Barrel twist rate for 125gr bullets and and less

[Twitch24]

First time post long time guest. Here is what I have done and I do hope that I did not make a mistake. I have ordered from MGM a 1 in 9 twist custom select barrel in a 21 inch tamper for a G2 Contender. I do not have any plans to shoot any bullets over 125 grains and will most likely stick with the 123 gr. SST if the set-up works for the particular bullet and barrel. I plan on hunting whitetail deer with this set-up. Will the 1 in 9 twist work with what I am looking to do???? I have purchased so far the 120 gr Ballistic Tip, Hornady 123 gr and the Barnes 100 gr TTSX in 100 gr. Information and opinions would be greatly appreciated. Thanks Twitch24

[JASmith]

I just ordered an 18" Bullberry Encore and had the same struggle -- their standard twist rate is 9" and I would have had to wait a few months to get a 9-twist.

I looked at calculated stability factors using the calculator available at JBM Ballistics and was pleasantly surprised to find that most of the bullets had comfortable stability factors. There might be some marginal stability with the 120 gr and heavier lead-free as well with very streamlined 130gr and heavier classic or bonded bullets.

The first step should be to run a box or so of factory 123gr SST through the rifle at 100 yards and at the longest range you plan to shoot at. If you are happy with the results, you are good to go with your plan!

Given that you're happy with the 123 gr SST factory load, one might ask "Why mess with something that works?" If you are like most of us the reloader's itch is darned near terminal, so looking at and trying other bullets is inevitable!

Looking at pages 33 & 34 of Volume II of the 6.5 Grendel Reloading Handbook tells us that you will be good to go with 120 gr bullets for even the heaviest deer (330 lb) but that you can use 100 gr bullets for the lighter ones typically found in the southern tier states (CA, AZ, NM, TX, GA, AL, FL). You should be pleasantly surprised to find that the 100 gr Nosler Partition will also work for the heaviest deer while the 100 TTSX or 125 gr partition gives the rifle an Elk capability.

[Bwild97]

A 1-9" twist will be absolutely perfect! I have been pushing 130g Bergers, 142g SMKs out of my 1-9"twist, 24" barrel for quite some time now with excellent accuracy, and no keyholes.

[VASCAR2]

I've shot 85, 90, 100, 120, and 123 grain cup n core bullets from Sierra, Nosler and Speer. I have also shot Barnes 100 grain TTSX in both my 1:9 twist barrels and all produce very satisfactory results. I have some 125 grain Nosler partitions but haven't loaded them. I know the 264 Win mag used 1:9 twist and I like my 1:9 twist 6.5 Grendel barrels.

[LRRPF52]

With longer barrels, the 1/9 twist works well for stability factor. For a 16", I think it makes sense to use a 1/8 or tighter twist.

For 14.5" and shorter, AA used 1/7.5 twist I think. Twist rate, barrel length ( or more so velocity), and bullet shank length combine to determine stability.

[Drifter]

Interesting info from Bill A posted on a previous thread:

When we were first working on the Grendel we followed what everyone said about 6.5 calibers and made the barrels with 8 twist rifling. Some barrels would shoot but more often than not the groups were open and the guns were tempremental. One of the very early test rigs had run a 9 twist and it actually shot well despite a less than optimum chamber so out of frustration we ignored conventional wisdom and build some 9 twist units at 24" and 20" barrel lengths. The change in accuracy for the group as a whole was unquestionable. Subsequent production of 9 twist barrels has proven that this is optimum for the caliber.

One of the contributors to the 9 twist is actually the Grendel itself. Pressure limits the ability to slug the bullet to the grooves and the case capacity holds the round to lighter bullets. The 168 grain roundnose nickel steel projectiles are simply not a consideration any more than the 142 and 155 grain SMKs

We have tested barrels as short as 14.5" in 9 twist (not recommended use 1:7.5 this short) with projectiles up to 152 grains and both accuracy and stability are maintained. Equally we have run 9 twist barrels out to 1600 yards (12" group) and the round remains stable and it would appear accurate through the transition velocity. Longer 8 twist barrels often demand velocity reduction for best accuracy

It is our conclusion that the 9 twist offers the best solution for the Grendel for barrels of 20" and longer while the 18" and shorter barrels thrive on 7.5 twist.

Link to source: http://www.65grendel.com/forum/showt...est-twist-rate

[adamjp]

I recently built a bolt Grendel and went with a 1:10 twist barrel as I didn't see myself shooting bullets over 125gn in weight.

I wish I had gone with a 1:9 as the Lapua 108gn Scenars (and others in this class) will not stabilise in the 1:10 at 100m. They are stable at 200m but the group size isn't terribly good.

Go with a 1:9.

[Twitch24]

Thanks for all of the information provided. From the replies it looks like I made the right choice. Since I am going to be utilizing the set-up for hunting, I wanted to get the maximum energy and speed out of the bullet/barrel combination out to about 300 yards. I now feel a lot better knowing that the 1 in 9 should do what I want. THANKS AGAIN FOR THE INFO. Twitch 24

[mickey]

I have had excellent results on South Texas White tail, with 100 gr. Hornady Speer point in my 600 rem. 18 inch barrel. 45 gr. 4350, this is a hot lode, punching through 1/2 inch steel at 100 yards.
Rem 600 .222, 18 .inch barrel with Hornady match bullet, this is the one with the four slices on the tip, which come together as a small , small hollow point. I don't remember the bullet weight or powder grains (67-87 ?) they brought down White tail. If they had made a Left hand 600 Rem I would build a 6.5 Grendel for Belle.
Regards Mickey