issue hitting 3025-3050...I bet the Kronos a tight bore.
Click to expand...
I should still be able to change powders and see a benefit even if that’s the case right?
 
#19
yes but what powder is going to depend on the free bore...do you know what the free bore is in your rifle also whats the fired and loaded neck size...i know you say plenty of clearance but id like to know those numbers.

my reamer has .109 free bore with a .275 neck...peterson match brass had a loaded neck at .2745...i had to turn .0025 to get my preferred .003 clearance.
with a 105 hybrid .015 off the lands my OAL is 2.762...i dont remember where the DTACs were because its been a few years since ive shot a 6CM but i do remember that the 115s seated pretty deep into the case.
 
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#21
qodeBebop said:
Kreiger. Ejector swipe and a little heavy at the top of the bolt lift
Click to expand...
IMO, by the looks of your brass in this pic, gas is coming back into your chamber. The shoulder clearly has carbon on it, the case-shoulder junction looks like it has a soot line also. This may not result in an ejector mark, but will make bolt lift stiffer. UNLESS you have over bumped your brass, then all this can be explained.
Try cleaning your chamber good, esp the shoulder, if carbon is built up there, never will get a seal off, and it is a cascading effect the more you shoot.
dtac.jpg
 
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#22
I think Milo is on to something with cleaning the chamber and checking shoulder bump...

I am using a Criteron barrel with the Northland match (.183 freebore) reamer and and Hornady brass. When it was new I settled on 41.2 grains of H4350 (I hit pressure approaching either 42 or 43 grains, I think it was 43 but that's off the top of my head right now) then about 900 rounds in I switched to 40 grains of H4350 and that tightened things back up. I started with .025" jump and have kept my seating depth the same on my die. it is now jumping around .060" at almost 1100 rounds fired. I have a slow barrel but I am only about 60fps slower with this load than the 41.2 when the barrel was new. 2930 verses 2870fps.
 
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#23
qodeBebop said:
.272 loaded .275 fired. The dtacs .20 off are 2.140 base to ogive or 2.78 overall. Thank you for your help.
Click to expand...

so you may have a short free bore...can you post a pick of a loaded round with a 115 next to it with tips even so we can see how much bullet is in the case?

milo may be on to something to...if your sizing to much it will cause false pressure signs.
 
#25
Op = interesting I found exactly the same as you, although my 28xx did not group as well, with Hornady once fired brass.

I even texted @47guy also scatting my head with great 115 group well over 3k but loose primers.

We talked about the similar issues I had trying to run Hornady’s 338 once fire really hot.

He suggested switching brass
 
#26
47guy said:
so you may have a short free bore...can you post a pick of a loaded round with a 115 next to it with tips even so we can see how much bullet is in the case?

milo may be on to something to...if your sizing to much it will cause false pressure signs.
Click to expand...
The cases are sized .002 under my fired rounds and here is a better picture of the shoulders of the fired cases as well as a loaded round and bullet.
0F245D82-BF46-45CE-8C9F-B18F70A26037.jpeg
4C02FE98-D4B4-4676-9946-D4AEC345DE49.jpeg
 
#27
Diver160651 said:
Op = interesting I found exactly the same as you, although my 28xx did not group as well, with Hornady once fired brass.

I even texted @47guy also scatting my head with great 115 group well over 3k but loose primers.

We talked about the similar issues I had trying to run Hornady’s 338 once fire really hot.

He suggested switching brass
Click to expand...
I thought about going the opposite way and loading some in Hornady brass to see if it made any difference but really wanted the alpha to work.
 
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#28
qodeBebop said:
The cases are sized .002 under my fired rounds and here is a better picture of the shoulders of the fired cases as well as a loaded round and bullet. View attachment 7107833View attachment 7107834
Click to expand...
Ok, first your seat depth is not optimal, but it is not that bad where premature pressures should occur, we have seen worse mismatches. But all your cases have some carbon on the shoulder, not sealing off, this is not good, Adding powder may be your only option if your bump numbers are correct and you want to continue to use this brass. I cannot say if a switch to Hornady brass will remedy your situation, I can say you will have to redo most of your load as alpha has way less capacity than the Hornady will.
Honestly,, I am not smart enough to say if the gas coming back toward you is enough to slam your brass into your bolt face causing an ejector mark.
 
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#30
47guy said:
not terribly deep but still in there a ways...you might be better off saving the 115s for the next barrel and run some 105s.
Click to expand...
He could try a hybrid, but he may have considerable jump or no bullet left in the neck. IME, the only bullet the dtac is compatible with freebore wise is the 108 Hornady.
 
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#32
I really appreciate the help. I have loaded a lot of rounds at this point in other calibers and never had these issues so this has been a learning experience for sure.
 
#36
qodeBebop said:
I cleaned after the first 100 rounds before starting the 115 testing and I am still under 200 rounds on the barrel so I hope that's not the issue.
Click to expand...
Easy test here if carbon ring is my definition, chamber a rd, on extraction get your finger in the port and do not let the bullet veer right and contact the side of the action, if the bullet is marked up, you may have a ring.
 
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#37
I have a 6mm creed 1/7 twist had very similar problems I was using 115 dtacs and it was destroying my alpha brass at 39 grains of H4350 so I changed to star line and haven’t had any issues since alpha brass is extremely soft I’ve noticed I changed out of it in my 6.5 creedmoor as well
 
#40
Did you trim the cases you necked down? The case mouths look crimped, like the neck is too long and the chamber is squeezing it down as you close the bolt.
 
#41
Just a suggestion from my f-ups necking down brass... Did you neck down with a standard FL die or did you use bushings? The few wildcats I used a bushing on had all kinds of mystery pressure problems. When I started over with a standard full length die, all the problems were gone. For me, I think the problem was the ol' donut on the inside of the neck shoulder junction, I could actually feel it with a pick run down the inside of the neck.
 
#42
7108566


You also have odd discoloration towards the front of the neck, it looks like an improperly adjusted bushing, or maybe the chamber if the length is long, something is rubbing the tips of your neck.

My bet is either too long after necking down or possibly the donut issue already mentioned. An expander mandrel run down the inside of the neck can help you avoid that when necking down. Definitely use a FL die as mentioned.

You can use bushings on subsequent firings no problem but the initial neck down really effs with neck thickness and tension. You should use a FL die, a mandrel for uniforming the inside of the neck, and then trim before firing.
 
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#43
LawnMM said:
View attachment 7108566

You also have odd discoloration towards the front of the neck, it looks like an improperly adjusted bushing, or maybe the chamber if the length is long, something is rubbing the tips of your neck.

My bet is either too long after necking down or possibly the donut issue already mentioned. An expander mandrel run down the inside of the neck can help you avoid that when necking down. Definitely use a FL die as mentioned.

You can use bushings on subsequent firings no problem but the initial neck down really effs with neck thickness and tension. You should use a FL die, a mandrel for uniforming the inside of the neck, and then trim before firing.
Click to expand...
I used a FL die with no guts,then a mandrel, them trimmed with a Giraud so trim chamfer and debur. I think the outside debur is what you’re seeing in my piss poor photos. I do appreciate any input. I just got out of bed to check lol and to look if there was any donuts and nothing that I can tell. I trimmed to 1.915.
 
#46
I think it’s just the perfect storm of heavy for caliber bullet, powder on the fast side for bullet weight, brass on the low end of capacity, chamber too short for optimal seating depth, and topped off with a tight bore.
 
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#47
qodeBebop said:
I think it’s just the perfect storm of heavy for caliber bullet, powder on the fast side for bullet weight, brass on the low end of capacity, chamber too short for optimal seating depth, and topped off with a tight bore.
Click to expand...
What is your coarse of action going to be then? One thing not brought up, what do fired and sized cases measure at the .2 line above the rim?
In the past 2 yrs I've seen more screwed up unanswerable crap than ever. I had a friend trying 110 Sierra's in a 6 creed, he could not win either. 1100 rds, Lapua, Peterson, and Starline brass, he never got to have an ounce of fun with the rifle.
Going to a slower powder, IMO you enter the dead zone of powders, H4831 should work, I hate that powder. But on paper I think IMR 4955 shines, but to me, the powder has been a disappointment. Look into RL 23 or 26.
And for the last time i'll say this, until you shut the gas off coming back towards you somehow, you are going to fight this.
 
#48
Milo 2.5 said:
What is your coarse of action going to be then? One thing not brought up, what do fired and sized cases measure at the .2 line above the rim?
In the past 2 yrs I've seen more screwed up unanswerable crap than ever. I had a friend trying 110 Sierra's in a 6 creed, he could not win either. 1100 rds, Lapua, Peterson, and Starline brass, he never got to have an ounce of fun with the rifle.
Going to a slower powder, IMO you enter the dead zone of powders, H4831 should work, I hate that powder. But on paper I think IMR 4955 shines, but to me, the powder has been a disappointment. Look into RL 23 or 26.
And for the last time i'll say this, until you shut the gas off coming back towards you somehow, you are going to fight this.
Click to expand...
I will check that measurement when I get home. I do plan on trying 4831 to see what happens. Why do you hate it? I annealed and sized some more brass too to see if that makes any difference but plan on changing one variable at a time. If the powder and annealing doesn’t help I’ll likely shelf the bullets and buy some 108’s
 
#49
qodeBebop said:
I will check that measurement when I get home. I do plan on trying 4831 to see what happens. Why do you hate it? I annealed and sized some more brass too to see if that makes any difference but plan on changing one variable at a time. If the powder and annealing doesn’t help I’ll likely shelf the bullets and buy some 108’s
Click to expand...
Good deal on the one thing at a time. Long story on H4831, can't pinpoint, lol, I kinda hate aoc too, yet never met her.
 
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