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The following are the most frequently asked questions by category that have come up about our products, manufacturing process, product specifications, and the meaning of life. Please take a second to look over them and learn something new that you probably didn’t already know about America’s Hardest Working Barrels.

Should you still have any questions or didn’t find the answer that you are looking for please feel free to e-mail us at

1-year product warranty

Rosco Mfg. is a proud manufacturer of quality barrels and as such will warranty its barrels for one year (from original purchase date). This warranty will extend ONLY to any defects stemming from manufacturing. Issues stemming from incorrect installation of the product, unauthorized modifications, performance issues when used with aftermarket accessories, using reloaded/ steel-cased/ non-SAAMI approved ammunition, or alterations made to the intended build that go against the original designs will not be covered by the warranty. If the barrel was purchased from a dealer, online retailer or distributor you must first contact them before the warranty claim can be made. This warranty will only be extended to the original purchaser/owner of the barrel and will not be extended to anyone else. Barrels that have been resold to another individual will be considered “used” and will not qualify for the one-year barrel warranty. Please review the returns policy for more information, for any other questions please e-mail


Rosco Manufacturing prides itself on creating a well-made product and taking care of its customers. That being the case we will warranty against any defects stemming from manufacturing, or if you received the incorrect part. To be eligible for a return, the customer must contact our Customer Service/ Sales Department and make them aware of the issue first. If the issue is related to a technical matter, we will try and resolve it by troubleshooting before we exchange the product or issue a return/ refund. If a return is authorized, we will send a shipping label to the customer to use and send the item back to us. The item must be in the original packaging, and have the receipt or proof of purchase in the box.

In the event that you receive a product that you changed your mind about or your build needs have changed, we will extend you the following refund policy:  The original customer has 30 calendar days to return an item from the date they received it, no exceptions. To be eligible for a return, your item must be unused and in the same condition that you received it. The item must be in the original packaging, and have the receipt or proof of purchase in the box. We ultimately still hold the right to deny a return if terms are not met, or there are other determining factors which prompt us to deny one.


Once we receive the item back, we will inspect it and notify you that we have received the returned item. We will immediately notify you on the status of your new product or refund after inspecting the item. If your return is approved, we will send you a new product or initiate a refund to your credit card (or original method of payment) minus a 10% restocking fee (depending on reason for return). You should receive the credit within a certain amount of days, depending on your card issuer’s policies.


If the issue stems from a manufacturing defect or we have determined that we need to have the product sent back in, we will issue a shipping label to the customer. For any other returns the customer will be responsible for paying their own shipping costs for returning the item. Shipping costs are non­refundable. If you receive a refund, the cost of return shipping will be deducted from your refund.

Yes, we proudly extend a 10% discount program for our MIL/LEO community. To be eligible you must be Active Duty Military, Law Enforcement, U.S. Military Veteran, Fire/ EMS, or First Responder. The perspective applicant must fill out our MIL/LEO program form first FOUND HERE and follow the instructions carefully. We do require proof of service or job status to set up your account. The applicant would need to submit a state or government issued ID, Service Record (DD-214 Member Form 4), or Currently Active Certifications verifying proof of service or employment. Once received you will qualify for our 10% MIL/ LE discount program.

That is a great question and the answer can be found on the product family’s individual product page. If you happened to miss it or glance past it quickly you can find the detailed info below.


Our “Bloodline” series family is our hardest working barrel. Whether you are an occasional builder, tactical shooter, or Law Enforcement Officer we have a barrel that will fit your needs. These barrels were designed to take more punishment than most barrels. We accomplished this through the material selected for construction and the coatings added for corrosion resistance which also add extra surface hardening. All our Bloodline barrels are 4150 Chrome Moly Vanadium steel and made from scratch in our Rhode Island facility and start life as a blank piece of steel. They are then treated in a Melonite finish which will protect the barrel from the elements and increases the surface hardness. I.E. Hard Use Hardware!!!


Our “Purebred” series is a testament to precision and quality manufacturing. We took a step back to see how we could create a barrel line that would be a culmination of all the lessons learned through years of making barrels for several OEM’s. The result is a barrel that will produce accurate results out of the box for any shooter that is looking to take their skills above and beyond. All our Purebred barrels are made from scratch in our Rhode Island facility and start life as a blank piece of 416R stainless steel. The barrel extensions are then micro polished before a Nickel Boron treatment is applied. The polished Nickel Boron will aid in corrosion resistance, surface hardness, and increased lubricity. I.E. Meticulous manufacturing leads to a precision instrument.


Our “K9” series is often referred to as the best of both worlds.  Each K9 barrel has it’s own standout attribute, whether it’s a featured length or a new gas system such as our proprietary Patrol length. The profile is a work of art, with weight shifted to the back of the barrel, modern attachments on the front of the rifle create a perfectly balanced and better handling weapon. Starting off as a blank piece of 416R, same as our purebred series, the barrels are made from scratch in our Rhode Island facility.  The K9 barrels are treated in the same Melonite finish as our Bloodline series.  The result is an accurate, yet durable barrel that only the modern shooter can appreciate.

No, we do not offer custom orders unless it is an OEM request (quantity based). Our focus on quality needs to be unwavering to make sure that the customer receives an awesome product every time. To make a low quantity “custom” or “one off” barrel would be to split our attention between repeatable quality and then disrupting the perfect operation of a machine to do a 2-hour set up for one specific barrel. What I can tell you is that we do a great deal of market research and testing. That way when we do bring a product to the market it is running the correct specs, will be a SKU that will be around for a while, and will be well priced because we are making them at wholesale level.

All our barrels are made 100% in house out of blank rods that we hand select from some of the best raw material specialists in the steel industry. Our Bloodline barrels are made from 4150 Chrome Moly Vanadium (CMV) steel and our Purebreds are made from true 416R Stainless Steel. We source all our raw materials from the USA, it is surprising how many “Made in America” barrel manufacturers source their materials from China. We stand behind our products with confidence, because we know what is going into them from start to finish.

Yes. We produce all our barrels from start to finish in-house. The process starts when the blank stock is delivered via flatbed trailer to our holding area within our facility and do not go into the production cycle until one of our in-house Quality Control (QC) folks inspects the lot. From there they are brought into the beginning of our production process and go through every station until it is turned into an awesome Bloodline or Purebred barrel.

Yes, we make barrel extensions in house from scratch. Once finished they are inspected by our QC department before they are released to our production department for final assembly. We then install all extensions after any coating has been applied so there is no chance of any heating process changing a torque value. All our AR15 extensions have M4 feed ramps, and our AR10 extensions are designed to SR25/ DPMS specs.

No, we do not MPI/HP test our barrels. The testing on our raw source material is very stringent and we look for conformity and consistency before it arrives at our facility. HP/MPI testing becomes unnecessary as the material is screened prior to even being considered for production as a rifle barrel. We source material that has already been tested for hardness and quality (same standard that MILSPEC material goes through). We do however verify hardness before and after the heat-treating process (which is done in-house). Then we surface finish test our chambers along with air-gauging the bore and groove. Other inspection points are headspace go/no go, runout on 4x separate dimensions (in front of extension, gas journal, muzzle, and threads to check concentricity).

Both our Bloodline and Purebred barrels are button rifled and then polished to make sure that a perfect bore is produced every time. We do have the option for other methods of rifling, but we are currently only offering the Button method. Companies that are interested in specific barrel specs are encouraged to check out our OEM section and fill out the request form for more info.

Yes. All our blank stock is delivered pre-stress relieved and we preform additional stress relieving in-house during the manufacturing process. These are the extra steps that we take to ensure that the quality of the product is maintained from start to finish.

No, you do not need to check our barrels for proper headspace. Typically you do not need to check head spacing on most all modern AR15 aftermarket/ replacement barrels. The majority of the industry has set a standard and follow the SAAMI specs very closely. Our QC department also makes it a point to check the head spacing of every barrel with the appropriate “Go/ No-Go” gauge before they go out the door. That means that once you install our barrel you will be good to go with any quality made Bolt & Carrier Group.

Yes, our Bloodline BCG’s are matched to both our Bloodline & Purebred barrels. What makes our Barrel/ BCG combos even better is that the tolerances have been measured carefully to allow for better lock-up while still maintaining proper reliability. This means that you will be able to squeeze out every potential bit of accuracy out of our barrels while still retaining the ability of fast follow up shots should you need it (I.E. 3-Gun, Tactical, LE/ MIL). Our Bloodline BCG’s are also backwards compatible with most other barrels found in the market, as long as they have been manufactured by a reputable barrel maker. These are just some of the ways that we can ensure that you will have a great experience with any one of our products, or all of them together as a system.

The gas port size for our Bloodline & Purebred barrels have been sized according to the caliber and length of each barrel. The goal is to take dwell times, reliability, and a long service life into account. We have also taken the extra effort to make sure that our barrels perform well under punishing conditions both suppressed and un-suppressed. Unfortunately, we cannot disclose more seeing as these measurements are proprietary production information.

We make barrels with pistol, carbine, mid-length, intermediate and rifle length gas systems. Our 11.5” & 12.5” K9 series features our proprietary Patrol Length gas system. These are noted in the individual barrel descriptions as well as twist rates, crown options, and thread patterns.

We currently machine the “journal” or seating area to accommodate a .750 diameter gas block for all our barrels. This includes our Bloodline and Purebred barrel families (9mm not included). The reasoning behind this choice is to give the customer a level of continuity and parts compatibility between platforms. All too often builders tend to re-barrel or re-chamber their uppers, why should they also be forced to spend additional money on another gas block if they do not have to? We build a lot of uppers & rifles ourselves for personal or training use, so we know these plights too well. As always, we recommend that you use the proper tools and techniques when installing one of our barrels. If you do not have the correct tools always play it safe and seek out a competent gunsmith.

Yes we do, but we only machine one dimple that is perfectly centered and matched to a backspace of .295. We use the one dimple method because the offset between the screws varies greatly between Gas Block manufacturers. This way you are dead centered when you put on your gas block and ready to roll. Now the place where the second screw lands is not as important, and you could even have your local gunsmith add a second one if you wish. As always, we recommend that you use the proper tools and techniques when installing one of our barrels. If you do not have the correct tools always play it safe and seek out a competent gunsmith.

This question is crucial to picking the correct Gas Block for your new Rosco barrel so please take vivid notes. We do not take the space in between the screws into account because that measurement is irrelevant to the actual back spacing of the Gas Block where it meets the end of the Journal area. We machine one dimple that is perfectly matched for a backspacing of .295. This measurement is industry average to all Gas Blocks in the aftermarket that have been made correctly and to spec. As always, we recommend that you use the proper tools and techniques when installing one of our barrels. If you do not have the correct tools always play it safe and seek out a competent gunsmith.

No, we currently do not offer that option. We suggest using a certified gunsmith for any gas block pinning services.

These are noted in the individual barrel descriptions as well as twist rates, crown options, and gas systems. These are the current thread patterns used on our Bloodline & Purebred barrels:

  1. 5.56 are threaded to ½ X 28
  2. 9mm are threaded to ½ X 28
  3. 300 BLK are threaded to 5/8 X 24
  4. 7.62 are threaded to 5/8 X 24

A well designed and machined crown can support the exiting projectile and enhance the grouping that a barrel will be able to produce. These are noted in the individual barrel descriptions as well as twist rates, gas systems, and thread patterns. We use the following barrel crowning methods for our Bloodline and Purebred barrels:

  1. Bloodline: For the Bloodline barrels we use a 10 degree “service” crown. It is a clean and consistently machined crown that will provide the exiting projectile the support needed once transferring into the turbulent environment under its own force. It is perfectly suited for duty carbines and hard use platforms as it provides the support that it needs to with out to much of an intricate method.
  2. Purebred: For the Purebred barrels we use a 10 degree “step” crown. This crown was designed to give the surface added protection by pushing it into (or creating a step onto) the barrel. It works especially well when you are using muzzle devices seeing as it creates a separation between the final point of the bore and the beginning of the muzzle device. When machined correctly this can be one of the most effective pieces to the precision barrel puzzle.

The typical lifespan of our barrels varies on a few of items. The terms in which a barrel will last comes down to the use, care, and environmental conditions for each shooter. A rifle barrel is a perishable item, much like an engine. If the engine is maintained well and not constantly abused it will last longer than most other engines and vice versa. If steady semi auto precision work is what you plan on doing, then you will enjoy one minute to sub minute groups for a while. Although, if your setup is more geared towards mag dumps you will just be speeding up the wear and tear process of any barrel. Another thing to consider is ammunition choice. If the ammunition that you run is over pressured, high velocity, or remanufactured you will be adversely affecting the life span of your barrel. Also, we only will only ever recommend that you use factory new SAAMI approved ammunition in our barrels. Anything else will void our warranty.

Bloodline: No, the Bloodline series of barrels do not require any type of break-in procedure. This is due to the fact that we electro-bore polish the barrels before the Nitride treatment is applied. This smooths out the lands and grooves first, and then lock them in for the life of the barrel with the Nitride treatment. The Nitride does not only protect the barrel from the elements, makes them easier to clean, and add lubricity, it also increases the surface hardness of the barrel by proxy. Increased surface hardness = Longer service life…

Purebred: These can benefit from our recommended break-in procedure seeing as they are naked stainless steel. The barrel blanks are honed throughout the rifling process to ensure that a perfectly smooth barrel is the result. However, the finished barrels may sometimes exhibit microscopic rough spots that can be buffed out with a proper break-in cycle. This can be accomplished several different ways, but we have a method that is effective and simple enough for the end user to do at the range during the initial test fire of the barrel. The result is a perfectly polished barrel that will produce repeatable results.

Our recommended break-in procedure for our Purebred barrels includes various steps which must be followed in perfect sequence. Any damage to your barrel stemming from incorrect use will not be covered by your warranty. The process is as follows:

  1. Inspect your firearm and make sure that it is unloaded!
  2. Only use “Match Grade” and SAAMI approved ammunition for this procedure.
  3. Clean your rifle and barrel first with a PH neutral cleaning solvent like Breakthrough Clean.
  4. Use a cleaning rod and run one solvent soaked patch and one dry patch through the barrel and wait till the solvent dries (about 3-5 mins). Run additional wet/dry patches if further cleaning is required.
  5. Shoot 1 round and clean in between each round fired using the cleaning method on step 3. Do this until you have fired the first initial 10 rounds through the barrel.
  6. Shoot 5 rounds and clean before firing the next 5 rounds using the cleaning method on step 3. Do this until you have fired the second set of 10 rounds through the barrel.
  7. Shoot 10 rounds straight and clean using the cleaning method on step 3. Do this after you have fired the last set of 10 rounds through the barrel.
  8. Once you have finished the recommend break in procedure and you are done firing the gun for that day make sure to clean it one final time. After the solvent has dried run an oiled patch through the barrel.

*If you prefer to use an alternate method of “fire lapping”, then we recommend that you use the Tubb’s “Final Finish” ammunition. These are bullets that have been professionally coated with different types of grit which will polish the inside of your barrel. Please read their instructions and proceed with caution. Any damage to your barrel stemming from incorrect use of this product will not be covered by our warranty. 

For our standard offerings in the Bloodline, Purebred & K9 Series, when using factory loaded, SAAMI approved, Match Grade ammunition you can expect MOA level accuracy (or better) out of our centerfire rifle barrels at 100 yards. Typically, our customers will experience 1 MOA to sub MOA groups from our centerfire rifle barrels. That however, cannot be guaranteed for every shooter. You must consider outside influencers like the ammunition used, the way the rifle was built, components used, shooter skill, and even environmental conditions. Another thing to consider is ammunition choice. If the ammunition that you run is inconsistent, over pressured, under pressured, remanufactured or was made by a guy out of his garage you will be adversely affecting the accuracy of your barrel. Also, we only will only ever recommend that you use factory new SAAMI approved ammunition in our barrels. Anything else will void our warranty. We will stand behind our barrels performing 1 MOA (or better) when Match Grade ammo is used, and all other factors have been met.