SIGM400 SRP with a Bushmaster 450 upper?

[BuckCreek]

Does anyone know how well a Bushmaster 450 upper would work with a SIGM400 lower? I would like to eventually buy an AR-15 in 5.56, and would like to be able to convert it to 450 for hunting deer. I have been looking at the SIGM400 SRP, but I wanted to know if that would work well with the Bushmaster 450 upper. Also would there be anything else I would need to switch out? I would greatly appreciate any insight into or advice on this. Thanks.

SIGM400 SRP
Bushmaster Upper Receiver Assemblies

 

[Regionnus Rattis]

I have the same model (love it BTW)...but you might want to call SIG to check. They have a tension pin under the rear take down pin to eliminate wobble and movement, so I'm not sure if that might be a problem or not. From the looks of upper and lower after taking mine apart, I don't think it would be a problem...but I'm not doctor, I just play one on TV

 

[BuckCreek]

Thanks. It is nice to hear from someone in this forum that actually has the SIG. I appreciate you sharing your opinion on it. Your comment is consistent with a lot of the reviews I saw about that model. Most people seem to really like it, especially for the price. I'll contact SIG to see what they have to say about it.

 

[BuckCreek]

Well I got the information I was looking for from the Bushmaster support.

My email to them:
Will the Bushmaster 450 Upper Receiver / Bbl. Assembly Part No:F1007571 fit and work with the lower from a SIG M400 SRP (SIG Item Number: RM400-16B-C-SRP)?
Thanks.


Their email to me:
Yes sir it will, the upper should fit nicely and work without issue. Thank you for choosing Bushmaster.

 

[Exodus]

My cousin and I both have M400s. Fantastic guns. My brother has a PSA that cheap thermolds wouldn't seat in but would seat in mine.