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Neck Tension Inconsistencies on Lapua 6.5CM Brass

straightshooter1
Rocketmandb said:
The first 45 bullets were out of one box of lot #1468 of Berger 220s. Then I ran out of bullets and had to open a new box of lot #1468 of Berger 220s. Nothing else changed. Same brass prep, same press setup, same time, same everything. Literally, all I did was get up, walk over to where all my bullets are, retrieve a new box of the same lot, and continued seating.

I contacted AMP to get their perspective and the first thing they said was, "measure the bullets."

Unfortunately, I had taken those last 45 bullets out to the hills the weekend before. Fortunately, if you want to call it that, one of those rounds had a bad primer. So, I pulled that one bullet and compared it to a few bullets out of the new box.

What I found:
- The OAL was essentially the same.
- The body of the bullet was ~.025" longer on the new-box bullets - measured by putting a comparator on both ends of the bullets.

Looking at the graph, you can see that the new-box bullets engaged around .025" earlier. That makes sense if the body is longer. You can also see that the slopes of the graphs are essentially the same. The reason the terminal forces on those bullets is higher is that there is more bearing area. In fact, if you just slid the orange plots to the right, they would match up.

EDIT: Morale of the story, measure your bullets every time you open a new box.
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Apparently, when you refer to the "body of the bullet" you're referring the the Bearing Surface.

Several years ago now, I discovered this difference in bearing surfaces between lots with two different lots of 168 SMK's where there was a difference of .033". So I sorted through them and set aside 20 that were .033" longer than 20 of the shorter. Loaded all 40 up and shot them into 10 round groups and chronoed all the shots. As I thought there might be, the .033" longer bearing surface rounds had a very different average velocity and a very noticeable difference in POI at only 100 yds.

Like you, I discovered it's a good idea to sample measurement for every new lot/box of bullets as there can be significant differences. But I'll point out too that the difference in bearing surface length being quite small, like .010" or less, isn't really going to show up on target or in velocity due to all the other noise that's going on.
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Opinions on VV N540 powder for 223/5.56 hand loads?

st1650
N540 is pretty good for heavy 223s. Give about an extra 25-50FPS over varget for the same pressure out of my 77TMK loads, accuracy was similar, tad worse than varget but SD wasn’t as good.
I was loading 25.0gr for a bolt gun load at 2.475in with the 77TMK. Lapua brass, CCI 450.
Apparently it reduces your throat/barrel life faster than N140 and Varget.
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Optics Nightforce NXS 5.5-22x56 MLR

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Nightforce NXS 5.5-22x56 MLR - $1500 shipped

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This scope is used, but it very good condition. Glass is perfect and everything functions perfectly, just shows typical normal cosmetic wear from use. This has MRAD turrets w/ 5 mils per revolution. It includes the original bikini cover, paperwork, and microfiber — as well as a sunshade, which does show some wear around the edges.

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7-08 vs 7 SAW vs 7CM vs ? for Large Frame

LRRPF52
iu


After the War, Army Ordnance and Fort Benning wanted a smaller COL than M2 ball (.30-06), but with the same performance. So they shortened the case to something similar to 300 Savage and increased the chamber pressure, added a boat tail to retain energy resulting in the T65 and later 7.62x51.

If they had done the same thing with the .450” case head .276 Pedersen, we would have had something with a 2.400 to 2.600” COL, running higher pressure in the M14, FAL, G3, and AR-10.
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Velocity differences between 6.5cm brass brands

straightshooter1
Rodney65 said:
I appreciate the feedback. I expect some change but some of the numbers just seemed all over the place.

I would like to be able to load an assortment of headstamps so they get close to the same velocity with a particular bullet but it just doesn't seem achieveable. Some brass gives tighter SDs, some is overworked and is disposable, some I have more of for when I need to load up for a match so I different uses for them.

I am trying to keep tabs on everything by recording velocities and putting them in a spreadsheet where I record the day's weather, powder/primer/bullet/case type and number of loadings.
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I think the best you can do when mixing headstamps is to measure each case's cases volume/capacity (not weight) and that should be a close as you can get for consistent velocities between them. Keep in mind there are other issues going on, like differences in the thickness and the alloy composition of the brass that'll react differently to the expanding gases as well as sizing which will effect pressure/velocity. It's simply best to stick to one headstamp of the same lot at a time. Otherwise, it just get complicated. ;)
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7-08 vs 7 SAW vs 7CM vs ? for Large Frame

LRRPF52
With Alpha Munitions 7mm SWC brass, the choice is pretty easy.

If there’s a cartridge I load for and Alpha makes brass for it, I will just buy that and not look back.

I’ve loaded for 7mm-08 in the past, and really love that cartridge. It’s what 7.62x51 should have been, and we should have known that from 7x57 Mauser performance already. 7x57 Mauser was one of the best military rifle cartridges ever developed and mass-produced.

Instead, we stubbornly stuck with the .30 cal bore because of institutional biases in Army Ordnance Board/CONARC. I don’t hate .30 cal, but you just get better performance from 7mm with higher sectional density for weight.

.276 Pedersen was our missed opportunity, which would have solidified 7mm in the US arsenal system going into the 1950s after the War. Would have made an awesome little AR-10 with a smaller frame, higher mag capacity, using the Pedersen’s case head.
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Mammoth Sniper challenge 2 AAR: very late edition

Yoteski
Jeff Karrels said:
In terms of placing, we did horrible, I think we were 22 or 23 or something... In terms of what we were there for we did great. New teammate who has never shot a competition before in which our only time together was to get him zeroed on one of my rifles. Our goals in order were to (1) Not get DQed (2) Not Zero a stage (3) Not come in last (4) Figure out our flow (5) Stay happy and healthy. We left some really easy points on the table, but we were able to meet most of our goals. We zeroed our first stage, but our first stage was the simultaneous shots from the back of the humvee on day one stage one. The rain and mist was good enough that we didn't even see the first sequence. We did get shots off because when we were coming onto time we just sent three at targets 2 in order to move past targets 1 but I made that call just a little too late. It was a grind, it was a blast, and heck yeah we met some great people.
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Congratulations man! The rain suuuucked! We dropped a ton of points on our very first stage Friday morning because of the downpour. Your hierarchy of goals mirrored ours.
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