Just got a poly MDT mag a while ago, works slick. Using it in a MDT XRS chassis on a Tikka build.
6gt
- Thread starter Dthomas3523
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If anyone is shooting alpha 6gt and 109 hybrids and has the Area 419 comparator set. What’s your CBTO? I’m removing my ejector and the bolt drops free at 1.911 with a light click at the top. I’m subtracting .025 to be 025 off the lands. Curious what others are getting with this setup.
I start at .055 to .060 off touch with 109's in Alpha. Load depends on barrel but usually I'm around 31.5 to 32.5 of varget in a 26" barrel and load to 2830 to 2850. It'll give you 3200+ good rounds and never needs to be retuned or touched.
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Relatively new to reloading and working up a 6gt load for my Bergara Premier Comp. I'm at around 85 rounds in, so realize things may change as far as velocity as the barrel breaks in.
Alpha brass
108 Hornady ELDM's
CCI 450 primers
Varget
I got pressure signs at 33.3 grains, which was 2881 fps. My concern is these pressure signs were ejector imprints/deformation of brass and a heavy bolt. But looking at all the brass, even down at 30 grains, I'm getting shiny marks from the ejectors. Is this normal...possibly from it being virgin brass? I obviously know the 33.3 is too hot, but it's hard to pick where the marks get "worse". Seeing many on threads like this getting higher loads, so also wondering if there is anything I may be overlooking on what I'm doing.
Alpha brass
108 Hornady ELDM's
CCI 450 primers
Varget
I got pressure signs at 33.3 grains, which was 2881 fps. My concern is these pressure signs were ejector imprints/deformation of brass and a heavy bolt. But looking at all the brass, even down at 30 grains, I'm getting shiny marks from the ejectors. Is this normal...possibly from it being virgin brass? I obviously know the 33.3 is too hot, but it's hard to pick where the marks get "worse". Seeing many on threads like this getting higher loads, so also wondering if there is anything I may be overlooking on what I'm doing.
Alright that’s I’m doing. Just touching the lands and not using jam as a measurement.
I’m going to use H4350 and start at 34.5grains. I’m running a Custom Rifle Barrel.
I have in the last few years seen a couple of rifles that leave ejector marks. Leaving ejector marks when a brand new, empty case is chambered and then extracted/ejected. I believe it is caused by a fairly strong ejector spring and a sharp edged ejector button. Heavy bolt lift and unusual expansion just above the case head are better indications of high pressure.
I own a rifle (MPA with Curtis action) that will mark a case with the ejector.
No marks just chambering and ejecting without firing. And at least on average, it gets more pronounced as load gets hotter. But no definitive marks that indicate this is the danger level compared to the previous loads. At least until I got some heavy bolt feedback and saw some peeling of the brass which occurred at the same time.
Going back off 0.5 grains from that load and do another ladder now that I have fire formed the brass. Realize things will change and maybe there is some affect from the brass not gripping the chamber as well when it's virgin???
I have not tried the MDT, however I have tried the Magpul, Ruger, and Amend2 poly mags with a Tika T3X in a KRG Bravo and they are a no go. The feed lips hit the edge of the Tika magazine cut on the bottom of the action. I can't file enough off the outside of the mag feed lips and don't really want to "relieve" the magazine opening on the action.
A little side project that I wanted to mess around with this winter was to see if I could get the remaining 95gr Nosler BTs (from a previous .243 Win project) to shoot out of my 6GT barrel.
I am also using N150 as the powder because I have 6lbs of it still, and no real project for it. It isn't as temp stable as others, so I'll have to keep that in mind as I'm messing with this stuff in the winter.
My goal is 3K FPS minimum, and 2/3 MOA @ 300 yards for 5 shots at least twice consecutively.
Doubt I'll hunt with it (it's a heavy ass AT-X), but so what? Itll be fun for me and I have a surplus of components...if that is possible.
Loaded 15 rounds and tried an uber-basic seating depth test today, starting at .030 and going to .075 in .015 increments. Just shot (3) groups of 4, and (1) group of 3. I did warm the barrel up. I shoot these in backwards order too (short to long)...Basically because if something shoots lights out all I have to do is seat the next group in a little bit and try to duplicate the results.
Anyway, .075 was UGLY. Well over MOA and vertically strung. .060 double grouped on me, then .045 and .030 hovered around the half-minute mark. Velocity for the two groups I recorded was right at my minimum with single digit SDs. I should mention here that my barrel has already done well with N150 and the 105 Hybrid at a similar charge weight, so this wasn't a shot in the dark.
It's a start. I'll load up some more in that seating depth window and play with charge weights a touch next. We'll see if it falls apart on round two.
Anyway, it's not a common/popular venture, but I figured I'd share.
I am also using N150 as the powder because I have 6lbs of it still, and no real project for it. It isn't as temp stable as others, so I'll have to keep that in mind as I'm messing with this stuff in the winter.
My goal is 3K FPS minimum, and 2/3 MOA @ 300 yards for 5 shots at least twice consecutively.
Doubt I'll hunt with it (it's a heavy ass AT-X), but so what? Itll be fun for me and I have a surplus of components...if that is possible.
Loaded 15 rounds and tried an uber-basic seating depth test today, starting at .030 and going to .075 in .015 increments. Just shot (3) groups of 4, and (1) group of 3. I did warm the barrel up. I shoot these in backwards order too (short to long)...Basically because if something shoots lights out all I have to do is seat the next group in a little bit and try to duplicate the results.
Anyway, .075 was UGLY. Well over MOA and vertically strung. .060 double grouped on me, then .045 and .030 hovered around the half-minute mark. Velocity for the two groups I recorded was right at my minimum with single digit SDs. I should mention here that my barrel has already done well with N150 and the 105 Hybrid at a similar charge weight, so this wasn't a shot in the dark.
It's a start. I'll load up some more in that seating depth window and play with charge weights a touch next. We'll see if it falls apart on round two.
Anyway, it's not a common/popular venture, but I figured I'd share.
Just reading all of the chatter about the poly AICS mags, which ones were working for you guys in the Tikka? I think someone said the Amend2 worked great, but someone else mentioned no go? I just bought a Grenade Chassis from MPA to throw in my barreled action and of course the CTR's are a no go. Anyone try CA's poly AICS?
For the ones that are working for you guys, any of them longer OAL than SAAMI? Meaning, I'll swap to .308 during killing season and run them long.
For the ones that are working for you guys, any of them longer OAL than SAAMI? Meaning, I'll swap to .308 during killing season and run them long.
I noticed not many reported using 108 ELD M
That’s what I can find local
Using Varget
GAP Hornady Brass and dies
I would sure appreciate some results with the 108 eld
Or if I’d be better off to try another bullet
That’s what I can find local
Using Varget
GAP Hornady Brass and dies
I would sure appreciate some results with the 108 eld
Or if I’d be better off to try another bullet
In my experience 108 eld's will shoot well using the same powder charges as other 105-110 grain bullets and a seating depth between.035-.060 jump is also a good place to start.
Piss off! What brass? I shot 109s with 32.8 of Varget on Alpha brass and BR4s after talking with GAP at their range. Was shooting 34. Even George said "thats on the hot side". But I sure wasn't seeing those velocities.
Alpha. Actually last weekend I discovered another load that showed me better results than H4350 and Varget…. RL 15.5. Shot a 5 shot group @ 300yds .631 then shot this 10rd just to confirm. Very happy with the results of RL 15.5
Attachments
if anyone is shooting a Custom Rifle Barrel with 109’s and h4350. I would like to know what charges you found that worked well. I’m at 100 rounds and about to start some load development. Using Alpha Brass with 109’s and have a ton of h4350.
Start at 35.5 and work up in .5 grain steps till you hit the velocity you want to be at. Usually you'll have a good one around 36-37 grains.
In the three barrels I’ve got some data on (a Bart 7.5, a Krieger 7.5, and Krieger 7 - all 26”), 35.5 ends up about 2820-2850 with a 109, for what it’s worth.
I ran the Bart up to 37.0, but best groups and velocity spreads were below that. But that was 2930 or so, I was targeting 2850, so lower made more sense for me.
I ran the Bart up to 37.0, but best groups and velocity spreads were below that. But that was 2930 or so, I was targeting 2850, so lower made more sense for me.
This was is my plan. I’m at 100 rounds. First CRB barrel so trying to figure out when it’s steady enough for load development.
36.5ish. probably going to bump up this season to about 2900 fps. H4350 es/sd seem to tighten up with the gt at higher velocities. I hypothesize it's due to case fill efficiency.
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There are a few older posts here about N150 but is anyone using N150 currently and is it a 1:1ish replacement for Varget?
It will be very close in the 6GT for the same velocity from my experience... in the 25GT it's still close but I need about a grain more varget to match.
36.8 gr H4350, 109 hyb jumping 40k, Cci450 in alpha brass. This is a 24in 7.5tw ace rem varm with a Scythe-Ti supressor, zermatt TL3. 400y 10 shot group. The low impact was the slowest of the 15 on chrono(shot 5 Rd zero confirmation prior) there was some suppressor mirage through the string as I shot all 15 rounds in prob 5-6 minutes in 30 degree weather. ES isn't great but it'll do.
That was unsuppressed.
It's 19f right now. I started warmer and it's only down 40fps.
That interesting, the listed post above I showed a 15 shot string, cold bore, suppressed and my first round fell inside the 23fps es range, it wasn't the slowest round either. I typically see a cold barrel cold suppressor 1st round be slow by 30-50fps. I know a handful of shooters who run suppressed during team matches, and they load their first round with a higher charge compared to the rest for the stage to keep velocity the same. I did it for my hunting rifle as I experienced it there too. However I have not experienced it with my 6gt and that suppressor combination.
Today I did my best to keep it from fully cooling. No big first round dips. All shot suppressed. It was 24 degrees by the time I was done. .2gr gets me back to the velocity I had when it was in the 50's. I'm guessing this is a combination of temps and throat erosion. For sure there is temp instability, It was a lot worse two weeks ago when I wasn't focused on keeping the gun warm. Yesterday it was warmer but 10mph to 20mph that cooled the gun down quick.
FWIW:
Load dev today with Berger 109 LRHT in the 6GT.
This is the first load up with 109 Bergers, seated at 0.060" off, was just a starting point in the middle somewhere... But it worked.
All groups were under .5 MOA at 100 meters. Best was 0.396 MOA, having not touched seating depth or the truner, promising.
Rifle: AI AT-X
Barrel: Bartlein 25" 1:7" (1704 rounds through it)
Reamer: Alpha .120FB
Powder: ADI AR2208 (Varget)
Primers: GM205M
Brass: Alpha
Seating depth CBTO: 1.880"
Sizing press: Area 419 Zero
Seating press: K&M arbor with standard force dial indicator
FL Sizing die: SAC modular
Seating die: Forster arbor with VLD stem
Scales: Auto Trickler V3
Chronograph: Garmin Xero
Load dev today with Berger 109 LRHT in the 6GT.
This is the first load up with 109 Bergers, seated at 0.060" off, was just a starting point in the middle somewhere... But it worked.
All groups were under .5 MOA at 100 meters. Best was 0.396 MOA, having not touched seating depth or the truner, promising.
Rifle: AI AT-X
Barrel: Bartlein 25" 1:7" (1704 rounds through it)
Reamer: Alpha .120FB
Powder: ADI AR2208 (Varget)
Primers: GM205M
Brass: Alpha
Seating depth CBTO: 1.880"
Sizing press: Area 419 Zero
Seating press: K&M arbor with standard force dial indicator
FL Sizing die: SAC modular
Seating die: Forster arbor with VLD stem
Scales: Auto Trickler V3
Chronograph: Garmin Xero
Sidetracked into absurdity again, I furtherd my little test into a hunting load with the 95gr Nosler BT and VV N150 that I have an excess of both. I'm only using these components for the testing.
My goal was 3K FPS and 2/3 MOA accuracy for consecutive five shot groups (27" barrel). I figured that it could be a dandy little coyote round out to 400 or so if I could meet those two parameters.
Unfortunately, I can't really say that the accuracy will be there. I shot today prone with a rear bag, so no chronograph numbers, but I did hit 3K FPS on the nose twice at 33.5gr during a seating depth test. Both times SDs were 4 and 6 respectively.
I think this is about as good as it is going to get. Not horrible for a hunting bullet across the board, but that group of 1.1" at 33.9 is probably the worst this barrel has shot. As such, I don't think that I hit my goal.
FWIW this barrel hammers with N150 and the 105 hybrid, it just hammers a little better with H4350.
It was a fun experiment anyway. I did have a bit of a perceived hang fire in the first group...don't know if that was me, or if it actually happened.
Dots are 3/4".
My goal was 3K FPS and 2/3 MOA accuracy for consecutive five shot groups (27" barrel). I figured that it could be a dandy little coyote round out to 400 or so if I could meet those two parameters.
Unfortunately, I can't really say that the accuracy will be there. I shot today prone with a rear bag, so no chronograph numbers, but I did hit 3K FPS on the nose twice at 33.5gr during a seating depth test. Both times SDs were 4 and 6 respectively.
I think this is about as good as it is going to get. Not horrible for a hunting bullet across the board, but that group of 1.1" at 33.9 is probably the worst this barrel has shot. As such, I don't think that I hit my goal.
FWIW this barrel hammers with N150 and the 105 hybrid, it just hammers a little better with H4350.
It was a fun experiment anyway. I did have a bit of a perceived hang fire in the first group...don't know if that was me, or if it actually happened.
Dots are 3/4".
I had to use a kinetic hammer to pull the initial load data lot after finding that some of the brass in that box still had media from the dry tumbler in the flash holes (idiot). Decided to not re-size the cases (still primed) and couldn't be bothered pulling the decapping pin out. The necks were at that point a bit looser, as seen on the arbor press force dial.
Die is a SAC 6 GT + 0.2410" Decapping Expander Mandrel with .263" Neck / Shoulder Bushing.
I was only able to fire one round of the 'loose' rounds at paper, mirage became a major issue at that point in the day so the rest were shot at steel to just get velocity information sorry.
The single group that can be compared:
| Charge | Tension | MV AVG | ES | SD | Group |
| 33.6 | Standard | 2860.2 | 29.5 | 9.5 | .399 MOA (11.6mm) |
| 33.6 | Loose | 2866.8 | 10.8 | 3.8 | .506 MOA (14.7mm) |
Overall, the velocity only jumped up marginally on the looser neck cases, but I'd be less inclined to trust them being beaten up the magazine and storage compared to the standard necks. It may never be an issue, but still.... They slipped in with almost zero effort on the arbor press.
Did you actually have misfires or hangfires? Or did you find in some unloaded cases and decide to be cautious? Just curious.
I eliminated this as a potential issue by moving to really fine grade walnut shell media - but I recall (and can't find a reference now) that Litz did some experiementation around corn cob in the flash hole, and found that it generally didn't make much/any difference (like, everything at least went bang normally in his experiments)
This is my first time shooting a Proof prefit. I can't complain about the results. I just picked a load that had the velocity I was looking for (2830ish). This is a bunch of 3 shot groups just checking for a good seating depth. These are the lengths with a comparator, so the numbers are funky. I can't swear that the larger groups aren't just my sloppiness. I don't have 200 rounds on the barrel yet, but still getting single digit SDs. Shooting with a KGM can.
I just started experimenting with it, and it seems like it takes a little less 150 for the same velocity. I'm running 32.6gr in a 26" Proof with 107SMKs at 2830ish.
Realize that with a .024 spread across all those seat depths, you're not really moving the needle enough between groups to see any appreciable difference due to seat depth changes. Heck, over 30 rounds, you moved the lands about .002 - almost a full interval (erosion of about .005 per 100 rounds). You might as well consider those all to be one big group (it's not a bad group - maybe one flyer). You really need to have bigger intervals to see real difference in seat depth effects - .020-030 between depths.
Right, I already had the general ballpark, just doing the fine tuning. I realize it's going to change. I was looking for the long size to load to, allowing for erosion ( essentially the shorter length/ longer jump) where it would open up. Not getting too wrapped around the axle about chasing the lands.
Y’all do seating depth test? I haven’t seen seating depth matter at all. Well not with my Berger 109’s or 140’s
I'm being a poor
. The SMKs are easier to find and cheaper. They don't seem to be very preferential to seating either, though.
Seat 107s at 25-35 off and go shoot stuff. They do well back around 70-80k off too. Found Berger hybrids to be very similar.I'm being a poor
Usually yes, sometimes no.
Since we're in the 6GT thread:
Mine has a definite preference for seating depth with the 105 Hybrid. It isn't a huge swing in accuracy, but it makes a difference of about 1/3-1/2 MOA. Is that repeatable? Yes. Can I shoot the difference prone/rested from my shop? Yes. Would I be able to shoot two 500 round groups and tell a difference? Who knows because I'll eventually throw a shot without realizing it, but consecutive 4x5s show the trend.
I've experienced this as well with the 130 AR OTM in 6.5x47L, and the 215 Hybrid in the 300NM also.
I've found that if asking genuine accuracy advice, it sometimes suits better to go over to https://forum.accurateshooter.com/ and ask the benchrest and F-class guys. Too many howler monkeys here (and I'm frequently one of them).
Absolutely. Haven't seen it matter depends on what your after.. When I do seating depth tests after finding my OCW, there is always a seating depth that stands out from the rest...
For example, all of these groups are probably more than acceptable for 90% of the people out there, but one clearly stands out from the rest and thats the one seated about 0.020" off lands..
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You might find this useful: https://precisionrifleblog.com/2020/04/28/bullet-jump-research-and-load-development-tips/
At least in terms of philosophy, anyway. If you're shooting PRS, you need to ensure you've got a jump distance that will work over, say, .010-.015 variation, if you're going to make it through a 200+ round weekend at a two day (depending on how much you shoot on the train up day). The data tends to show that short jumps - .010-.030 - can work really well, but they fall apart quickly as the lands erode, so you have to "chase the lands". Same goes for jammed loads. Those techniques work really well - for games that you're shooting smaller round counts, or where you're loading at the range to suit changes in the rifle's condition through the match, etc. Meanwhile, for many bullets, jumping .050-.070 seems to also work - maybe not quite as tight as .020, but it tends to hold together through a lot of erosion from there.
For instance, over the last two years, I shot the 108 Berger BT in 6GT. I started with a .060 jump, and it was still shooting the same after about 1200 rounds. For giggles, I measured the lands - I was now jumping about .120. I adjusted my seating die to jump .060 again, and ran it for another 1300 rounds with no changes.
I've since switched to the 109 LRHT - and it seems to be just fine at .060, as well. One of the bullets used in the PRS Blog study is the 105 Hybrid - it's pretty much same (and the guys I know shooting that bullet have had results that match the data in the blog)
I just haven’t seen this be such a measurable change to be relevant. I measure on new barrels and put it .050-.060 and leave it there. I don’t think I’m not placing in the top 10 because of bullet seating but that’s me. I’ve done the tests and read those articles but that’s just what I’ve found. In my experience it’s the Indian and not the arrow. Ive talked to a few very good shooters winning matches and they can’t even tell you their jump. To each their own.
I'm in the camp that doesn't think seating depth matters much. These days I load as short as I can while still keeping the bullet's bearing surface above the neck/shoulder junction, and voila, always shoots. I don't even know where my lands are and haven't bothered to measure to find out over my last couple of barrels.
That said, given a choice, I'd always rather have a healthy jump than be really close to the lands or jam. I feel like I always get less vertical dispersion and a better waterline downrange past 600 yards with more jump, and I like that my barrel doesn't change much at all as the rounds add up without me having to change anything.
