Any 6.5 twist .223 shooters in here?
- Thread starter Shiyfire
- Start date
30” 6.5t, PAC Nor, .169” freebore, 90 gr VLD’s, 23.5 grains of H 4895, .008” jam
Ned Ludd
Silver $$ Contributor
The 6.5-twist barrels will obviously shoot with 90 VLDs. However, there are a couple considerations to going with a twist rate that fast. The first is, you don't need it at most shooting venues. A 7.0 twist will net you almost the full intrinsic BC; according to Berger's Twist rate calculator, a 7.0-twist barrel pushing the 90s at 2830 fps at 500 ft elevation and 65 degrees is only giving up about 2%. As the elevation/temperature increase, that only gets better.
The second issue with a faster than 7.0-twist barrel concerns jacket failures. These seem to occur more frequently with barrel twists faster than 7.0. They also seem to be exacerbated by high temperatures. In a different thread, it has been suggested that frictional heat at the jacket/rifling land contact points causes the surface of the lead core to melt. When combined with a small crease or tear in the jacket, molten or vaporized lead will exit through the hole, creating "comet tails" around the bullet holes on the target face. This event seems to be associated with, or at least, preliminary to, jacket failure. There are ways you can try to minimize the possibility of jacket failure, such as running a couple wet patches of Kroil followed by a few dry patches after each course of fire to minimize carbon fouling, moly-coating your bullets, using a powder/load that tunes in at slightly lower velocity than H4895 in a 30" barrel, using a more "jacket-friendly" land/groove shape such as 5R rifling, etc. Nonetheless, losing a jacket in most F-Class competitions will put you totally out of the running, so it's not something you want to have happen, even once. Not everyone running a faster than 7.0-twist barrel has experienced this problem, so there are clearly other contributing factors we don't as yet fully understand.
Shiyfire - I'm not trying to scare you off about the 6.5-twist barrel here, just bringing up the considerations for other readers that might be thinking of running a twist rate of less than 7.0 with the 90 VLDs. With your 22" barrel length, I doubt you will be approaching the velocities with 90 VLDs (2800+ fps) achieved from 30" barrels where this issue seems to be more of a problem. With the appropriate long freebore (>/= 0.169") and COAL (>/= ~2.630"), Quickload results suggest that with a 22" barrel, you might find accuracy nodes somewhere in the neighborhood of ~2575 fps with H4895 and ~2550 fps with Varget. Those values may seem a little slow as compared to 30" barrel velocities, but are actually pretty impressive for a 22" pipe with such a heavy bullet, given that most commercial 77 gr SMK loads only have predicted velocities of 2600-2650 fps from a 24" test barrel. I'm guessing the faster twist rate won't be an issue with a 22" barrel. Have fun with it!
The second issue with a faster than 7.0-twist barrel concerns jacket failures. These seem to occur more frequently with barrel twists faster than 7.0. They also seem to be exacerbated by high temperatures. In a different thread, it has been suggested that frictional heat at the jacket/rifling land contact points causes the surface of the lead core to melt. When combined with a small crease or tear in the jacket, molten or vaporized lead will exit through the hole, creating "comet tails" around the bullet holes on the target face. This event seems to be associated with, or at least, preliminary to, jacket failure. There are ways you can try to minimize the possibility of jacket failure, such as running a couple wet patches of Kroil followed by a few dry patches after each course of fire to minimize carbon fouling, moly-coating your bullets, using a powder/load that tunes in at slightly lower velocity than H4895 in a 30" barrel, using a more "jacket-friendly" land/groove shape such as 5R rifling, etc. Nonetheless, losing a jacket in most F-Class competitions will put you totally out of the running, so it's not something you want to have happen, even once. Not everyone running a faster than 7.0-twist barrel has experienced this problem, so there are clearly other contributing factors we don't as yet fully understand.
Shiyfire - I'm not trying to scare you off about the 6.5-twist barrel here, just bringing up the considerations for other readers that might be thinking of running a twist rate of less than 7.0 with the 90 VLDs. With your 22" barrel length, I doubt you will be approaching the velocities with 90 VLDs (2800+ fps) achieved from 30" barrels where this issue seems to be more of a problem. With the appropriate long freebore (>/= 0.169") and COAL (>/= ~2.630"), Quickload results suggest that with a 22" barrel, you might find accuracy nodes somewhere in the neighborhood of ~2575 fps with H4895 and ~2550 fps with Varget. Those values may seem a little slow as compared to 30" barrel velocities, but are actually pretty impressive for a 22" pipe with such a heavy bullet, given that most commercial 77 gr SMK loads only have predicted velocities of 2600-2650 fps from a 24" test barrel. I'm guessing the faster twist rate won't be an issue with a 22" barrel. Have fun with it!
Last edited:
I have run a bartlien 22” 6.5tw 223 match chambered barrel on my r700 target rifle for 4+ years. I’ve shot 60-90gr pills through it with no issues. Recently I tried some of the lighter 60 tipped smk’s, after tumbling using super moly, and they shot extremely well. Never had any problems with jacket separation although I have heard it can be an issue, especially with Nosler and Barnes bullets since they have a slightly thinner jacket. Personally I don’t shoot Nosler brand, I’m more of a hornady, berger, sierra man.
The one thing I was advised to do, by a fellow shooter, was use moly on the lighter weight bullets to help reduce friction, especially during the summer when temps are above 80F. Since I do a fair amount of varmint shooting in the summer months with 60-70gr pills, I’ve always heeded his advice and tumbled my rounds in moly prior to loading. Don’t know if the coating helps, but it certainly doesn’t hurt, especially when 300 or more rounds a day through one rifle are the norm. Not only does it reduce fouling, but it also gives about a 20fps boost over non coated rounds loaded to same specs. Rifle currently has 2100+ rounds through it and no measurable change in accuracy.
In my experience stay in the 69-80gr range of bullets for under 400y and you’ll be very happy with the results. The 90s I only use for longer ranges, 500+, as I think they take a fair amount of distance to settle.
Here’s the short list of bullets I’ve used in the 6.5tw barrel:
100-300y
60 TMK
62 SC
200-400y
68 BTHP
69 SMK
69 TMK
70 VLD
73 VLD
73 ELD
75 ELD
400-600y
77 SMK
77 OTM
80 ELD
80 SMK
80 VLD
500y+
90 VLD
90 SMK
Good luck with your new pipe.
The one thing I was advised to do, by a fellow shooter, was use moly on the lighter weight bullets to help reduce friction, especially during the summer when temps are above 80F. Since I do a fair amount of varmint shooting in the summer months with 60-70gr pills, I’ve always heeded his advice and tumbled my rounds in moly prior to loading. Don’t know if the coating helps, but it certainly doesn’t hurt, especially when 300 or more rounds a day through one rifle are the norm. Not only does it reduce fouling, but it also gives about a 20fps boost over non coated rounds loaded to same specs. Rifle currently has 2100+ rounds through it and no measurable change in accuracy.
In my experience stay in the 69-80gr range of bullets for under 400y and you’ll be very happy with the results. The 90s I only use for longer ranges, 500+, as I think they take a fair amount of distance to settle.
Here’s the short list of bullets I’ve used in the 6.5tw barrel:
100-300y
60 TMK
62 SC
200-400y
68 BTHP
69 SMK
69 TMK
70 VLD
73 VLD
73 ELD
75 ELD
400-600y
77 SMK
77 OTM
80 ELD
80 SMK
80 VLD
500y+
90 VLD
90 SMK
Good luck with your new pipe.
What is your OAL with .169 FB and the 90 vld? Thx
Ned Ludd
Silver $$ Contributor
COAL = 2.641" @ .018" off the lands, chamber cut with PTG's 223 Rem ISSF reamer, 0.169" freebore. Typical COAL values with such a setup will depend on seating depth, how eroded the lands are, and the average length of the specific Lot# of 90 VLDs, but will usually be between about 2.63" and 2.65".
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.