Michelangelo Challenger - Bosis Challenger 2010

TECHNICAL SPECIFICATIONS OF PREMIUM QUALITY
MARAGING STEEL AND TITANIUM ALLOY USED IN THE
"BOSIS CHALLENGER 2010" O/U SHOTGUN WITH BARRELS IN AEROSPACE HIGH STRENGTH STEEL ALLOY
MARAGING 300 VAR PREMIUM QUALITY
IN COMPLIANCE WITH USA AMS 6514-E STANDARDS

ACTION AEROSPACE TITANIUM ALLOY "Alfa-Beta"
Ti-6Al-4V VAR PREMIUM QUALITY
VACUUM ARC REMELTING
TREATED WITH STA CYCLE
IN COMPLIANCE WITH AMS 4928-N AND Mil-T-4790G SPECIFICATIONS

"Bosis Challenger 2010"

A. BARRELS are in "Maraging 300 VAR Premium Quality" high strength steel produced in compliance with aerospace industry standards USA AMS/ Aerospace Material Specification, VAR /Vacuum Arc Remelting.

A.1. The "Premium Quality" brand applies only to steel and titanium alloys obtained through "Special processes" of Primary Melting Metallurgy or Secondary Remelting Metallurgy in compliance with AMS standards. These standards call for production cycles in furnaces with electric arc and remelting plants as follows:

1st phase: primary steel melting in furnace with electric arc or under vacuum;

2nd phase: single remelting, multiple or combined:
a. ESR / Electro Slag Remelting;
b. VIM/Vacuum Induction Melting + VAR/ Vacuum Arc Remelting.

Examples of simple multiple remelting:
a. ESR + ESR
b. VAR + VAR

Examples of combined multiple remelting:
a. ESR + VAR
b. ESR + VIM VAR
c. VIM VAR + VAR
d. VIM VAR + VAR + VAR

A.2. Over 99% of barrels in sporting guns are manufactured using steel alloys from primary melting in furnaces with electric arc. Approx 70% of such barrels have the chemical composition of a.; approx. 30% of b. and c.

Maraging steel alloy:

Elements a. SAE 8641 b. 42CrMo4 c. AMS 6514-F

Binders standard steel standard steel "Maraging 300 VAR P.Q"

Carbon 0,38 - 0,43 0,38 - 0,43 0,03 max
Silicon 0,20 - 0,35 0,15 - 0,38 0,10 max
Manganese 0,75 - 1,00 0,75 - 1,00 0,10 max
Phosphor 0,040 max 0,025 max 0,010 max
Sulphur 0,040 max 0,025 max 0,010 max
Chrome 0,40 - 0,60 0,80 - 1,10 0,50 max
Molibdenum 0,15 - 0,25 0,15 - 0,25 4,60 - 5,20
Nickel 0,40 - 0,70 0,25 max 18,0 - 19,0
Cobalt - - - - 8,50 - 9,50
Titanium - - - - 0,50 - 0,80
Alluminum - - - - 0,05 max
Copper - - - - 0,50 max

Density gr/cm3 7,85 7,85 8,20 pag. 1 di 4

"Bosis challenger 2010"

A.3. The higher the % of the special alloy elements in a steel, the better its mechanical, physical and technological features. An additional improvement comes from simple remelting and especially from the multiple ones under vacuum VIM VAR. The optimization of the steel mechanical features happens through a specific heating and cooling treatment which is of the utmost importance to give finished barrels the best resistance and strength characteristics.

A.4. All PH / Precipitation Hardening steel- including the maraging alloys with 17-19% of nickel, harden while heating up. To the contrary more traditional steels like the SAE 8641 and 42CrMo4 harden while cooling down. However only the "Maraging 300 VAR Premium Quality" reaches the following minimum vales:

- Yielding 0,2"%, longitudinal 1862 N/mm2 - transversal 1862 N/mm2

- Resistance to traction longitudinal 1930 N/mm2 - transversal 1930 N/mm2

- Stretching %, longitudinal 5 - transversal 4

- Contraction %, longitudinal 30 - transversal 25

The mechanical values above can be reached only after 6 hours at 480-510 C. In compliance with AMS 6514 Standards.

It is very important to notice how the transversal mechanical values are similar to the longitudinal ones which is a metallurgic feature typical of all Maraging steel and all PH/Precipitation Hardening steel in general.

A.5. The barrels in "Maraging 300 VAR Premium Quality" steel on the "Bosis Challenger 2010" O/U shotgun have been treated through a specifically designed 6-hour-long precipitation process at 680-690 C. This was indispensable to reach the following mechanical features:

- Yielding 1120 - 1220 N/mm2

- Resistance to traction 1300 - 1400 N/mm2

- Stretching 5% min.

- Contraction 60% min.

These are the best possible values obtainable with "Maraging 300 VAR Premium Quality" steel after solubilization treatment (special annealing) and especially after precipitation (hardening) at 680-690 C.

Special High Strength Precipitation Hardening Steels started what can be compared to a Copernican revolution for steel over 50 years ago. The metallurgic innovation of high strength steels and in general all PH /Precipitation Hardening steels was possible thanks to the aerospace industry which needed new steel alloys to allow military aircrafts to fly at supersonic speeds in total safety.

"Bosis Challenger 2010"

A.6. The production of a pair of smooth bore barrels in high strength aerospace steel "Maraging 300 VAR Premium Quality" is an exceptional event and not only for the gun industry - especially now that the world depressed economy is penalizing the metallurgy and engineering industries. This steel is very challanging to machine and work by hand due to the high % of binding elements (> 30%) and the high hardness at the solubilized state. The steel has over 1000 N/mm2 mechanical resistance

A.7. To complete this brief technical report, we need to mention that the "rumor" barrels in Maraging steel were built in Sweden in the mid 60s has been circulating in the gun making industry for over 40 years. No factual information or document have ever been found. The Swedish were probably the ones who started this rumor back then supported by a few Italian hunters and shooters who were famous at international levels for their performances.

B. The action in the "Bosis Challengere 2010" is in titanium alloy "Ti-6Al-4V VAR Premium Quality" produced with "double melt VAR / Vacuum Arc Remelting" in compliance with USA AMS 4928-N aeronautic standards.

B.1. The Titanium alloy "Ti-6Al-4V" is the oldest in the "Alfa-Beta" class and is the most widely used in the production of mechanisms and frames not only in the aerospace industry. In the USA it is called "Popular Alloy" due to its popularity. In the aerospace industry it is widely employed in the production of hollow cables and piping with very low wall thickness which have to withstand very high pressures

The exceptional technological features of the "Ti-6Al-4V" and of all other alloys in the Alfa-Beta class are: resistance, light weight, resistance to rust and biocompatibility.

B.2. The titanium "Ti-6Al-4V VAR Premium Quality" in the action has been treated with the cycle called STA / Solution Treated and Aged in mandatory compliance with the AMS / Aerospace Material Specification and Mil-T-9047G specification in order to get the best resistance, resistance to pressure and corrosion.

D.1. The careful and complete application of the technological solutions described in the manuals and specifications mentioned in this document guarantee the best physical and technological features of the "Maraging 300 VAR Premium - Quality" steel and titanium alloy "Ti-6Al-4V VAR Premium Quality".

Guns specifics:
- Challenger Over Under
- Titanium action and Maraging 300 steel barrel
- 12 gauge
- New lock with the hidden window
- New thin forend tip
- Barrel lenght 29" - 73,5 cm
- Chokes : 5 tenths and 9 tenths that correspond to Mod and Full
- Barrel weight : 1.137 kg
- Bored 15.70
- Chamber 70mm
- No top rib
- No middle ribs
- Total gun weight 2.689 kg