1/7.5 or 1/8 twist 18" 6.5 Creedmoor?

[m6z]

1/7.5 or 1/8 twist 18" 6.5 Creedmoor?

Noticed that a few places have the option of 1/7.5 and 1/8 on 6.5 barrels. Any benefit of going with the faster twist on the 18" barrel?

I plan on shooting factory ammo, I figured I'd start with the Hornady 140's or Prime 130's. Suppressed 100% of the time.

 

[VegasHKShooter]

If you’re shooting ALL 130’s and 140’s, is day no. I have 2 6.5 CM. Both are 1/8. One is a Bartlein on my GAP-10, the other is a Brux, on my A.I.. Both will shoot absolutely lights out with 140’s. Now, IF you were going to venture into the newer 150’s that are popping up, I’d probably look at the 1-7.5. For what you describe, 1/8 is likely the ticket.

 

[buskin]

I have a 1/8 twist with a longer 24" barrel but it definitely shoots the 130's and 140's fine as well. As stated above, unless you plan on shooting heavier bullet weights, the 1/8 works.

 

[davsco]

when i emailed hornady a year ago, they said their recommended twist for their ammo (140-147g) was 1-8.

 

[molzarella]

If you’re shooting ALL 130’s and 140’s, is day no. I have 2 6.5 CM. Both are 1/8. One is a Bartlein on my GAP-10, the other is a Brux, on my A.I.. Both will shoot absolutely lights out with 140’s. Now, IF you were going to venture into the newer 150’s that are popping up, I’d probably look at the 1-7.5. For what you describe, 1/8 is likely the ticket.

Agree.

 

[padom]

1:8

 

[m6z]

Thanks guys. I will stick with the 1/8 twist.

 

[Hunt]

Some are looking at the 7.5 twist to be able to shoot the new Sierra 150 gr Matchking. If you aren't shooting these, you'll be fine with the 8 twist which was the standard for the last few years. The other question to ask yourself is whether then 150s will allow enough powder in a 6.5CM to drive them at their needed velocity.

 

[ra2bach]

jumping on here - what barrel length for 6.5 - 20 or 24?..

 

[BullzeyeNJ]

I think 24” is the ideal length as far as velocity output but can get a little cumbersome if using a suppressor. If using a can then I would go a little shorter.

 

[VegasHKShooter]

I’d definitely go longer. No reason to cut the legs off of a 6.5 by going short. If you’re not running a can, go 24”. If you’re going to suppress it, go 22”. The can will likely give you back the small velocity loss.

 

[Lowlight]

When you go short, you can add twist, the extra spin helps with the longer ranges when you lose velocity.

It’s not about heavies with a short barrel, because your velocity is down. I am currently shooting a 20” 1-7 twist and it works, even with 130. My current load with 136 Scenars is 2857fps and it hammers.

The learning experience is that little bit extra spin helps when your velocity is down. If you overspin it and keep your velocity high you risk damaging the bullet.

But a 1-8 works too I have an 18” 6.5CM with a 1-8 it works.

 

[stello1001]

Do a gain twist instead, Frank was commenting not too long ago in a different thread how these barrels with a gain work. These help with being able to stabilize a much wider range of bullet weights as well as giving you the benefit of burning more powder before running into pressure issues. Since you are going short, I would see this as a benefit because with running a hotter load, you'll be able to compensate for the velocity loss that comes with shorter barrels vs longer barrels. Just some food for thought.

 

[Lowlight]

Gain Twist is the right answer if you can swing it, order a 8-7 or 8 to 7.5 as Bartlein recommends a 3/4 gain, I would think 8-7 is good, my AI 260 is 8.25 to 7.75

 

[BallisticPrimate]

Slightly off topic here but is it the accepted standard that lighter bullets perform better in shorter barrels across the board? Does the same rule apply to a .308 for example? With the 6.5's it seems that you don't get a huge BC drop off going from 140's to 130's, but in a .308 the 170gr + class of bullets appears to have significantly better BC's than the 150's for example - though I do need to look more closely at the specifics

 

[el_cazador713]

I'd like to hear about the bullet weights as well. I've been thinking of building another 6.5 with a 20" barrel and would still like to shoot the 140s or 143s but it seems most are recommending a little lighter bullet

 

[stello1001]

I'd like to hear about the bullet weights as well. I've been thinking of building another 6.5 with a 20" barrel and would still like to shoot the 140s or 143s but it seems most are recommending a little lighter bullet

They're probably recommending lighter pills just so you can get them up to speed but nothing wrong with shooting 140s at 2500 to 2700 if you're not going to stretch them out to long distances. With a gain twist barrel, you can load just a bit hotter before running into pressure issues so it's probably something to consider. I'm not talking from experience because I have never used a gain twist barrel but I say this because of a recent conversation we had in a new thread a few days ago and Frank was able to comment on this and back this up. So don't take my word, take his lol...

 

[Ledshot0331]

When you go short, you can add twist, the extra spin helps with the longer ranges when you lose velocity.

It’s not about heavies with a short barrel, because your velocity is down. I am currently shooting a 20” 1-7 twist and it works, even with 130. My current load with 136 Scenars is 2857fps and it hammers.

The learning experience is that little bit extra spin helps when your velocity is down. If you overspin it and keep your velocity high you risk damaging the bullet.

But a 1-8 works too I have an 18” 6.5CM with a 1-8 it works.

I know this is an older post but what kind of distance are you shooting with the 20”? I ask because I just ordered a 1:7 bart

When you go short, you can add twist, the extra spin helps with the longer ranges when you lose velocity.

It’s not about heavies with a short barrel, because your velocity is down. I am currently shooting a 20” 1-7 twist and it works, even with 130. My current load with 136 Scenars is 2857fps and it hammers.

The learning experience is that little bit extra spin helps when your velocity is down. If you overspin it and keep your velocity high you risk damaging the bullet.

But a 1-8 works too I have an 18” 6.5CM with a 1-8 it works.

i know this is an older post but what kind of distance can you consistently achieve with the 20”? The reason I ask is I just ordered a 6.5CM 1:7 MTU and would like to be in a 20” if it can still hit a mile. I greatly appreciate any info y’all can give this boot....btw I went with a 1:7 off of a recommendation from warner tool for their flatline bullets. Thanks.