What have you guys found to be the optimal barrel twist rate for the 7x64/280Rem(or other simular 7mm) when using 175grain bullets?

And would it be optimal to choose a differant twist rate if using 150grain bullets?

What would be a good compromise for being able to use both these bullet weights, if there is much differance between what twist rate is recommended for them?

A 9" twist will handle all your needs just fine...

Erik, twist rates are determined by bullet length not weight. That said, only because the more modern bullets trend to greater length due to higher ratios of jacket/core material...copper being less dense than lead...and streamlined shapes such at the Ballistic Tips and such, all of which make lighter bullets longer than in the past...now where was I? Oh, well, the old standby for the 7mm has been 1:9" twist, which will stabilize the 175-190 grain RN designs of old. Many eschew such bullets these days, and in the main a 1:10 will do the trick for the likes of the 150 gr BTSP designs. I suppose it even possible that a 9" twist won't work for the long heavy target bullets or VLD designs that are popping up here and there...I don't know the length, don't know the answer. There are a number of Ballistic Web Sites in Cyberspace that make the Greenhill formula available, but without bullet length you are lost...

More simply put, a 9" twist won't hurt a short bullet, a 10" won't stabilize the long ones.

1:9" looks like the sensible choice...

Twist Rate Recommendations From Shilen, Courtesy of Benchrest.com

- mike

quote:

twist rates are determined by bullet length not weight.

True statement, but "most" heavy for bore are both long and heavy.

On a 7 bore of any chamber, a 1-9 twist is a good start. Personally I prefer a 1-8.5 or 1-8.75 twist. Krieger makes a 1-8.5 twist 7mm and if I was building another 7mm that would be my first choice. I just built a 280 on a 1-9 match Shilen, good barrel twist is OK, I regret not taking the time and ordering the Kreiger now though, I would also check Woodie at Lothar Walther, he thiks metric and I bet he is making them I know the spec in metric and I am too lazy to work out the 220, 240 260 mm twist rates out to SAE, but I guess one of those is the right one.

In my opinion the Europeans started the metric 7 bore, and were light years ahead of this side of the pond 7mm fans, years has changed that and it isn't quite that way now, but most European 7mm's are chambered in the slightly faster metric equivilant twist and I see no reason to reinvent the wheel, which works out to the 8 and something number.

Not saying the 1-9 is wrong, and like I said I just did one that way, but I kind of wish I had been patient ( the only reason I didn't do it was I could get the Shilen on sale, right now overnight it tommorrow, and the other barrels all had lead time issues, with a wait for a few weeks to couple of months. Regret not waiting now a little bit, but it is a Winchester which is a correct twist for that action.

Thanks for your help guys.

It seems that I'll have to think a bit over choosing between a 1:9 or a 1:8.5 twist.

Out of curiousity, I e-mailed Speer to hear what they had to say. And here was their reply:

quote:

Erik: I have to believe that Remington expected the heavy (160/175 gr) bullets to be used in the 280 Rem (aka 7x64), they chose a 1 in 9.5", that might be the exact, either 9" or 10" would be a minor compromise.
Due to the longer length of the TBBC bullet, the 10" would be the best.
Shoot Straight!
Coy Getman
CCI/Speer Technical Service Coordinator
(800) 627-3640 # 5351 (pound key must be used)
Fax: (208) 799-3589

So if I am reading his reply correctly, he is concluding with that a heavy/long bullet in 7mm should have a 1:10 twist. Which is the exact opposite of what everyone else says!

This is one caliber that always puzzles me as far as twist is concerned. I know of few people, if any, who would think of anything but a 1 in 10 inch twist in a 270 Winchster. Why is it that a 280 which has practically the same length bullets need a quicker twist? I can possibly see a little merit in that idea if a person was using 175 grain and heavier bullets, but few people I know do that with any regularity. It just seems to me that a 1 in 10 should work fine. In the past I have had 280s with everything from a 1 in 9 to a 1 in 11 inch twist. After building a 7X57 with a 1 in 9.5 I myself would never go quicker than a 1 in 9.5 should I ever decide to build another 280.

quote:

Originally posted by ErikD:
Out of curiousity, I e-mailed Speer to hear what they had to say. And here was their reply:

quote:

Erik: I have to believe that Remington expected the heavy (160/175 gr) bullets to be used in the 280 Rem (aka 7x64), they chose a 1 in 9.5", that might be the exact, either 9" or 10" would be a minor compromise.
Due to the longer length of the TBBC bullet, the 10" would be the best.
Shoot Straight!
Coy Getman
CCI/Speer Technical Service Coordinator
(800) 627-3640 # 5351 (pound key must be used)
Fax: (208) 799-3589

So if I am reading his reply correctly, he is concluding with that a heavy/long bullet in 7mm should have a 1:10 twist. Which is the exact opposite of what everyone else says!

I'd bet they made a typo in the reply and meant to write 9, not 10, for the heavier bullets.

BTW, I think the Rem standard is 9.25, and Ruger stadard is 9.5. I had a 284 with a 10" twist and that worked fine with 175s, so anything in there would probably be fine. It really doesn't matter that much as long as your stay somewhere in this general range.

My 1/9 shoots 140s great. I have not broke out the 160s yet

I also asked Krieger out of curiousity, and got this reply:

quote:

You will need the 1-9 twist to stabilize the 175 gr bullets. 1-10 if 150's are as heavy as you want to go, but you DO need the twist rate fast enough for the heaviest/longest bullets you want to shoot.
Thanks For the inquiry,

Technical Support
Krieger Barrels, Inc.
2024 Mayfield Rd
Richfield WI, 53076
262-628-8558 phone
262-628-8748 fax

FWIW, this was the same answer as Border Barrels in England gave me too.

quote:

Originally posted by ErikD:
Out of curiousity, I e-mailed Speer to hear what they had to say. And here was their reply:

quote:

Erik: I have to believe that Remington expected the heavy (160/175 gr) bullets to be used in the 280 Rem (aka 7x64), they chose a 1 in 9.5", that might be the exact, either 9" or 10" would be a minor compromise.
Due to the longer length of the TBBC bullet, the 10" would be the best.
Shoot Straight!
Coy Getman
CCI/Speer Technical Service Coordinator
(800) 627-3640 # 5351 (pound key must be used)
Fax: (208) 799-3589

So if I am reading his reply correctly, he is concluding with that a heavy/long bullet in 7mm should have a 1:10 twist. Which is the exact opposite of what everyone else says!

He is just plain ol', flat WRONG! The 1/9 would be better! Some people have experienced severe understabilization with the Sierra 175-grain PSPBT bullet in 1/10" twist barrels. I don't know how this 175 Sierra bullet compares, lenght-wise, with the 175 TBBC, (thik it's longer) but you'd be better off shooting long 175-grain 7mm bullets with a 1/9" twist, and a 1/8.5" would be even better!

If you are having a custom rifle built, get the tightest twist rate available to you. That way you can shoot any bullet you are likely to come across. An extreme tight twist will only hurt short bullets if they are used at ranges beyond 500/600 yds and it is unlikely that you would want to do that, as it makes no sense. I think Lilja is making 7mm barrels down to 1:7" or 1:7.5" now. The tighter the twist, the more it extends the versatility and range of the rifle.

I understand that the faster twist such as 1-9 would be more desireable. However, why do you suppose that companies like Browning (A bolt) and Sako (75 action) use the 1-10 twist in the 280 but use 1-9.5 for 7 Rem mag and 7-08?

1-10 seems to be the most common twist for the 284 Win according to several sources I found. Early 7mm mags, notably Winchester and Weatherby products also used 1-10.

It seems that 1-9.5 is the basic industry standard for 7 mm caliber chamberings. How much difference could there possibly be in 1-9.5 and 10 twist as far as the spread of usable bullet weights?

I think that the average 7 mm hunter/shooter probably shoots mostly 130-160 grain bullets anyhow. The 175's and up would be more of a specialty.

Any thoughts?

Factories follow the laid down CIP and SAAMI specifications. The idea is that, generally, factory ammo for a caliber will work in most of the factory built rifles in that caliber. As soon as you start handloading and having custom rifles built for yourself, you are free of these constraints and you can do what you want to improve performance any way you wish. The first CIP/SAAMI specification that handloaders toss out the window is cartridge overall length, even in factory spec rifles.