[jasonbterry]

Hello, everyone! I'm up against something that has me stumped. I e gotten pretty meticulous with my hand loads for my rifle but the variance in velocity still seems way outside the acceptable range. I.e., last week I loaded 18 rounds using 67.5gn of hodgdon retumbo under a 150gn Speer lead tip. All my case lengths are trimmed within .002 of one another. I use a balance type RCBS powder scale and regularly add or remove single pieces of powder to get the weight exact. I only take three shots at a time before letting someone else have a turn while I spot at the range. All this adds up to an average of 2950 ft/sec with a standard deviation of 30+ ft/sec! My brother in law's factory ammo was keeping things within a range of 20+ ft/sec.
It just seems that with all the trouble I'm going to, I should have more consistent velocities... Particularly more than some factory ammo that was charged by a machine! Should I try a more moderate powder? May e a lighter bullet? What gives? Thanks for the help...

[119er]

I am no guru, but can offer my limited experience and observations. I do not load that caliber or any large capacity cartridges, but through a search on Hodgdon's site your charge seems to be lower in the charge range. In my experience, loads closer to the top end produce better consistency, especially when the powder fills the case well. I have also noticed interesting changes in relation to seating depth. Usually the short mags have shorter barrels due to a claimed better efficiency. Maybe you should try a little faster powder like H414, one of the 4350's, or Reloader 22 if you can't get the Retumbo to give you what you're looking for. Also, I have started checking my beam scale (RCBS 10-10) against a digital. Both calibrate perfectly with check weights but I tend not to be as precise on the beam scale due to lining up marks rather than reading a display. Good luck!

[hoghunting]

What do your groups look like? If you're getting 1/2" groups, then the difference in velocity wouldn't be a concern, but if you're getting 2" groups, you have more problems than the velocity difference.

[GooseGestapo]

Retumbo is the problem. It's rather a bit slow for the .270wsm.
Try H4350, and RL17. These are closer to the burning speed of the factory ammo. Will likely give better s.d.'s than the Retumbo.
Retumbo is best matched to the very large "over-bore" magnums such as the .300wby, .300rum, and .30/378wby. I've used a bit of Retumbo in my .300rum. Even there, it's trending on the slow side.
Don't get overly caught up with s.d. It's an "indication" of variance, but dosen't tell the whole story. Your s.d. is still quite low, so don't fret it. Over 50 and definitely over 100, you'd have something to dwell on. I see velocity variation of as much as 100fps with the .300rum. No big deal.. as this is perhaps 1/2" on target at 100yds, if that much.... Now if I was shooting 1,000yd bench rest, then I'd get concerned over a 30fps s.d.

Another powder recommendation is IMR4831. I've seen some really low s.d.'s with this powder in the likes of .257roberts,.25/06, and .270wcf.

[JimKirk]

Retumbo will work well in the 270 WSM ... but you do need to get toward the upper part of the loads for it to preform like it should ...

I'm loading 71 grs of Retumbo(Hodgdon's web site Max) under a 140 gr Nosler Accubond and getting great groups ... have yet to connect with a deer to see the results.

Any of the "Very slow" powders like Retumbo, RL 22, RL 25, IMR 7828 ... will need be near max loads to preform like they should ...

[jasonbterry]

thanks for the advice, fellas... as for my groups... at 100 yards, a three shot group will be about 1" or so...this takes into account the fact that these are lead-tip groups and for hunting i will load up Nosler Ballistic tips, which should group a little smaller due to the greater consistency of shape. i know those will fly a little different, but i figured i'd do the majority of my "blind hog finding an acorn" loads with cheaper bullets so that i can save a little money and then fine tune with my actual hunting bullet... perhaps this is a bigger variable than i had estimated.
the burn rates of the powders you guys listed as suggestions fall in line with some alternatives i had been looking at. H4831, in particular. they also offer 4831SC which is still extruded (which i like) but Shorter Cut. they say that it is for more consistent drops for charges, but i also know it will have more charge density... wouldn't that be counterintuitive to the whole idea of extruded powder or am i misinformed (wouldn't be the first time) and there's actually an advantage to a higher charge density? of a similar burn rate, but not mentioned, and much newer is Hodgdon's Hybrid 100V... anyone have any experience with that powder? the velocities listed on the charts between that and 4831 are only about 30 fps. do you lean on the tried and true 4831 or venture into the new tech and try the 100V?

Related: when i'm not specifically preparing for a hunt i do love long range "pseudo-sniper" type shooting... the thought of one day hitting a target from 1000 yards (which i know my gun is capable of) is quite exhilarating to me. i know that rome wasn't built in a day, but i'm always looking to learn as much as possible. Just today i actually gained access to a new piece of property which i understand offers opportunity for shots to be taken at 600-700 yards. i feel i'm a little ways from that at this point, but we all know what it's like to see a big one outside of our realistic effective range and have to do the responsible thing...

one last thought... i have gone with the 150 grain bullets at this point because i've been told that a slower/heavier bullet won't "blow up" as much on impact as a faster/lighter one and would be less likely to destroy as much meat. do you agree with this? in either case, could i logically expect to get better consistency from a 130 for any reason? thanks again for the help, everyone...

[7mmb]

I don't load for 270 WSM either but I do for several other cartridges and have been chronographing my loads for years. My chrono will tell me the SD of a string in fps and as a percentage of AV. I use the percentage, not the fps, because it's a better way to compare different loads at different velocities that is easier and more realistic. I have found that factory pistol ammo will give SDs in the 1.5%-2.5% range and if my handloads fall in that range I figure I have a decent load. Anything under 1% is an excellent load, although I have gotten decent accuracy with higher SD loads, and that's where your handloads should really be measured, on paper. The reason I use percentage instead of fps can be illustrated by your SD of 30fps. Whether or not 30fps is a good or bad SD depends on the AV. If the AV is 1000fps then a 30fps SD translates into 3% deviation, on the upper end of acceptable; keep experimenting because there is a better load to be had. If the AV is 3000fps then a 30fps SD translates into 1%, which is a very good load. I've gotten sub-1% loads in 7mm-08 and they are also sub-MOA. I'm pretty sure your 270 WSM is going at least 3000fps so your 30fps SD loads are actually very good. Your brother-in-law's factory fodder is just very good too, but the difference in consistency is actually just a few fractions of 1%. You can likely improve your consistency by going to a faster powder as others have suggested. I have found when working up loads that starting loads will usually have poor consistency, which then tightens up as you approach max, and usually start opening up again at max. Where the SD drops the lowest is usually the sweet spot but always verify on paper. Good luck with your loading.

[jasonbterry]

7mmb, thanks for that... what you're saying does make a lot of sense. my AV for those loads was right around 2950, so your'e not far off.
a couple of things i'm not doing to my cartridges right now that i've considered are:
- flash hole deburring
- primer pocket uniforming
- weighing/grouping casings
- using a bullet comparator to measure cartridge length instead of measuring total length
are any of the above things that i could expect to get a major advantage from? I know that doing a lot of little things to improve consistency will add up fast, but if i were to only pick one of the above, which would you guys suggest i start with?

[10 Spot Terminator]

I'm with 119er and JimKirk on your issue with your load. Fist off is your charge weight being used is quite low and Retumbo typically does not perform well until it reaches the upper load limits. I too use the exact same 71.0 gr. load behind the 140 gr. accubond with sub 1 inch groups at 200 yds clocking at 3,175 fps. with very low ES and SD numbers . As for a heavier bullet grain weight not blowing up as easily as a bullet of lighter grain weight it really depends on the construction of the bullet and the speed it is traveling when it hits the animal. There are a wide range of differences in bullet constuction and performances designed to perform specific tasks withing certain speed ranges that can make or break a good clean kill in the field. Few bullets cover a large perfomance range of being able to expand well at slower speeds yet hold together and retain high bullet weight retention at magnum velocities. Bullets such as the Barnes TSX series solid copper bullets are the closest thing I have found to filling that niche to date. There are other good bullets out there that tend to be known more for bullet weight retention at higher velocities under what I will call bone breaking contacts than others that lend themselves nicely to todays magum velocitys such as Noslers Partion, Hornadys Interbond, Remingtons Core-Lokts, Swifts A-frame, Speer Grand Slams, just to name a few. It all comes down to choosing a bullet that fits your highest probability percentage based on the range you will most likely shoot your animal at and what you want the bullet to do. If he steps out at 50 yds. and you have your hyper velocity round set to do the job at 300 yds. is it shoot or dont shoot ??? You make the call ... ;)

[gamestalker]

I don't load that cartridge either, but I do load for other's with slow burner's. I have found that they perform best when pushed up to the upper end of the charge table.

GS

[119er]

- flash hole deburring
- primer pocket uniforming
- weighing/grouping casings
- using a bullet comparator to measure cartridge length instead of measuring total length

I do all of these because I'm a consistency freak and it eliminates or reduces known variables. Those are things I don't have to wonder about when I get puzzling or varied results. I have also seen seating depth change my ES and SD to sometimes surprising amounts. For bolt guns I'll typically start a load .015" off the lands and move from there. For flash hole deburring, make sure you trim to length first and take time setting up the tool to get consistent results. FWIW, If I was to purchase a bullet comparator again it would be the Sinclair unit over the Hornady. I am going to buy the Sinclair inserts for my Hornady OAL comparator. I think the Hornady inserts are undersized and give conservative results. I could be wrong , do your research and good luck!

[murf]

you might try a 140 grain bullet. your rifle may be having problems spinning that big boy fast enough.

murf

[BillB204]

Other than handguns and .223 for AR, I load .260 and .284 for long range precision. As I was reading the replies to your question, everyone was taking the words out of my mouth. Goosegestapo and 119er got most of the issues. And as Goose stated, out to about 200 yards, your SDs really aren't going to matter much. But when you start punching out to 500+, your SDs really should be close to or in the single digits.

Retumbo is definitely part of your problem - way to slow for .270. My .284 likes 4831 but the .260 doesn't. So it might also be a bit slow for .270. 4350 and RL17 would be much better. My .260 likes RL15. I've tried the V100. It burns hotter than the 4350. I got okay, but not great accuracy in both the .260 and the .284. But it would definitely be worth a try in a magnum .270. RL19 might also be worth a try. You might also want to try different primers. I was getting very different SD results with different primers. My best results were with Federal Magnum Match.

Probably the next most important element is bullet seating depth. If you're simply seating to the book's recommended OAL, you're missing one of the most critical issues. You need to get a good bullet seating gauge. Each bullet type will likely have the olgive in a slightly different position. So you have to measure where the olgive touches the lands for each different type bullet you use. Then, as 119er said, start by seating the olgive .015" off the lands, then try .025" then .035" until you hit the gun's sweet spot. You'll see a very noticeable difference in both accuracy and SDs.

As far as case prep, do it all! The more consistent your cases are, the more consistent your MVs will be. You'll also need to anneal your brass after every 4th or 5th reload to keep the case necks flexible. And don't put too much neck tension on the bullets. .001" to .002" is enough to hold the bullet firmly enough without risking runout. Any more than that will cause inconsistent bullet release / pressure / and MVs.

[Cleftwynd]

Consistent and good neck tension can reduce both SD and ES in my experience as well.

[jasonbterry]

@JimKirk - i was just reading back through this old thread and saw that you said you are loading 71 grains for a 270 WSM? I thought the max in the manual was 70. are you actually loading above spec (your perogative) or are you using something other than the hodgdon reloading data?