Velocity degrading accuracy

[Clinton]

Still trying to work up a load for my 308 Win for the C312-185. For kicks I loaded ten rounds up with 10grs of SR-7625. I had tried 12grs of the same powder with the C312-155 and it shot 3/4" - 7/8" 5 shot groups at 100 yards. And I'm finding this bullet is producing similar results.

C312-185 over 10gr of SR7625 5 shots at 100 yards 7/8".
123470

Whenever I try to use a slower powder such as IMR4227 or 5744 I get groups like this.....
123471

What do you think is causing this? Can I rule out sizing, lube and seating depth because of the good results I get with faster powders? Could my lead be too soft? I'm 100% sure I'm not getting any leading because the top target was actually shot last and I cannot see any in the bore.

[Tatume]

Try going slower still. My recommendation would be H4895; it is slow enough to get good velocities and forgiving enough to be safe at the low velocity end.

[Clinton]

Don't have H4895 but I have IMR4895 not sure how similar they are. But from what I've shown, all signs point to bullet sizing and seating are correct?

[Tatume]

Probably, but very mild charges of powder can be very forgiving of discrepancies. Try IMR4895 at the low end, minimum or possibly even less.

http://www.hodgdonreloading.com/

[popper]

Bad burn with low loads of 4227. Try dacron filler. You must be pushing them real slow.

[runfiverun]

I prefer imr 4895.
28.5 grs and a tuft of Dacron will give good results, I haven't seen too many 308's not shoot that load fairly well.
17 grs of 2400 with a rifle primer will shoot right along side it in a 308 with no drama too.

and like popper said.
the 4227 is probably too low, I'd be looking in the 20 gr area.
I used more than 10grs in my 22-250 with cast boolits.

[Clinton]

The load I used with IMR 4227 was 21 and 22 gr. The load with SR7625 was 10 gr. I'd like to stay away from dacron filler if I can, just adds another step to the process. If I can find a powder that burns better without it that's the route I'd prefer.

[kbstenberg]

Were all loads loaded exactly the same? Except for the powder.

[Clinton]

Yes all exactly the same.

[cbrick]

Any chance ya have any SR 4759? Standard primer and 18 or 19 gr with 180-185 gr bullets

Rick

[Clinton]

Any chance ya have any SR 4759? Standard primer and 18 or 19 gr with 180-185 gr bullets

Rick

No I do not but the local gun shop usually has some. Still weird I got such dismal results out of IMR4227 and 5744. I thought one or the other might show some kind of promise. Anyway I just loaded 30 rounds with 28, 28.5 and 29 gr of IMR4895. Will shoot them tomorrow and see what happens.

[Clinton]

Just back from the range. Tried 28, 28.5 and 29gr of IMR4895 no filler. The best group was the first load at 28gr and shot just over 2" at 100 yards.
123526

Every .5 grain increase from there opened the group by about an additional inch. I'm wondering if I should try going the other direction and decrease the charge .5gr at a time. Any idea what the velocity of a 185 gr cast bullet over 28 gr of IMR4895 in 308 Win is?

[dtknowles]

Just a swag but 1800 to 2100 fps.

Tim

[Clinton]

So I should still have a respectable velocity if I go down a little in charge weight. The lack of a filler maybe what's hurting me but I want to proceed without it for now.

[Tatume]

You shouldn't need a filler with charges of IMR4895 in the twenty-something range. There will always be powder near the primer, unless you're hunting fish from a tree in Virginia. :-)

http://www.dgif.virginia.gov/fishing/waterbodies/display.asp?id=147&section=fishing

[Clinton]

You shouldn't need a filler with charges of IMR4895 in the twenty-something range. There will always be powder near the primer, unless you're hunting fish from a tree in Virginia. :-)

http://www.dgif.virginia.gov/fishing/waterbodies/display.asp?id=147&section=fishing

Reminds me of when I was a kid and me and a couple of friends spent one day sitting on a railroad bridge over a stream. We were shooting small fish about 30 feet below with 22 rifles. I don't think you even had to to hit them. Just the concussion from the bullet hitting the water near them was knocking them out. I'd run down fast as I could and hang from the bottom of the bridge to catch them as they floated by. Not a mark on them.

[Tatume]

That's exactly how we hunt suckers in Virginia. It's a tradition as old as America, and only survives (legally) in one county.

[tomme boy]

How are you sorting your bullets? What kind of gas checks are you using and how are you seating and crimping them? Also what lube? And alloy? All matter.

Load the 5744 at 19-20 grs It should be 1800 fps or close depending on the length of your barrel. I have had really good luck with a 200 gr and 21 grs. It shows 1850 fps with the 200.

[popper]

Check the 4227 in service rifle thread. 40 gr. 4895 gives me 2400 fps for 168 gr boolit in 308, 20 gr. is 1300 fps in 30/30 with same boolit. 20 gr. 4227 with lots of dacron gives a 150 gr. ~1900 in 308MX (slightly less volume than 308W), MOA performance. Dacron gets the pressure up for a good burn, not just holding the powder against the primer. I get 1800 with 4227 in 300BO but case efficiency is much better.

[trapper9260]

When I work the loads for my semi auto and try different powders and amount and then I was ask did I weight the bullets after I size and lube and GC them and then put them in .05 +- 1gr groups and then go with the ones that is the most of one group that is on the heavy side and then after that and all my groups got tighter after and when I try a lighter bullet I had what you had on your last pic of not group.I did not use any filler in my lads just the powder and boolit .Hope this might help.

[Clinton]

For now I've not sorted any bullets other than throwing back obvious defective ones. I may in the future if I cannot achieve what I feel is acceptable accuracy. But I'll tell you what I don't get and part of the reason I'm being so hard headed about not using dacron or weighing bullets, how can I shoot 3/4" groups with bullets I know have huge weight variance using really small quantities of really fast powders that don't even come close to filling up the case? If it's true for fast powders, shouldn't it be true for slower powders? I just want to see for myself before I start sorting bullet weights and using fillers.

[dtknowles]

For now I've not sorted any bullets other than throwing back obvious defective ones. I may in the future if I cannot achieve what I feel is acceptable accuracy. But I'll tell you what I don't get and part of the reason I'm being so hard headed about not using dacron or weighing bullets, how can I shoot 3/4" groups with bullets I know have huge weight variance using really small quantities of really fast powders that don't even come close to filling up the case? If it's true for fast powders, shouldn't it be true for slower powders? I just want to see for myself before I start sorting bullet weights and using fillers.

I would say yes if the pressures and velocities of the fast burning powder and slow burning powder loads were the same. Once you start moving up to velocities over 1500 fps, alloy, lube, bullet fit, start becoming more important.

Tim

[Clinton]

Yes I suppose. I'm on my last batch of test loads which I will shoot tomorrow. If I don't get improved accuracy I will have nothing left to do but sort bullet weights and possibly try fillers or harder bullets.