Looking for advice on twist rate for a 300 ultra to shoot 155 to 168gr bullets.Have had 2 Rem PS and 1 Rem Sendaro barrel on the rifle with 10" twist and all three will shoot 180gr and up well. However when I drop below 180s, groups suffer and open up.I have emailed Sierra and they suggested an 11 or 12 twist with no preference for one or the other with these bullet weights. I am about to have a short throated tight neck reamer made and order a new barrel. Has anyone out there tried something like this???
The recommendations that Shawn gave are spot on so I have nothing to add there. What I would like to add is that you may want to consider that the reason the lighter bullets are not shooting as well may be due to the round you are shooting them out of at least in part.
Let me explain. You have a round with a 100 gr case capacity. In my opinion, the 300 RUM should be loaded with at least 180 gr bullets to get the most consistant results with this size of a case capacity. In fact, the heavier the bullets, generally the easier it is to fine a quality consistant load with these big rounds. The 180s are good, the 200 even better.
Just seems the heavy bullets allow the large case capacity to work much more consistantly compared to lighter bullets.
Also, remember that most 150 to 168 gr bullets are not in any way designed for the velocity potential of the 300 RUM. When most were designed the biggest round out there was the 300 Wby and to be honest, most were used and tested in rounds like the 308 and 30-06.
As such, they are not generally designed for the velocity potential of the big 300 RUM and that may also result in some accuracy issues.
Again, not trying to tell you which way to go with your project, but I will say on averge, it is much easier to find a truely consistant and accurate long range load using a heavy for caliber bullet with these large case capacities. Plus you get the advantage of better ballistic and terminal performance as well.
In some cases light bullets work very well though so it greatly depends on what you want to do with the rifle.
Good Shooting, just some things to think about! [img]/ubbthreads/images/graemlins/grin.gif[/img]
Allen Precision Shooting
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Thank you to all who responded. The thought process behind shooting the lighter bullets was to obtain better expansion on groundhogs. I have placed some good hits with 180gr Nosler BTs, 190gr Sierra MKs and Hornady A-max's and have not had clean kills. I understand that these bullets are intended for large game. I thought that if I drive a 150 to 165gr bullet to the max in the 300 ultra I might see expansion more like my 22-250ack on small game.
Kirby, I read your post and what you stated makes sense to me as to the accuracy issue with the light weight bullets (should have thought of this myself). In my mind I was blaiming the accuracy problem entirely on the 1 in 10" twist. Now I am scratching my head wondering if I should persue this idea at all. I crono almost every time I go to the range and will have to see if I saved my data from shooting the 165-168gr bullets. I think in my frustration with less than desired accuracy I may have thrown out this data.
Any recommendations on a twist rate for 180gr Nosler BTs and 180gr Siccroccos only at 3350-3375fps??? Thanx Jim
Walt Berger said that the twist recommendation on his bullets was the minimum recommended twist. I had asked him If I was wasting my time chasing accuracy with 168's as opposed to 185 or 190's. This in regards to shooting his 168's which had a 13 reco in my gun, which I thought was probably a 12. (.300 RUM RMEF Edition from about 5 years back, not sure on the twist specs) He said it would be fine as long as I was at least 13. Now, I can't say his reply would have been the same if I'd have said I was shooting a 1:8 barrel, but I thought I'd share that with you.
One theory, (that I have yet to test on prairie dogs) is that a hollow point match VLD bullet will respond more violently in the relatively few inches that a small critter has vs something like the Scirrocco or Nosler that is designed to penetrate and take down big game.
I would try the 175-190 gr Bergers or 178gr A-max, I've run the 168s out of a 300Win mag and they diden't like the velocity potentail of that round so I'm thinking that the 300RUM would be the same. The Bergers and the A-max will expand very quickly and make a pretty big mess.
when I use the Bergers for varmints I use a meplat uniforming tool and cut the hollow point back a little bit farther than normal to make a larger frontal area and they absolutly explode , you loose a little bit in the BC area but the expansion is awsome.
Hell a 190gr Berger with the meplat cut back to make a 3/16 wide tip would still have a higher BC than the 168gr bullets I believe.