New 280AI build... big problems

[Rozzer]

Hey, I'm a relatively new member here and currently building a new 280AI on a new savage long action. I bought a brand new Savage .270 and stripped the stock and barrel off immediately. I ordered a Manners T2 and a new McGowan 280AI barrel. The barrel specs are 26" 1/9 twist varmint contour. I installed everything using some PTG go/no go gauges. I've installed Savage barrels before and everything went together perfectly. The problem I'm having is I measured the overall cartridge length after my barrel install and it measured out to be 3.215". That's with the 180SMK just touching the lands of the rifling. To me this seems to be way too short for a 280AI. The SAAMI specs for the 280 max OAL is 3.330".

I have a box of Remington Express Core-Lokt 280 ammo that I was going to use to fire form the brass. I took several measurements of the overall length on those and got 3.269". That means I can't even shoot these factory rounds without the bullets being jammed into the rifling .040". To confirm this I loaded one of the factory 280 rounds in the chamber very carefully. I got resistance when closing the bolt. I ejected the round and saw distinct marks on the bullets Ogive... indicating the bullet was definitely jammed into the rifling.

I'm thinking the problem is with the barrel's throat begin cut too short. To make sure I installed everything correctly I took the rifle apart and reinstalled the barrel using Manson .280 Ackley Improved gauges and got the same results. Is there anything else that could cause this or does the barrel need to be sent back for inspection?

 

[sortafast]

While I have no first hand experience with McGowan barrels, from what I have read, they can be iffy on quality sometimes. I could be wrong. Could also be that they designed the reamer/chamber around a lighter, flatter shooting bullet for hunting or something. I am thinking that you may have to get the throat cut a bit deeper. One option, that would cost more $$ would be to have someone like SSS or something make you a "prefit".

 

[selfbowhunter]

they probably used a SAAMI speced reamer designed to shoot a 140gr bullet. having a short throat doesn't mean anything is "seriously wrong" it just means you didn't do your homework when ordering your barrel! also, there should be some resistance on an AI chamber when using factory ammo. .040 jamb is not going to hurt anything at factory pressures and I would have no reservations shooting the factory ammo to form brass. if you are planning on shooting heavies, your going to be eating up a lot of case capacity though.

chuck

 

[Capt Beach]

My first instinct is the barrel is short throated...personally I would fire several cases and load one or two of the fire formed cases and then verify again...

I also agree your going to use up a lot of case capacity on those heavies...get on the phone with McGowen tomorrow am and talk with them and see what they say...

 

[LeoC8541/2112]

From what you wrote I am believing that you bought a pre chambered 280AI barrel so if that is the case and you didn't specify a length on your throat then it should come to you as a SAAMI spec chamber. Seat the bullet that you want to shoot at the depth that you want it loaded provided that it fits in your mag box unless you want to single load your ammo and do the math from the amount that you have to the amount that you want and call Dave Manson and buy you a throating reamer and handle and lengthen the throat the difference that you come up with and call it good.

 

[mr280]

I'll tell you what I did back when I built my 280 Ackley from a 25-06 Savage I had. Since at least some brass was to be fire-formed from 280 Remington - the rest I made by fire-forming 30-06, 270 and 25-06 using the "Cream of Wheat" method. First, I pulled the bullet from a factory fresh 280 round and head-spaced the barrel so there was slight resistance upon closing the bolt. I think Ackley called for four thousandths interference. Best to checked Ackley's book where he tells how to head space an Improved. Anyway, since doing it this way I've fired approximately several hundred rounds of factory 280 and probably as many hand loads through a new barrel with no problems. Reloaded rounds using Lee dies fit fine. Accuracy is pretty good. Almost 0.5 MOA. Maybe this will help you out.

 

[Roger C]

Doesn't McGowen supply "short chambered" barrels that have to finish chambered?