6gt

[NiteQwill]

Im breaking in a new barrel with 32gr 4166 and 108bt bergers running 2780. They're jumping 70ish thou? Not certain but man does it shoot. My previous match load from old barrel with 109 lrht is shooting in the 2s and 3s. This hawkhill shoots better than the bartlein it replaced.

I've settled on shooting Hawk Hills going forward. Not only for the performance but availability and contour (Heavy Comp).

 

[4O6shootist]

I've settled on shooting Hawk Hills going forward. Not only for the performance but availability and contour (Heavy Comp).

This is a hvy comp 7.5tw finished at 28" screwed to an Archimedes action. Had a 26" 7tw Marksman cut to a tl3 for the womans first prs rifle as well. Oddly her 26" is only 10fps behind my 28" with the same load. Granted I have 50k more freebore and hers the faster twist which probably the difference.

 

[activereality]

Anyone with any 110 Atip jump experience? Finally caved and went with the atips cause i cant find 109's for the life of me (local shop caters to a couple of shooters and gives them the heads up with no limits on whatever he brings in - so shopping elsewhere now).
Gonna do initial testing at ~0.020" off the lands with some h4350.
Interested in what others have found that works well for them.

 

[lycokayaker]

Have a 6gt barrel about to do some sort of load development on this weekend. I am using h4350, Berger 105 hybrids. Is there a optimal speed for barrel longevity? Only shooting this for PRS this season. I thought I read some where most are staying in the 2850-2950 speed for barrel life and a good speed? Help me out.

 

[Jarhead94]

Have a 6gt barrel about to do some sort of load development on this weekend. I am using h4350, Berger 105 hybrids. Is there a optimal speed for barrel longevity? Only shooting this for PRS this season. I thought I read some where most are staying in the 2850-2950 speed for barrel life and a good speed? Help me out.

Well, it's a good combination to start. I know several that use this combo with great results. My guess would be your best results are gone be in the upper velocity range with h4350 and 105. With my 26 inch Gt barrels, 34.5 - 35.5 of h4350 will get me in the 2850-2950 range. Most of my combos settle in around 2875 ish. I wouldn't be to concerned with barrel life, it's a 6mm after all. Like most others, It's probably gone die around 1500-2000.

 

[Jakeweb09]

Tried to go stretch the gt out this past weekend but fog was thick so just did some 100 yard paper punching. 10 round group repeated exactly as I had hoped. Looks like I should probably come down a tenth but she’s dialed. Praying for some good weather soon

 

[MilSpecOkie]

Did some searching and couldn’t find it but do I need a special stem for the 109 ELDMs? Running the RCBS match master set now

I don’t think so. I used the one it came with when I was running 109s.

 

[xocyrusx]

Thank you!

 

[fgregory]

HELP HUGE SHOULDER BUMP​

Happy holidays everyone. I wanted to ask if anyone has any insight with what I am seeing that has me stumped.
I got my 6GT from GA Precision spring 2022 and what an amazing rifle. So far I have loaded and shot 100 new alpha brass for break in process with 105 Nosler RDF because it’s what I had. By the way 34.7 Varget gets barely over 3000 fps and about .2 MOA.
The issue is now I go to reload those original once fired brass and the shoulder bump is HUGE. I have tried two good die’s with Same result. Also using zero press.
Fired brass measures from 1.3040 to 1.3100 with SAC comparator
— When I run SAC die to contact shell holder I get .031 bump
— When I run Micron die to contact shell holder I get about .026 bump
I unscrewed the SAC die until I got the proper .002 shoulder bump and then measured gap between shell holder and bottom of die body and as expected it was about .032
THATS A WHOLE LOTTA BUMPIN’
not sure I have seen that much bump in contact with shell holders for other cartridges. The guys over at SAC are incredible to work with way beyond generous and offered to help troubleshoot so I gave them some examples of fired brass and my die to troubleshoot.

Are you all seeing this much bump when contacting the shell holder? Could something be wrong with my chamber?

Any help I would be thankful for
Thanks

Ok I have root cause!
First SAC is amazing, they took my once fired brass and determined rifle had too much headspace and because they work with George at GA Precision sent him a note with the measurements. I offered to pay SAC and they refused saying just wanted to help their customer!
I contacted GA Precision told them the deal and next thing you know I get a call from George. He said not sure what happened but wanted to receive it and check it himself and they would pay for shipping. GA Precision then calls me when they get my rifle and next day George calls me again and says that it did have excessive headspace the exact amount that is the difference between an Impact action and my Defiance action. His Smith setting barrels that day did a bunch of Impact first and didn’t make the adjustment when he put barrel on my Defiance. I told George that I appreciated it getting done so fast and he told me that it doesn’t happen often because of their quality processes but if they get a warranty item in, it goes first and offered to send me new brass to replace what I ruined troubleshooting this issue.

This is amazing service from both GAP and SAC. This is why I will work with both of them again every chance I get and you should too.

If GAP and SAC is reading this, very appreciated guys, class acts!

Fred

 

[4O6shootist]

@fgregory did they get you a brand new barrel, or chop your tenon and re-thread/chamber with proper headspace? Clearly GA machinist didn't verify headspace with gauges or this would been found immediately. That's a fail!

 

[drglock]

Anyone here running Reloader 15.5 and notice the difference in felt recoil or am I losing my mind. My setup now is Impact in a Foundation with a 1-7 proof competition contour running 109 ELDM’s, 33.9 RL15.5 at 2880. Last year same action and Foundation but with a 1.75 MTU and 32.8 Varget at 2840 with 109 ELDM’s. I’m not saying the recoil felt is more but just feels snappier if that makes since.

 

[John Glidewell]

Yes. Different burn rate. Different recoil impulse. 15.5 is all we run in them.

 

[Roksliding]

Anyone here running Reloader 15.5 and notice the difference in felt recoil or am I losing my mind. My setup now is Impact in a Foundation with a 1-7 proof competition contour running 109 ELDM’s, 33.9 RL15.5 at 2880. Last year same action and Foundation but with a 1.75 MTU and 32.8 Varget at 2840 with 109 ELDM’s. I’m not saying the recoil felt is more but just feels snappier if that makes since.

This probably doesn’t help, cause I don’t shoot 15.5 particularly, but your not loosing your mind. (For the first few shots after the powder change) I can tell a difference in recoil impulse when changing types of powder… after shooting the new powder for a “few” rounds the feeling dissipates, and then it’s just recoil again.

 

[ghostrider_OneOne]

Looking for some insight regarding a GAP PPR 6GT. I bought a PPR from GAP a little over a year ago. LOVE it! So much I decided to get another one. One for matches, one for training. My PPR in a serial number 300's last year of the tenacity action. I found a used PPR also tenacity action serial number 100's. When I bought my rifle I had another barrel spun up for it from GAP knowing I would burn through it and need another (side note I got 3100 rounds before significant loss of speed and groups opened up). So I'm at 540 rounds on second barrel. It hammers, just like first one. My loads are the same, nothing needed to change. So when I got the second rifle I was hoping things would be the same or close for reloading purposes since actions and barrels were the same (both tenacity, both bartlein 7.2 to 1, 26". The second rifle also hammers. I've very happy with it! What I can't figure out is why it is so much slower. The other rifle has app 600 rounds on it. I believe that to be true. I stripped barrel with Iosso and bore scoped it, beautiful condition! I did same to my second barrel on original rifle because I wanted to compare data and have an equal starting point. I generally shoot three loads. I will list them below and the differences. I will say it is clear I am going to have to do a completely new load development for second rifle, ES and SD's are just not even close to my acceptable range or that of first rifle. My guess is may be the second rifle had a larger free bore? Not sure why this rifle is over 100fps slower over almost all loads. It hammers, no doubt! I shoot a 3" group at 600 yards with Varget and 112 MBs, rifle is fantastic just different. Any ideas on what the difference is? I'm guessing it is obviously the barrel cut with different reamer but didn't realize (maybe wrong) they used more than one reamer on PPRs.
Loads:
112MB 37.3 RL16 alpha brass CCI450
original PPR 2908fps ES 16 SD 5.1 for 10rounds
2nd PPR 2802fps ES 35 SD 10.2 for 10rounds

105hybrids H4350 35.6 horn brass S&B primers
original- 2892fps ES 15 SD 4.6 10rounds
2nd- 2788fps ES 40 SD 12.4 10 rounds

112MB Varget 34.5 alpha brass CCI450
original- 2924fps ES 20 SD 6.3 10rounds
2nd- 2828fps ES 26 SD 8.6 10 rounds

Any ideas on cause of different speeds?

 

[4O6shootist]

Dbl post, please delete.

 

[4O6shootist]

Looking for some insight regarding a GAP PPR 6GT. I bought a PPR from GAP a little over a year ago. LOVE it! So much I decided to get another one. One for matches, one for training. My PPR in a serial number 300's last year of the tenacity action. I found a used PPR also tenacity action serial number 100's. When I bought my rifle I had another barrel spun up for it from GAP knowing I would burn through it and need another (side note I got 3100 rounds before significant loss of speed and groups opened up). So I'm at 540 rounds on second barrel. It hammers, just like first one. My loads are the same, nothing needed to change. So when I got the second rifle I was hoping things would be the same or close for reloading purposes since actions and barrels were the same (both tenacity, both bartlein 7.2 to 1, 26". The second rifle also hammers. I've very happy with it! What I can't figure out is why it is so much slower. The other rifle has app 600 rounds on it. I believe that to be true. I stripped barrel with Iosso and bore scoped it, beautiful condition! I did same to my second barrel on original rifle because I wanted to compare data and have an equal starting point. I generally shoot three loads. I will list them below and the differences. I will say it is clear I am going to have to do a completely new load development for second rifle, ES and SD's are just not even close to my acceptable range or that of first rifle. My guess is may be the second rifle had a larger free bore? Not sure why this rifle is over 100fps slower over almost all loads. It hammers, no doubt! I shoot a 3" group at 600 yards with Varget and 112 MBs, rifle is fantastic just different. Any ideas on what the difference is? I'm guessing it is obviously the barrel cut with different reamer but didn't realize (maybe wrong) they used more than one reamer on PPRs.
Loads:
112MB 37.3 RL16 alpha brass CCI450
original PPR 2908fps ES 16 SD 5.1 for 10rounds
2nd PPR 2802fps ES 35 SD 10.2 for 10rounds

105hybrids H4350 35.6 horn brass S&B primers
original- 2892fps ES 15 SD 4.6 10rounds
2nd- 2788fps ES 40 SD 12.4 10 rounds

112MB Varget 34.5 alpha brass CCI450
original- 2924fps ES 20 SD 6.3 10rounds
2nd- 2828fps ES 26 SD 8.6 10 rounds

Any ideas on cause of different speeds?

Are both 236 bore? Perhaps the new barrel is 237 bore and reduces psi/velocity? Your speeds on new pipe do seem slow. Even comparered to my 7.5tw 237 bore barrels.

 

[ghostrider_OneOne]

Are both 236 bore? Perhaps the new barrel is 237 bore and reduces psi/velocity? Your speeds on new pipe do seem slow. Even comparered to my 7.5tw 237 bore barrels.

Really don't know what the bore size is. Just assumed since both were done by GAP same reamer was used, but don't know that for a fact.

 

[PinesAndProjectiles]

Really don't know what the bore size is. Just assumed since both were done by GAP same reamer was used, but don't know that for a fact.

They may have used the same reamer, but bore size is completely different.

Bore size is essentially the diameter of the barrel.

Are both barrels made by the same company?

 

[ghostrider_OneOne]

Both barrels are Bartlein same twist same length.

 

[30cal user]

check headspace and check distance to the lands vs each other

 

[ShootnFool8]

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.

 

[davere]

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.

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

 

[Swampbug]

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.

 

[Swampbug]

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.

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.

 

[Dooby]

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.

 

[ShootnFool8]

Thanks for the info gents.

 

[inertia]

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.

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.

 

[Niles Coyote]

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.

 

[mr.quick]

26" proof, .170 alpha reamer, alpha brass, FGMM primers and 110 Atips. View attachment 8063098
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

 

[Cascade Hemi]

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.

 

[mr.quick]

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 .

 

[giumau1]

@Niles Coyote you deserve a riteintherain kit for your notes. thanks for sharing. Feelin' cold for ya.

 

[Cascade Hemi]

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 .

That's understandable. This is a colder year than normal for this area and, I think, many other areas.

 

[Sinful Silence]

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 .

 

[357Max]

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.

 

[Sinful Silence]

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 .

 

[Niles Coyote]

@Niles Coyote you deserve a riteintherain kit for your notes. thanks for sharing. Feelin' cold for ya.

My pen kept freezing on me

 

[Varmint7]

what barrel life are guys getting now that's it been out a bit?

My buddy said his took a dump at ~1000-1200rds he was pretty bummed.

another said he pulled his at 1800. but only because it was a good time to switch to his second GT barrel. he said it was still shooting well

I pulled my GT barrel after 2,300 rounds and it was still shooting well.

 

[Dooby]

Bartlein 400MODBB currently @ ~3300rnds
Avg velocity - 2880fps
H4350 @ 36gr
Still shooting <1/2" @ 100yds
Will probably pull bbl at 4k rnds

 

[ghostrider_OneOne]

I pulled my GT barrel after 2,300 rounds and it was still shooting well.

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

 

[Varmint7]

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.

 

[Jakeweb09]

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

 

[ghostrider_OneOne]

Finished break in for new barrel and was hopeful my previous load would work.
Here are the results. GAP PPR
Benchmark 26" 7.5twist straight jacket chambered.
RL16 37.3 Alpha brass CCI450 112MB
200yard zero/steel

Eat your heart out F Class!

 

[ghostrider_OneOne]

Barrel now at 145 rounds. Gonna put it on ice for matches!

 

[mr.quick]

wow look at that ES, not to shabby

 

[Bater]

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?

 

[DLS]

The Remington 71/2 ‘s have a hard cup just like the 450’s.
I would give them a try as they may surprise you how well they do.

 

[drglock]

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

 

[CK1.0]

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:

 

[MilSpecOkie]

You windage was on!