Looking for help for a mandrel size for the 6gt. Never used a mandrel, other than what comes on redding dies. If u can even call it that. But, have a SAC die with Alpha OCD brass. Don't have a micrometer (ball). Any help would be appreciated.
6gt
- Thread starter Dthomas3523
- Start date
You're just wanting to know which mandrel? I'm just getting started on 6GT, so I haven't resized any brass, yet. But, based on experience with 25CM and 6.5CM, if you're annealing each time, a .240 mandrel should put you at .0030 or .0035 neck tension, depending on your bushing. Go up in mandrel size from there to decrease neck tension.
And, it's turning out that pin gages work really well for measuring neck ID, FWIW
Generally start at .002 less than bullet size, so .241
21st Century has excellent mandrels that come in
.0005 sizes. You have to have a mandrel neck sizing die to use them.
21st Century has excellent mandrels that come in
.0005 sizes. You have to have a mandrel neck sizing die to use them.
Also, you still have to first use a bushing die to squeeze the neck down before using a mandrel to expand it. Typically people use a bushing that is .004 - .005 less than what your loaded round measures. There are a gazillion posts on this.
I use a Lee Collett Die with a .239" mandrel.
Lee mentioned if I wanted .003" neck tension, to go with 0.239". I originally requested .240".
I anneal so could be up .004" neck tension.
Had to get a custom 6GT LCD from Lee. Not sure if it's readily available now.
Lee mentioned if I wanted .003" neck tension, to go with 0.239". I originally requested .240".
I anneal so could be up .004" neck tension.
Had to get a custom 6GT LCD from Lee. Not sure if it's readily available now.
I started with the SAC 242 mandrel and that was not enough neck tension for my alpha brass so I an on the 241 now. Still testing but looks like I will stay there.
26" proof, .170 alpha reamer, alpha brass, FGMM primers and 110 Atips.
My previous outing was plagued by hang fires... just enough of a delay that you could feel/hear the pin drop before the discharge on each shot. On this outing I used a different primer and while it performed better I was still having hang fires about every 4th shot.
I'm going to clean my firing pin and firing pin channel and also change out my spring with a new one and see if it continues.
Temps were 16-18 degrees while shooting these.
My previous outing was plagued by hang fires... just enough of a delay that you could feel/hear the pin drop before the discharge on each shot. On this outing I used a different primer and while it performed better I was still having hang fires about every 4th shot.
I'm going to clean my firing pin and firing pin channel and also change out my spring with a new one and see if it continues.
Temps were 16-18 degrees while shooting these.
how in the world can you shoot in those conditions? WAY WAY TO COLD for this TEXAN
We saw -21F overnight on Sunday and had a week straight of -10 in December. This is why SRPs are less than ideal.
That weather is just insane , us over here in Deep South Texas , it is in the low 40’s and it is freezing for us .
@Niles Coyote you deserve a riteintherain kit for your notes. thanks for sharing. Feelin' cold for ya.
That's understandable. This is a colder year than normal for this area and, I think, many other areas.
Any one shoot the 115g berger vld’s ? I haven’t seen them much in this thread . I got a few pounds of n-555 and was thinking of trying the 115g vlds with that powder . Figured I’ll give it a try since I can’t find the 109’s to save my life .
I haven't tried the 115 Bergers, 115RDF's shoot well in my barrel. Currently running 109 Berger's with 38.6 N555 for 2940fps. Not a hot load in my gun.
Curious to see how they work out for you. I'd probably start around 37.4 of 555 with those 115's.
I just worked up a load with the 109’s with Varget and got really good accuracy but had some ejector marks pretty Early on but I’ve been reading this is common with alpha brass so I didn’t let it discourage me and found a good load a 33.8 g was getting 2860 fps . It’s a 24’’ bartlein with 1/7.5 twist . it shoots great .it’s my first bolt action rifle and I’m very happy with the way it has shot so far . Built it get Into some prs type shooting .
Bartlein 400MODBB currently @ ~3300rnds
Avg velocity - 2880fps
H4350 @ 36gr
Still shooting <1/2" @ 100yds
Will probably pull bbl at 4k rnds
Avg velocity - 2880fps
H4350 @ 36gr
Still shooting <1/2" @ 100yds
Will probably pull bbl at 4k rnds
I got 3100rounds out of Bartein 5r 7twist 26" barrel Mtu contour.
Shot 2 loads
105,s h4350 35.6 cci450 2856fps
112mb RL16 37.3 cci450 2902fps
Nice! I could have ran it longer but I didn't want to take a chance of it going down during a match. My Bartlein barrel shat great when it was pulled.
I’ve got 8lbs of hybrid 100v I haven’t found a use for, so I decided to load up into the gt. Accuracy definitely isn’t what h4350 gave me but still respectable. Shooting right about 1/2” at 100 with an ES of 11. I’ll continue to mess with it as I’d like to save my 4350 for my nrl 25 creed. I’ve ram from 36-38.6 grains so far. No obvious pressure but suspect I’m about as close as I want to get with a powder like 100v. 38-38.2-38.4 all shot between 2998 fps to 3009 fps though so next outing I’ll be loading 38.2 and seeing how it holds up at range
My first 6GT should be done in a month or two and I am collecting components. I have 3k Rem 7.5 BR primers but don’t know if I’ve ever seen them mentioned in 6GT recipes. Maybe a softer cup? Any reason to spring for some CCI450’s over the 7.5’s?
Impact 737
Proof 1-7 comp contour @ 26”
Mason .120 fb reamer
Alpha brass 6x fired
CCI 450
Reloader 15.5 33.9grs
109 ELDM’s
CBTO 1.920
Neck tension .0015
Temp 62
Humidity 40%
Elev 896
.3” at 100yds
500yd velocity trueing group
Proof 1-7 comp contour @ 26”
Mason .120 fb reamer
Alpha brass 6x fired
CCI 450
Reloader 15.5 33.9grs
109 ELDM’s
CBTO 1.920
Neck tension .0015
Temp 62
Humidity 40%
Elev 896
.3” at 100yds
500yd velocity trueing group
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First time out with my first 6GT barrel yesterday...
I was surprised by how much softer it shot than the already soft 6CM I've been running for the last ~2 years (at a slow-ish ~2900fps). The 6GT recoil impulse has a totally different character than the 6CM had for me with my rig, softer, but also kind of snappier/quicker. I didn't expect it to be so noticeable. Seemed almost like going from a .45ACP to a 9mm lol, I dig it I think.
After my usual barrel break-in ritual (3 dry patches lol), I shot 100rds over the course of the afternoon, and it sped up from ~2750ish to ~2880fps.
I've still got 200 more rounds in virgin brass loaded up that I will put through it before I do any load development, but the "generic load" I guessed on shot great, so looks like load development will be a piece of cake (or maybe not even really necessary).
Barrel: Proof SS Origin prefit 26" 7.5T SKU133484
Generic guess/first-firing/virgin brass load:
Alpha OCD Gay Tiger headstamp
CCI450
32gn Shooter's World Precision Rifle
112gn Barnes Match Burner
1.96" BTO 2.61" COAL
Shot #100 at 1000 yards:
I was surprised by how much softer it shot than the already soft 6CM I've been running for the last ~2 years (at a slow-ish ~2900fps). The 6GT recoil impulse has a totally different character than the 6CM had for me with my rig, softer, but also kind of snappier/quicker. I didn't expect it to be so noticeable. Seemed almost like going from a .45ACP to a 9mm lol, I dig it I think.
After my usual barrel break-in ritual (3 dry patches lol), I shot 100rds over the course of the afternoon, and it sped up from ~2750ish to ~2880fps.
I've still got 200 more rounds in virgin brass loaded up that I will put through it before I do any load development, but the "generic load" I guessed on shot great, so looks like load development will be a piece of cake (or maybe not even really necessary).
Barrel: Proof SS Origin prefit 26" 7.5T SKU133484
Generic guess/first-firing/virgin brass load:
Alpha OCD Gay Tiger headstamp
CCI450
32gn Shooter's World Precision Rifle
112gn Barnes Match Burner
1.96" BTO 2.61" COAL
Shot #100 at 1000 yards:
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I just load for speed at this point. No real load development since the first round of load development. I check SDs/EDs and that's about it.
Hahaha, I was playing with trueing my MV at 600 and then my BC at 750/1000 throughout the day... but with the barrel still speeding up, I had to remind myself now and again to just have fun shooting and not worry about it yet... but, yep, if setteled in, and MV is still right at 600, BC might need to come up a click at 1000.
If that, even... ha ha. That looks closer to .05 mil, even...BC might need to come up a click at 1000.
Well, now that you said that, it was off a Shmedium/tank trap and I'm still adjusting to a new eyes/contacts Rx... so it could've just been me. I find most times it's the monkey pulling the trigger that's the problem, don't want to rule that out too fast lol.
So, the other day when it looked like I was a click or so low or my BC was slightly off at 1000, it wasn't that...
I noticed that Strelok was showing I was getting 2880fps... which seemed wonky and/or too good to be true for 32gn of Shooter's World Precision Rifle (AKA "fake Varget", known to usually be a grain or so slower than Varget).
Seemed hot to me for only 32gn, and I started to wonder why I was getting so much speed?
I decided to measure the distance to the lands, and my generic-break-in/virgin-brass-load was only 0.009" off. That's too close for me, so I decided to seat the remaining rounds I've already got loaded deeper to .100" off like I'd prefer to run it for its lifetime. I figured that would scrub off a little speed, not a huge amount, but something.
Well, got to the range, and the first shot at 100 (to confirm zero before going out further) showed me at least 2-3 tenths low. That was the problem... I hadn't fixed my zero after the barrel had sped up during that first 100 rounds.
My MV wasn't 2880fps, it was more like 2720fps (which jives) and my zero was messed up lol.
The moral of the story is, it's almost always the monkey pulling the trigger...
(FWIW the usual .100" off w/ 112gn Match Burner looks good, 5 at 750, Shmedium/tank trap ...with correct dope this time lol.)
I noticed that Strelok was showing I was getting 2880fps... which seemed wonky and/or too good to be true for 32gn of Shooter's World Precision Rifle (AKA "fake Varget", known to usually be a grain or so slower than Varget).
Seemed hot to me for only 32gn, and I started to wonder why I was getting so much speed?
I decided to measure the distance to the lands, and my generic-break-in/virgin-brass-load was only 0.009" off. That's too close for me, so I decided to seat the remaining rounds I've already got loaded deeper to .100" off like I'd prefer to run it for its lifetime. I figured that would scrub off a little speed, not a huge amount, but something.
Well, got to the range, and the first shot at 100 (to confirm zero before going out further) showed me at least 2-3 tenths low. That was the problem... I hadn't fixed my zero after the barrel had sped up during that first 100 rounds.
My MV wasn't 2880fps, it was more like 2720fps (which jives) and my zero was messed up lol.
The moral of the story is, it's almost always the monkey pulling the trigger...
(FWIW the usual .100" off w/ 112gn Match Burner looks good, 5 at 750, Shmedium/tank trap ...with correct dope this time lol.)
I’m just getting to know my 6. Still the 6.5 is continuing to impress with 2200+ rounds down the tube.
Back to the point, it seems really quick to get to the next target. Running back to back short stages, the 6GT is consistently beating the 6.5 CMon time However, it must be my old blood or worse, my shooting too many hard kickers through the years, but I for one cannot tell much difference in the recoil. I suppose a steady diet of shooting heavily loaded 35’s and occasionally something in the 40’s for rifles and 44 magnums and magnum loaded 45’s kind a ruins a fellow for a fine shooting light recoiling rifle.
However, as mentioned, I have noticed the recoil impulse between the Creedmoor and the GT is different, with the GT snappier. Now the RPR in 6.5 Creedmoor does have a noticeable difference in recoil, but it is markably different from my two rifles in MPA chassis.
Back to the point, it seems really quick to get to the next target. Running back to back short stages, the 6GT is consistently beating the 6.5 CMon time However, it must be my old blood or worse, my shooting too many hard kickers through the years, but I for one cannot tell much difference in the recoil. I suppose a steady diet of shooting heavily loaded 35’s and occasionally something in the 40’s for rifles and 44 magnums and magnum loaded 45’s kind a ruins a fellow for a fine shooting light recoiling rifle.
However, as mentioned, I have noticed the recoil impulse between the Creedmoor and the GT is different, with the GT snappier. Now the RPR in 6.5 Creedmoor does have a noticeable difference in recoil, but it is markably different from my two rifles in MPA chassis.
I'll only be running it this slow for its first 300 rounds, for the first firing on the brass. I loaded them all up with a generic load months ago.
I'll add another grain or two and see what I get...
~2850fps would be ideal IMO, but I don't see myself adding more than two more grains at most, I'll see I guess.
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Quite a few of the better PRS shooters in the country run their BR variants or 6gt’s in the 2750 area.
You don’t lose much at all
High 2700's to mid 2800's is a good place to be on my last 3 barrels.
Just an FYI/PSA…
I’ve had 11 FTFs over my first 200rds with some brand new Alpha OCD “Gay Tiger” head-stamped brass purchased through GAP.
Not a huge deal, but it was annoying until I figured it out (with the help of another experienced shooter because at first I didn’t think of it and was starting to think I was going crazy). I've bumped some shoulders back a little too much and learned that lesson before, but never expected to see it with new brass. There's a first time for everything though lol.
Apparently, the virgin brass’ headspace is too short (6 thou below SAAMI minimum which is 1.357"). The shoulder datum on the ones that fired is now 1.360", while the still-virgin ones that didn't go off measure 1.351".
I guess I’ll have to disassemble them and then put them back together long to jam them a little in order to blow them out.
Just something to look out for if you purchased some of this stuff or ever run into this… I'm glad I didn't have to learn this lesson at a match or I'd be pissed lol.
ETA: FWIW, I did some more measuring detective work, and looks like my Origin/Proof SS prefit combo (checked with Go/No-Go gauges) will still light off cases that are ~4 thou below SAAMI minimum (~1.353", which is what most of the new brass measures), but seems the ~2 thou difference between those and the ones that are ~1.351" is enough to make them not go bang.
I’ve had 11 FTFs over my first 200rds with some brand new Alpha OCD “Gay Tiger” head-stamped brass purchased through GAP.
Not a huge deal, but it was annoying until I figured it out (with the help of another experienced shooter because at first I didn’t think of it and was starting to think I was going crazy). I've bumped some shoulders back a little too much and learned that lesson before, but never expected to see it with new brass. There's a first time for everything though lol.
Apparently, the virgin brass’ headspace is too short (6 thou below SAAMI minimum which is 1.357"). The shoulder datum on the ones that fired is now 1.360", while the still-virgin ones that didn't go off measure 1.351".
I guess I’ll have to disassemble them and then put them back together long to jam them a little in order to blow them out.
Just something to look out for if you purchased some of this stuff or ever run into this… I'm glad I didn't have to learn this lesson at a match or I'd be pissed lol.
ETA: FWIW, I did some more measuring detective work, and looks like my Origin/Proof SS prefit combo (checked with Go/No-Go gauges) will still light off cases that are ~4 thou below SAAMI minimum (~1.353", which is what most of the new brass measures), but seems the ~2 thou difference between those and the ones that are ~1.351" is enough to make them not go bang.
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Origin, the primers are 6 thou below the case head (that's the first thing I thought too, it's not that), the brass was just "born" with the shoulders too short.
Can a case even move .006" in an Origin when the breech is locked? My alpha brass has short primer pockets and I get zero to -.001 below flush. Honestly, .012" of firing pin travel shouldn't be a problem. I'd call Zermatt and run it past them. Protrusion should be .045" which should leave you plenty of firing pin travel for proper ignition.
I exchanged emails with Ray at Zermatt about it, and per usual he was willing to try and help me by shipping me out a new firing-pin assembly before I'd even asked... I told him "thanks, no thanks" for now, because I honestly don't think it has anything to do with that.
It looks like it's just the new brass with the really short shoulder, but yeah, if I have further issues with it I'm going to try a different firing-pin assembly because I agree, the firing-pin protrusion is worth looking at.
I've got something like ~5000rds on the Origin with maybe 2-3 FTF's over that whole time before I started with this new brass... and I even just installed a fresh firing pin spring (preventative maintenance while sussing out and replacing a faulty TT Diamond).
Until they all go bang the jury is still out, but I'm pretty confident it's just the brass. I could be wrong, wouldn't be the first time lol. I'll see I guess...
(You're making me a little paranoid now though haha, I'm going to have to measure my firing-pin protrusion now lol.)
Another option may be to seat primers shallower until you get all of the brass fire-formed. It isn't optimal but neither is ignition failures.
