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Old January 2, 2013, 02:09 PM   #1
hounddawg
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can bullet affect SD ?

doing a load of playing with loads lately on my .204. Noticed the standard deviation on some sets. On my 39 gr SBK's I averaged in the low 20's, on the 34 gr dogtowns I had 2 sets in the 80's and 1 in the 90's.

It might have been a lack of concentration on my part but I thought I had consistent technique. I saw on a another thread where not holding the rifle tight enough could cause a lot of deviation, I can't say for sure but I don't think that was the issue. I was doing the touch the thumb to the nose trick to endure a consistent cheek weld. The powder was RL10x and was measured on my Chargemaster. Now the decapping pin on my neck sizer broke while I was neck sizing that bunch and it might have been a bit bent earlier. I am wondering if I was getting consistent neck tension. Thoughts?

Also opinions on best neck sizer without breaking the bank ? Currently using a Lee collet which I have been pretty happy with.

I have also read that some use full length sizing each and every time with a bushing incorporated into the die to adjust neck tension. The Redding Type S - Full Length Resizing / Bushing Die seems to be popular. Anyone here doing that ?
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Old January 2, 2013, 08:11 PM   #2
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Yes, bullets have an affect on velocity SD. The more uniform the bullets the more uniform your SD will be if all else is equal.

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Old January 3, 2013, 05:49 PM   #3
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thanks Jim, that was what I was thinking. Odd thing is these Dogtowns are very consistent in weight. I will be playing with them more next week. I found 2 good nodes with the RL10x, now to see if I can get consistent results. Only three of the ten five shot groups were above 34 FPS and the rest were in the low 20's and teens do it could have been poor technique on my part

one other question not related to my original but I noticed some bolt stickiness even though I have been pushing the 39 gr SBK's harder. I saw not other signs of pressure but when I got home I was processing the brass and notice I had some whose necks were in need of trimming. This brass was on it's second firing after being necksized. The necks were up to .005 longer than SAMMI specs and wondering if that could have caused my bolt tightness
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Old January 3, 2013, 06:01 PM   #4
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Without having access to your bullets and rifle to see what is going on I can't give you any real advice on the stickiness other than to play with seating depth to see if the bullets do well with a longer jump.

Or it could just be time to anneal the brass.

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Old January 3, 2013, 06:06 PM   #5
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Yesterday I was using a .030 jump, I am going take it out to .040 or .045 since that is where it likes the 39 SBK's. 204's like a long jump. Had a couple of other people look at the fired cartridges whose opinion I trust, no one could see any other pressure signs and I am trimming that brass back before I fire it again so we shall see. Anyway one of the nodes that really shot well was at the low end of the charge ladder so that is the one I am going to see if I can fine tune
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Old January 4, 2013, 08:22 AM   #6
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Yep !

Different bullets, different performances. Very few bullets of a given grain weight made by different compamies in a similar configuration act the same as you have just found out for yourself. The length of the load bearing surfaces can vary quite a bit and will create different pressures as will the gliding metal composition and the sheer thickness of the jackets used in the construction of the bullets. Within reasonable limits dont read too much into SD as a controlling factor for accuracy unless you are an extreme long range competition shooter.
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Old January 4, 2013, 09:16 AM   #7
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If you are trying to improve SD, several things may be done.

1. Make sure your powder burn rate is compatible with the bullet and its weight. A powder that is too slow for the bullet weight and case size is harder to ignite consistently and will have trouble burning as completely as it should.

2. Make sure your primers are seated hard enough. Failing to set the primer bridge properly causes erratic ignition. In general, you want to see the small primers at least 0.003" below flush with the primer pocket.

A better approach is to measure the depth of your primer pockets and the height of your primers, including the anvil feet. Subtract the latter from the former, then add 0.002 inches. That's the minimum your primer should be below flush with the case head. Federal likes to stick with that number for a small rifle primer, and wants you to add 0.003 inches for a large rifle primer. Remington and Olin, in documents from the 80's, recommended to the military that 0.002" minimum and 0.006" maximum addition should be used. I find if you aim for the middle of that range, 0.004" addition, you generally do well, even with Federal primers. Note that these numbers are just depths that are in addition to where the anvil feet just kiss the bottom of the primer pocket.

3. Uniform the bullet pull force. Polished brass can stick to gilding metal in irregular degrees. Run a bore brush into each sized case neck and turn it a couple of times to remove carbon and lightly scuff the surface. Apply a dry lube, like graphite powder suspended in alcohol, inside the neck with a cotton swab to prevent brass-on-gilding metal bonding and to uniform the friction of the bullet release (note, this can affect your sweet spot load, so be prepared to adjust it).

4. Find each bullet's favorite seating depth. This Berger procedure for their VLD's is something to try, though in the little 20 caliber you may want to reduce the adjustment steps to 0.020".

5. If you're worried about hard holding, read this. Practice, practice, practice.

In general, a free recoiling (like floating in space) rifle's rearward velocity at the moment the bullet leaves the muzzle is just the muzzle velocity divided by the ratio of the rifle weight to the weight of the bullet plus about 40% of the powder charge weight (the portion that chases the bullet down the bore). This is due to Newton's second law of motion which says the momentum of the gun and all forward traveling ejecta must be equal and opposite at that moment the bullet base arrives at the muzzle. So if the bullet is going 3000 fps and the gun weighs 1000 times more than the bullet, then the free recoil velocity of the gun at the moment the bullet gets to the muzzle will be 3 feet per second. That's as much as it can affect muzzle velocity. Far more influential are the powder position in the cartridge, the barrel temperature, and whether or not your bullet goes through the chronograph screens perfectly parallel to the axis between the screens.

6. Chronograph setup. High readings, low readings, and erratic readings can all can all be caused by bad lighting conditions and, most of all, failure to set the instrument far enough back to avoid muzzle blast triggering. We had one board member with a .338 Lapua Magnum that had to set his chronograph back 18 feet before his readings settled. Based on the size of your cartridge, that much shouldn't be required, but you are asking for trouble if you use less than 10 feet with a rifle other than a .22 Rimfire. I use 15 feet normally, just because that's what the SAAMI standards screen midpoint is.


Your use of the Lee Collet Die is just fine. I combine them with the use of a Redding Body Die for shoulder setback and which leaves the neck alone. This makes sizing a two-step operation. If you can't stand the extra work, then a Redding S type FL sizing die with bushing or a similar device in another brand would combine the efforts into one. Just be aware that where the Lee Collet Die is immune to neck brass thickness variation the bushings are not, and you will want to segregate your brass by lot and history for the purpose of choosing the most appropriate bushing size for the job. The bushing die with no bushing and no expander in place can serve as a body die. It just costs more to get into the bushing dies.
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Last edited by Unclenick; January 4, 2013 at 09:22 AM.
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Old January 4, 2013, 09:21 AM   #8
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Bullets can cause variations in SD, especially in light calibers since many light bullets are too short to touch the rifling in a long chamber an still have any appreciable amount of bullet in the neck.

If the bullet has a short body and has a pretty long tip, it might not have a full caliber equivalent left to fit in the neck if you seat it out to get close to the rifling. Seating such a bullet close to the rifling might could cause variations in the neck seating pressure since there would be a smaller amount of bullet body touching the neck and a greater chance for neck tension related pressure variations. That gets even more exacerabated by a boat tail bullet since the rear boat tail portion won't be touching the neck either.

Neck sizing tension probably can cause more variation in SD than a few 10th of a grain of powder.
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Old January 4, 2013, 10:10 AM   #9
hounddawg
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some good advice here guys thank's.

Interesting info on the primers Unclenick, I started priming this load on my LnL but it did not like my Winchester cases and I ended up using the RCBS hand tool on it, however there were 4 or 5 that I started on the Hornady but finished with the hand tool

as you can see from the range sheet there is not a lot of rhyme or reason although the groups with the higher standard deviation in a couple of the groups also had the higher group sizes

I would love to get these to shoot consistent .5 groups. I shoot the .204 for long range practice becasue it is so inexpensive even with the SBK's but getting the bullet cost down another couple of cents each would be even better


Code:

22.0 RL10x     2.00 OAL     3637 FPS        SD 65 FPS        .6 group
22.5 RL10x     2.00 OAL     3721 FPS        SD 18FPS          2 inch group with one a inch to the right and another 2 inches low
22.7 RL10x     2.00 OAL     3735 FPS        SD 22 FPS        .5 group
23.0 RL10x     2.00 OAL     3754 FPS        SD 34 FPS        .5 group 4 were in .2 range with one flyer
23.2 RL10x     2.00 OAL     3757 FPS        SD 88 FPS        .8 group
23.4 RL10x     2.00 OAL     3764 FPS        SD 94 FPS        .9 group
23.6 RL10x     2.00 OAL     3774 FPS        SD 22 FPS        .7 group
23.8 RL10x     2.00 OAL     3842 FPS        SD 85 FPS         1.0 group
24.0 RL10x     2.00 OAL     3875 FPS        SD 22 FPS        .3 group
24.2 RL10x     2.00 OAL     3878 FPS        SD 22 FPS        .8 group
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Old January 4, 2013, 10:45 AM   #10
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I run into inconsistent progressive priming on Dillon's, too (though a 1050 can be set up to a fixed primer depth). The best priming tools cost most. You can adjust the Sinclair hand tool to protrude a fixed 0.004" to .005" above flush with the case head, then just drive all the way home each time. The K&M primer/gauge tool is even more elaborate, zeroing each individual primer to the individual primer pocket into which it will be seated, then letting you read the exact amount of bridge set on the dial. Slow going, but maximum repeatability of the bridge set.

If you want to avoid further investment, though, Dan Hackett wrote in the Precision Shooting reloading guide that he had simply taken to seating primers "hard". Probably not crushing them to the point of distortion, but pretty hard. He claimed that even with long cases like those based on the .30-06, he'd been able to get standard deviations down to under 10 fps when doing that. So that would be the first thing I tried if I were in your shoes.
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Old January 4, 2013, 11:07 AM   #11
hounddawg
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thanks Nick, I normally just use the hand primer on all my rifle except the .223 plinking stuff. Just got lazy the other night. Thought something was out of adjustment or something but it just did not like those Winchester cases at all It primed a Hornady .204just fine as well as some Lake City .223. I miked the case rims and they were fine, one of those darnediffiknows
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