October 26th, 2015

Tech Tip: Changes in Humidity Can Alter Powder Burn Rates

Tech Tip Norma Powder gunpowder moisture temperature humidity

We’ve all heard the old adage: “Keep your powder dry.” Well, tests by Norma have demonstrated that even normal environmental differences in humidity can affect the way powders burn, at least over the long term. In the Norma Reloading Manual, Sven-Eric Johansson, head of ballistics at Nexplo/Bofors, presents a very important discussion of water vapor absorption by powder. Johansson demonstrates that the same powder will burn at different rates depending on water content.

Powders Leave the Factory with 0.5 to 1.0% Water Content
Johansson explains that, as manufactured, most powders contain 0.5 to 1% of water by weight. (The relative humidity is “equilibrated” at 40-50% during the manufacturing process to maintain this 0.5-1% moisture content). Importantly, Johansson notes that powder exposed to moist air for a long time will absorb water, causing it to burn at a slower rate. On the other hand, long-term storage in a very dry environment reduces powder moisture content, so the powder burns at a faster rate. In addition, Johansson found that single-base powders are MORE sensitive to relative humidity than are double-base powders (which contain nitroglycerine).

Tests Show Burn Rates Vary with Water Content
In his review of the Norma Manual, Fred Barker notes: “Johansson gives twelve (eye-opening) plots of the velocities and pressures obtained on firing several popular cartridges with dehydrated, normal and hydrated Norma powders (from #200 to MRP). He also gives results on loaded .30-06 and .38 Special cartridges stored for 663 to 683 days in relative humidities of 20% and 86%. So Johansson’s advice is to keep powders tightly capped in their factory containers, and to minimize their exposure to dry or humid air.”

Confirming Johansson’s findings that storage conditions can alter burn rates, Barker observes: “I have about 10 pounds of WWII 4831 powder that has been stored in dry (about 20% RH) Colorado air for more than 60 years. It now burns about like IMR 3031.”

What does this teach us? First, all powders start out with a small, but chemically important, amount of water content. Second, a powder’s water content can change over time, depending on where and how the powder is stored. Third, the water content of your powder DOES make a difference in how it burns, particularly for single-base powders. For example, over a period of time, a powder used (and then recapped) in the hot, dry Southwest will probably behave differently than the same powder used in the humid Southeast.

Reloaders are advised to keep these things in mind. If you want to maintain your powders’ “as manufactured” burn rate, it is wise to head Johannson’s recommendation to keep your powders tightly capped when you’re not actually dispensing charges and avoid exposing your powder to very dry or very humid conditions. The Norma Reloading Manual is available from Amazon.com.

Real-World Example — “Dry” H4831sc Runs Hotter

Robert Whitley agrees that the burn rate of the powder varies with the humidity it absorbs. Robert writes: “I had an 8-lb. jug of H4831SC I kept in my detached garage (it can be humid there). 43.5-44.0 gr of this was superbly accurate with the 115 Bergers out of my 6mm Super X. I got tired of bringing it in and out of the garage to my house for reloading so I brought and kept the jug in my reloading room (a dehumidified room in my house) and after a few weeks I loaded up 43.5 gr, went to a match and it shot awful. I could not figure out what was going on until I put that load back over the chronograph and figured out it was going a good bit faster than before and the load was out of the “sweet spot” (42.5 – 43.0 gr was the max I could load and keep it accurate when it was stored in less humid air). I put the jug back in the garage for a few weeks and I now am back to loading 43.5 – 44.0 gr and it shoots great again. I have seen this with other powders too.”

If you have two jugs of the same powder, one kept in a room in your house and one somewhere else where it is drier or more humid, don’t expect the two jugs of the same lot of powder to chrono the same with the same charge weights unless and until they are both stored long enough in the same place to equalize again.

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October 26th, 2015

Bargain Finder 6: AccurateShooter’s Deals of the Week

Accurateshooter Bargain Finder Deals of Week

At the request of our readers, we have launched a new “Deals of the Week” feature. If this proves popular, we’ll try to run this every Monday. Here are some of the best deals on hardware, reloading components, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.

1. CDNN Sports — HK 416 .22LR Rimfire Rifle

AccurateShooter Deals of the Week .22LR rimfire discount HK 416 ar15 tactical rifle ammo sale bargain

If you are looking for an AR-type .22 LR rifle for cross-training and rimfire tactical matches, the HK 416 is a fine choice. Made by Walther under license, these HK 416 D145RS rimfire rifles are accurate and reliable. This is a fantastic deal at $369.88! The HK 416 normally sells for $550.00 to $600.00. One purchaser writes: “Great .22. I have had this gun a couple of months and have put about 500 rounds of 5 different brands of ammo through it. Not one FTE. I have shot other brands that can’t get through one 30-round mag without a failure.” CLICK HERE for Product Details.

2. Amazon.com — Howard Leight Electronic Earmuffs $39.86

AccurateShooter Deals of the Week Muffs hearing protection Howard Leight earmuffs sale bargain

Every shooter should own a pair of Electronic muffs, even if you prefer shooting with earplugs and/or standard muffs. Electronic muffs are great when you are doing spotting duties or are working near the firing line. They allow you to hear ordinary conversations while still providing vital hearing protection. Right now Amazon.com has the Howard Leight Impact Sport Electronic Muffs on sale for just $39.86. This is good deal — these NRR 22 muffs are currently Amazon’s #1 seller in the category. NOTE: For regular, sustained shooting we recommend muffs and/or earplugs with a higher NRR rating.

3. Brownells Discount Codes (Valid Oct. 26 – Nov. 1, 2015)

AccurateShooter Deals of the Week .22LR rimfire discount bucket bullets ammo sale bargain

With the following Discount Codes (K4K, K4M, K4N) you can save up to $60.00 on your orders at Brownells.com. Don’t Delay — these codes expire at midnight on November 1, 2015. The coupon codes are as follows:

K4K: $20 Off Orders $200+ | K4M: $40 Off Orders $350+ | K4N: $60 Off Orders $500+

4. CDNN Sports — Remington .22 LR Ammo, 1400-round Bucket

AccurateShooter Deals of the Week .22LR rimfire discount bucket bullets ammo sale bargain

If you need bulk .22 LR rimfire fodder for plinking and general fun shooting, here’s a good deal. The 1400-round Bucket of Bullets costs just $139.88 now at CDNN Sports. That works to less than ten cents a round, under $5.00 for fifty rounds. The “Bucket of Bullets” makes a nice gift for a youth program. NOTE: The product contains 1400 live loaded rounds of .22 LR ammunition, not just bullets.

5. Bass Pro Shops — Barnes Varmint Grenade Lead-Free Bullet

AccurateShooter Deals of the Week varmint grenade bullets ammo sale bargain

Do you hunt in an area where lead-core bullets are not allowed? Then consider Barnes Varmint Grenade bullets, on sale now at Bass Pro Shops. Varmint Grenade bullets feature frangible, copper-tin composite cores. These bullets can take the ultra-high velocities deliveed by popular varmint cartridges such as the .204 Ruger and 22-250. Here are SALE prices for 100-count boxes by caliber:

.20 Cal 26gr $19.99/100 | .22 Cal 36gr $22.99/100 | .22 Cal 50gr $25.99/100 | 6mm 62gr $25.99/100

6. Bruno Shooters Supply — Norma Powder SALE, $22.95/lb

AccurateShooter Deals of the Week .22LR rimfire discount bucket bullets ammo sale bargain

Right now, Bruno’s has the most popular Norma powders on sale for just $22.95 per pound. Norma makes very good powders with excellent lot-to-lot consistency. If you shoot the 6mmBR or .308 Win, consider Reloder 203B. It is virtually identical to Alliant Reloder 15 (since it is made by the same manufacturer in the same plant). Norma MRP and URP and good choices for larger calibers.

7. Grafs.com — 33% Off Nosler Ammunition (.308 Win and .30-06)

AccurateShooter Deals of the Week varmint grenade bullets ammo sale bargain

Grafs.com is running a big sale on Nosler ammo. With close-out pricing, you’ll save up to 33% on .308 Win and .30-06 loaded ammunition. In addition, Grafs has other cartridge types on sale, including: .223 Rem, .270 Win, and 300 RSAUM. The Nosler Custom ammo is loaded with very good, strong brass.

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October 26th, 2015

Seattle Gun and Ammo Tax Challenged by Firearms Groups

Seattle Gun ammo tax

Seattle recently passed a law imposing special taxes on the sale of guns and ammunition. Labeled a “gun violence” tax, the Seattle ordinance is designed to discourage firearms use and, presumably, drive gun and ammo vendors out of the city. City Council President Tim Burgess, author of the controversial Seattle ordinance, likened the gun/ammo levy to “sin taxes” on alcohol and tobacco: “We’ve been working on this for several years. We tax cigarettes and alcohol and even wood-burning stoves for public health purposes. Why not guns and ammunition?”

Opponents of the new law have taken the city to court. The NRA, Second Amendment Foundation (SAF), NSSF and other organizations have challenged the so-called “gun violence tax” recently passed by the Seattle City Council. A motion for summary judgment has been filed citing Washington State’s long-standing preemption statute which “fully occupies and preempts the entire field of firearms regulation within the boundaries of the state.”

Gun group lawyers argued that the city “is well aware of this restriction on its legislative power” because Seattle’s most recent attempt to regulate firearms was emphatically struck down by the Court of Appeals in the case of Chan vs. Seattle. (That lawsuit derailed an attempt by the city under former Mayors Greg Nickels and Mike McGinn to ban guns in city park facilities.)

Seattle Gun ammo tax

“Seattle is trying to be too clever by half,” said SAF Executive Vice President Alan Gottlieb. “This so-called ‘gun violence tax’ clearly seeks to limit access to firearms and ammunition by imposing what amounts to a regulatory fee on the sale of all firearms and ammunition within City limits. The city can’t do that, and we’re confident the court will tell them so. In the final analysis, this is an attempt to skate around, and thus erode, our state’s model preemption law. That cannot be allowed to stand. The City of Seattle is not an entity unto itself, but still part of Washington State, and therefore the city has to abide by the same laws we all follow.”

Public domain Seattle photo by Rattlhed.

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