Thinking of a gain twist 6.75 to 6-1 barrel just for these bullets...? Anyone have any firsthand experience with these bullets? It will be on an Improved 220 Swift. Has anyone determined an optimum speed for accuracy with 90 gr bullets? I imagine I could push them to their limits with the improved Swift. Thanks for any input.
Optimum barrel for 90 gr VLD .224 bullets
- Thread starter Paul Arey
- Start date
Ned Ludd
Silver $$ Contributor
I've run them for some time in a .223 Rem at ~2850 fps from a 7-twist barrel. According to Berger's twist rate calculator, at 65 degrees and 1000 ft elevation I'm giving up approximately 2% of the theoretical maximum BC (Sg - 1.45). Believe me, they shoot just fine. If you can push them to at least 3050-3100 fps, the Sg value would go up to about 1.49. I have read some reports of people pushing the 90s in those velocity ranges using 7.2 twist barrels, and they seemed satisfied. I wouldn't go under 7.0-twist for a couple reasons. First, if they shoot fine out to 1000 yd at 2850 fps from a .223 Rem, there's no real need to do so in your setup. Second, there have been a few reports of jacket failures shooting these bullets at .223 Rem velocities. I think the jury is still out on the exact cause (there may be several different causes). However, there's no reason to tempt fate by running an uber-fast twist barrel when a 7-twist barrel should do everything you want.
Agree with above post. If you wonder why Berger recommends a 6 twist, I'm assuming it's because some service rifle shooters (ar-15) with 20" barrels are shooting 90 VLD's and need that twist rate to stabilize.
I had a 6.5 TW then when I re barreled, went to a 7 shooting at sea level with no issues.
A friend has been trying gain-twist barrels of various configurations (we have a friend who makes barrels and has the shop to make it happen). He is having no luck with them. The folks successfully running .223s for Palma are using 7" twist barrels 30" long for 2800+ (as mentioned above). Some have had excellent results at 1000 yds. in Palma matches.
I use a 1-6.7 Bartlein and it shoots amazingly well.
Kurz
Silver $$ Contributor
Having a buddy in the barrel making business can be a significant boon when I'm in need of a special twist or bore size. It can also lead to endless questions which I think require resolution by making a new rifles/barrel combination. Testing is an addiction.
The Swift has always intrigued me as a cartridge simply from all the anecdotal information derived from stories told by shooters far older than I am. It got even more intriguing when the conversations turned to 'improving' the case. I decided that I really should have an improved Swift barrel just to see... I started it at 30" in order to allow for the inevitable set backs, but we set the twist rate at 1:8" after several runs of calculations based on the 90 grain VLDs and the expected velocities. Because we were in the area of 3,500 fps., the twist rate held true for these bullets out to 1,000 yards. However, the changes in powder with resulting loss of velocity played havoc with the stability when we fell below 3,400 fps. In the area of 3,200 fps approximately, the 1:7.5" twist was suitable but anything below 3,100 fps. really would do better with the 1:7" because it has a safety buffer for stability.
If you are planning on using the Swift Improved at the uppermost velocities, I see no reason whatsoever to consider your choice of a fast twist rate let alone the gain twist. In fact, I would be thinking more along the lines of 1:7" to 1:7.5" depending on your need for speed. I run a 4-groove standard configuration barrel currently with excellent accuracy. I don't think a 5R will compromise the accuracy much, if at all, but the 4-groove has worked well for me.
If high velocities don't interest you then select another, more efficient cartridge in the velocity range you want to use.
Regards.
Thanks for the info. There are so many variables to think about when trying to decide what route to go on a barrel for this gun. My thoughts were if the bullets shoot good and hold together at those higher speeds I will probable go that route. I really don't have the time to do a bunch of actual hands on R&D work with different barrels myself. Thus my inquires here to check around out there to see whats working for other folks. I had been told When you start pushing any bullet at 3400 fps or more and the bullet RPM is 300,000 or more with a barrel length that is over 28 inches you may be in the danger zone of causing excessive copper/carbon fouling and throat/barrel condition from heat & friction...? Did you actually shoot 90 gr VLD in 3500 fps range successfully with good consistent accuracy...? I can't get any data from anyone in that speed range...! I'll be running two guns on dog towns and I'm planning on this being my reach out there and touch em gun for the long long range shots, so not going to be shooting it as much as my regular intermediate range gun, another 1-14 Improved Swift gun shooting 52 grainers. Thanks again
Could you share what speeds your getting your good consistent accuracy with and are you shooting 90 VLD bullets..? That would really help me out. I can really really pour the coal to those 90s with my Improved Swift if I want to, I'm trying to decide on what speed I'm going to try running the 90s at right now so I can pick the optimum twist.Thank for any help
I have one in 1-7" twist and with 35.5 grs. H4350 it's death on coyotes a long ways out!! The 90 gr. Sierra is all I shoot in it! Coyotes ain't the only thing it wipes out....PRONTO! In 22/250 caliber.
Rem M700 Heavy barrel by Sharps Man, on Flickr
Rem M700 Heavy barrel by Sharps Man, on FlickrKurz
Silver $$ Contributor
The short answer is yes.
I had managed to get a case of Re-26 a while back before the supply dried up so that's what I was using for powder. It was 3500 fps and change. Very consistent and accurate at 600 yards which is where I stopped testing before a PD shoot. This is a 30" barrel in a 6" barrel block in an MBR stock. We used outline targets of prairie dogs and all shots stayed inside the body profile. This was prime time testing on the desert, early morning, virtually no wind, great light on the target.
Even with the 90 VLDs, the wind will bite you hard if you don't watch it.
For entertainment though, I bring the .416 Rigby along to use for volley practice. Loaded with 420 grain Cutting Edge bullets, no prairie dog is safe!
Regards.
You happen toknow what fps that load gives you...? ThanksI have one in 1-7" twist and with 35.5 grs. H4350 it's death on coyotes a long ways out!! The 90 gr. Sierra is all I shoot in it! Coyotes ain't the only thing it wipes out....PRONTO! In 22/250 caliber.
I built a 220 swift with a 30" McGowan 7 twist. I don't remember the exact load but it was H4831 and 3050 fps was my best node. There was still more to go but I was trying to a thousand rounds out of the barrel so I didn't want to push it to hard. If I ever get the barrel set back I would go improved just to slow down the brass flow.
Don't have a clue! Coyotes don't know either!
I am just a bit confused as to why the majority of the competition shooters that are shooting 90 vlds are using around 1-7+ twist for the .224 Berger 90 VLDs when Berger's Twist rate stability calculator indicates marginal stability for that twist rate...? I see barrel length doesn't seem to be part of the stability calculator formula does that have something to do with it? Is Bergers calculations based on a particular short barrel length...? That part just has me a bit confused why the pros are choosing the slower twist rate as their preference..? They typically use 30 inch barrels and seem not to be having stability problems.
Ned Ludd
Silver $$ Contributor
Paul - the stability is not "marginal". Years ago, when Bryan Litz came out with his first book, "Applied Ballistics for Long-Range Shooting", he advocated using a barrel twist rate that would produce a gyroscopic stability coefficient (Sg) of at least 1.4. Based upon further testing and analysis, he now advocates a twist rate that produce an Sg of at least 1.5. Berger's twist rate calculator utilizes the Sg of 1.5 value in it's determination of how much of the theoretical maximum BC a bullet will retain in a given barrel twist rate, velocity, atmospheric conditions, etc. In these calculations, velocity is critical, barrel length is not, because different loads can produce a wide range of velocities out of any given barrel length.
Shooting a bullet with an Sg of 1.2 doesn't mean it will fall out of the sky. In fact, an Sg of greater than 1.0 (in theory) will keep the bullet stabilized, although I wouldn't try that knowingly. A twist rate that produces an Sg of 1.5 or greater means that the pitch and yaw of the bullet as it exits the bore is minimized, thereby allowing it to "settle down" in the shortest possible distance, resulting in the maximum BC, or lowest drag, the bullet's shape is theoretically capable of.
Stability for a bullet of given length at a given linear velocity requires a given spin rate. Because linear velocity decreases at a much greater rate than rotational velocity (i.e. spin rate), bullets become more gyroscopically stable the farther they fly. This is because at longer distances they're spinning much faster relative to their linear velocity than they are when they exit the bore. Shooting a bullet out of a slightly slow twist rate that gives an Sg of less than 1.5 doesn't mean it will keyhole at the target. It simply means that the increased yaw/pitch as it exits the bore and during the early part of its trajectory will make it behave as though its BC were slightly lower than the actual value due to the increased drag during that time. What that effectively means is that the bullet will require more elevation to reach the same distance, and be influenced more strongly by the wind, both of which are directly related to the "effective" BC of the bullet. I'm giving up about 2% of the theoretical maximum BC of the 90 VLD by running it out of a 7-twist barrel (Sg = 1.45 at 2850 fps, 1000 ft elevation, 65 degrees F). However, I also point the bullets, which gains back the lost BC plus a tick more. A 2% loss is really not a huge amount, whereas as a loss of 5-7% or more of the theoretical maximum BC would start to become noticeable. That kind of BC loss would be analogous to moving down one weight class of bullet, which most of us would not choose to do.
If you really wish to preserve 100% of the theoretical maximum BC of the 90 VLDs, you can have a 6.8- or 6.7-twist barrel cut. There is nothing wrong with that approach and most of the major barrel manufacturers can cut any twist rate you want. However, the lead time for receiving such a barrel might be as long as 8-12 months. In contrast, there are a number of barrel suppliers that commonly keep 7-twist barrels suitable for F-TR rifles in stock. Further, there have been reports of jacket failures with some of the 90 VLDs. As far as I can tell, the underlying cause(s) of this are not completely clear. However, it is certainly possible that faster twist rates might exacerbate such issues. For that reason, it is not absolutely necessary to use a 6.0- or even 6.5-twist barrel with the 90s. There may not be anything wrong with that approach, but it is not essential for stability. If you want the full BC without using a faster-than-necessary twist rate, simply special order a 6.8- or 6.7-twist barrel and then wait for it to come in. Otherwise, it is much more likely that you will find a suitable 7-twist barrel in stock somewhere that you can have in-hand within days, rather than months.
Last edited:
I currently use a Bartlein 6.7 twist and shoots amazing. With that said I ordered my first BRUX barrel in a 7 twist.
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.