Printable View
Barrel question....Looking to reach out 5-600 yds with a 308, Sav 10 action. What is the optimal length of the barrel for that distance if using 150grainers with 1:10 twist using select match grade barrel? Will i be able to use heavier projectiles ( up to 200gr) and maintain accuracy with the same barrel length? Is there a formula for figuring this out?
500 to 600 yds is done all day long with barrels starting @ 24 inches and longer! I have a 26" barrel that loves 155 & 190's, 10 twist.
I am not aware of a formula, but there are twist recommendations for all bullets! IMO, I believe a 12 twist will get the job done, 155's up to 190's, with at least a 26" barrel. I shot both, but I was using a 28" barrel.
I don't believe that there is an optimal barrel length but to find out if the 10 twist will stabilize a long heavy bullet plug your numbers into the JBM Stability Calculator.
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
Longer barrel means more speed but at long range wind drift is more of a problem than drop.
I have a factory 24" 1/10 twist 308 barrel on a model 10 action. Averages 1/4 to 1/2 MOA at 100 yds and 1/2 to 3/4 MOA at the 700 yd mark with 168 amax. I've shot 150 sierras in this gun as well and had 5 shots in .35 moa at 100 yds. Didn't shoot these any further than 100 yds as they were a "backup" hunting bullet if I needed them. The 155 amax shot well to.
If the match barrel comes in 24-26" I'd stay in that range. I also have a 28" .308 barrel on another build I run 178's out of but thats for in the 1000 yd range. A little more than you really need if your just shooting for 5-600.
16 inch barrels can 1000, if u want to supersonic beyond x yrds, u will a long barrel and slow burning powder.
Here's an interesting article on the subject.
http://www.tacticaloperations.com/SWATbarrel/
+1 Good articleQuote:
Originally Posted by big honkin jeep
There is such a thing as optimanal barrel length, but it changes based on cartridge, bullet weight/twist, and powder. The only way to truly find out, is to take a long barrel, and cut a inch at a time, re-tune the load, the problem with the method is, once you have found optimal, and you cut down past it, you cant gain it back. There has been a few shooters that have done this. In most cases a barrel that is around 24-26 inchs usualy preforms best in most calibers. Now some people will say "Benchrest shooters use a 21 3/4 barrels so that has to be the best." and that is not true. For one, benchrest shooters shoot 6 PPC, with light bullets and fast burning powders. The main reason why the barrel lengths at short is they have to make weight, it is hard to make weight of 10.5 lbs when you use a barrel longer than 22 inches. On the other side of things people may say "Well long range benchrest shooter, and f class shooter use a 30 inch barrel, so that must be optimal," again that is not true. These shooters use long barrels because they plan on completly cutting the chamber off, and re-chambering, and recrowning the barrel several times, usualy when they are done they have a barrel around 26 inch long. The best thing to do , is find out what works best for the combination you plan on using.
For a 308, at those ranges, I'd probably go no longer than 20".
There are folks shooting 208 A-Max @ 2450fps from 1:10 twist 16.5" barrels with moderate loads of RL17...
Accuracy is not really the issue, all my short barrels are extremely accurate. Just find a length that feels right to you. You can get to 1K with a 20" shooting 175 SMKs.
JBM is a good start, the Greenhill formula is helpful, but not exact.
YES 200+ gr bullets from a 308 will stabilize in a 10-twist. I have fooled with the 190-ish SMK's for my 1,000 yard loads. I personally like the 175's or 155's better, but that is not based on performance. I have several loads of 220's I did for hunting. Don't need that bullet, but hey I got them for free!!
A good .308W for 600y is a 26in. barrel with 1-10 twist. Load with 168gr Nosler BTHP or 175gr Sierra MatchKing using Varget powder, whatever brass you like and match primers. You'll need about 15 to 18 MOA from a 100y zero.
My 24" FP with a VERY easily achievable launch of 2550 fps with a 175 SMK:
100 yard zero, shooting to 600 needs 16.8 MOA.
Your atmosphere will change that however.