View Full Version : 308 Winchester Twist Rate
I picked up a winchester M70 a couple of years ago, and finally got around to shooting it. The rifle is from the early 70's and has a Hart replacement barrel on it. First shot is in the black but it keyholed. The round was handloaded Hornady 150gr FMJ, that I shoot in my Garands and M1A with no Problems. The barrel appears to be brand new and is not bent or damaged. The barrel says 1-14 twist, H2. I noticed that my reloading manual test rifle has a 1-9 twist. Could this twist rate be too slow to stabalize a 150gr FMJ bullet? If so what type of bullet would work in this barrel? TIA
Was it just one bullet that keyholed?? If not here is my guess, if the bullet(s) are hitting in the black but keyhoeling the bullets you are using are the absolute maximum length that will stabilize at all out of your Model 70.
It is my understanding that most .30-06 rifles have 1 in 10" twist rifleing. 1 in 14" does sound slow for that cartridge. If it won't stabilize 150 Gr my guess is it sure won't stabilize anything longer.
I stopped after the first shot. I wanted to check the rifle to make sure that I did not do something stupid. It was a clean keyhole at 100 yards. My thought was to try 110gr bullet next. I wonder what the barrel was designed for and what the H2 marking means.
The rifle has a Palma barrel (the Palma course is fired with 155 gr bullets at 800, 900, and 1000 yds). While designed for 150 gr balls...your barrel requires a BIG load to stabilize the bullet (2900 fps give or take). If you load it down, it'll keyhole every time!
John is absolutely right. alot of people forget that when stabilizing a bullet, velocity is an important factor. At normal velocities(26-2800fps) a 308 150 works great with a 1 in 11 or 1 in 12 twist. Remember, the slower the twist the smaller the bullet in weight or the higher the velocity.
Thanks for the info. I will try 110-125gr bullets and see what happens. Thanks again!
sounds like the chamber is throated too long..real popular in the 60,s and 70,s Winchester played with the idea, and had key hole issues...
try this, if you load your own..
remove the cocking assembly..
then, seat the bullet as long as you can, seat the bullet deaper and deaper,till the bolt closes easy, see how far the bullet seats. it should just touch the rifling..you might be suprised...sounds like the bullets jumping into the rifling.
While not argueing with you about long-throated barrels in the 60's....but I AM questioning whether Hart barrels ever made any of them! Hart was primarily a maker of competition barrels....and you don't cut a long leade in any of them!
I bought the rifle from the CMP a couple of years ago. It had an AMU tag attached to the trigger guard basically saying that it was a M70 with Hart barrel installed. The rifle was also shipped in a broken ramline stock. I bid on another ramline stock from the CMP and to my surprise it was inletted exactly the same and fit perfectly. This would suggest that there was more than one rifle like mine built. I have no idea what they could have been used for. I will take Chucks advice and see what the OAL is. Thanks again!
Like I said.....it's an older Palma Rifle and THAT'S what it was "used" for!
Thanks John. I will try some lighter bullets next week and post the results.
And yet again.....you don't NEED lighter bullets, just a faster load!
If you can't or won't load your own, then you are probably screwed and should consider selling the rifle and getting something a bit more pedestrian from Wally World that'll shoot most commercial .308 loads. For your rifle, a 155 gr Sierra MK on top of 45.5 gr of Vihtavuori N550 should be more like it...all safe loading caveats apply. You have a high-performance "race car" and are trying to run it on the cheapest economy unleaded fuel you can find....and are surprised and somewhat mystified that it isn't working? Feed the rifle what it was built for, not what you think you might get away with! To learn more about what that rifle was made for, go to: http://www.palma.org/
Mr. Moderator....this thread really should be over at the "On The Firing Line" forum. The OP has a comp rifle, doesn't know how to run it, and needs the input from a wider selection of people that do.
Points well taken. I will work up some loads with the 155 palma as per my Sierra manual. Any thoughts on the ramline stock used with this rifle? It almost seems out of place. Thanks again to all that replied.
Again, like I said earlier....you have an old AMU Palma Rifle, likely circa the later 1970's, hence the Ram-Line stock.
Powered by vBulletin™ Version 4.0.2 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.