I am relatively new to handloading. I have loaded for both the 300 Weatherby and 22-250 Remington. I am now starting to work-up loads for a new 300 WSM. Yesterday, I shot 180 gr. Speer Grand Slams using both Re22 and IMR4831. Let's focus on the Re22. The starting charge for this powder published by Speer is 64.5 gr and should develop 2797 ft/s with a 24" barrel (1-10 twist). The rifle I shot has a somewhat shorter 22-7/16" barrel with a 1-11 twist. My velocities are consistently well below the published values. For example at the starting charge, my velocities were: 2494, 2525, 2511, and 2499 (average of 2,507 ft/s). These velocities are about 10% below published. Why the big difference? I would expect a slightly shorter barrel would yield a little lower velocity but 10%. Any suggestions here? Should I move up to a faster burning powder with the shorter barrel?

Thanks,
douglast

You answered your own question with your last sentence. RE22 is way too slow for the 300 WSM. The slowest I have ever tried was IMR 7828, It shot bad groups, so I never checked velocities on that load. I'm surprised Speer even had it listed. My best results were with XMR AA4350, H -4831SC and RE-19. I tried WW 760, but found it ran into pressure problems well before getting close to published velocity. 760 might be okay for 150 grainers, never tried it there.

With your shorter barrel, you're not going to get what is listed for a 24" barrel. My Browning with it's 23 inch barrel is actually quite close to what the 24 inchers run for velocity.

I think you are finding out that what many have said about the WSM series is, indeed true: that you won't be satisfied with anything less than top-end loads. You will also find out that it takes more pressure in a smaller case to do the same "work" as something larger.

More answers:
-the 1-11 twist is different. I wouldn't choose any bullet heavier than 180 grains. Why: if you can't get this one to move out, you won't get a heavier one to either. Some other 300s used a 1-12 twist, but for the most part are now gone;
-stick to the med-slow burners for powder choices (4350-4831). Unsatisfactory results, then try something different;
-expect to lose something like 50-100 FPS/1" of barrel, conversely add 50FPS/1" of barrel length assuming a 24" barrel as standard.

Best of luck on your project

As your new, there are a few variables you may not be considering.
200fps between 2 identicaly chambered (same reamer & smith) barrels is not unusual.
100fps is not unusual between chambers that are on the outside edges of spec.
Powder can vary 10% from lot to lot. I've seen 250fps change with just a new lot# powder, all other factors (gun, bullet, primer, case, weather) remaining the same.
Most of the manual makers use minimum spec. chambers and premimun barrels, along with selecting powder lot's that are on the "hot" side of the spectrum. IOW they are doing everything that can be done to increase the chamber pressure so that when you build a "max" load right from the start (no work-up) you won't experance trouble.

Douglast,

Well, you have gotten alot of information to your post which some I agree with and alot I do not.

First off, Rl-22 is not to slow for the 300 WSM, in fact if one looks in the Nolser manual #4 you will see that this powder produces the highest velocity of all with the 180 gr bullet in the 30-06. The '06 has a significantly smaller case then the WSM so the comment about Rl-22 being to slow for this case is flat wrong.

Also, it is a fact that you will loose some veocity with your shorter barrel, certainly not 100 fps for each inch, more like 30 fps with a round like the WSM.

Your 1-11 twist will also reduce velocity with same powdercharges compared to a 1-10 because it is easier to drive a bullet down a 1-11 twist then the tighter 1-10. It will not effect it much but it will some. Good thing here is that you will get a bit more veocity with the same chamber pressure compared to a 1-10 twist.

Your biggest problem is that you are just using a starting load. Velocity is a function of time and pressure. That is how much pressure is behind your bullet and for how long as it travels down the bore.

Point being, powder charge is really only a guideline. Since you can measure velocity, this is a more accurate judge of pressure.

If several loading books say the 300 WSM will hit say 3000 with a 180 gr bullet, I would bet all three use a different powder charge to get that same velocity.

This is because of differences in chamber volume, case volume, neck dimensions, throat length and diameter, bore diameter, bore smoothness and a host of other things.

Thing to do is start increasing your powder charge a grain at a time and shoot them over a chrony and keep track of your velocities. Your pressure will be translated into velocity. The 300 WSM will hit 3000 fps with a 180 gr bullet in a 24" barrel.

Since your barrel is shorter, assume on the side of safety that you will only be able to hit 2900 with your slightly shorter barrel.

Increase your load until you near this level.

First thing to watch for as you increase is accuracy, it will generally get better as your pressures increase. Your Extreme spread in velocity will usually decrease as well.

If your accuracy goes away before you reach your velocity goal, thats the all important thing. An extra 100 or even 200 fps means little if you do not have confidence in your load.

You must always watch for pressure signs on the case and with a case the diameter of the 300 WSM it is realtively easy to do.

Watch for flattening primers, cratered firing pin holes on the primer, any resistance in bolt lift on a fired case.

Your rifle may just need 2-3 grains more powder to get to safe max velocites.

This can only be done with the use of a chronograph though.

If your nervous about where to stop increasing your load, get a box of factory rounds and fire them through your rifle and see what they chrony at. This will give you a safe base line for velocity.

Most importantly, there is nothing wrong with your rifle as long as you see no machanical failures as far as case failure goes. Your rifle will talk to you, just listen to it and study what data it give you.

Good Shooting!!!

50

You have to realize that just because one rifle with a given barrel length will deliver a given velocity with a given powder and bullet ,it does not mean that all rifles with the same length barrel will deliver the same velocity with the same powder and bullet while producing safe pressures.I have chronographed several rifles in the same chambering with the same length barrel and the maximum velocity obtained before pressure signs appeared varied by up to over 150fps between these rifles.Two of these rifles were even chambered with the same reamer and they varied by 60fps at maximum load before pressure signs appeared.All components including bullets,primers,brass and powder were identical and from the same lot.It should be mentioned that I reduce my powder charge a full two grains if any pressure signs appear since pressure signs often do not appear until well above design pressure.

I agree that RL-22 is not too slow for the 300 WSM. It maybe too slow for your particular rifle. Definatly try RL-19. Powder lots vary and with those variables comes burn rate. A differant lot of rl-22 will burn totally diffeant than the lot speer developed thier loads in. Also primer selection can influence it, barrel quality, free bore, chamber dimensions and a whole list of factors. Generally, if a manual list a max charge of 70.3 grains at 3012 FPS with THEIR 180 gr bullet, then you should not exceed 3012 FPS regardless of the charge it takes you in your rifle to get there. This is a general rule of thumb. I have had rifles that were too hot when using the minimum published charge. Each rifle and powder lot# will be differant.



Regards.



p.s. Contrary to what some will tell you, you can safetly get a small amount of greater velocity with the 11 twist than with the 10 twist. It will allow SLIGHTLY higher velocity with slightly less pressure It seems like you would get more velocity with the tighter twist due to the increased pressure, but please be assured that its the extra resistance that drives up the pressure and with that increased resistance, less velocity is generated with higher pressure from the tighter twist.

Try accurate's magpro powder. Alot of guys are getting excellent accuracy and velocity with it in the wsm.

One possibility that hasn't been mentioned: How accurate is your chrono? Try factory rounds in several calibers. If they are consistently low, that might be it.

Contrary to others experience, my 300WSM shoots VERY well with reduced loads, especially with 150-165 Gr. loads. 55 Gr Varget and a 165 BT or 168 Matchking will give 1/2" groups every time, if I do my part! That is well below max.

Keep working at it, but don't automatically assume that the chrono is magically the most accurate piece of equipment on the bench!

My short mag shot best with IMR 7828.I could equal factory velocities with ease.

I have a 300 WSM F class rifle that I shot the throat out of first barrel with Vithavouri N550 and the 175 Sierra MatchKing. Before I settled on N550 I tried H 4831 SC and RL 22. The faster burning N550 produced higher velocity and better accuracy that the slower powders did. H 4350 and RL 19 also gave excellent results with the 175 MatchKing. In my testing the 4350 class of powders worked better. I know of several 1000 yard benchrest shooters that are having good success with the 4350 class of powders. From what I have seen the shorter barrel won't lose that much velocity compared to the 24" test barrel. I strongly suspect your rifles bore is on the large side of SAMMI spec's. Which would account for the lower velocities due to lower pressures. Just my .02 cents worth. Go to the 4350 class of powders and slowly work up looking for the pressure signs mentioned above.

May I be half the man my grandson thinks I am...RiverRat

My winchester model 70 likes 69grs of RL-22 and 180 Partitions for just under 3000.
My HS Precision (26inch barrel) likes 71.0 grs of RL-22 with 180 Barnes TSX for a little over 3000.
Optimum burn rate may be in the RL-19 to IMR-4350 range but I've had tremendous luck with RL-22 in most magnums.
Make sure your chronograph is level etc. -those readings seem suspect.

douglast

I have had the best luck with H4350 with 300wsm 180 grain loads. You might think about that powder.

good luck

Good news! I just completed a bit more work on this problem. I switched up to Win-760 powder and loaded two different bullets. The first was a Speer 180 gr Grand Slam. The second was a 180 gr Hornady Interlock BTSP. Here are the results:

For the Speer, my best group was 0.623" (100 yds) with 65 gr of Win-760 and a velocity of 2,866 ft/s. Note, this velocity is about 75 ft/s below what Speer published in its table for this max load.

For the Hornady, my best group was 0.537" (100 yds) with 66 gr of Win-760 and an average velocity of 2,886 ft/s which is within 60 ft/s of what Hornady published in its tables.

Here are my conclusions.

1.) The faster burning 760 made a difference in getting the velocities up.

2.) I am slightly slower than table values but I have a bit shorter of a stick than used by the manufacturers.

I will now start fine tuning these two loads and see if I can get them below 1/2". At this point though, I am pretty happy getting these groups from a hunting rifle (Sako model 75 Finnlight).

Thanks everyone for your thoughts.

douglast

also, what distance is your chrony from your barrell. I set at 12ft.
If you have a friend w/ a chrony, check over both